超声波—缺氧好氧组合体系的构建 翻译与原文总稿

超声波—缺氧好氧组合体系的构建 翻译与原文总稿 本科 毕业设计 机械毕业设计下载球磨机的毕业设计下载关于网络爬虫的毕业设计下载关于网络爬虫的毕业设计下载河南城建学院毕业设计论文下载 ( 论文 政研论文下载论文大学下载论文大学下载关于长拳的论文浙大论文封面下载 ) 外文参考文献译文及原文 学 院 环境科学与工程学院 专 业 环境工程 年级班别 级(4)班 学 号 学生姓名 指导教师 2009 年 6 月 目 录 译文1 ......................................................................................................................................... 1 超声波空化作用在生化工程/生物技术应用的研究 ............................................................... 1 1.1 介绍 ............................................................................................................................ 1 1.2 反应器的设计 ............................................................................................................ 2 1.3 空化应用领域的探讨 ................................................................................................ 6 1.4 结论 .......................................................................................................................... 20 参考文献 .................................................................................................................................. 21 原文1 ....................................................................................................................................... 29 A REVIEW OF APPLICATIONS OF CAVITATION IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY .................................................................................... 29 2.1 INTRODUCTION .................................................................................................... 30 2.2 REACTOR DESIGNS .............................................................................................. 31 2.3 AN OVERVIEW OF AREAS OF APPLICATION OF CAVITATION ................. 37 2.4 CONCLUDING REMARKS.................................................................................... 58 REFERENCES ......................................................................................................................... 60 译文2 ....................................................................................................................................... 68 超声波破除促进厌氧好氧消化 .............................................................................................. 68 3.1 介绍 .......................................................................................................................... 68 3.2 方法——加强厌氧消化 .......................................................................................... 69 3.3 方法——加强好氧消化 .......................................................................................... 71 3.4 结论 .......................................................................................................................... 72 参考文献 .................................................................................................................................. 73 原文2 ....................................................................................................................................... 74 IMPROVING ANAEROBIC AND AEROBIC DEGRADATION BY ULTRASONIC DISINTEGRATION OF BIOMASS ........................................................................................ 74 4.1 INTRODUCTION .................................................................................................... 74 4.2 METHODS—ENHANCING ANAEROBIC DIGESTION ..................................... 75 4.3 METHODS—ENHANCING AEROBIC DIGESTION........................................... 88 4.4 CONCLUSION......................................................................................................... 80 REFERENCES ......................................................................................................................... 82 外文文献译文及原文 超声波空化作用在生化工程/生物技术应用的研究 Parag R.Gogate,Abhijeet M.Kabadi (化学工程部，化学技术研究所，Matunga,Mumbai , 40019,印度) 摘 要:超声波空化作用能够导致热点、高度活泼自由基、以及与能够引起强化大量物理/化学操作的回流液体相关的紊流的产生。目前的研究存在一种超声波空穴现象在生物化学工程/生物技术独特领域应用的看法，对应用领域、超声波空化的作用的讨论，随着观察研究的不断深入得出超声波空穴是由于对一些典型有代表性样品的辅助照明产生的。诱导超声波空化作用的不同方法以及空化作用的显著优势，大多是关于生物技术在不同领域运用所考虑到的能量需求。在此课题中的主要应用研究包括微生物细胞分裂对酶的释放或提取、微生物灭菌、废水处理、结晶过程、生物柴油的合成、乳化作用、生物化学提炼、冻结作用以及基因转移到细胞或者组织。一些最优的操作/几何设计参数的建议已经被提出。总之，该技术的应用有赖于物理学界、化学界、生物学界的共同努力，化学工程要求把超声波反应器更加有效地运用到工业化运作中。 关键词:超声波反应器;微生物细胞分裂;水体消毒灭菌;生物柴油生产; 生化工程 1. 介绍 工业进程发展需求不仅仅关于在产品质量、能耗或生产时间、或者从经济方面讲，都要求最高效操作方式的实施。在以一种对环境友好方式维持或者加强产品质量的同时，可供选择的新颖技术不断的实践尝试降低总的运营成本。超声波空化在以一种低能耗方式强化维持物理或化学过程中提供了巨大的可能性。空穴作用一般定义为形成、生长和穴腔瓦解，从而形成局部高能量密度。超声波空穴作用，当它在反应器中出现时，形成条件需要非常高的局部温度和压力(1000-5000大气压和5000-15000K的温度)，但是全部的反应环境要与周围大气条件维持一个相当量。从而使能够在大量物理过程或 1 外文文献译文及原文 者需要限制条件的化学反应的环境状况下有效的进行。而且，自由基在被空化气泡所收集的水蒸气的离解过程中生成，这种物质能够强化化学反应或变更反应设备。空化现象也能导致反应器中局部紊流和液体微循环(声流)的形成，加强传输过程的速率;另外，也能够消除多相系统中大部分传输阻抗，基于能根据压力和温度大小被描述的强度水平，超声波空化既可以分为瞬间不稳定和稳定类型。这两种类型形成的能量需求是明显不同的，因此，当为特殊运作类型选择操作参数时一定要合适恰当。短促的超声空化是一个能使所形成的气流分离区/空穴，在原有的大小上最终瓦解成微小分馏物的过程，气泡里现存的气体会经由一个相当剧烈的反应过程被消散到周围的液体中，以声音冲击波和可见光方式释放出一种有重要价值的能量。接近全部分裂状态时，气泡内水蒸气的温度可能要几千开氏度，压力可能要几百大气压。在持稳或非常态超声空化的情况下，由于某些形态能量的输入从而强迫液体中的小气泡在形状或大小上产生振荡，例如一种声场，能量能量输入的程度不足以引起全部气泡的分裂。这种空化形式比瞬间的超声波空化更能明显产生有意义的平和超声波效果。超声波空化基于形成方式也可以分为四种类型:声音、水力、光和颗粒。仅仅声音和水力空化已经被发现能在运行过程中有效产生所希望的化学/物理变化，光学空化和颗粒空化独特地利用到单个气泡的超声空化中，在大批量的溶液中不能诱导任何物理或者化学变化。利用超声波处理产生空化现象的惊人功效已经更多的普遍应用到食品和生物过程的工业中。相似的空化现象也能够很容易在相关的水力运行系统中形成。工程师对于由于在用水设备中产生气蚀引起的器械的腐蚀问题通常都很谨慎，研究初期的所有努力主要是为了消除这种现象以避免对显露表明的侵蚀。然而，一种严谨的系统设计允许空穴瓦解产生的条件与声空化相似。使不同的反应需要改变超声空化强度已经在利用与声化学反应器相比较更低输入能量声音空化现象中成功的研究出来。最近十来年，全世界为数不多的研究人员对水力空化的惊人效应在化学/物理转换的作用进行了集中精力的研究。目前的研究进展提出了空化反应器根据在生物化学工程和生物技术不同操作特点运行条件也是不相同的观点。 2. 反应器的设计 依靠超音速而形成空化的反应器通常称作声化学反应器，依靠流体能效用而产生空穴的反应器一般称作水力空化反应器。 2 外文文献译文及原文 声化学反应器 超声喇叭，在声化学反应器中是最为普遍应用的反应器设计，尽管它的超声空化效应仅仅能够接近振动表面。超声空化密度随着喇叭远移而成倍降低并且在低至2–5 cm的距离中消失，主要依赖设备所提供的能量和操作频率。因此，大规模操作运行中的超声喇叭型系统的功效与基于复合换能器的系统是不能相比的，由于超声喇叭在通过大量液体容器中不能够有效的传递声能。加之，超市喇叭型反应器，会遭受侵蚀和由于表面的高能量密度而在传送末端表面脱落;空化闭塞(声音解耦)，大型换能器的移位(振幅)增加了结构材料的应力，导致应力诱变老化失效的可能。这些有代表性的反应器被推荐到实验室的特性研究中或者应用到具有足够引起所希望变化较低停留时间的大规模操作工艺中。 反应器基于复合换能器辐射恒定或合乎逻辑的相近的不同频率的运用。复合换能器的运用也能够在低能量运行中产生相似的耗能水平，因此，超声空化解耦冲蚀和颗粒脱落的问题在传递表面有所减少。换能器的位置能够容易的改动以适应依靠独特换能器重叠而形成的波型，引起空间高于超声空化阈值的均质和无无粘聚力的声型通过反应器工作区。结构排列例如在超声波浸没情况下的三角形人造树脂，带有两个末端辐射换能器或一个末端换能器和一个反应器的管状反应器，平行板反应器每一块板极能够辐射同一或不同频率，还有六角形流动细胞按照图示1作为代表性研究。容器能够在浸没方式中操作或用于在复合单元能够以同样可以增加停留时间的连续方式结合的持续运作的大 2规模运转工艺。总计，大多数低电换能器和声能换能器(1–3 W/cm)产生25–150 W/L，理想的范围是40–80 W/L。这种动能能够连续不断地产生或以脉冲激发的方式形成。 分裂压力和温度的大小以及超声空化后自由基形成的数量，强烈的依赖于声化学反应器的运行参数。协同换频器物理结构的辐射强度和频率和液相物理化学属性影响到原子核最初大小和核化过程。运行条件，液体物理参数和物理化学特性的恰当选择决定了所需运行中超声波空化反应器的效能。基于从现存文献中获得的详细液泡动力学 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 ，一些定性的建议已经作为最优的运行参数被提出，例如下面所给出的: 辐射强度大小的最优选择基于各自独特的运行;利用复合传感器引起更高活泼的超声空化体积。 3 外文文献译文及原文 最好运用合适的辐射频率;提供过高的频率通常在开始阶段需要更高的动能并且会导致侵蚀问题。 液体低蒸汽压、低表面张力和低粘度适宜作为诱导空化反应器的反应介质。 目前的附加剂例如气体或者固体颗粒能够降低空化现象的形成并且一般也能导致更高的空化效应。 .水力空化反应器 在液体流动中水力空化的普遍形成可以借助压缩物诸如锐孔板、扩散管或节流阀。在压缩物中，液体的反应动力学动能和流通速度提高，相对应的局部压力会降低。如果节流足够控制周围流体静压在空化临界压力下(通常介质的蒸汽压控制在运行温度)，空穴就会形成。连续不断，当液体喷射膨胀，压力回复，导致空穴的瓦解。在液体通过阻塞物界面的通道中分层现象就会发生，大量的能量由于局部紊流导致以持久压力降形式而被浪费掉。高密度的紊流也会在压缩物的下游处形成;它的强度依赖于压力降大小和压力修复的速率，结构的物理参数和液体流动条件，还有紊流的规模。紊流的强度对空化强度有很大的影响。所以，通过对物理参数和反应器运行条件的控制，使所希望达到的物理或化学变化所要求的空化强度以最大能效的方式形成。 基于水力空化现象而普遍应用的设备是高压均质器，本质上是高压容积泵根据高压释放操作原理结合节流设施构成的。典型的高压均质反应器由给水箱两个节流阀组成，作为第一阶段和第二阶段对水力空化反应器运行压力的控制。空化的初始形成和有效空穴的产生通过关键性的排出压力获得。然而，在空化活动体积和压力脉冲大小上没有充分控制会在空化事件的末端产生，从而限制基于细胞内相对应位置胞内酶选择性释放的可能性。因此，这些反应器有限制的运作特别是生物工业过程中细胞分裂、空化所需的能量大小是有要求的。这些反应器一般适合于食品乳化过程、制药和生物工业过程。 空化同样在旋转式设施中产生。当旋转器边缘速度达到临界速率，旋转的液滴接近外围压力并接近液体蒸汽压。这就会导致水蒸气空穴的形成。当液体从旋转器移动到容器边缘，液体压力修复到动压头损失阶段。就会引起空穴随液体体积大小而破坏。类似于高压均质器，在空化初始形成阶段存在一个关键性速度。可知在这些类型的反应器中能量的消耗是很大的，设计参数的灵活性与基于多孔锐孔板反应器相比是较低的。 4 外文文献译文及原文 基于锐孔板原理的反应器，流体通过压缩物区域流经主干线时局部流通速度由于流域的还原而突然升高，导致更低的压力甚至降低到液体介质蒸汽压以下。一套有图解的、有代表性的安装工艺已经在图2中给出。在水力空化反应器系统中选择正确的装配流程对于所希望达到的最大空化效果和最有效的经济方式是最重要的。压缩设备可以是一个扩散管、一个单孔或多孔的锐孔板。利用多孔锐孔板(图3)能协助达到不同的空化强度。再者，空化事件在反应器中的产生次数是很多的。因此，锐孔板的安装根据操作(进口压力的控制、进口流速、温度)和物理几何条件(锐孔板的不同孔型，诸如圆形、三角形节距等等，还有锐孔板自身能够改变合成液体的剪切，导致不同空化强度的几何孔型)提供了巨大的灵活性。 Sampathkumar and Moholkar最近已经提出一个新颖水力空化反应器设计概念，利用收敛-发散喷口来产生驱使液泡运动所需速率的压力来代替前面所讨论到的锐孔板。空化气泡或核心在水体流动外形上被形成，利用一个喷淋器的喷口溯流而上。 不同的气体能够被用于液泡的产生。当然，气体分布器(通常是玻璃料过滤器板)大小，空气贮罐中气体的流动速率和气体压力，为了达到空化所需的最初大小可以通过拉开空气贮罐适当控制形成条件，能够有效的影响生成物的空化程度。然而，与锐孔板安装相比较，从控制空化强度的灵活性方面来说是持续降低的，只有喷口的长度和直径在这种情况下是可以变化的物理参数，在这种状况下的锐孔板的数量、大小和孔型是可以不一样的。根据运作类型和在特殊运作条件下强度需求利用收敛-发散喷口和节流孔串联作用是有价值的。 从上述关于许多水力空化反应器的研究讨论中，可以很容易得出结论就是，锐孔板的设置提供了最大的适用性，可以运用到相对大规模的运营操作。同时也可以注意到此类反应器当随着大小(流速和排速)的增加而提高用泵的效率而按比例增加也相对容易，将会维持最优化操作在更高能效，以下的建议可以运用到仪器设计和运行参数的选择中: (1)节流孔的流动构型对于强烈的化学反应是必须的，对于较为温和过程(典型设计是15-20条范围)和物理转化，扩散管被建议到构型中。 (2)在机械压缩部分的上流选择较高的进口压力，但仅仅要低于超空化开始所需的压力。 5 外文文献译文及原文 (3)选择液体物理性能最优组合，使前面所讨论到的初期最低空核能够容易产生。 (4) 对于锐孔板的设置，孔的最优数量和直径要在运行类型的基础上与自由流水区相均匀;运行中大直径小数量孔洞需要更高的空化强度，例如复杂的化学破坏，小直径高数量孔洞则需要相对较低的强度，例如细胞分离。 (5)水体流通以较低的自由流域设计水力空化反应器。 (6)在高速搅拌器的状况下，所选择的转速一定要高于空化反应开始阶段的临界速度，低于空气诱导空化的替代速度。 3. 空化应用领域的探讨 3.1微生物细胞分离 在重要的微生物成分工业化经济生产中的一个关键因素是有效的大规模细胞分离过程。高效的微生物细胞分离操作的需要经常妨碍细胞内衍化的商业生物技术产品的大规模生产。对于微生物的大规模分离，粉碎机诸如高速搅拌器、珠粒碾磨机和高压均化 10%.的范围。剩余的能量以热器已经很普遍的提供，但是上述方法传统的能效是在5– 的形式被浪费掉，为了保持这些精致生物产品的完整性而需要有效的排除。带着改善细胞分离过程效能的目标，在近十年来最新的技术狂热的发展，包括声波空化和水力空化。Harrison and Pandit是首位提出通过运用一个节流阀作用形成空化的构型用于细胞分离过程的空化反应器的利用。不久，Shirgaonkar等人清楚的证实在高速高压均化器中空化效应所产生的大量酶和蛋白质释放的需求。Shirgaonkar等人提出蛋白质的释放速率在10,000 rpm比在高速搅拌器的5000 rpm更高。这个可以由Kumar and Pandit所提出的高速均化器单元在空化反应起始阶段的产生速率8000 rpm的机理得到解释。在10,000 rpm速率下，主要靠空化和机械压作用于细胞分离，在5000 rpm下，仅仅是机械剪切压对全部细胞分离起作用。因此，系统中空化形成条件在所给的输入能量下对于细胞内酶的最大释放是非常重要的。 Save等利用基于节流阀的水力空化反应器用加压酵母细菌的方式来分离面包酵母和酿酒酵母，并提出处理时间的增加和数量的减少导致细胞分离程度的对应提高。悬浮液的浓度显著地影响到分离过程。酵母菌细胞的生长期是另一个影响能效的参量。 6 外文文献译文及原文 Preliminary用新鲜的发酵培养基做实验，并与被贮藏或冻结的细胞对照表明，细胞在指数生长期对分离是相当易受影响的。与不同操作方式的能效对比，包括水力空化搅拌机和超声破碎机，表明水力空化设备安装的能量需求比其他两种方法在两组大小等量蛋白质释放所需的要低。在定量期限，在水力空化反应器中能量利用每毫升酵母菌悬浮液获得相同程度释放出的蛋白质是20.7 J/ml，超声波辐射是1500 J/ml，混合搅拌器是900 J/ml。早期研究的变型是按比例增加。Save等人还有Balasundaram和Pandit利用水力空化反应器控制在200 L和 50 L的操作条件下研究细胞分离过程，各自都指出相似的能效结果。最后确立的结论，尽管空化现象的生成需要非常高的温度和局部压力，并伴随着自由基的形成，从细胞中释放出的活性酶仍然保持性质不变。这归功于仅存在非常小间歇时间(典型到几微秒)的剧烈状态的事实，因此对释放出的酶不会产生任何的灭活作用。葡萄糖苷酶和转化酶的活性在中性状况下是不会有影响的。然而，长时间的暴露(在3 atm大气压下处理60分钟)会导致酶活性下降大约10%。因此，通过选择系统运行合适的操作手段和物理参数来控制空化强度和大小与处理时间是一样重要。 可知细胞分离过程的机理因所用的设备不同而不一样。细胞分离经由某些设施中独特细胞的完整破裂而得以进行，或能够被剪切而仅对细胞壁进行破坏，导致细胞壁或周质中现存酶的释放(缓慢溶滤)。Balasundaram and Pandit研究利用超声波降解法、高压均化和水力空化作用分解啤酒酵母达到释放转化酶的目的。被提出在使用锐孔板产生水力空化的情况下，转化酶释放的程度比全部可溶蛋白质还要高。可能是由于酶胞质的场所原因。鉴于酶和蛋白质的释放方式，在水力空化分离中可以释放出所有可利用蛋白质(也即细胞质)的细胞被完全毁损前的早期希望转化酶(胞质)能够选择性释放。对于超声波感应空化，转化酶的释放速率可与蛋白质的释放相比较，归因于声音空化情况下空化强度的激烈程度，可与水力空化相比较。剧烈的空化导致细胞的完全破裂，在水力空化反应器中平和的空化强度引起细胞由于被剪切而被碰撞研磨，提高了细胞壁比完整细胞更加容易破裂的程度。Balasundaram and Harrison研究了水力空化对大肠杆菌细胞局部分离的运用，并指出作为空化强度的机能，周质和细胞质酶的选择性释放与全部可溶性蛋白质相关联。 Balasundaram and Pandit利用定位因子的观点对细胞内特定位置酶释放程度的从属性进行定量分析。定位因子可以定义为酶的释放速率与蛋白质释放速率的比例。典型的，位于外周胞质酶的定位因子大于1，位于细胞质的酶的定位因子小于1. 对于转化酶和 7 外文文献译文及原文 青霉素酰基转移酶的释放，在所有空化装置中定位因子的观察都远大于1，从而使酵母菌细胞和大肠杆菌细胞中两种酶各自所处的胞质位置得到巩固，此外，研究表明与超声波降解和高压均化相比，定位因子在水力空化反应器的情况下更高，由于剪切作用，巩固了通过碰撞研磨细胞达到分离的细胞分离设备的功能。对于乙醇脱氢酶(ADH)，定位因子接近约0.5，加强了细胞周质中目前大部分的ADH。Balasundaram and Harrison也指出在不同酶中定位因子相似的属性，例如葡萄糖苷酶(胞质的)、蔗糖酶(细胞壁保护)、ADH (细胞质的)和6-磷酸葡萄糖脱氢酶(G6PDH;细胞质的)，在系统的空化强度下生成。 从上述研究中可以明确，酶的定位因依靠空化反应器而从细胞中释放，实实在在的影响到能量需求的程度。一些预处理措施在细胞悬浮液被全部支配到细胞分离过程前可以利用于细胞中酶位置的变更。酶通过预处理从细胞质迁移到外周质能够利用于细胞分离效能的改善和降低能量需求。一些用于转移的技术，像在文献中提到的，热应力、发酵过程的常规时间、pH操作参数和化学预处理。 总而言之，可以说用于细胞分离的水力空化的作用在大量应用中已经结论性证实，并且与音速(超声波)空化反应器相比较具有更高的能效。加之，所有空化反应器的探究与基于机械能的常规技术相比具有更高效的能源效应。一种独特的反应器结构选择可以根据空化器的物理几何参数和运行参数，例如进口压力和回流速率可以基于细胞中独特酶的位置和介质细胞浓度选择。预处理措施诸如热、pH和化学处理在能量供求明显降低时能够辅助提高目标酶的选择。 3.2 微生物灭菌 这些年来，水体微生物的消毒灭菌已经通过大量的化学方法和物理方法达到处理效果;然而，这些方法还存在的很大缺陷诸如诱变信息和致癌物质，大剂量物质转移的限制因素引起更高的处理时间等等，某些时候会超出它们的能效范围。同时，微生物在某方面会产生成团附聚成球形或大串的结肠和孢子。这些团簇的化学处理可能会在表面破坏微生物细胞，在最里面的有机物就完整保留。因此，就有必要发展研究一些水体消毒的轮替技术。超声波空化根据热点、高度活泼自由基和与液体回流产生强大的紊流而形成的惊人效果而被作为水体灭菌的有效手段。通过超声空化微生物的消毒工程一般是以 8 外文文献译文及原文 下效果的组合: 物理效应:包括回流液体紊流和剪应力的产生。 化学效应:包括活性自由基的形成。 热效应:局部热点的出现(需要非常高的温度和局部压力)。 复合处理效应:当利用化学复合(Cl,HO,O)处理时，明显的压力变化通过微生2223 物细胞膜改善了化学氧化的渗透。同时，空化作用促进了溶液中微生物团块的瓦解，提高了其他化学灭菌的效应。 观察研究表明物理效应是造成微生物灭菌消毒的主要原因，化学和热效应处于辅助的地位。超声波微束导致持稳的空化能够产生充分的压力去分解细胞膜。物理处理建议用于紊流产生的起始阶段，该阶段的紊流在接近剪切速率时形成的旋涡比通过液体容器时的更大。Doulah也已经证实酵母细胞在超声波空化中分裂的形成依赖从振动波末端增加的粘性耗损中形成的剪应力。 运用于超声波反应器对微生物的灭菌已经大规模地研究，在这个课题的研究热点是可以被广泛利用的。甚至尽管水力空化与声音空化反应器相比更加有效，也仅仅是近年来才广泛应用到微生物灭菌领域。Jyoti and Pandit用不同的水力空化反应器(高速均化器、高压均质器和设置锐孔板)来研究钻孔井水的消毒，与超音波喇叭形辐射体反应器(操控在22 kHz协同240 W动能比率)形成超声空化的效能进行比较。研究指出空化的所有形式在钻孔井水样本的消毒效果是等同的，在用超音波喇叭形辐射体和高速均化器处理少于30分钟时能够达到灭菌接近90%的效果。消毒的程度稍微低于锐孔板的设置类型，归因于运行的高额量和较低空化强度的形成。根据每单位消毒水平所提供的动能大小对所有的设施进行对比，表明在全部空化反应装置中锐孔板的设置在一个更高的运行压力是最有效率的。数量上，在设置锐孔板的情况下灭菌的程度在310 CFU/J，设置超音波喇叭形辐射体时仅仅45 CFU/J，高速均化器是55 CFU/J，与其他空化装置相比灭菌速率更高，但是总的能效非常低(5 CFU/J)。 除了处理被污染的饮用水体，空化反应器对船只上从一个区域运送到另一个区域的压舱水也能有效处理。海运是全球经济的主链，能够促进全球90%商品的流通。估计每年在全球产生压舱水二三十亿顿。通过海运转移的生物体(生物入侵)是威胁到自然进 9 外文文献译文及原文 化的生物多样性的一个重大问题，这个问题产生的后果在今年来有所增加。尽管一些处理技术诸如自净过滤系统、臭氧化、脱氧、电离、气体过饱和、还有化学处理等已经被采用，但不能控制由此导致的环境威胁效果。Pandit提出超声空化处理压舱水的应用，所设计的超声空化反应器复合工艺用在实际的船只上。经验研究表明水力空化(利用大 2小21.5 mm，其圆孔直径2 mm，小部分的敞开面积=0.75，流速=1.3 lps，压力=3.2 kg/cm的多孔锐边锐孔板来产生)能够破坏99%的细菌和80%浮游动物。回流时间和操作压力的增加提高了空化强度并减少了处理时间。系统中对多孔锐孔板的循序排列的运用也能引起破坏程度的提高。设计者对该运行类型设计目的应该是使该反应过程能够在单次处理可行，考虑到处理液体的容量和压舱水流通的典型管道系统，实际上压舱水的多次处理是不可能的。 上面两种以真实污染水体(可能包含大规模的细菌/微生物)进行的研究证明了空化现象用于微生物消毒杀菌的适用性。处理费用是确保空化处理能够作为一种替代传统灭菌方法的技术被应用的另一个重要因素。Jyoti and Pandit估计了不同类型空化反应器的处理费用并以用臭氧和氯化等常规方法的费用进行比较，指出利用高速搅拌器或设置锐孔板来形成水力空化感应与声化学反应器或高压均化器(处理费用在14.88和6.55美 33元/m)相比是最经济高效的处理措施(各自的处理费用在0.81 和1.4美元/m)。然 3而，这个处理费用仍然比氯化处理(处理费用在0.0071美元/m)或臭氧化处理(0.024 3美元/m)要大，这个估计是基于小型运作工艺的。因此，水力空化更广的应用到溶罐处理(诸如压舱水处理或大型复合水体处理装置)或普遍与常规处理方案结合对末端处理水体再处理处理以预防危险副产物的形成。 常规消毒技术与空化技术的结合，例如氯、臭氧、过氧化氢和次氯酸盐的运用等等，是另一种相近的高效经济的处理方式。当为了达到更快的灭菌速率时，这样的技术组合就期望能够产生协同效应并减少化学品剂量需求。yoti and Pandit确实提出过混合技术比其他任何单独的物理处理技术在水体处理上占据很大的优势。微生物聚集体的分解观察加强了该结论的真实性。微生物尝试凝结成块来保护最内部的微生物;如果这些凝块被破坏，增加了内部的微生物暴露消毒，就能达到更好的灭菌效果。Boucher等也提出超声波加快漫射使有毒的气体分子具有更快的渗透力而进入到微生物中。数量上，Dahl and Lund指出与单独臭氧化处理相似时间相比，超声臭氧化处理在消耗臭氧50–80%左右时灭活速率成3–4个概数的对数增加。 10 外文文献译文及原文 Phull等研究了以超声波与氯化作用结合的灭菌技术用于大肠杆菌的应用，并提出超声波降解法扩大了常规氯化效果，技术的组合比单独的超声波降解更有意义。加之，由于超声波降解的应用也大大减少了消毒所需的氯气。超声诱导的紊流也有利于颗粒团块的瓦解破碎，通常从排放的污水发现的颗粒大小已经从40m减少到1m。Blume and Neis也提出污水处理设施(STP)在经过超声波辐射结合氯化处理后排放出不同浓度的悬浮固体。 总之，可以说利用超声空化与常规化学方法的组合比单独的操作更加适用。不仅仅从本质上降低处理时间，也在最优状况下减少化学需求。 3.3 运用空化作用作为预处理技术增强生物降解能力 生物氧化技术的效能通常被现存的抗生物难降解物质的限制，尽管这是最常用最经济的重要处理方法。空化技术可以作为常规生物氧化的辅助技术来降低排放物的毒性，换言之，就是提高生物降解能力。Mastin等提出与生物处理(构筑湿地型反应装置)组合的超声空化反应器处理氯化烃类(三氯乙烯和全氯乙烯)和水溶液部分石油的观点。依据TCE最初浓度而定，指出用空化反应装置((137 W, 20 kHz的超声波喇叭形辐射体，20摄氏度，2 L容量)降解TCE的有效范围是40–80%;最重要的是超声空化处理末端的残留浓度通常低于微生物氧化处理残留的毒性。Sangave 和Pandit还有 Sangave 等也提出利用超声波反应器相类提高了蒸馏废水的生物降解能力。 3.3.2 厌氧消化的改进 在生物废水处理中，产生了大量的生物固体(污泥)。这些污泥非常容易退化，因此，为了维持一个环保安全的利用和处置需要对污泥进行厌氧消化稳定化处理。厌氧消化过程可以通过几个步骤实现:水解、酸化、甲烷化。由于生物污泥水解的限速阶段，厌氧生物降解是一个缓慢的过程，所以大型的发酵器是必须的。