SAF生物反应器对污水处理冲击的载荷作用外文翻译.doc

saf生物反应器对污水处理冲击的载荷作用本研究比较了有机和水力性能对冲击负荷的影响，淹没式滤池（safs）带上羊毛，作为一种新型的媒介和媒介方面的kaldnes环总有机碳（toc），悬浮固体（ss）和氨的去除。safs实现超过95%的toc去除率，平均为99.8%的ss去除效率，氨氮去除率100%，即使在受到冲击载荷。氨氮的去除也比其他参数更敏感，这是归因于硝化细菌的生长缓慢，这是竞争对手的空间差与基板。带上羊毛有能力克服液压冲击比saf与kaldnes，归因于更好的过滤性能，然而，无论怎样表现出在短期和长期的冲击加载条件下正常运行。倍频的有机负荷，反应器的反应不同，迅速应对冲击，但不稳定。长期的有机负荷冲击造成了更大的干扰，直到有足够的量增长到补偿，这表明传质比生长动力学不重要。关键词：淹没式滤池 新型羊毛媒体 流体力学 停留时间分布 生物量 废水处理1、简介 对污水处理排放标准更加严格的控制系统已导致比传统的生物处理过程更复杂的解决方案。固定发展的生物反应器保证了显着的进步的知识与这种类型的处理中的应用。相比传统的单位，固定膜生物反应器进行较高的有机负荷率由于更有效的生物量导致更高的细胞停留时间在反应区，生物反应器的稳态性能与他们的生物量浓度。潜在的有害环境的变化，由于污水废物变性质往往造成冲击负荷。因此，冲击器的稳定性是生物处理系统的最重要的设计方面。进水浓度的突然变化，或产生有机负荷冲击，能够最终不稳定的处理性能系统。性能劣化的程度取决于微生物的持续时间和冲击和适应性的速率。在有机冲击限制整体反应的主要因素，效率似乎是生物动力学。高浓度生物量的影响在好氧反应器通常提高其稳定而不是提高cod去除。相反，在液压冲击的底物传质的速率冲击载荷发生在这两种方式，无论是作为一个短期的，短暂的，只能持续几小时，或作为一个长期的在反转回原始的数天到数周的变化操作条件。在短期冲击，恶化的程度变化将取决于你的持续时间和微生物的休克幅度和适应性速率。研究已经证明，生物反应器可以处理短期和长期的冲击负荷，有时甚至容忍三有机负荷率（olr）。长期的冲击会导致新的“稳定状态”是对原有的操作条件相同的从toc去除率和其他参数。时间达到稳定状态与生物质的浓度成正比，即高浓度生物量在反应器的设计，增加其稳定性。考虑到高固体停留时间增长缓慢生物量和高浓度生物量的能力，saf在在这项工作中，对装满了羊毛的saf冲击载荷进行了研究。2 实验2.1 媒介 实验研究了两种类型的媒体：羊毛和kaldnes。羊毛纤维直径20um，由工业碱精练的标准方法将羊毛除去羊毛脂。这是最常见的高档羊毛用于纺织品和地毯。kaldnes是一个工业聚乙烯基，直径9mm，长度7.5mm，比表面面积500m2m3，密度0.95克/立方厘米，空隙率75%。2.2 安全设计与施工两个相同规模的safs实验室进行了这项工作，在部门车间。他们被设计操作来模拟一个缩小的试点单位的版本。制备出的滤波器（140毫米内径）聚丙烯柱。每个反应器的总高度610mm和过滤器的空床液体的体积为6.93 l，一个挤满了羊毛的saf与kaldnes。以上两种反应器的一个网格过滤面积高380mm，这意味着，该滤波器的70%卷装与媒介。safs被通过蠕动泵。入口位于下方的管道直径为15mm，和网格130mm以上的底部支撑，媒介和分离滤波器为两个主要领域：过水区和污泥区。污泥区高度50mm，污泥是通过管排出（直径15mm）固定在滤波器。曝气和入口均高于污泥面积。泥区过滤器的上方也提供了空气。这些环直径为120mm，气孔均匀位于圆形曝气回路。出口（直径10mm）位于反应器的中心，滤波器下35mm。2.3 综合废水探讨反应器去除污染物，safs规模的实验室用人工合成废水解决污水，即原出水。综合污水具有均匀的特点没有有毒或工业部件的危险。污水合成是基于原污水组成用phanapavudhikul研究实验室和中试规模对活性污泥温度的影响。化学成分的合成及其浓度污水在表1中给出。该过滤器的进水需每两天更换避免明显的老化。进水是用热水溶解浓缩配方制备的，其次是在进料罐用自来水稀释（500升）的所需浓度。然后废水使用两个蠕动泵送入反应器。在实验期间，saf的溶解氧（do）维持上述4mg/l（溶解氧测定仪，ysi模型58）。这也是保证低溶解氧没有限制。 在所有的实验中，任何冲击荷载之前，合成废水是在反应器底部的入口（图1）。整体体积在每个反应器的合成体积为6.8 l和保持恒定并反应器顶部借助溢流。压缩空气通过空气回路供给（图1）。短期冲击加载条件下，水力停留时间从22小时减少到11小时增加一倍，从原来的流量0.00525分钟1。正常操作条件短期冲击负荷后12小时恢复。冲击负荷后，两个反应器的操作在正常条件下，监测到9天后hrt进一步恢复到最初的22小时观察的，复苏和任何的长期影响冲击载荷。性能效率进行toc，ss、氨。在有机冲击负荷的液压流量保持不变和有机负荷的加入提高了合成废水的双组分浓度，该模型解决了污水进行32天正常运行后从液压冲击试验恢复。2.4 分析2.4.1 总有机碳 罗斯蒙特dohrmann总有机碳分析仪dc-190用于测定总碳（tc）和无机碳（ic），toc是由减法计算。样本量为50 l，注射用注射器。平均值和标准偏差通过分析计算，只有那些标准值偏差小于1%被记录和使用。分析按标准方法进行。这个分析报告精度是5%。2.4.2 总悬浮固体 与标准的技术进行了分析。样品充分混合，然后通过过滤加权的whatman gfc（70mm）与孔径大小的过滤器1.2 m0.3，渣留在滤纸上干燥，在105c为1小时，放在干燥器和加权直到体重变化对加热小于4%或0.5毫克。增加总悬浮固体在滤波器的权值时调整对样品的体积。报道分析的精度是5%。2.4.3 氨氮 用纳氏试剂分析氨氮，方法纳入百灵达系统。10ml稀释样品将氨氮浓度为0.10毫克/升的基础上，污水和稳态性能。检测前准备氨1号和2依次加入搅拌，离开10分钟。然后，样品用光度计读（百灵达5000）在波长640 nm处。这种精度分析报告是5%。3 结果与讨论3.1 短期负荷冲击 从瞬态液压冲击停留时间（hrt）减少一半至11小时的水力停留时间为12小时，24介绍了24。瞬态加载后污水浓度的测量从24小时开始。结果，ss，浊度为safs羊毛氨氮去除与kaldnes媒介都显示在图。24。3.1.1 toc的去除结果表明，减少水力停留后时间（hrt）的一半在冲击研究（图2），safs在3天发现适应新的进料浓度。因此，两种反应器的toc的流出物从羊毛与kaldnes处从4到6毫克/升立即增加超过10毫克/升（图2），在时间1天后，加载液压冲击。反应堆稳定这种状态，并在72小时内返回稳定运行后停止这是适用于半天。它花了22个小时对冲击负荷进行消散作用。恢复后，最大toc的降解效率为95.63%和95.72%，分别用 saf羊毛与kaldnes。safs的快速恢复遵循液压冲击载荷的部分原因可能是因为一个适应和活性生物量，有效地降低了额外的水力负荷的增加。的对液压冲击过程中的性能恶化原因，可能是由于将提高液压压力作为一个结果，导致生物量和衬底之间更少的接触时间。nachaiyasit和斯塔基在以后的工作中注意减少20小时增加至10小时，在短的水力停留时间，将必须有在床上发生的，和床的性能使它承受液压冲击。这表明，该系统在高水力负荷为较低的去除性能，看到在这项工作的safs发生可能是由于发生死区和短路。基板只是通过水洗不被代谢，可能是因为将生物质中的床上发生的，或很短的接触微生物和衬底之间的时间。生物质冲刷可以解释的出水ss减少，但这不是由结果支持。相比其他进程的冲击引起的稳定，李森科和惠顿性同时指出。在他们的实验冲击是短期的冲击（30分钟）5.23升容量，生物过滤器充满媒介对498.7m2/m3比表面积的影响研究氨氮去除。它被发现是更有效的利用除氨比滴滤器。他们认为该不敏感的干扰由于滴过滤器有不同一些混合和传入的废水在safs稀释。滤池中常见的saf生物膜的保护嵌入式细菌可能有害的环境条件。一旦有利的环境条件下恢复，细菌就恢复以前的水平，降解。toc的出水浓度saf与羊毛的恢复时间与kaldnes类似。3.1.2 ss的去除hrt的减小对出水ss浓度没有明显的影响（图3）。在悬浮固体浓度为3mgl第一天有轻微的增加，在反应器中填充羊毛冲击负荷。然而，ss数据对该系统的波动在42天的期限。ss去除率达到了100%和98.67%，分别为saf羊毛与kaldnes而经历短期shockwithout代谢。这种现象与短的水力停留时间也被grobicki和斯塔基观察到。这表明，较低的ss的去除性能系统在高水力负荷由于液压冲洗出来的固体。3.1.3 氨氮去除氨氮的去除观察到最大的效果是液压冲击从图4可以看出，这是对一个额外的0.14克氨进行了介绍。短期冲击负荷，出水氨氮浓度从两个反应器用羊毛与kaldnes从1.0mgl到17毫克/升和25毫克/升迅速增加，分别为。氨浓度第一天迅速从saf羊毛下降，恢复到预冲击操作并通过第三天的性能。saf的恢复期与kaldnes比saf再显然的一天羊毛（图4），这表明，羊毛在共同安全与其他数据增加到克服水力冲击负荷的能力与kaldnes的saf相比。之前的冲击使羊毛saf与kaldnes平均氨氮去除为 99.1%和98.7%，这减少了60.61%和42.42%，而冲击最大后氨的去除效率为99.8%和99.7%，它类似于平均氨效率。下面的液压冲击负荷引起的快速恢复可以归因于活性和固定的硝化细菌，整个实验有效地回收和退化的衬底。它是不可能有足够的时间来刺激额外的生物量增长。在目前的研究中，氨氮降解明显比其他参数更敏感，如toc和ss，确认硝化作用是更容易的改变实验条件。其原因可能是由于硝化细菌缓慢自养生长。他们是空间和氧贫穷的竞争对手，因此他们只发现生物膜，他们很容易在低氧气浓度长满了异养生物。一些研究表明，异养微生物被安排在下部的上流式saf在大多数有机转换发生。硝化细菌就能够占据显着的硝化作用发生的上部。这是该模式在营养物去除活性污泥并在单独的室是专为toc去除率，硝化，除磷富集硝化。hrt的减少都会削弱这些硝化细菌的活性，通过增加竞争，从异养微生物硝化细菌的生长速度和降低抑制物质，为了尽快异养微生物反应能力，导致出水氨氮浓度的增加。此外，较低的去除性能的系统在高水力负荷在safs发生是由于发生死区和短路。此外，液压冲击，包括独立的生物硝化细菌可以冲刷性能降低。3.2 长期的冲击载荷长期有机冲击负荷时，饲料的有机负荷率（olr）增加了一倍，并且持续了40天，在这期间toc，ss为safs羊毛去除氨和kaldnes做出了贡献。进水的ph值和出水保持在7和8之间。进水浓度增加，模拟可能发生的事故。3.2.1 toc的去除 长期有机冲击负荷，出水toc浓度增加到4天之后它开始调整两种反应器（图5）。即使双重加载的两个saf反应堆稳定的快速反应也休克。两个safs达到新的稳定状态相当迅速，所需的时间大约是四hrt。这时间允许增加微生物的生长来应对冲击载荷是足够的，之后，反应堆回到他们的稳定性能。新的olr为0.22公斤/立方米，toc d，两次稳态运行。平均toc去除率超过95.25%，在以前的较低，甚至更高的有机负荷（羊毛与kaldnes反应器分别在94.26%和93.30%）。这表明更大的去除过程没有完全加载。结束实验运行稳定持续（39天），表明该organicshock负荷稳定，他们保持着一个类似的toc的去除，即使当加载效率增加了一倍。两个safs挤满了羊毛与kaldnestoc去除率之间的差异是微不足道的（图5）。一倍的进料浓度在厌氧折流板的影响反应器的8 g / l的cod在20小时的水力停留时间为20天，发现反应器也能适应双有机冲击载荷和保持相同的去除效率。在有机冲击负荷的增加（olr为2.60 tcodg /升/天增加到3.92 tcodg /升/天一个最大的6.25 tcodg /升/天）sbrs很少，在可溶性化学需氧量（scod）和临时性的影响挥发性脂肪酸（vfa）的去除效率。这些研究符合本研究的结果。虽然nachaiyasit 认为在液压冲击基板的质量转移到生物量聚集率似乎是限制因素。在理论上的主要限制因子在有机冲击的总体反应率应该是由生物量和消费的吸收动力学。