传统的消化时间是大于30-40天。超声波反应器能够有效用于改善污泥的水解，有效减少消化时间。Bougrier等指出在间歇式厌氧消化中超声波诱感空化反应有利于污泥的增溶和沼气生产。超声波能量的供应使COD 和氮的溶解度提高，导致沼气生产量的增加。这种增强的效应归因于减少的絮凝物体积和细胞溶解，观察表明效应低于总固体1000 kJ/kg的最佳值，所有 11 外文文献译文及原文 的能量被用于降低絮凝物大小，高于这个准值的额外能量则用于细胞的破坏，从而达到允许有机物排放到水体的程度。 Nickel and Neis研究了在污泥连续厌氧消化中超声波处理生物污泥破碎的影响并提出超声波在全过程提高挥发性固体降解速率(大约40%)的效能上确实能引起很大意义的改善，增加沼气产量和使每一种类型生物污泥存在的难降解有机物从60%降低到52%。在Neis的课题组早期的研究工作中也提出相类似的结果。 3.3.3 活性污泥工艺的改良 活性污泥处理以其合理的效应已经在全世界最大化使用，典型的生物需氧量(BOD)降低范围接近90%，化学需氧量(COD)是 80%。自从该法的开始出现，活性污泥法在连续不断的发展中，许多改良工艺已经工业化，其中包括膜生物反应器(MBR)、序批式反应器(SBR)和氧化沟。近来，新的技术的使用表明通过改善活性污泥工艺来提高活性污泥的微生物活性的可能性。近来应用的一种提高污泥微生物活性的方法是经由简单传统的物理化学方法来刺激沼气的形成。众所周之，低频率低剂量UV辐射能够促进细菌的生长，近来超声波被发现一样具有相似的效应。低频率低能量超声波能够增加微生物浓度和加强生物反应器发酵和糖化的功能。Schlafer等也同样指出在0.3 W/L和25 kHz超声波辐射5个小时之后能增加生物量230%，辐射7小时之后能够提高啤酒酵母活性50%。这种方法被利用于加强葡萄酒合成废水的处理，减少葡萄糖浓缩物排放。研究表明低频率比高频率更有效果，说明空化物理效应比化学效应更加显著。上述研究中一个持续的问题是能量的消耗非常高。原因是超声波直接作用在主要成分是水的生物反应器，吸收了超声波能量。因此，被利用于生物量刺激的声能非常低。Zhang等把一个外部超声波处理器结合到活性污泥系统，活性污泥通过沉淀被浓缩，影响到外部超声波处理器，然后重新回流到废水处理系统。被浓缩的污泥量接近真实废水体积的10%，因而超声波能量供应可以降低90%。 3.3.4 利用超声波空化处理生物污泥脱水 需氧或厌氧工艺是污水处理最普遍的应用。工艺前期产生大量的活性污泥，最后排放出的是被消化的污泥。两个处理过程产生的污泥主要包含生物量、胞外聚合物(EPS) 12 外文文献译文及原文 和大量的水。污泥的含水量一般高于95%。EPS是把生物量和水融合到细胞基质的重要物质，存在于能够影响到生物膜传递方式的一个完好组织。污水提纯产生大量污泥，估计占全部处理水量的5% 到 25%。在市政污水处理厂中生成的污泥可以转化成肥料，但是从工业废水处理厂中形成的污泥因包含大量有毒化学物质而很难处置。因此，通过改善脱水性能来降低污泥量有利于整个污水出来过程。 超声波能量被指出对诸如混凝剂和污泥等的悬浮液的脱水有十分显著的效果。污泥结构和性能的改变影响到脱水效果。Sarabia等提出在10到 20 kHz高能超声波处理可用于改善污泥饼化过程的固液分离。Bien等利用高分子电解质和超声波(20 kHz,60 s)结合处理无机物污泥的脱水，并指出最终含水量减少20%。超声波场的应用引起高分子电解质内部结构的改变，这些改变增强了污泥的高分子电解质活性。存在一个关键的超声波能量水平能使絮凝体有效的降解。Chiu等也提出强碱和超声波(20 kHz,120 W)的复合处理也能产生相似的有利效应。 3.4 结晶化 超声波的应用提供了一种改良晶化方式工艺操控能力的无损伤途径，主要是通过控制大小的分配和晶体的特性形态。会产生如下的好处: 改善产品和工艺的黏稠度; 改善结晶纯度; 改善产品的二代物理性能(流动性、组装密度等等); 缩短晶化周期; 缩短并提供更可靠的流水线生产工艺。 另外，超声波能够用于在难成核系统中代替晶种作为成核剂，依靠改变超声波能量和持续时间，晶体大小的分配可以根据最优化的流水线生产工艺特制。超声波成核可以给出一个标准来增加晶体大小，但是连续的超声波辐射能大大减少该过程的晶体尺寸已经被观察出来。晶体产品的大小属性能够被用于达到以下的目的: 更快的过滤:晶体更为均匀的体积和作用习性可以过滤得更快; 13 外文文献译文及原文 相似的，更好的内结晶大大改善清洗和干燥的速率，可达到最优的纯化水平; 结晶提炼是一个会对产品和环境形成交叉污染的复杂工艺。依靠超声波修整晶体大小分配，并在提炼过程中一起消除污染风险; 因为超声波处理晶体核化比常规的生产通常运作得非常好(由于倒圆)，能量补充能够确保该工艺的可靠性。产品的密度大小也可以得到改善。 基于文献中图解的概述，大体上可以说超声波在晶化工艺中的正面影响是在过饱和以及亚稳态还原阶段的生动变形来展示的。这种影响的处理可以通过改变超声波相关的参量诸如频率、强度、能量甚至超声波处理设备的物理属性(喇叭形状、喇叭大小和转换器的排列或超声波压力场)来实现的。声波处理溶液的容量和辐射时间也可以改变以使在具体的超声波作用于结晶工艺确立最优的参数组合。然而，获得的结果显示了晶体大小的分布和晶体形状是可以通过恰当超声波处理来特制的。如下是一些在晶化运行过程中有效利用超声波技术的合理的建议: 超声波的辅助处理大大降低晶化工艺起始阶段所需的诱导时间，主要依靠通过介质中气泡的生成来提供附加成核场所。效应主要低于过饱和水平并能够在逐项的基础上达到最优化。为了提供定量分析基础, Lyczko等指出硫酸钾结晶化的诱导时间从9000 S降低到1000 S。Guo等通过超声波处理罗红霉作为模拟混合物的应用而提出降低诱导时间的相似结果。 亚稳态(MZW)主要通过影响核化和局部过饱和程度来降低超声波的应用水平。通过观察研究可知超声波在低能耗水平的使用也能达到效果，高能耗的使用可能不是有利的或者有时由于超声波提高了热的耗散甚至引起有害效应。Lyczko等提出亚稳态的产生是在硫酸钾晶化中低能量超声波(50 W/L，相比下高能超声波是120 W/L)使用中获得的。 超声波的使用可以提高晶化速率因此减少全过程所需时间。Bund等指出在超声波辐射5分钟的情况下乳糖的修复非常高 (91.48%)，非辐射的样品是14.63%。Amara等也指出明矾晶体化的相似结果。不仅仅是加速了晶化进程，而且晶化产物都有均匀的外形和相对平均的晶体大小。可知超声波能量耗散和超声波传感器的大小会影响晶体大小的分配，这些传感器大小主要影响反应器中存在的声流和紊流的量值。能量的耗散通常伴随晶体大小的降低。晶体大小分布在超声波脉冲以从大型晶体中导致的过饱和能量急 14 外文文献译文及原文 迫作用于核化的情况下得以控制，通过工艺的持续时间来使用连续(或者可能是较长时间的单次突发)超声波，从而形成更加小的晶体。脉冲或超声波间歇使用起到中间效应。 在多态系统超声波合理应用在恰当的过饱和水平可以辅助孤立基态多晶型物(最大的热力学效果和最少气泡)或接近基态。使能够减少在超声波反应中所形成的多态是重要的参量，特别是在制药工业中。 结晶化工艺的能效降低主要靠高度活泼的晶化状况下，过饱和水平的快速生成，其表明超声波的使用不仅仅是降低核化诱导时间，也导致均质晶体的形成和由于反应混合物效能引起较高的过程速率并避免局部过饱和。在这些条件下，主相变换成为所提供表面结晶化生长单元的限制性速率，超声波强化装置能够提高生长速率。Li等人提出用超声波代替7-ACDA酸基结晶反应中的搅拌是非常有利的。SEM的构图清晰表明在当前的超声空化中通过适当的混合能够以更低尺寸形成质地均匀的晶体，由于无效率的混合搅拌而形成结晶附聚物，导致局部过饱和。 超声波晶化也能够避免蓄意晶种问题的解决，该技术在工业晶化工艺中应用广泛。蓄意晶种的效应包括MZW的缩小、诱导时间的缩短和对颗粒大小分布的操控，该操控可以通过利用在能耗和处理时间最优化水平下的超声场来有效达到。 3.5. 生物柴油的合成 大量从植物油中衍生的产品已经被提议柴油机的替代燃料。今天，“生物柴油”提供于简单烷基脂肪酸酯研究提取作为基于柴油燃料的石油。目前由于石油价格的上涨，生物柴油在日前的研究中非常重要，有限的化石燃料储量和生物柴油的环保效能(酸雨和在燃烧过程中CO、SOx 、难燃碳氢化合物排放量的减少)。基于这些因素和其较容2 易的生物可降解性，生物柴油的生产被认为比化石燃料更有益。生物柴油合成的常规技术涉及到化学反应晶化形成植物油，用乙醇产生酸碱酯和甘油。常规技术传统的运行温度在70–200摄氏度，压力在6–10 atm大气压，反应时间高达70小时以得到基于所用半成品材料(通常是从废物中得到的脂肪酸混合物)的转化范围在90–95%。反应通常受到质量传递速率和不同相混合的约束;因此，超声空化反应装置的应用具有很大的潜力。空化现象利用超音速和水体流动来产生，例如水力空化已经被指出能够有效强化生物柴油合成过程。Gogate用不用的植物油作为起始材料来用于超声波反应装置中生物柴油合 15 外文文献译文及原文 成研究，并指出超声空化是可以非常成功地应用到酯基转移反应，在短至15分钟的反应时间，每化学计量法生产的产品高于90%。这项技术因此看起来比常规技术更高效，可以从基于能效定量标准的不同技术的比较中明显看出。水力空化比声音空化将近40次间隔的能差，比常规搅拌/加热/回流方法将近160–400次间隔的效能差。Jianbing等也同样指出水力超声空化的巨大效能，Stavarache等也研究了一个有重要意义的工艺来强化超音速空化处理纯净植物油酯基转移。除了这些学术研究，也同样存在基于超声空化反应装置的生物柴油合成的商业性技术。 超声波反应装置能够协助改善生物柴油合成的生物途径。厌氧消化普遍应用于污泥的稳定化，降低最终生产的量;这个过程是十分缓慢的并需要大规模容量的反应器。污泥厌氧转化中可供选择利用的主要是甲烷(CH)和二氧化碳(CO)，Anger-bauer等发现从42 污泥中获得的碳化物能够通过厌氧微生物被转化成液体。这些液体可以作为生物柴油生产的半加工材料。L.starkeyi指出利用碱或酸的水解、加热或超声波来对污泥进行预处理，会导致液体的积聚，可能是由于空化作用，用超声波进行预处理可以获得最高的价值。在他们的研究中，Angerbauer等发现C/N对于L.starkeyi.所说的液体积聚是一个重要的参量。当有机物在合成培养基积聚到相当高的液体量(接近干物质的70%)，对活性污泥的生长没有任何意义。然而，污泥的预处理，特别是通过超声波处理，能够使反应物接近L.starkeyi所描述的。 3.6.超声波乳化 目前乳化从人造奶油到调味品广泛应用在大量的食物产品中，乳化剂是两种不溶液体的分馏物，一种以完好液滴或颗粒的形式从另一种液体中分离。乳化剂形成机理包括不溶液体的物理混合以及表面活性剂分子积聚到两种相界面所需时间。物理动能通过叶轮搅拌系统提供，或通过高压均化器产生。不幸运的是，这些设备消耗了大量的能量并对液滴大小分布的操控作用较小。超声波也是生产乳化剂可供选择的方法，当两种不溶液体的相界面持续用超声波辐射就会形成乳剂，一种液体的微小液滴被分离进另一种液体(离散相)，即是组成连续相的液体。超声波能够提供过量的能量用于新界面的作用;因此，即使缺少表面活化剂也有可能获得乳化物。任何高于阈值的强度，就会有一个相应的乳化物最大浓度(分离相滞留量的百分比)，这个浓度仍然保持相对稳定。这个乳 16 外文文献译文及原文 化形成的最大浓度随着超声处理的强度增加而提高。总之，超声波的优势包括低能耗、表面活化剂的少用或不用，还有比物理工艺生产更加均匀的乳化产品的生产。 超声波乳化的效能一般依赖于辐射时间、辐射能量、油/水比和油的物理化学性质。我们现在给出一些在乳化运行中高效的超声波处理建议: 用超声波时，液滴的体积(沙得直径,d32)比在相同条件下的物理搅拌所形成的液滴体积要小得多，从而使声波乳化更加稳定。瞬间超声波的出现需要更佳的超声波能量效应; 通常，辐射时间的增加提高了乳化液中分离相的体积，同时降低分离相液滴的尺寸。在某一运行时间内使液滴大小均匀平衡是可能得到的，过多的超声波能量使用是无效的; 随着超声波辐射时间的增加，部分分离相的量也会增加，同时分离相液滴的体积会减少。在某些状态下，一个适当的能量输入是客观存在的，这个能量可以使液滴聚凝和约束超声空化气泡的形成; 流体中更小的液滴通常观察表明具有较低的粘度，可能是系统中高度超声空化的结果; 超声波的使用通常能降低表面活化剂的需求来获得相同大小的液滴。 3.7.超声波萃取 从植物资源中萃取溶解性物质的传统技术是基于对与利用热或搅拌相结合的溶剂的正确选择。溶剂萃取的有机成分是在植物体内和种子中获得，超声波能量的利用大大改善了这个过程。超声波的物理效能基于超声波微束的作用而使大量的溶剂渗入细胞物质和改善传质过程。这个结合是超声波提取工艺附加效能。生物细胞壁的破坏促进内含物的释放。总之，超声辅助萃取技术因明显降低工艺时间、增加产量和高质量萃取而被认可为高效的萃取技术。Vinatoru已经研究了超声波不同的使用强化了从草本植物中萃取生物活性物质的水平。其他一些新近的应用包括从柑橘剥落的苷皮中提取桔皮苷，从卫矛中提取芸香苷和栎精酸，从椰子壳粉末中提取苯酚以及从烟草种子中提取油。基于现有文献对超声波用于萃取的详细分析，以下的信息可以有益地用于设计参数的选 17 外文文献译文及原文 择: 超声波的运用大大增强常规技术诸如物质萃取或浸渍离析。加之，，超声波的运用能有效减少工艺过程中溶剂所需量的。Hromádkováet等已经指出在两种方式中提取的水溶性多糖的量是相似的，对于全部单糖的超声波辐射需要2% NaOH和5分钟的处理时间，而传统工艺需要大约80分钟和5%NaOH.。 该有利的功效通常在低频率辐射中产生，超声空化的物理效应从紊流和液体的聚集方面说是显著的。 适当的操作温度通常是客观存在的，在不同条件下的特殊应用决定了温度的选择。例如，Boonkird等提出用95%的乙醇作为溶剂，温度从30摄氏度提高到40摄氏度能有效加强超声波处理的修复，但是当温度从45摄氏度上升到60摄氏度时修复的百分比是平稳变化的。 超声波能够与微波辐射有效组合而产生协同效果。Lianfu和Zelong指出微波辐射与超声波复合应用于番茄红素从西红柿中的提取，可以导致大约30分钟到6分钟的较低萃取时间，并可以减少相似产量所需的溶剂量。Cravotto等也提出过用超声波和微波相结合提取植物油的相似功效。 3.8. 超声波促进冻结 空化能够通过超声波微束的作用而出现，从而加强热和传质来完成冻结过程。在空化中产生的气泡也能作为冰雪核化开始阶段的核子，并提高冰雪核化的速率。晶体的破解是另一个与超声波能量传递相关联的明显现象，可以引起晶体体积的减少。由于这些音速效应，强大的超声波证明是辅助食品冻结的有效方式，其功用已经广泛应用。另外，超声波的传统操作能够加速冰雪的核化进程，同样能够用于冰冻浓缩和结冰干化工艺从而控制冰冻产品中晶体体积的分布。如果其被应用于新鲜食品的冰冻，超声波不仅仅能提高冰冻速率，还能改善冰冻产品的质量。超声波强大能量的应用也能通过减少晶体大小来生产冰淇淋，防止冰冻表面积垢等等。 在冻结工艺中超声波应用的效能依赖于产品因素诸如产品结构、含湿量和分布、液体温度和粘度、最初的气体成分和气泡大小，同样还有超声波的运行参数诸如能量和超声处理时间、超声波频率和超声波辐射模式。根据文献的仔细分析，如下的信息是可以 18 外文文献译文及原文 利用的: 声能能够直接产品，例如，超声波探头可以直接沉浸到流体中，或间接从一个传感器耦合到另一个容器，因此，根据产品和冰冻设备的类型来分，超声波仪器的独特形式是非常多的。 如果仅是辅助核化工艺，典型的能量需求是2 W/L，较低的操作频率(20–40 kHz)通常是首选的。然而，如果操控的物理参数是用于晶体的破坏，则高耗能(典型操作强度是10–30 W/L)则是首选的。一般来说超声波客观存在一个关键性的能量需求。 超声波能量水平对冰冻速率也有较大的影响。在变相的初始阶段，处理产品的温度随着高声波能量的提高而快速下降，由于在高声能中更多紊动的产生。然而，在最后阶段，更高能量的应用会导致相反的结果，可以通过冷冻剂的高速流动或超声波操作的两个相段来补偿，诸如，在开始阶段使用较高能量，在最后阶段使用较低能量。 3.9. 基因转换 植物中基因转换的目的或重要性主要有两方面:改善经济作物和具有疗效蛋白质或化学产品的特性。生物技术改变了全球的农业，在巨大的加速度下把新的遗传特性转移进作物。基因工程是基因变异的新类型。可以有目的的把外部基因添加到有机体的基因组中。一个基因控制着遗传信息，能够形成有机体的特性，诸如昆虫抗药性，除草剂抗药性等，基因工程能够把DNA移进一个有机体内并把一个或多个特性转化到另一个有机体中。近来，超声波感应空化已经成功应用到基因转换。目前，精确的超声透化仪器已经不用完全理解，下面的两个可能性还是应该被考虑: 空化气泡的剧烈瓦解能产生高压高温的振动波，可能引起原生质膜的局部破裂和对外生溶液的摄取，随后便是生物膜的完整修复。 第二种可能的假设是从电流物理模型中发现并判断关键性流体静压力的存在，在其作用下生物膜内部电位电势足够诱发生物膜的物理性破坏。 因此，通过超声波场或起源于空化破坏的高压振动波作用可以产生高压振荡，从而 19 外文文献译文及原文 产生极高的流体静压力导致可透性生物膜破坏的发生。上述提到的两种可能性可以说非常有关联并可以起协调作用。超声波作为一种物理途径是多功能的，很少依赖于细胞的类型。从另一方面说，转基因植物对于人类复杂的具有疗效的蛋白质的生物产品形成有很大的意义，主要由于基因转换的便利、人类的病原体缺乏潜在的污染、真核细胞的保护需要调停蛋白质变异、生物量生产的低成本。一些相近的研究已经被尝试性把基因转移到植物细胞或组织。在控制条件下，超声波是传递DNA或核酸到细胞的有效方式。细胞中的DNA分子随后表明需要依赖在细胞瞬间破坏和细胞死亡间的平衡。 4. 结论 目前的研究使我们能够清晰证实了，在生物技术/生物化学工程通用领域中，通过超声波和流体动力方式产生的空化现象的重要性。观察指出与空化现象的化学效应相比，在这些应用中物理效应更加显著。水力空化的效应通过与超声波引起的空化相比得到很好的确信，特别是细胞分裂很水体消毒的应用，然而，其应用需要在其它研究工作中测试。声化学反应器的未来发展主要是多频率复合换频器基础反应装置的设计，用于流体动力空化反应器、锐孔板类型结构的最优化。总之，可以说空化反应装置提供了在生物技术特殊领域中强化化学/物理工艺应用的实质性许诺。 20 外文文献译文及原文 参 考 文 献 [1] K.S.Suslick, The chemical 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[101]Y.Liu, H.Yang, A.Sakanishi, Ultrasound:mechanical gene transfer into Plant cells by sonoporation, Biotechnol.Adv.24(2006)1. 28 外文文献译文及原文 A review of applications of cavitation in biochemical engineering/biotechnology Parag R.Gogate Abhijeet M.Kabadi Chemical Engineering Department,Institute of Chemical Technology,Matunga,Mumbai 40019,India a b s t r a c t,Cavitation results in the generation of hot spots, highly reactive free radicals, and turbulence associated with liquid circulation currents, which can result in the intensification of various physical/chemical operations. The present work provides an overview of the applications of the cavitation phenomenon in the specific area of biochemical engineering/biotechnology, discussing the areas of application, the role of cavitation, the observed enhancement and its causes by highlighting some typical examples. The different methods of inducing cavitation and the dominance of one over the other, mostly with respect to energy requirements, in different areas of biotechnological application are discussed.The major applications discussed in the work include microbial cell disruption for the release or extraction of enzymes, microbial disinfection, wastewater treatment,crystallization, synthesis of biodiesel, emulsification, extraction of bio-components, freezing and gene transfer into cells or tissues. Some recommendations for optimal operating/geometric parameters have also been made. Overall, it appears that the combined efforts of physicists, chemists, biologists and chemical engineers are required to effectively use cavitational reactors for industrial applications. Keywords:Cavitational reactors，Microbial cell disruption，Water disinfection， Biodiesel production，Biochemical engineering 29 外文文献译文及原文 1. Introduction The process industry demands that operations be performed in the most efficient way with respect to either product quality, energy or time, or in terms of economics. Alternative novel technologies are constantly being sought to reduce the total processing cost while maintaining or enhancing product quality in an environmentally benign manner. Cavitation offers immense poten-tial for intensification of physical or chemical processing in an energy-efficient manner.Cavitation is generally defined as the generation, subsequent growth [1]and collapse of cavities,resulting in very high local energy densities. Cavitation, when it occurs in a reactor, generates conditions of very high temperatures and pressures(100–5000 atmospheres of pressure and 500–15000 Kof temperature)locally, but with the overall [1]environment remaining equivalent to ambient atmospheric conditions. This enables the effective execution under ambient conditions of the various physical processes or chemical [2–3]reactions that require stringent conditions. Moreover, free radicals are generated in the process due to the dissociation of vapors trapped in the cavitating bubbles, which results in either intensification of the chemical reactions or in alteration of reaction mechanism. Cavitation also results in the generation of local turbulence and liquid micro-circulation(acoustic streaming)in the reactor, enhancing the rates of transport processes; [2]in addition, they also eliminate mass transfer resistances in heterogeneous systems. Based on the degree of intensity, which may be described in terms of the magnitude of pressure or temperature, cavitation can also be classified as either transient or stable. The energy requirements for the generation of these two types are significantly different, and hence proper care must be taken when selecting the operating parameters for the specific type of [4]application. Transient cavitation is a process where the generated bubble/cavity will eventually collapse to a minute fraction of its original size, at which point the gas present within the bubble dissipates into the surrounding liquid via a rather violent mechanism, releasing a significant amount of energy in the form of an acoustic shock-wave and as visible light. At the point of total collapse, the temperature of the vapor within the bubble may be 30 外文文献译文及原文 several thousand Kelvin, and the pressure may be several hundred atmospheres. In the case of stable or non-inertial cavitation, small bubbles in a liquid are forced to oscillate in size or shape due to some form of energy input, such as an acoustic field, when the intensity of the energy input is insufficient to cause total bubble collapse. This form of cavitation causes significantly milder cavitational effects than the transient cavitation. Cavitation is also classified into four types based on the mode of generation: acoustic, hydrodynamic, optic and particle. Only acoustic and hydrodynamic cavitation have been found to be efficient in producing the desired chemical/physical changes in processing [2,5]applications, whereas optic and particle cavitation are typically used for single bubble cavitation, which fails to induce any physical or chemical change in the bulk solution.The spectacular effects of cavitation phenomena generated using ultrasound (acoustic [6]cavitation)have been more commonly harnessed in food and bioprocessing industries. Similar cavitation phenomena can also be generated relatively easily in hydraulic systems. Engineers have generally been cautious regarding cavitation in hydraulic devices due to the problems of mechanical erosion, and thus all initial efforts to understand it were mainly with the objective of suppressing it in order to avoid the erosion of exposed surfaces. However,a careful design of the system allows for generation of cavity collapse conditions similar to acoustic cavitation. This enables different applications requiring varying cavitational intensities that have been successfully carried out using acoustic cavitation phenomena but with much lower energy input as compared to sonochemical reactors. In the last decade, concentrated efforts were made by few researchers around the world to harness the [7]spectacular effects of hydrodynamic cavitation for chemical/physical transformation. The present work provides an overview of different applications of cavitational reactors with an emphasis on different operations in biochemical engineering/biotechnology. 