休克负载可以提供到反应器的反应预测的见解，例如短路和经济增长之间的相互作用。这项工作是在冲击器工作首先提出安全率模型的限制因素。该显示的稳定性在该生物膜中发挥了重要的作用，抗有机负荷冲击。在高有机质较高的去除性能荷载作用下发生的比较研究为例，其他的研究，nachaiyasit归因于较高的生物量浓度和更好的混合。3.2.2 ss的去除 羊毛纤维良好的过滤能力是体现在有机冲击负荷的结果。ss排放浓度从羊毛安全带上很低是相对稳定的。相反，ss出水浓度saf与kaldnes介质波动明显（图6），ss值高达100毫克/升。这是特别，昨日（1日开始14）在调试过程中，但也很明显，在实验期结束（32天和39天）的冲击载荷作用下。sd出水ss值的有机冲击负荷在较大（9.11和50.32，分别为羊毛和kaldnes saf）非稳态期saf羊毛和kaldnes分别为3.66和14.11，如氨可以作为一个指标的不稳定性。看来最有可能的是，ss高负荷下，一些有影响的ss不被保留或生物降解的saf的停留时间内与kaldnes。早期的结果表明，流体湍流是一个因素。toc是不受影响的（图5）但固体损失saf与kaldnes均增加，所以可溶性物质生物量和过滤器的能力无法应付额外的固体有机物即使液压流量是不变的。因此，尽管稳定的toc结果，不同的ss出水浓度可能表明，固体停留成为关键，对绩效表现较弱的saf与kaldnes的关键，。fullplants的调查（大型污水处理厂）在印度证实ss的去除性能也会受到影响，甚至10%增加流量。saf的羊毛有稳定的出水ss（图6）提示无论是动力学的生物量或流体力学湍流成为saf挤满了羊毛的限制。在我们的研究液压冲击对ss比有机不利负荷可能是较好的反应器混合条件的结果。3.2.3 氨氮去除 safs为挤满了羊毛与kaldnes出水氨氮浓度媒介上升至最高，经过4天（图7）之后，有回收废水氨浓度。saf与kaldnes反应器氨的排放浓度的波动超过大多数羊毛的有机负荷冲击。这不是安全与稳定的。因此，有机的冲击荷载引起的干扰去除氨氮，即使生物量的不足已经补偿，持续了34次的增长率。硝化细菌增长率被认为是10天左右。硝化细菌的生长速率慢，使他们很容易竞争。3.2.4 温度对toc的影响，ss和氨氮去除该报告为不易变异的环境温度与活性污泥，在实验过程中的温度变化从15到21c ，对液压冲击，从11到20.5c的有机冲击载荷作用下的。与温度之间的关系有没有确凿的toc，ss和氨氮去除。对ss的去除的一些趋势被检测到。因此，羊毛与kaldnes 在14和17c平均ss的去除效率分别为97%和92%，实现更好的ss的去除效率在17和20.5c之间，用羊毛与kaldnes safs导致的平均值分别为97.5% 95.5%。一个更大的固体从羊毛的产量是因为预期的故障羊毛被预期但这一定是生物降解。4 结论 （1）在这项工作中的测量参数，toc，ss和氨通过瞬态水力冲击负荷对saf 影响用羊毛或kaldnes媒介。氨去除明显比其他参数更敏感，这是归因于硝化细菌作用的缓慢增长，这是空间和基板的对手。 （2）挤满了毛safs或kaldnes环展出后短期快速返回到正常操作条件和较长的冲击载荷。总的来说，羊毛的saf的能力最好，克服液压冲击比saf与kaldnes。这表明，传质和生物量的增长更重要的是通过生物量冲洗损失。快速恢复建议safs是这些不敏感干扰比滴流过滤器。该显示的生物膜稳定性和混合的条件对抗有机冲击负荷发挥了重要作用。 （3）在短期的液压冲击的研究，无论是羊毛kaldnes saf均恢复正常运行的冲击历时半停止一天后的72小时内。toc的降解效率的最大速率95.63%和95.72%，氨氮去除率最高效率为99.8%和99.69%，分别为安全带羊毛与kaldnes媒介。 （4）长期有机冲击负荷时，4天之后出水的toc浓度的影响，这是能够调整。在反应堆回到稳定状态，平均去除率达95%以上，没有区别，休克前和稳定运行继续实验结束时（39天）。在toc去除safs挤满羊毛和kaldnes的差异是微不足道的。 （5）羊毛纤维良好的过滤能力是体现在出水ss浓度较低（主要是，少于20毫克/升），并与出水ss浓度变化不大，然而，ss的出水浓度saf与kaldnes显著波动。在安全带上羊毛提出了这水动力动荡不成为限制条件。在我们的研究中液压冲击比有机负荷以及不利的建议在反应器中的混合条件。 （6）有机负荷增加一倍，反应器的反应快速的冲击而不稳定的建议的波动在氨氮，出水ss和。长期的有机负荷冲击造成了更大的干扰，直到有足够的生物质补偿，这表明传质比生长动力学不重要。致谢：作者感谢拉夫堡大学和德蒙特福特大学的设施catalytic strategies for industrial water re-usef.e. hancocksynetix, billingham, cleveland, ts23 1lb, ukabstractthe use of catalytic processes in pollution abatement and resource recovery is widespread and of significant economic importance r.j. farrauto, c.h. bartholomew, fundamentals of industrial catalytic processes, blackie academic and professional,1997. for water recovery and re-use chemo-catalysis is only just starting to make an impact although bio-catalysis is well established j.n. horan, biologicalwastewater treatment systems; theory and operation, chichester, wiley, 1990. this paper will discuss some of the principles