2. Reactor designs Reactors in which cavitation is generated by ultrasound are usually described as sonochemical reactors, whereas reactors in which cavities are generated by virtue of fluid 31 外文文献译文及原文 energy are described as hydrodynamic cavitation reactors. 2.1.Sonochemical reactors Ultrasonic horns are the most commonly used reactor designs among the sonochemical reactors, although the cavitational effects are only observed close to the vibrating surface. The cavitational intensity decreases exponentially on moving away from the horn and vanishes at a distance of as low as 2–5 cm, depending on the supplied energy to the equipment and on the [8]operating frequency. Thus, the efficacy of the horn type system with larger scales of operation is poor compared to systems based on multiple transducers due to the fact that ultrasonic horns cannot effectively transmit the acoustic energy throughout a large process fluid volume.Additionally, ultrasonic horn type reactors, suffer from erosion and particle shedding at the delivery tip surface due to high surface energy intensity; cavitational blocking(acoustic decoupling), and large transducer displacement(amplitude)increases stress on the material of construction,resulting in the possibility of stress-induced fatigue failure.Typically, these reactors are recommended for laboratory scale characterization studies or for larger scale operations where lower residence times are sufficient to bring about the desired change. Reactors based on the use of multiple transducers irradiating identical or different frequencies seems to be a logical approach. The use of multiple transducers also results in lower operating intensities at similar levels of power dissipation, and hence, problems of cavitational blocking, erosion and particle shedding at the delivery surface are reduced. The position of the transducers can also be easily modified in order for the wave patterns generated by the individual transducers to overlap, resulting in an acoustic pattern that is spatially uniform and non-coherent above the cavitational threshold throughout the reactor working volume. Arrangements such as triangular pitch in the case of ultrasonic baths, tubular reactors with either two ends irradiated with transducers or one end with a transducer and other with a reflector, parallel plate reactors with each plate irradiated with identical or different frequencies, and hexagonal flow cells are possible as represented schematically in 32 外文文献译文及原文 [8–10]Fig.1. The vessels can be operated in a batch mode or, for larger-scale work, in a continuous mode where multiple units can be combined in a sequential manner, which also increases residence time.In summary, a plurality of low electrical and acoustic power(1–3 2[10]W/cm)transducers produce 25–150 W/L,with an ideal range of 40–80 W/L.The power can be applied continuously or in a pulsed mode. The magnitudes of collapse pressures and temperatures, as well as the number of free radicals generated at the end of cavitation events,are strongly dependent on the operating parameters of the sonochemical reactors. Intensity and frequency of irradiation along with the geometrical arrangement of the transducers and the liquid phase physicochemical properties affect the initial size of the nuclei and the nucleation process. Proper selection of the operating, eometric parameters and physicochemical properties of the liquid phase decides the efficacy g of the cavitational reactors in the desired application. Based on the careful bubble dynamics [11]analysisobtained from the existing literature, some qualitative recommendations can be made in the optimization of these operating parameters, as given below: 1. Select an optimum intensity of irradiation based on the specific application; use of multiple transducers results in higher active cavitational volume. 2. It is better to use an optimum frequency of irradiation; applying excessive frequencies usually requires higher power for inception and leads to erosion problems. 3. Liquids with low vapor pressure, low surface tension and low viscosity are preferred as the reaction medium for conducting cavitational reactions. 4. Presence of additives such as gases and/or solid particles eases the generation of cavitation events and generally results in overall higher cavitational effects. 2.2 .Hydrodynamic cavitation reactors Hydrodynamic cavitation can simply be generated by using a constriction such as an orifice plate, venturi or throttling valve in a liquid flow. At the constriction, the kinetic energy/velocity of the liquid increases, with a corresponding decrease in the local pressure. If the throttling is sufficient to cause the pressure around the point of vena contracta to fall 33 外文文献译文及原文 below the threshold pressure for cavitation(usually vapor pressure of the medium at the operating temperature), cavities are generated.Subsequently, as the liquid jet expands, the pressure recovers, resulting in the collapse of the cavities. During the passage of the liquid through the constriction, boundary layer separation occurs and a substantial amount of energy is lost in the form of a permanent pressure drop due to local turbulence. Very high intensity fluid turbulence is also generated downstream of the constriction;its intensity depends on the magnitude of the pressure drop and the rate of pressure recovery, which, in turn, depend on the geometry of the constriction and the flow conditions of the liquid, i.e., the scale of turbulence. The intensity of turbulence has a profound effect on cavitation intensity. Thus, by controlling the geometric and operating conditions of the reactor, the required intensity of the cavitation for the desired physical or chemical change can be generated with maximum [7]energy efficiency. A commonly used device based on hydrodynamic cavitation phenomena is the high-pressure homogenizer, which is, in essence, a high-pressure positive displacement pump with a throttling device that operates according to the principle of high-pressure relief.Typically, a high-pressure homogenizer reactor consists of a feed tank and two throttling valves, designated as first stage and second stage, to control the operating pressure in the hydrodynamic cavitation reactor. There is a critical discharge pressure at which cavitation inception occurs,and significant cavitational yields are obtained beyond this [12]discharge pressure.However, there is not enough control over the cavitationally active volume and the magnitude of the pressure pulses that will be generated at the end of the cavitation events(cavitational intensity), thereby limiting the possibility of selective release of intracellular enzymes based on the relative location of the enzymes in the cell.Thus, these reactors find limited application in bioprocess industries especially, in cell disruption,where cavitation with varied intensity is required. These reactors are suitable generally for the emulsification processes in food, pharmaceutical and bioprocess industries. Cavitation can also be generated in rotating equipment. When the tip speed of the rotating device(impeller)reaches a critical speed, the local pressure near the periphery of the impeller drops and approaches the vapor pressure of the liquid.This results in the generation 34 外文文献译文及原文 of vaporous cavities. Subsequently, as the liquid moves away from the impeller to the boundary of the tank, the liquid pressure recovers at the expense of the velocity head. This causes the cavities that have traveled with the liquid bulk to collapse.Again, similar to the [12]high-pressure homogenizer, there exists a critical speed for the inception of cavitation. It should be noted that the energy consumption in these types of reactors is much higher, and flexibility over the design parameters is lesser as compared to reactors based on the use of multiple-hole orifice plates. In reactors based on the use of orifice plates, the flow through the main line passes through a constriction where the local velocities suddenly rise due to the reduction in the flow area, resulting in lower pressures that may even decrease to below the vapor pressure of liquid [13]medium. A schematic representation of the setup has been given in Fig.2. Choosing a correct flow arrangement in the hydrodynamic cavitation reactor system is of paramount importance to maximize the effects of cavitation in desired and cost effective manner. The [7]constriction can be a venturi,a single hole or multiple-holes in an orifice plate. Use of multiple-hole orifice plates(Fig.3)helps to achieve different intensities of cavitation.Additionally, the number of cavitational events generated in the reactor varies.Thus, the orifice plate set-up offers tremendous flexibility in terms of the operating(control of the inlet pressure, inlet flow rate, temperature)and geometric conditions(different arrangements of holes on the orifice plates, such as circular,triangular pitch,etc., and also the geometry of the hole itself, which alters the resultant fluid shear, leading to different cavitational intensities). [15]Sampathkumar and Moholkarhave recently proposed a conceptual design of a novel hydrodynamic cavitation reactor that uses a converging–diverging nozzle for creating pressure variation in the flow necessary for driving the bubble motion, instead of the orifice plates as discussed earlier. The cavitation bubbles or nuclei are introduced in the water flow externally, upstream of the nozzle using a sparger. Different gases can be used for the introduction of the bubbles. Also, the size of the gas distributor(usually a glass frit), flow rate of gas and the pressure of gas in the reservoir(or source) from which it is withdrawn can be suitably controlled in order to achieve the desired initial size of the cavitational nuclei,which significantly affects the resultant cavitational intensity.However, as compared to the orifice 35 外文文献译文及原文 plate setup, the flexibility in terms of controlling the cavitational intensity is substantially reduced, as only the length and diameter of the nozzle are the geometric parameters that can be varied in this case, whereas the number, size and shape of the holes in the case of the orifice plate can be varied.It might be worthwhile to use a combination of converging–diverging nozzle and orifice in tandem, depending on the type of the application and intensity requirements for the specific application under question. From the above discussion about various hydrodynamic cavitation reactors, it can be easily concluded that the orifice plate set-up offers maximum flexibility and can also be operated at relatively larger scales of operation. It should be also noted that the scale-up of such reactors is relatively easier, as the efficiency of the pump increases with an increase in size(flow rate and discharge rate), which will necessarily result in higher energy efficiencies. For optimum operation, the following recommendations can be made for selecting the [7,14]: equipment design and operating parameters (1) An orifice flow configuration is necessary only for the intense chemical reactions, whereas for milder processes(typically between 15 and 20 bar)and physical transformations,a venture configuration is recommended. (2) Select higher operating inlet pressures upstream of the mechanical constriction,but just below the onset of super-cavitation. (3) Select optimum combination of liquid physical properties so as to enable easy generation of lower initial size nuclei, as discussed earlier. (4) For orifice plate setup, optimize the number and diameter of the holes for equal free flow area based on the type of applications;smaller number of large diameter holes for applications that require higher cavitation intensity, e.g.,destruction of complex chemicals,and higher number of smaller diameter holes for applications requiring relatively lower intensities, e.g.,cell disruption. (5) Design the hydrodynamic cavitation reactor with lower free area for the flow. (6) In the case of high speed homogenizers, choose the speed of rotation much above the critical speed for the cavitation inception and below the speed where air induction takes place. 36 外文文献译文及原文 3. An overview of areas of application of cavitation 3.1.Microbial cell disruption A key factor in the economical production of industrially important microbial [16,17]components is an efficient large-scale cell disruption process. The need for an efficient microbial cell disruption operation has always hindered the large-scale production of [16]commercial biotechnological products of intracellular derivation . For the large-scale disruption of micro-organisms, mechanical disintegrators such as high-speed agitator bead mills and high-pressure homogenizers are commonly employed, but the typical energy efficiencies of the above methods are in the range of 5–10%. The rest of the energy is dissipated in the form of heat, which needs to be efficiently removed to retain the integrity of [17]these delicate bio-products. With the aim of improving the efficacy of the cell disruption process, keen interest has developed in the last decade in newer techniques, including acoustic nd hydrodynamic cavitation.Harrison and Pandit[18]were the first to report the use of a cavitational reactors for cell disruption process using a configuration where cavitation was [12]generated using a throttling valve. Later, Shirgaonkar et al.clearly demonstrated the requirement of cavitational effects for the release of significant amount of enzymes/proteins .[12]in a high speed and high-pressure homogenizer.Shirgaonkar et alhave reported that the rates of protein release at 10,000 rpm are much higher than at 5000 rpm in a high-speed homogenizer. This can be explained on the basis of cavitation inception, which occurs at the [19]speed of 8000 rpm, as reported by Kumar and Panditfor a high-speed homogenizer unit. At 10,000 rpm, the major contribution to cell disruption is by cavitation and mechanical forces, whereas at 5000 rpm, only mechanical forces(shear)are contributing to the overall cell disruption. Thus, the generation of cavitation conditions in the system is very important for maximizing the release of intracellular enzymes at a given energy input. .[20]Save et alused a hydrodynamic cavitation reactor based on throttling valves for the disruption of baker‘s yeast and brewer‘s yeast cells in pressed yeast form and reported that an increase in the time of treatment and number of passes resulted in a corresponding increase in 37 外文文献译文及原文 the extent of cell disruption. The concentration of cells in the suspension influenced the disruption process significantly. The growth stage of the yeast cells is another parameter that affects the energy efficiencies.Preliminary experiments with fresh fermentation broth indicated that the cells in an exponential growth phase are far more susceptible to disruption, compared with those that are either stored or frozen.Comparison of the energy efficiencies for different operations, including hydrodynamic cavitation, mixer-blender and ultrasonication, indicated that the energy requirement of a hydrodynamic cavitation setup is lower than that of the other two methods by more than two orders of magnitude for equivalent protein release.In quantitative terms, energy utilization per ml of yeast suspension to obtain the same level of protein release was 20.7 J/ml for hydrodynamic cavitation reactor, 1500 J/ml for ultrasonic irradiation and 900 J/ml for the mixer blender. In a scaled up version of earlier work, Save et .[21][22]aland Balasundaram and Panditinvestigated the process of cell disruption using hydrodynamic cavitation reactor operating at a capacity of 200 L and 50 L, respectively,and reported similar results for energy efficiency. Also, it was conclusively established[21]that even though cavitation is known to generate conditions of very high temperature and pressure locally,along with the generation of free radicals, activity of the released enzymes from the cells remains unaltered. This can be attributed to the fact that the intense conditions only exist for very small intervals of time(typically few micro-seconds)and hence do not result in any [21]deactivation of the released enzymes. It has been reportedthat the activities of the glucosidase and invertase enzymes were not affected under normal circumstances. However, a prolonged exposure(60 min treatment at 3 atm pressure)resulted in about 10%decrease in the activity of the enzymes. Thus, it is important to control the intensity of the cavitation phenomena by suitably adjusting the operating and geometric parameters in the system as well as the time of treatment. It should be also noted here that the mechanism of the cell disruption process is also [22]different depending on the equipment used .Cell disruption process can proceed via complete breakage of the individual cells in certain devices,releasing all intracellular enzymes,or it can be shear driven,where only the cell wall breaks,as result of which,only the enzymes present at the wall or periplasm will be released(leached slowly). Balasundaram and 38 外文文献译文及原文 [22]Panditinvestigated the release of invertase enzyme by disruption of S.cerevisiae cells using sonication, high pressure homogenization and hydrodynamic cavitation. It has been reported that in the case of hydrodynamic cavitation generated using an orifice plate, the extent of release of the enzyme invertase was found to be higher than total soluble protein. This could be due to the periplasmic location of the enzyme. Based on the release pattern of enzyme and protein,a selective release of invertase(periplasmic)is expected in the early stages of disruption by hydrodynamic cavitation before complete mutilation of the cells, which releases all the available proteins(cytoplasmic as well). For the case of ultrasonic-induced cavitation, the rate of release of invertase enzyme was comparable with that of proteins, which can be attributed to the severity of the cavitational intensity in the case of acoustic cavitation as compared to hydrodynamic cavitation.Severe cavitation results in complete breakage of the cells, whereas mild cavitational intensity in the case of hydrodynamic cavitation reactor results in an impingement/grinding action on the cell due to the shear, giving rise to the breakage of the cell wall rather than the complete cell. Balasundaram and [23]Harrisoninvestigated the application of hydrodynamic cavitation for the partial disruption of E.coli cells and reported selective release of periplasmic and cytoplasmic enzymes relative to the total soluble protein as a function of cavitational intensity. [24]Balasundaram and Pandithave quantified the dependency of the extent of release of enzymes on their location in the cell using a concept of location factor.Location factor can be defined as the ratio of release rate of the enzyme to the release rate of total proteins. Typically, for enzymes located in the periplasm, location factor is greater than 1, and for cytoplasmic enzymes, location factor is less than 1.For the release of invertase and penicillin acylase, the location factor was observed to be greater than 1 for all the cavitation equipments, which confirms the periplasmic location of the two enzymes in the yeast and E.coli cells, respectively. Further-more ,it was observed that the location factor is higher in the case of hydrodynamic cavitation reactor as compared to sonication and high pressure homogenization, confirming that the mechanism of cell disruption in this case is by impingement/grinding action on the cell due to shear, as discussed earlier.For the alcohol dehydro-genase(ADH)enzyme, the location factor value was approximately 0.5, confirming 39 外文文献译文及原文 [25]that ADH is present mostly in the cytoplasm of the cell.Balasundaram and Harrisonhave also reported similar dependency of the location factor of the different enzymes, such as-glucosidase(periplasmic), invertase(cell wall bound), ADH (cytoplasmic)and glucose-6-phosphate dehydrogenase(G6PDH; cytoplasmic), on the cavitational intensity generated in the system. It can be established from above studies that the location of the enzyme indeed affects the extent of energy requirement for its release from the cell by cavitational reactors. Some pretreatment strategies can be used to modify the cellular location of the enzyme before the cell suspension is subjected to the actual cell disruption process. Translocation of enzymes from cytoplasm to periplasm by pretreatment can be exploited to improve the efficacy of the [26]cell disruption and also reducing the energy requirements. Some techniques used for [27,28]translocation, as reported in the literature, are heat stress, time of culture in the [25][29][30]fermentation process, variable pH operationand chemical pretreatment. Overall,it can be said that the use of hydrodynamic cavitation for cell disruption has been conclusively proven for large-scale applications, and done so with much higher energy efficiencies as compared to acoustic(ultrasound)cavitation reactors. Addition-ally, all cavitational reactors explored are more energy efficient compared to the conventional techniques based on the use of mechanical energy. A particular reactor configuration in terms of geometry of the cavitation chamber and operating parameters such as inlet pressure and circulation flow rate can be chosen based on the location of the specific enzymes in the cells and cell concentration in the medium. Pretreatment strategies such as heat, pH and chemical treatment can aid in enhancing the selectivity of the target enzyme while significantly decreasing the energy requirements. 3.2.Microbial disinfection Over the years,disinfection of micro-organisms in water has been achieved by various [31,32]chemical and physical means; however, these methods are associated with major drawbacks such as formation of mutagenic and carcinogenic agents, severe mass transfer 40 外文文献译文及原文 limitations resulting in higher treatment times, etc., which can sometimes outweigh their [32,33]efficacy. Also, certain species of micro-organisms produce colonies and spores that agglomerate in spherical or large clusters. Chemical treatment of such clusters may destroy micro-organisms on the surface, leaving the inner-most organisms intact. Thus, there is a need for developing some alternate techniques for water disinfection. Cavitation, due to its spectacular effects in terms of generation of hot spots, highly reactive free radicals and turbulence associated with liquid circulation, offers potential as an effective tool for water disinfection. The mechanism of disinfection of micro-organisms by cavitation is generally a [34]combination of the following effects: 1. Mechanical effects:includes the generation of turbulence, liquid circulation currents and shear stresses. 2. Chemical effects:includes the generation of active free radicals. 3. Heat effects:generation of local hot spots(conditions of very high temperature and pressure locally). 4 Combined treatment effects: when used in combination with chemical treatment(Cl,HO,O), the intense pressure gradient improves the penetration of the 2223 oxidizing chemicals through the microbial cell membrane. Also, cavitation can facilitate the disagglomertion of micro-organism clusters in solution and thus increase the efficacy of other chemical disinfectants. It has been generally observed that the mechanical effects are more responsible for the [34]microbial disinfection,and the chemical and heat effects play only a supporting role. Microstreaming resulting from stable cavitation has been shown to produce stresses sufficient [35]to disrupt cell membranes. The mechanism proposed is the onset of turbulence,which creates vortices in whose proximity the shear rates are higher than those throughout the bulk [36]of the liquid. Doulahhas also confirmed that yeast cell disintegration in ultrasonic cavitation occurs by shear stresses developed by viscous dissipative eddies arising from shock waves. Use of ultrasonic reactors for microbial disinfection has been substantially investigated, 41 外文文献译文及原文 [34,37,38]and excellent reviews on this subject are available. Even though hydrodynamic cavitation has been found to be much more efficient as compared to acoustic cavitation based reactors, it is only in the recent past that it has been applied to the area of microbial [39]disinfection. Jyoti and Panditinvestigated the disinfection of bore well water by different hydrodynamic cavitation reactors(high speed homogenizer, high pressure homogenizer and orifice plate setup)and compared their efficacy with that of ultrasonic horn type of reactor(operating at 22 kHz with the power rating of 240 W)generating acoustic cavitation.It has been reported that all forms of cavitation are equally effective in the disinfection of bore well water samples, and about 90%disinfection can be achieved in less than 30 min of treatment for ultrasonic horn and high speed homogenizer. The extent of disinfection was somewhat lower in the orifice plate type setup, which was attributed to higher volumes of operation and generation of lower intensity cavitation. Comparison of all the equipments in terms of extent of disinfection per unit energy supplied, however, indicated that orifice plate setup at higher operating pressures was the most efficient among all the cavitational reactors. Quantitatively, the extent of disinfection in case of orifice plate setup was 310 CFU/J as compared to only 45 CFU/J in the case of ultrasonic horn and 55 CFU/J for the high-speed homogenizer. In the case of high-pressure homogenizer, the rate of disinfection was substantially higher compared to the other cavitating equipments, but the overall energy efficiency was extremely poor (5 CFU/J). Apart from making contaminated water potable, cavitational reactors can also find utility in a ship to treat ballast water that is being transported from one region to another. Shipping is the backbone of global economy and facilitates transportation of 90% of the commodities. It is estimated that 2–3 billion tons of ballast water are carried around the world each year.Translocation of organisms through ships(bio-invasion)is considered to be one of the important issues that threaten the naturally evolved biodiversity, the consequences of which are being realized increasingly in the recent years.Although many treatment technologies such as self-cleaning screen filtration systems,ozonation, de-oxygenation, electro-ionization, gas supersaturation and chemical treatments are adopted, they cannot limit the environmentally [40]hazardous effects that may result from such practices. Panditreported the application of 42 外文文献译文及原文 cavitation for ballast water treatment and the design methodology for the incorporation of cavitational reactors in actual ships. Experimental investigations indicated that hydrodynamic cavitation(generated using multiple-hole sharp edge orifice plate of size 21.5 mm having a circular hole of diameter 2 mm;fraction of open area=0.75, flow rate=1.3 lps and pressure=3.2 2kg/cm) resulted in the destruction of 99%of the bacteria and 80%of the zooplanktons. An increase in the recirculation time and operating pressure increases the intensity of cavitation and lowers the treatment time. Use of multiple-hole orifice plates arranged sequentially in the system also resulted in an increase in the extent of destruction. The aim of the designers of this type of application should be to make the process viable in a single pass, as it is practically impossible to have multiple passes in the ballast water treatment, considering the volume of the liquid to be treated and a typical piping network for the ballast water flow. The above two studies with actual contaminated water(possibly containing a wide range of bacteria/micro-organisms)confirm the suitability of the cavitation phenomena for microbial disinfection. Cost of the treatment is another important factor that needs to be ascertained before cavitation can be recommended as a replacement technique for the conventional [39]methods of disinfection. Jyoti and Panditestimated the cost of treatment for different types of cavitational reactors and compared it with the costs associated with conventional methods of using ozone and chlorine. It has been reported that hydrodynamic cavitation induced using high-speed homogenizer or orifice plate setup is the most cost effective treatment 3strategy(costs of treatment being 0.81 and 1.4$US/m,respectively)as compared to sonochemical reactors or high-pressure homogenizer(cost of treatment as 14.88 and 36.55$US/m).However, this cost of treatment is still orders of magnitude higher than 3chlorination(cost of treatment being 0.0071$US/m) or ozonation(cost of treatment being 30.024$US/m),estimated based on small-scale applications. Thus, hydrodynamic cavitation is more applicable to bulk treatment(e.g.,ballast water treatment or large scale municipal corporation water treatment plants)or when the end use of treated water precludes formation of hazardous by-products commonly associated with the conventional treatment schemes. Combining cavitation with conventional techniques for disinfection,such as the use of chlorine,ozone,hydrogen peroxide, hypochlorite,etc.,could be another cost effective approach. 