behind developing chemo-catalytic processes for water re-use. within this context oxidative catalytic chemistry has many opportunities to underpin the development of successful processes and many emerging technologies based on this chemistry can be considered .keywords: cod removal; catalytic oxidation; industrial water treatment1.introduction industrial water re-use in europe has not yet started on the large scale. however, with potential long term changes in european weather and the need for more water abstraction from boreholes and rivers, the availability of water at low prices will become increasingly rare. as water prices rise there will come a point when technologies that exist now (or are being developed) will make water recycle and re-use a viable commercial operation. as that future approaches, it is worth stating the most important fact about wastewater improvement avoid it completely if at all possible! it is best to consider water not as a naturally available cheap solvent but rather, difficult to purify, easily contaminated material that if allowed into the environment will permeate all parts of the biosphere. a pollutant is just a material in the wrong place and therefore design your process to keep the material where it should be contained and safe. avoidance and then minimisation are the two first steps in looking at any pollutant removal problem. of course avoidance may not be an option on an existing plant where any changes may have large consequences for plant items if major flowsheet revision were required. also avoidance may mean simply transferring the issue from the aqueous phase to the gas phase. there are advantages and disadvantages to both water and gas pollutant abatement. however, it must be remembered that gas phase organic pollutant removal (voc combustion etc.,) is much more advanced than the equivalent water cod removal and therefore worth consideration 1. because these aspects cannot be over-emphasised，a third step would be to visit the first two steps again. clean-up is expensive, recycle and re-use even if you have a cost effective process is still more capital equipment that will lower your return on assets and make the process less financially attractive. at present the best technology for water recycle is membrane based. this is the only technology that will produce a sufficiently clean permeate for chemical process use. however, the technology cannot be used in isolation and in many (all) cases will require filtration upstream and a technique for handling the downstream retentate containing the pollutants. thus, hybrid technologies are required that together can handle the all aspects of the water improvement process6,7,8.hence the general rules for wastewater improvement are: 1. avoid if possible, consider all possible ways to minimise. 