43 外文文献译文及原文 Such a combination is expected to give synergistic effects and lead to reduced requirement of the chemical dosage while resulting in much faster rates of disinfection.Jyoti and [39,40]Panditindeed reported that hybrid techniques are far superior for treating water as compared to any other individual physical treatment technique. The observed intensification has been mainly attributed to declumping of aggregates of micro-organisms. Microbes tend to be present in clumps that protect inner microbes;if these clumps are broken,then better disinfection can be achieved, as the exposure of the inner microbes to the disinfectant [41]increases. Boucher et al.also reported ultrasonic acceleration of diffusion, allowing more rapid penetration of the toxic gas molecules into the micro-organism. Quantitatively, Dahl and [42]Lundhave reported that inactivation of the logarithmic order of 3–4 is obtained at around 50–80%lower ozone consumption by the sonozonation process as compared to ozonation alone in similar treatment times. [37]Phull et al.investigated the application of ultrasound in combination with chlorine as a disinfection technique for E.coli and reported that sonication was seen to amplify the effect of normal chlorination and the combination was significantly better than sonication alone.Additionally, the amount of chlorine required for disinfection was also significantly reduced due to the application of sonication. The turbulence induced by ultrasound was also beneficial to the disintegration of the particle agglomerates, and the size of particles generally [43]found in sewage effluent was reported to reduce from 40 to 1 m.Blume and Neisalso reported similar effects for sewage treatment plant(STP)effluents with different concentrations of suspended solids after exposure to sonication in combination with chlorine dosage. Overall, it can be said that the use of cavitation in combination with conventional chemical methods is far more suitable than individual operations.It not only results in substantially lower treatment times but also reduces the requirement of the chemicals under optimized conditions. 3.3. Intensification/improvement of biological wastewater treatment 44 外文文献译文及原文 3.3.1.Enhanced biodegradability using cavitation as a pretreatment technique The efficiency of the biological oxidation techniques is often hampered by the presence of bio-refractory materials, though these are the most conventionally used and economically important treatment strategies. Cavitation can be used as a supplementary technique to conventional biological oxidation to reduce the toxicity of the effluent or, in other words,to [44]increase the biodegrad-ability. Mastin et al.have investigated the idea of combining cavitation reactors with biological treatment(constructed wetland type of reactors)for the treatment of chlorinated hydrocarbons (trichloroethylene and perchloroethylene)and petroleum fractions in aqueous solutions. With cavitational reactors(137 W, 20 kHz ultrasonic horn,20?C,2 L capacity), degradation of TCE was reported to be in the range of 40–80%,depending on the initial concentration of TCE;most importantly,the residual concentration at the end of cavitation treatment was always below the toxicity levels for the [45][46]biological oxidation. Sangave and Panditand Sangave et al.also reported similar enhancement effects on the biodegradability of the distillery wastewater using ultrasonic reactors. 3.3.2.Improvement in anaerobic digestion In biological wastewater treatment, large quantities of biosolids (sewage sludge)are produced. The sludge is highly susceptible to decay.Therefore,the sludge has to be stabilized by anaerobic digestion in order to enable an environmentally safe utilization and disposal. Anaerobic digestion process is achieved through several stages:hydrolysis,acidogenesis and methanogenesis. Due to the rate-limiting step of biological sludge hydrolysis, the anaerobic degradation is a slow process, and large fermenters(digesters)are necessary. Typical digestion times are more than 30–40 days. Ultra-sonic reactors can be effectively used to improve [47,48]sludge hydrolysis , resulting in significant reduction of the digestion time. Bougrier et .[47]alhave shown that ultrasound induced cavitation during batch anaerobic digestion has an effect on sludge solubilization and on biogas production.It has been reported that COD and 45 外文文献译文及原文 nitrogen solubility increased with supplied ultrasonic energy, resulting in increased biogas production. The intensification has been attributed to floc size reduction and cell lysis, and it has been observed that below the optimum value of 1000 kJ/kg total solids, all of the energy was used to reduce floc size;additional energy above that value was used to break cells,which permitted the release of organic substances into the liquid phase. [48]Nickel and Neisinvestigated the impact of ultrasonic biosolid disintegration on subsequent anaerobic digestion of the sludge and reported that ultrasound indeed resulted in a significant improvement in the overall process by virtue of increased volatile solid degradation rate(about 40%), increased biogas production and a reduction of the non-degradable organic matter that exists in each type of biosolids from 60 to 52%.Similar [49,50]results have also been reported in some of the earlier works by the group of Neis. 3.3.3.Improvement in activated sludge process Activated sludge treatment has been most commonly used worldwide, with acceptable efficiency and a typical reduction of biological oxygen demand(BOD)by around 90%and of chemical oxygen demand(COD)by 80%[51]. Ever since its inception, the activated sludge method has been under continuous development, and many improvements have been industrialized,including membrane bioreactor(MBR), sequential batch reactor(SBR),and [52–54]oxidizing ditch.Recently, new techniques have become available, providing possibilities to improve the performance of activated sludge by increasing its microbial activity. One of the recently used approaches to increase the sludge microbial activity is to stimulate the biomass via simple physical–chemical methods. It is well known that low dose UV irradiation can stimulate the growth of bacteria, and recently ultrasound has been found to have similar [55]effects. Ultrasonic waves at low frequency and low energy were found to increase the concentration of micro-organisms and to enhance the bioreactor performance for fermentation [55].[56]and saccharification. Schlafer et alalso reported that ultrasonic irradiation at 0.3 W/L and 25 kHz increased the biomass by 230% after 5 h of irradiation and increased the S.cerevisiae activity by 50%after 7 h of irradiation. The method was used to enhance the 46 外文文献译文及原文 treatment of synthetic wine wastewater, reducing the effluent glucose concentration. Studies showed that low frequency was more effective than higher ones, indicating that the mechanical effects of cavitation are dominant rather than the chemical effects. One persistent problem in above studies was that the energy consumption was very high. The reason was that ultrasound waves were directly applied to the bioreactor in which the major component was water, which absorbed the sound energy. Therefore, the sound energy used for the biomass [57]stimulation was very low. Zhang et al. incorporated an external sonication chamber into the activated sludge system. The activated sludge was concentrated by settling, then treated in the external sonication chamber, and returned to the wastewater treatment system. The volume of the concentrated sludge was around 10%of the volume of the actual wastewater and thus the ultrasonic energy application could be reduced by 90%. 3.3.4.Dewatering of biosolids using ultrasonic cavitation Aerobic or anaerobic processes are most commonly used in wastewater treatment applications. The former produces large amount of excess activated sludge, while the latter drains out digested sludge. The sludge in both of these processes mainly contains biomass, extracellular polymeric substances(EPS)and large amounts of water. The water content in sludge is generally more than 95%. EPS is an important material to combine the biomass and water into a matrix and is organized in a fine structure, which influences the properties of the biofilm. The purification of wastewater produces large amounts of sludge, estimated at between 5 and 25% of the total volume of treated water. The sludge generated from municipal waste treatment plants can be converted into useful fertilizers, but the sludge generated from industrial waste treatment plants is difficult to dispose as it contains large amounts of noxious [58]chemical substances. Thus, any improvements in reducing the quantity of sludge by virtue of efficient dewatering are always beneficial to the overall wastewater treatment process. Ultrasonic energy was reported to be quite effective in dewatering of suspensions such as [58]slurries and sludges. Changes of structure and properties of sludge influence the efficiency [59]of the dewatering process. Sarabia et al.reported that the effect of high power acoustic 47 外文文献译文及原文 treatment,at 10 and 20 kHz, could be used to improve solid/liquid separation in cake filtration .[60]processes. Bien et alused a combination of polyelectrolyte and ultrasound (20 kHz,60 s)for mineral sludge dewatering and reported about 20%reduction in the final water content. Application of ultrasonic field results in changes of the inner structure of polyelectrolytes and these changes intensify the polyelectrolyte activity on sewage sludge. A critical ultrasonic power level exists above which the floc structure can be effectively disintegrated. Chiu et [61]al.also reported similar beneficial effects for combined treatment of alkali and ultrasound(20 kHz,120 W). 3.4.Crystallization The use of ultrasound provides a non-invasive way of improving crystal properties and process controllability, chiefly by controlling the size distribution and the habit and [62–64]: morphology of the crystals. The following benefits accrue * Improved product and process consistency; * Improved crystal purity; * Improved secondary physical properties(flowability,packing density,etc.)of the product; * Shorter crystallization cycle times; * Shorter and more reliable downstream processes. Additionally, ultrasound can be used to replace seeding as a nucleator in difficult-to-nucleate systems. By varying the power and duration of insonation, the crystal size distribution can be tailored to optimize downstream processing. Nucleation by insonation shows a marked increase in the mean crystal size, but with continuous insonation a dramatic reduction in the mean crystal size has been observed. The size and habit of the product crystals can be manipulated to achieve the following benefits: 48 外文文献译文及原文 * More rapid filtration:crystals of a more uniform size and compact habit can be filtered much more rapidly. * Similarly,better access to the intercrystal voids greatly improves the speed of washing and drying,as well as the achievable decontamination level. * The milling of crystals is a messy process that risks mutual contamination of product and environment.By sonically tailoring crystal size distribution,the milling step may be eliminated altogether. * Powder filling operations can be rendered much more reliable and unproblematic because sonically nucleated crystals usually flow much better(due to rounding)than those produced conventionally.The bulk density of the product may also be improved. [10,62–68]Based on the overview of the literature illustrations, in general it can be said that the positive influence of ultrasound on crystallization processes is shown by the dramatic reduction in the induction period, supersaturation conditions and metastable zone width.Manipulation of this influence can be achieved by changing ultrasound related variables such as frequency,intensity, power and even geometrical characteristics of the ultrasonic devices(e.g.,horn type,horn size and transducer arrangement or ultrasonic pressure field).The volume of the sonicated solution and irradiation time are also variables to be optimized in a case-by-case basis as the mechanisms of ultrasound action on crystallization remain to be established.Nevertheless, the results obtained so far indicate that crystal size distribution and crystal shape can be?tailored‘by an appropriate selection of the sonication conditions. The following are some recommendations for effective utilization of the ultra-sound effects in crystallization operation with specific reference to bioprocessing applications: Ultrasound aids in significantly reducing the induction time required for the onset of crystallization process, mainly by providing additional nucleation sites due to cavities/bubbles generated in the medium .The effect is more predominant at lower supersaturation levels and [68]should be optimized on a case-to-case basis. To provide a quantitative basis,Lyczko et al. have shown that induction time is reduced from 9000 s to about 1000 s for the 49 外文文献译文及原文 .[67] crystallization of potassium sulfate. Guo et alhave reported a similar effect of reduction in the induction time via the application of ultrasound for roxithromycin as the model compound. 2. The metastable zone width(MZW)can also be reduced by the application of ultrasound, mainly by influencing the nucleation and local supersaturation levels.It has been generally observed that ultrasound application at low power dissipation levels is also sufficient for these effects, and application at higher power dissipation might not be useful or sometimes even lead to detrimental effects due to enhanced heat dissipation by ultrasound. Lyczko et [68]al.have shown that a decrease in MZW is obtained by application of low ultrasonic power(50 W/L as compared to 120 W/L)for the crystallization of potassium sulfate. 3. The use of ultrasound can also enhance the rate of crystallization and hence reduce [66]the total time required for the process. Bund et al.reported that lactose recovery was much higher(91.48%) in the case of sonicated samples when compared with non-sonicated [65]ones(14.63%)at the end of 5 min. Amara et al.have also reported similar results for crystallization of potash alum. Not only is the process of crystallization rapid, but also the resultant crystals are uniform in shape and have a much lower average crystal size. It should also be noted here that the crystal size distribution is also affected by the ultrasonic power dissipation and the dimensions of the ultrasonic transducers, which mainly affect the magnitude of the acoustic streaming and turbulence existing in the reactor. The mean crystal [65]size usually decreases with an increase in the power dissipation. It is possible to―tailor‖a crystal size distribution between the extreme cases of a short burst of ultrasound only for nucleation at lower levels of supersaturation,resulting in large crystals, and the use of continuous(or perhaps a longer single burst)ultrasound application throughout the duration of the process, resulting in smaller crystals. Pulsed or intermittent application of ultrasound can give an intermediate effect. 4. Judicious application of ultrasound to a polymorphic system at the right level of supersaturation can assist in isolating the ground-state polymorph(the most thermodynamically favored and least soluble)or the one very near the ground state. This 50 外文文献译文及原文 availability to induce the formation of a given polymorph under ultrasound action is of paramount importance, particularly in the pharmaceutical industry. 5 .In crystallization processes induced by the addition of an antisolvent or reactive crystallization, where high supersaturation levels may be produced very rapidly, it has been shown that the application of ultrasound not only reduces the induction times of nucleation, but also results in uniform crystals and higher processing rates due to efficient mixing of the reactants and avoiding local supersaturation. Under these conditions, bulk-phase mass transfer becomes rate limiting in supplying growth units to the crystal surface, and its ultrasonic [69]enhancement will enhance the growth rate.Li et al.reported beneficial effects of using ultrasound in lieu of agitation for the acid–base reaction crystallization of 7-amino-3-desacetoxy cephalosporanic acid (7-ACDA).SEM images have clearly shown that uniform crystals with much lower mean size are formed in the presence of sonication due to proper mixing, whereas in the presence of agitation, agglomerates of crystals are formed due to inefficient mixing, resulting in local supersaturation. Sonocrystallization also avoids the problems involved in intentional seeding, which are very common in industrial crys-tallization process. The effects of intentional seeding include narrowing of the MZW, shortening of induction times, and control of particle size distribution, which can be effectively, achieved using ultrasonic field under optimized levels of power dissipation and treatment times. 3.5. Synthesis of biodiesel Various products derived from vegetable oils have been proposed as an alternative fuel for diesel engines. Today, ―biodiesel‖is the term applied to the esters of simple alkyl fatty acids used as an alternative to petroleum-based diesel fuels.Importance of biodiesel in the recent context is increasing due to rising petroleum prices, limited fossil fuel reserves and environmental benefits of biodiesel (decrease in acid rain and emission of CO,SOx and 2 unburnt hydrocarbons during the combustion process).Due to these factors and due to its easy biodegradability,production of biodiesel is considered to be advantageous over that of fossil 51 外文文献译文及原文 [70,71]fuels. The conventional techniques for the synthesis of biodieselrefer to a catalyzed chemical reaction involving vegetable oil and an alcohol to yield acid alkali esters and glycerol. The conventional techniques typically utilize temperatures in the range of 70–200?C,pressures in the range of 6–10 atm and reaction times of up to 70 h for achieving conversions in the range of 90–95%based on the type of raw material used(usually mixtures of fatty acids obtained as waste). The reaction is usually limited by mass transfer rates and mixing of the different phases;hence, there is a great potential for the application of cavitational reactors.Indeed,cavitation generated using both ultrasound and flow,i.e., hydrodynamic cavitation, has been reported to significantly intensify the synthesis process for [72]biodiesel. Gogateinvestigated the use of cavitational reactors for synthesis of biodiesel with different vegetable oils as starting materials and reported that cavitation can be very successfully applied to trans-esterification reactions with more than 90%yield of the product as per stoichiometry in a reaction time as short as 15 min.The technique hence appears to be much more effective than the conventional approach, which is also evident from the comparison of different techniques based on the quantitative criteria of energy efficiency.Hydrodynamic cavitation is about 40 times more efficient than acoustic cavitation and 160–400 times more [72][73]efficient than the conventional agitation/heating/refluxing method.Jianbing et al.have also reported the greater efficacy of hydrodynamic cavitation reactors, while Stavarache et [74,75] al.have also shown a significant process intensification using acoustic cavitation for trans-esterification of pure vegetable oil.Apart from these academic investigations, there also exist commercial scale technologies for the synthesis of biodiesel based on the use of [76,77]cavitational reactors. Ultrasonic reactors can also aid in improving the biological route of synthesis of biodiesel. Anaerobic digestion is commonly used for the stabilization of sewage sludge, reducing the volume of resulting end products; this process is rather slow and requires large reactor capacity. As an alternative to the anaerobic conversion of sewage sludge to mainly [78]methane(CH)and carbon dioxide(CO), Anger-bauer et al.found that the carbon 42 compounds contained in sludge could be converted into lipids by aerobic micro-organisms. 52 外文文献译文及原文 These lipids can serve as a raw material for the production of biodiesel. Pretreatment of sludge by alkaline or acid hydrolysis, or thermal or ultrasonic treatment lead to accumulation of lipids by L.starkeyi, with highest values obtained with ultrasound pretreatment, probably [78]due to cavitation. In their study, Angerbauer et al.found that the C/N ratio is a crucial parameter for the accumulation of lipids by L.starkeyi.While the organism can accumulate high amounts of lipids(approximately 70%of dry matter)in a synthetic medium, there was no significant growth on raw sewage sludge.However, pretreatment of sludge, especially by ultrasound, can make this substrate accessible to L.starkeyi. 3.6.Ultrasonic emulsification Emulsions are present in a wide variety of food products, ranging from margarine spreads to dressings. An emulsion is a dispersion of two immiscible liquids, one of which is dispersed in the other in the form of fine droplets or particles. The formation of an emulsion includes the mechanical mixing of the immiscible liquids and the time for surfactant molecules to organize at the interface of the two phases. The mechanical energy can be supplied by using stirring, rotor-stator systems, or by using high-pressure homogenizers. Unfortunately, these devices consume lot of energy and provide little control over the droplet size distribution. Ultrasound is also an alternative method to produce an emulsion. When the interface of two immiscible liquids is ultrasonically irradiated, an emulsion is formed, i.e., tiny droplets of one liquid(dispersed phase)are scattered into the other liquid, which constitutes the continuous phase. Ultrasound can provide an excess energy for the new interface formation; hence, it is possible to obtain emulsions even in the absence of surfactants(emulsifiers). For any intensity above the thresh-old, there is a corresponding maximum(limiting)concentration of emulsion(percentage of the dispersed phase hold-up), which remains relatively stable. This limiting concentration of emulsion increases with increasing ultrasound intensity. Overall, the advantages of ultrasound include lower energy consumption, use of less or no surfactant, and production of a more homogeneous emulsion than by a mechanical process. 53 外文文献译文及原文 The efficacy of ultrasonic emulsification generally depends on the irradiation [79–82]time,irradiation power, oil/water ratio and physicochemical properties of the oil. We now give some recommendations for effective utilization of the ultrasound effects in the emulsification operation: 1. With ultrasound, the droplet size(Sauter diameter,d32)is much smaller than that given by mechanical agitation under the same conditions, which makes insonated emulsions more sta-ble. Occurrence of transient cavitation conditions is necessary for better efficacy of ultrasonic energy. 2. In general,an increase in the irradiation time increases the dispersed phase volume in the emulsion, while decreasing the dispersed phase droplet size.It might be possible that beyond a certain time of operation where equilibrium droplet size is achieved, further use of ultrasonic energy is ineffective. 3. With an increase in the ultrasonic irradiation power, there is an increase in the fraction of volume of the dispersed phase, while the droplet size of the dispersed phase decreases. In some cases, an optimum power input might exist, beyond which droplet coalescence and cavitational bubble cloud formation can restrict performance. 4. Smaller droplet size is generally observed for liquids with low viscosity, possibly attributed to higher cavitational effects in these systems. 5. Use of ultrasound generally lowers the requirement of surfactant to obtain the same mean droplet size. 3.7. Ultrasonic extraction The classical techniques for the solvent extraction of materials from vegetable sources are based upon the correct choice of solvent coupled with the use of heat and/or agitation. Solvent extraction of organic compounds contained within the bodies of plants and seeds is significantly improved by the use of power ultrasound. The mechanical effects of ultrasound provide a greater solvent penetration into cellular materials and improve mass transfer due to 54 外文文献译文及原文 the effects of microstreaming. This is combined with an additional benefit for the use of ultrasound in extractive processes:the disruption of biological cell walls to facilitate the release of contents. Over-all, ultrasound-assisted extraction is now recognized as an efficient extraction technique that dramatically cuts down working times, increasing yields and often [83–85][85]the quality of the extract. Vinatoruhas reviewed different applications of ultrasound in the intensification of extraction of bioactive materials from herbs. Some of the other recent [86]applications include extraction of hesperidin from Penggan(Citrus reticulata)peel, [87],extraction of rutin and quercetin from Euonymus alatus(Thunb.)Siebextraction of phenolic compounds from coconut(Cocos nucifera)shell powder[88]and extraction of oil from [89].tobacco(Nicotiana tabacum L.)seedsBased on a detailed analysis of the existing literature [83–94]on the use of ultrasound for extraction,the following information can useful in selecting design parameters: 1. The use of ultrasound results in significant intensification over conventional techniques such as soxhlet extraction or maceration.Additionally, the use of ultrasound can lead to a significant reduction in the quantity of solvent required for the process. [93]Hromádkováet al.have reported that for similar yields of water-soluble polysaccharides from both extraction steps and for total isolated polysaccharides, ultrasonic irradiation required 2% NaOH and 5 min of treatment time, whereas the classical process required about 80 min of time with 5%NaOH. 2. The beneficial effects are generally observed at lower frequencies of irradiation, where the mechanical effects of cavitation phenomena in terms of turbulence and liquid circulation are dominant. 