2. keep contaminated streams separate. 3. treat each stream at source for maximum concentration and minimum flow. 4. measure and identify contaminants over complete process cycle. look for peaks, which will prove costly to manage and attempt to run the process as close to typical values as possible. this paper will consider the industries that are affected by wastewater issues and the technologies that are available to dispose of the retentate which will contain the pollutants from the wastewater effluent. the paper will describe some of the problems to be overcome and how the technologies solve these problems to varying degrees. it will also discuss how the cost driver should influence developers of future technologies. 2. the industries the process industries that have a significant wastewater effluent are shown in fig. 1. these process industries can be involved in wastewater treatment in many areas and some illustrations of this are outlined below. fig. 1. process industries with wastewater issues. 2.1. refineries the process of bringing oil to the refinery will often produce contaminated water. oil pipelines from offshore rigs are cleaned with water; oil ships ballast with water and the result can be significant water improvement issues. 2.2. chemicals the synthesis of intermediate and speciality chemicals often involve the use of a water wash step to remove impurities or wash out residual flammable solvents before drying. 2.3. petrochemicals ethylene plants need to remove acid gases (co2, h2s) formed in the manufacture process. this situation can be exacerbated by the need to add sulphur compounds before the pyrolysis stage to improve the process selectivity. caustic scrubbing is the usual method and this produces a significant water effluent disposal problem. 2.4. pharmaceuticals and agrochemicals these industries can have water wash steps in synthesis but in addition they are often formulated with water-based surfactants or wetting agents. 2.5. foods and beverages clearly use water in processing and cod and bod issues will be the end result. 2.6. pulp and paper this industry uses very large quantities of water for processing aqueous peroxide and enzymes for bleaching in addition to the standard kraft type processing of the pulp. it is important to realise how much human society contributes to contaminated water and an investigation of the flow rates through municipal treatment plants soon shows the significance of non-process industry derived wastewater. 