3. Optimum operating temperature usually exists and has to be determined based on [94]the specific application under question. For example, Boonkird et al.reported that with 95%ethanol as a solvent, the increase in temperature from 30 to 45? significantly enhanced capsaicinoid recovery, but the percentage recovery leveled out when the temperature was raised from 45 to 60?. Ultrasound can be effectively combined with microwave irradiation to yield synergistic 55 外文文献译文及原文 [91]results. Lianfu and Zelongreported that use of microwave irradiation in combination with ultra-sound for extraction of lycopene from tomatoes results in lowering of the extraction time from about 30 min to 6 min and reducing the solvent requirement for similar levels of yields. [92]Cravotto et al.have also reported similar efficacies for ultra-sound and microwave assisted extraction of vegetable oils. 3.8. Ultrasonic assisted freezing Cavitation results in the occurrence of microstreaming, which enhances the heat and [95]mass transfer accompanying the freezing process. The gas bubbles generated during cavitation can also act as nuclei to initiate the ice nucleation process and increase ice nucleation rate. Crystal fragmentation is another significant phenomenon associated with the transmission of power ultrasound, which can lead to crystal size reduction. Due to these acoustic effects, power ultrasound has proved itself as an effective method in assisting food freezing, and its benefits are wide-ranged. In addition to its traditional application in accelerating ice nucleation process, it can also be applied to freeze concentration and freeze drying processes in order to control crystal size distribution in the frozen products. If it is applied to the process of freezing fresh foodstuffs, ultrasound can not only increase the freezing rate, but also improve the quality of the frozen products. Application of power ultrasound can also benefit ice cream manufacture by reducing crystal size, preventing [95]incrustation on freezing surface, etc.. The efficacy of use of ultrasound in freezing is dependent on the product factors such as product structure, moisture content and distribution, liquid temperature and viscosity, initial gas content and bubble size, as well as on the operating ultrasound parameters such as power and duration of ultrasound, ultrasound frequency and the mode of ultrasonic irradiation. [95–100]Based on a careful analysis of literature, the following information can be useful: 1. The acoustic energy can be applied directly to the product, e.g., by direct immersion of ultrasonic probes into the process fluid, or indirectly from a transducer coupling 56 外文文献译文及原文 to parts of process vessels; therefore, the particular form of ultrasonic apparatus used will vary according to the product and the type of freezers. 2. For assistance in nucleation process only, typical power requirements are 2 W/L and lower operating frequencies(20–40 kHz) are usually preferred. However, if the controlling mechanism is the breakage of crystals, higher power dissipation levels(typically operating intensities of 10–30 W/L)are preferred. Usually a critical power requirement for ultrasound exists. 3. Ultrasonic power levels also have a significant effect on the freezing rate. During the initial stage of the phase changing period, temperature of the products treated with higher acoustic power declines more quickly, since more turbulence was created at high acoustic power.However, at later stages,application of higher power results in negative effects, which can be compensated for by having higher refrigerant flow rates or two stage operation with ultrasound, i.e., higher power in initial stages and lower in later stages. 3.9. Gene transfer The purpose or significance of gene transfer in plants is mainly in two aspects:trait improvement of economical crops and therapeutic proteins or chemicals production.Biotechnology is transforming world agriculture, adding new traits to crop plants at a greatly accelerated rate. Genetic engineering is a new type of genetic modification. It is the purposeful addition of a foreign gene or genes to the genome of an organism. A gene holds information that will give the organism a trait, such as insect resistance, herbicide resistance, and salt tolerance. Genetic engineering is not bound by the limitations of traditional plant breeding. Genetic engineering physically removes the DNA from one organism and transfers the gene(s) for one or several traits into another. Recently, [101]ultrasound-induced cavitation has been successfully applied for gene transfer. At present, the exact mechanism for acoustic permeabilization has not been fully understood, though the following two possibilities should be considered: 57 外文文献译文及原文 1. The violent collapse of cavitation bubbles can generate high pressure and high temperature shock waves, which could potentially cause localized ruptures of the plasma lemma and lead to the uptake of exogenous solutes, followed by reestablishment of membrane integrity. 2. The second hypothetical possibility originates from the electro-mechanical model predicting the existence of a critical hydrostatic pressure, at which the intrinsic membrane potential is sufficiently high to induce mechanical breakdown of the membrane. Consequently, it is possible that the high oscillating pressure generated by the ultrasonic field and/or the high pressure shock waves originating from collapsing cavitation could produce such high hydrostatic pressures that reversible membrane breakdown would occur. The two above-mentioned possibilities are said to be closely related and may act in concert. Ultrasound as a mechanical method is often more versatile and less dependent on cell types. On the other hand, transgenic plants have significant potential in the bioproduction of complex human therapeutic proteins due to the ease of genetic manipulation, lack of potential contamination with human pathogens, conservation of eukaryotic cell machinery mediating protein modification, and low cost of biomass production. Many approaches have been attempted to transfer genes into plant cells or tissues. Under controlled conditions, ultrasound is an effective means of delivering DNA or nucleic acids into cells. The subsequent expression of DNA molecules in cells depends upon a balance between transient cell damage and cell death. 4. Concluding remarks The present work has enabled us to clearly exemplify the importance of cavitation phenomena generated by using both ultrasound and hydrodynamic means in the general area of biotech-nology/biochemical engineering. Generally it has been observed that the mechanical effects are more dominant in these applications as compared to the chemical effects of cavitation phenomena. The efficacy of hydrodynamic cavitation is well established 58 外文文献译文及原文 as compared to ultrasound generated cavitation, especially in applications of cell disruption and water disinfection;however, its applicaion needs to be tested for other areas considered in the work. The future of sonochemical reactors lies in the design of multiple frequency multiple transducer based reactors, whereas for hydrodynamic cavitation reactors,orifice plate type configuration appears to be most suitable. 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[101]Y.Liu, H.Yang, A.Sakanishi, Ultrasound:mechanical gene transfer into Plant cells by sonoporation, Biotechnol.Adv.24(2006)1. 67 外文文献译文及原文 超声波破除促进厌氧好氧消化 122UWE NEIS, KLAUS NICKEL and ANNA LUNDE′N 1 汉堡理工大学，污水控制和水体保护研究所，汉堡，德国 2 超声波有限责任公司，水体和环境技术，汉堡，德国 摘 要:生物细胞的溶解是生物固体厌氧降解的限速阶段。由于反应进程的缓慢，需要安装诸如沼气池类大型处理装备或采取技术的协助。高能超声波用于细菌细胞的溶胞已经被利用为事先厌氧消化的预处理过程。通过该应用，作为一个试点，可以增加30%的沼气，同时增加细菌30%的破灭和处理污泥量的减少。将超声波技术用于好氧处理过程是一个新颖和具有创新性的研究。通过稳定可用的内部碳源来改善反硝化过程，剩余污泥的减量使超声污泥在整个污水生物处理过程中起着积极作用。综上所述，该技术在技术上和经济上都是可行的。 关键词:厌氧消化;好氧消化;超声波降解;生物量 介绍 在大多数污水处理厂生物固体的稳定化是通过厌氧消化完成的。在全球范围，这是污泥稳定化主要的首选方法，因为该过程提供了三种非常有吸引力的好处:(1)沼气是厌氧食物链中产生的终端产物;(2)进一步的处理是可能的，特别是脱水处理;(3)需要处理的污泥体积也有所减少。随着人口的增加污水处理厂也在增加，厌氧消化的优化和持续的尝试性改善是必需的。 一种可替代生物废水处理的选择是在有氧条件下操作的，活性污泥处理过程是重点。有机成分的生物有效性是全过程特别是反硝化过程效率的决定性因素。对于活性污泥过程，操作仪器也面对挑战例如与污泥膨胀和发泡问题的矛盾。这些情况是位于气候区的处理厂重复发生的现象。 目前市场上有许多可行的技术，可以达到改善污水处理厂厌氧和好氧消化的目的。在超声波及其应用于污泥对污泥的影响效果引起了人们极大的关注。十年前该领域的调 68 外文文献译文及原文 查研究已开始进行，随后在该领域的研究和全过程运行在不断的发展进步。研究证明低频率超声波(低于100 kHz)所产生的与污泥降解相关的空化现象需要产生机械剪切力。 2与高强度超声波在25–50 W/cm的组合，细胞将被破坏，细胞内部的物质被释放到胞质。 方法——加强厌氧消化 控制条件 为了增强厌氧沼气池的性能，超声波可以用于污水活性污泥在被排入到沼气池前的降解。利用高能量的超声波产生空化降解在污水污泥处理中是一个相对新颖的领域。污泥中的细菌细胞被分解和破坏，机械空化作用的效果是非常强大的，微生物细胞壁当空化作用产生的泡沫破裂时被破坏。细胞的成分随即释放进胞质中，引致剩余存活微生物更高水平的生物有效性。实际上，酶法生物水解，是厌氧食物链通过污泥的物理降解被取代和催化的最初的限速阶段。 早期在污水活性污泥发酵的试点研究已经进行，我们可以简要地叙述。五个200升 ?的沼气池在37C下同时运行。试验仪器通过德国巴特布拉姆施泰特产的超声波处理器 2产生声振，控制装置接收未处理的污泥。超声波在8 W/cm强度和31 kHz频率下处理90分钟已经被广泛应用，水力停留时间在4—16天。细胞分解的程度可以参照方程1，由被离心的污泥样本的上清液决定，作为常规的参数。 DDCOD = [(CODU超声波? COD0)/ (CODNaOH ? COD0)] *100 [%] (1) CODU超声波 是降解样品的化学需氧量(用超声波处理)，[mg/L]，COD0 是未 是对照样品在20?，0.5摩尔NaOH溶液处理样品的化学需氧量，[mg/L], CODNaOH 中化学水解22小时的化学需氧量, [mg/L]. DDCOD，是在沼气池中与超声波处理污泥同时消化的气体的产出量，与未处理的污泥比较显示出更高的价值。在水力停留时间16天时超声波处理生物固体的消化速率，与在相同水力停留时间中常规消化比较增加了30%。沼气池中运作的水力停留时间在8天更能展示出效果。比较这对反应池的消化程度，高于40%的消化速率是可以改善的。在沼气池中所观察到的被破灭的最高速率是运行在最短的水力停留时间(4天)。与在 69 外文文献译文及原文 水力停留时间为16天的常规沼气池比较，沼气池在水力停留时间4天时消化速率以接近4的指数增加。在水力停留时间运行在4天时可以观察到沼气池中最为显著的生物气产出量。所有的沼气池注入用超声波处理的污泥，当与常规对口消化池比较时生物气的产出量有所增加。 利用超声波进行预处理可以显著加快厌氧消化进程。在200升消化池中进行试点研究提供了一个显著的结果，就是整个工艺装备需要有更高技术和效率的操作水平。 全流程条件 Meldorf废水治理工厂。在2005年2月，在Meldorf废水治理工厂65,000 PE条件下，经过3个月的测试阶段后进行全尺寸安装。这个厂经历了在厌氧消化池中因污水活性污泥中丝状菌的过量生长导致的发泡膨胀问题。安装超声波处理器的目的是为了消除膨胀问题，从而确保厌氧消化不受干扰。在将100%厚度污泥投放到污水厂厌氧消化池前进行超声波处理。 在Meldorf废水治理工厂安装超声波装置后不久，污泥膨胀现象不再是一个问题。此外，当污泥到达发酵罐时提供一些必须条件以促进污泥高效消化。 同时，稳定化的污泥中的VS，即生物固体干燥的百分比，从60%降低到 45% 。对于生物气的产出量，安装超声波处理装置后与未安装超声波处理装置相比增加了30%。这些改善相应地改善了供能的自给自足和降低污泥排放量。另外，营养基质的供给又为厌氧消化进程的稳定化提供了可能性。污水厂可以处理当地食品厂的废水，这样就让污水处理厂和食品厂得到双赢。 Bamberg废水治理工厂.在2004年8月，德国Bamberg废水治理工厂(确切处于 330,000 PE)，带有两个超声波反应器的全规模安装已经完成。超声波的应用效果曾经在污水厂持续4个月的试验期中成功得到验证。超声波应用的目的是加强降解消化使其达到最低水平45%，从而避免了另外一个厌氧消化池的建造花费。为了达到这个目的，在污泥被投入到厌氧消化池前25%的TWAS要进行超声波处理。 有机物在污泥中厌氧食物链中被转化为甲烷。气体产出量，与常规性消化相比，是增加的。因为超声波处理会增加有机物的量。通过将经超声波处理的污泥来投放到消化池，在Bamberg废水治理工厂中，沼气的产出量增加接近30%。甲烷也略有增加，使沼气成为更加具有吸引力和富于能量的产品。消化污泥中的VS%从60%降到了54%，期 70 外文文献译文及原文 望目标是达到最小45%甚至超过改值。 破坏的增加意味着污泥中的有机物在消化过程中被代谢。生物气产量的增加，污泥中较少有机物意味着在消化进程中碳源已经被代谢产生沼气。通过沼气的增加，污水厂的自给自足的能量供应也得到改善。在很大程度上，污水厂可以从厌氧消化进程中获取它运转所需的能量。当然，这是一个非常有利的经济指标。 方法——加强好氧消化 为了加强好氧消化进程，在活性污泥重新回流到活性污泥池前进行超声波处理作为一种创新可以加强反硝化。需要提供内部碳源从而通过在该改良工艺中最终引起的尚未明了的反应机理来加强反硝化速率，在超声波处理污泥而改善厌氧消化的研究中提供了有价值的线索。 通过超声波处理，污泥中的微生物被抑制生长和微生物群落被破坏。丝状菌通过空化气泡破裂产生的强大剪切力而被破坏，减少或者完全消除了它们存在而造成的负面效应。另外，一般认为被破坏的细胞的胞质释放能够促进污泥的生物代谢过程。特别是，释放出的酶在刺激生物代谢过程中充当显著的角色。被破坏的细胞物质自身作为非外来碳源供污泥中其余微生物利用。在这种方式中我们可以达到加强反硝化的目的。 全流程条件 Bünde废水治理工厂。从2006年9月以来全装置安装在Bünde废水治理工厂(确切处于54,000 PE)中已经被代换。4个月的试验阶段，已经成功的完成，并且在试验阶段获得的令人信服的结果是随后着手安装的基础。工艺中氮的消除发生在间歇反硝化过程。在工艺中执行超声波技术的原因是反硝化效率受到所提供给反硝化细菌的碳源不足的制约。利用超声波声振能量作为内部碳源来增强污水活性污泥来改善反硝化是可行的。总计，日常30%的TWAS流是声振，可以重新回到活性污泥容器，高效的反硝化效率需要提供进程所需碳源。 在2006年7月停止超声波处理后，无机氮浓度再次回升到2005年未用超声波处理的水平。在投放回活性污泥池前对部分增稠的污水活性污泥进行超声波处理，从而提供 71 外文文献译文及原文 必须的碳源促进反硝化作用的改善。 有效的超声波TWAS作为改良反硝化作用的一种内部碳源产生了许多方面积极的效应。首先，在工艺中环流的氮显著的减少，意味着反硝化作用的改善。另外，还有一些间接效应有助于工艺运转的综合效率。剩余污泥可以减少25%，并且污泥脱水能力改善了2%。污泥中存在的有机分馏物可以降低，活性污泥池中的泡沫和污泥膨胀事实上也可以削减。 很明显，许多积极、肯定的益处通过利用超声波处理污泥而达到。经济上投资的回笼比较快速，同时降低污泥处理处置费用和氮浓度。因此，随着自身的运作程度可以达到一种显著的经济指标。所增加的经济利益，一定会提及工艺改善了厌氧和好氧降解，从而避免被迫采用外部碳源。工艺最终可以保存能源，使进程最优化，通过与超声波技术的结合获得更为稳定的运行水平。 结论 对于厌氧消化，已经被证实通过超声波辐射污泥可以改善消化的引导部分和全消化过程。在运行和经济上的益处是显而易见的。从全规模运行装置中得到的使用经验，我们可以得出该应用在技术和经济上都是适宜的。利用超声波改善好氧消化是一个十分新颖的运用，微生物处理过程的机理需要进一步研究以确立新陈代谢的有效性。全规模运行装置的应用经验，告诉我们超声波对好氧和厌氧过程产生的效应是相似的。细菌细胞被分解和破坏，意味着有大量生物可用的碳源供剩余微生物代谢。结果是加强了反硝化作用和减少了过剩污泥量。在运转程度上，可以减少泡沫形成和污泥膨胀，随着处理进程中对这些现象起到作用的有机物被分解或破坏。 72 外文文献译文及原文 参 考 文 献 [1] Malina, J.F.; Pohland, F.G. Design of anaerobic processes for the treatment of industrial andmunicipalwastes. InWater Quality Management Library; Technomic Publishing Company: Lancaster, PA, USA, 1992. [2] Vera, M.A.; Nickel, K.; Neis,U.; Ritchie, J. Disintegration of sewage sludge for improved biodegradation, in: Proceedings of the IWA Specialised Conference on Sewage Sludge, South Africa (Paper 204) 2005. [3] Tiehm, A.; Nickel, K.; Zellhorn, M.; Neis, U. Ultrasonic waste Activated sludge disintegration for improving anaerobic stabilization. Water Res. 2001, 35 8), 2003–(2009. [4] Neis, U.; Nickel, K.; Tiehm, A. Enhancement of anaerobic sludge digestion by ultrasonic disintegration. Water Sci. Tech. 2000, 42 (9), 73–80. [5] Shimizu, T.; Kudo, K.; Nasu, Y. Anaerobic waste activated sludge digeston bioconversion mechanism and kinetic model. Biotechnol. Bioeng. 1993, —A 41, 1082–1091. [6] European Union, Community Research and Development Information Service (CORDIS). Project name: Ways of Innovation for the Reduction of Excess Sludge (W.I.R.E.S.). Project reference: EVK1-CT2000-00050. , 2007-01-24. 73 外文文献译文及原文 Improving anaerobic and aerobic degradation by ultrasonic disintegration of biomass 122UWE NEIS, KLAUS NICKEL and ANNA LUNDE′N 1Hamburg University of Technology, Institute of Wastewater Management and Water Protection, Hamburg, Germany 2Ultrawaves GmbH, Water and Environmental Technologies, Hamburg, Germany ABSTRACT,Biological cell lysis is known to be the rate-limiting step of anaerobic biosolids degradation. Due to the slow pace by which this reaction occurs, it is necessary to equip treatment plants with large digesters or alternatively incorporate technological aids. Highpower ultrasound used to disintegrate bacterial cells has been utilized as a pre-treatment process prior to anaerobic digestion. Through this application, as seen on pilot- and full-scales, it is possible to attain up to 30% more biogas, an increase in VS-destruction of up to 30% and a reduced sludge mass for disposal. Utilizing ultrasound technology in aerobic applications is a newand innovative approach. Improved denitrification through a more readily available internal carbon source, and less excess sludge mass can be traced to the positive effects that sonication of sludge has on the overall biological wastewater treatment process. Reference full-scale installations suggest that the technology is both technically feasible and economically sound. Keywords: Anaerobic digestion， aerobic digestion， ultrasonic disintegration， biomass. Introduction The stabilization of biosolids produced in most wastewater treatment plants is done by anaerobic digestion.Worldwide, it is the preferred method used for sludge stabilization 74 外文文献译文及原文 primarily because the process provides three very appealing benefits: (i) biogas is the end product attained in the anaerobic food chain, (ii) further handling is made possible, especially [1]dewatering, and (iii) the sludge volume for disposal is reduced. With the ever-increasing number of people that are becoming connected to sewer treatment plants, the optimization of .[2]and continuous attempts to improve the anaerobic digestion process are essential Should one instead choose to view the process of biological wastewater treatment that operates under aerobic conditions, the activated sludge process lies in focus. The bio-availability of the organic components is decisive in the efficiency of the overall process and specifically denitrification. Regarding the activated sludge process, operators are also faced with challenges such as combating bulking and foaming sludge. These situations have proven to be reoccurring problems for plants located in temperate climate zones. There are several available techniques on the market today, which can be employed in order to achieve improved anaerobic and aerobic digestion on wastewater treatment plants. Great interest has been devoted to ultrasound and the effects that the application has on sludge. Investigations in the field originated over a decade ago, and since then advancements have been made both in the area of research and full-scale applications. It has been proven that low-frequency ultrasound (below 100 kHz) generates the cavitation necessary to produce the [3]mechanical shear forces associated with sludge disintegration. Combined with ultrasound of 2[3]high-intensity, 25–50 W/cm, the cells are actually destroyed and the intracellular material [4]is released into the medium. Methods—Enhancing anaerobic digestion Controlled conditions In order to enhance the performance of anaerobic digesters, ultrasound can be used to disintegrate waste activated sludge (WAS) before it is fed to the digester. Using high-power ultrasound for disintegration by cavitation is a relatively new application in sewage sludge [3,4]treatment. The bacterial cells in the sludge break apart and are subsequently destroyed, as the effects of mechanical cavitation are so powerful that microbial cell walls are broken when 75 外文文献译文及原文 the cavitation bubbles implode. The contents of the cell are then released into the medium, resulting in a higher degree of substrate bio-availability for the remaining living microorganisms. In effect, enzymatic-biological hydrolysis, which is the initial and rate-limiting step of the anaerobic food chain, is substituted and catalyzed by this mechanical [5]disintegration of the sludge. Earlier pilot studies (1998–2000) on the fermentation of waste activated sludge (WAS) [4] have been conducted, upon which we would like to report again briefly.Five 200-liter ?digesters were operated at 37C in parallel. The test reactors were fed sonicatedWAS fromtheWWTPBad Bramstedt, Germany, and the control reactors received untreated sludge. Ultrasound treatment for 90 seconds at intensity of 8 W/cm2 and a frequency of 31 kHz was applied. The hydraulic retention time was varied between 4 and 16 days. The degree of cell disintegration (DDCOD) according to Equation 1 was determined in the supernatant of the [4]centrifuged sludge samples as well as a number of standard parameters. )/ DDCOD = [(COD ? CODUltrasound0 (COD ? COD)] ? 100 %] (1) NaOH0 where CODU is the chemical oxygen demand of the disintegrated sample (here by ltrasound sonication), [mg/L], COD0 is the chemical oxygen demand of the untreated sample, [mg/L], COD is the chemical oxygen demand of a reference sample hydrolyzed chemically in a NaOH ?0.5 molar NaOH solution at 20C for 22 hours, [mg/L]. The DDCOD, gas production and VS-degradation in the digesters fed with ultrasonically treated sludge, all exhibited higher values as compared to the digesters fed with untreated sludge (Table 1). The VS-degradation rate of the sonicated biosolids at HRT = 16 days increased by more than 30% as compared to conventional digestion at the same retention time. The effects are even more pronounced in the digesters that operated at a retention time of 8 days. Comparing the degree of degradation for this pair of reactors, an improvement in degradation of more than 40% is noted. The highest rate of VS-destruction, however, was observed in the digester operating at the shortest HRT (4 days). The volumetric degradation rate of the digester operating at a 4-day retention time increased nearly by a factor of 4, as compared to the conventional digester operating at a HRT of 16 days (1011:257). The most 76 外文文献译文及原文 significant biogas production in relation to the digester‘s volume can be seen in the digester that was operated at a HRT of 4 days. All digesters fed with ultrasonically treated sludge, however, displayed an increased biogas production when compared to their conventional digester counterparts. It is apparent that the anaerobic digestion process is significantly accelerated by the use of ultrasonic pre-treatment. The pilot studies conducted with the 200-liter digesters have provided the significant results needed in order to knowledgably and effectively handle challenges that arise on fullscale installation venues. Full-scale conditions WWTPMeldorf. Afull-scale installationwas implemented at Meldorf WWTP (65,000 PE) in February 2005 after a 3-month test period. The plant was experiencing problems with foaming in the anaerobic digester as a result of excessive growth of filamentous bacteria (Microthrix parvicella) in thewaste activated sludge. The purpose of the ultrasound installationwas to eliminate the source of the foaming problems and thereby ensuring an undisturbed anaerobic digestion. Sonicationwas applied to 100% of the thickenedwaste activated sludge (TWAS) flow before it was sent to the two anaerobic digester tanks present at the plant. A short time after the installation of the ultrasound equipment at the MeldorfWWTP, the problems with foaming sludge were no longer an issue. This, in turn, provided the conditions necessary for a smooth and effective digestion of the sludge when it reached the fermenter. The VS, expressed as percent of dry solids, were reduced from 60% to 45% in the stabilized sludge (Fig. 1). With regard to biogas production, a 30% increase after the ultrasound installation was noted as compared to before the installation. These improvements correspond to improved self-sufficiency with regard to energy supply and a reduced sludge mass for disposal. In addition, the feeding of cosubstrates was made possible as a result of the improved stability of the anaerobic digestion process. The plant was able to accept process liquids from a local food producer, which serves the interests of both parties. WWTP Bamberg. A full-scale installation with two ultrasound reactorswas completed 77 外文文献译文及原文 inAugust 2004 at theWWTP in Bamberg, Germany (actual load 330,000 PE). The ultrasound application had previously successfully been tested at the plant during a trial period that lasted for 4 months. The purpose of the ultrasound application was to enhance the VS-degradation to a minimum of 45% in order to avoid the costly task of constructing another anaerobic digester. In order to achieve this, 25% of the TWAS was sonicated before it was sent to the anaerobic digester. Ideally, organic material that is available to the organisms in the sludge is converted to methane in the anaerobic food chain. The gas production, compared to conventional digestion, increases as a greater amount of organic material is made bio-available through sonication. By feeding the digester with ultrasonically treated sludge, the gas production has been shown to increase by almost 30% at the WWTP in Bamberg (Fig. 2). The methane content also increased slightly, making the biogas a [2]more attractive and energy rich product. The residual VS content in the digested sludge was reduced from 60% to 54%. The desired goal to reach a minimum of 45% VS-degradation was met and surpassed. The increase in VS-destruction implies that more of the organic matter in the sludge was metabolized in the digestion process. This coincides with the increase in gas production; less organic matter in the sludge means that the carbon source must have been metabolized in the digestion process to yield biogas. Through the increase in gas production, the self-sufficiency of the plant with regard to energy supply was improved. To a larger extent, the plant was able to supply its operative processes with energy obtained from its anaerobic digestion process. This is, of course, advantageous seen from an economic perspective. Methods—Enhancing aerobic digestion In order to enhance the aerobic digestion process, sonicating activated sludge before returning it to the activated sludge tank (as return activated sludge) has emerged as a new and [6]innovative approach to intensify denitrification. We are following this approach, which 78 外文文献译文及原文 entails providing an internal carbon source in order to enhance the efficiency of denitrification. Though the mechanisms governing the reactions that ultimately result in this improvement are not fully known or understood, research in the field of ultrasonically treated sludge to improve anaerobic digestion provides valuable leads. Upon sonication, the microorganisms in the sludge become stressed and the colonies break apart. Filamentous colonies are destroyed by the powerful shear forces created by the implosion of cavitation bubbles, reducing or completely eliminating the negative effects associated with their presence. In addition, it is believed that the biological processes that proceed in the sludge are stimulated by the release of intercellular material from the destroyed cell. Specifically, released enzymes are thought to play a significant role in stimulating various biological processes. The destroyed cellular material itself serves as a non-foreign carbon source for the remaining viable microorganisms in the sludge. In this way we are able to reach an intensified denitrification. Full-scale conditions WWTP B?unde. A full-scale installation has been in place at the B?undeWWTP(actual load 54,000 PE) since September 2006. A test period of 4 months had, by this point, been successfully completed and the decision to proceed with the installation was based on the convincing results obtained during the test period. The nitrogen elimination at the plant occurs via intermittent denitrification. The reason for implementing the ultrasound technology on the plantwas that denitrification efficiency was suffering as a result of insufficient carbon source for the denitrifying bacteria. Using sonicated thickened waste activated sludge as an internal carbon source to improve denitrification was seen as a viable option. In total, 30% of the daily TWAS stream was sonicated and led back to the activated sludge tank, providing the process with the carbon source needed for elevated denitrification efficiency. After sonication ceased in July 2006, the N-inorganic concentrations again climbed to the pre-sonication levels seen in 2005. Sonicating a partial stream of the thickened waste activated sludge before leading it back to the activated sludge tank provided the carbon source necessary to facilitate the improvement in denitrification. 79 外文文献译文及原文 Utilizing sonicated TWAS as an internal carbon source for the purpose of improving denitrification yielded several positive effects. First, a significant reduction of nitrogen in circulation at the plantwas achieved,which means that denitrification had been improved (Fig. 3). In addition, there were several secondary effects that contributed to an overall efficiency of the plant operations.Excess sludgewas reduced by 25% and the dewaterability of the sludge was improved by 2%. A reduction of the organic fractions present in the sludge was attained and foaming and bulking sludge in the activated sludge tank was virtually eliminated. It is apparent that several positive advantages were reached through the usage of ultrasonically treated sludge. Regarding economics, reimbursement of the investment was immediate as reduced sewage fees associated with sludge disposal and nitrogen concentrations were achieved. Hence, the advantages are visible from an economic perspective as well as on the operational level itself. Adding to economic advantages, it must be mentioned that the plant Improving anaerobic and aerobic degradation avoided being forced into purchasing an external carbon source. The plant was ultimately able to conserve resources, optimize the existing process and acquire a higher degree of operational stability through the incorporation of this ultrasound technology. Conclusion With regard to anaerobic digestion, it has been proven both on the pilot scale and on full scale that digestion is improved through the use of ultrasound to sonicate sludge. The benefits are visible on the operational level and economically. Using experiences fromfull-scale installations as references, we can gather that the application has proven itself both technically and economically feasible. Using ultrasound for the purpose of improving aerobic digestion is quite a new application and the mechanisms of the microbiological processes need to be researched further in order to establish the significance of metabolic processes that take place. First experiences with full-scale installations do, however, indicate that we achieve similar 80 外文文献译文及原文 effects in aerobic applications as with anaerobic. That is, bacterial cells are broken apart and destroyed, which means that there is a larger amount of bio-available carbon for the remaining microorganisms to metabolize. The result is intensified denitrification and a reduction of the excess sludge mass. On the operational level, less foaming and bulking sludge is attained, as the organisms responsible for these phenomenons are broken apart or destroyed in treatment process. 81 外文文献译文及原文 References [1] Malina, J.F.; Pohland, F.G. Design of anaerobic processes for the treatment of industrial andmunicipalwastes. InWater Quality Management Library; Technomic Publishing Company: Lancaster, PA, USA, 1992. [2] Vera, M.A.; Nickel, K.; Neis,U.; Ritchie, J. Disintegration of sewage sludge for improved biodegradation, in: Proceedings of the IWA Specialised Conference on Sewage Sludge, South Africa (Paper 204) 2005. [3] Tiehm, A.; Nickel, K.; Zellhorn, M.; Neis, U. Ultrasonic waste Activated sludge disintegration for improving anaerobic stabilization. Water Res. 2001, 35 8), 2003–(2009. [4] Neis, U.; Nickel, K.; Tiehm, A. Enhancement of anaerobic sludge digestion by ultrasonic disintegration. Water Sci. Tech. 2000, 42 (9), 73–80. [5] Shimizu, T.; Kudo, K.; Nasu, Y. Anaerobic waste activated sludge digeston bioconversion mechanism and kinetic model. Biotechnol. Bioeng. 1993, —A 41, 1082–1091. [6] European Union, Community Research and Development Information Service (CORDIS). Project name: Ways of Innovation for the Reduction of Excess Sludge (W.I.R.E.S.). Project reference: EVK1-CT2000-00050. , 2007-01-24. 82