3. the technologies the technologies for recalcitrant cod and toxic pollutants in aqueous effluent are shown in fig. 2. these examples of technologies 2,6,8 available or in development can be categorised according to the general principle underlying the mechanism of action. if in addition the adsorption (absorption) processes are ignored for this catalysis discussion then the categories are: 1. biocatalysis 2. air/oxygen based catalytic (or non-catalytic). 3. chemical oxidation 1. without catalysis using chemical oxidants 2. with catalysis using either the generation of _oh or active oxygen transfer. biocatalysis is an excellent technology for municipal wastewater treatment providing a very cost-effective route for the removal of organics from water. it is capable of much development via the use of different types of bacteria to increase the overall flexibility of the technology. one issue remains what to do with all the activated sludge even after mass reduction by de-watering. the quantities involved mean that this is not an easy problem to solve and re-use as a fertilizer can only use so much. the sludge can be toxic via absorption of heavy metals, recalcitrant toxic cod. in this case incineration and safe disposal of the ash to acceptable landfill may be required. air based oxidation 6,7 is very attractive because providing purer grades of oxygen are not required if the oxidant is free. unfortunately, it is only slightly soluble in water, rather unreactive at low temperatures and, therefore, needs heat and pressure to deliver reasonable rates of reaction. these plants become capital intensive as pressures (from _10 to 100 bar) are used. therefore, although the running costs maybe low the initial capital outlay on the plant has a very significant effect on the costs of the process. catalysis improves the rates of reaction and hence lowers the temperature and pressure but is not able to avoid them and hence does not offer a complete solution. the catalysts used are generally group viii metals such as cobalt or copper. the leaching of these metals into the aqueous phase is a difficulty that inhibits the general use of heterogeneous catalysts 7. chemical oxidation with cheap oxidants has been well practised on integrated chemical plants. the usual example is waste sodium hypochlorite generated in chlor-alkali units that can be utilised to oxidise cod streams from other plants within the complex. hydrogen peroxide, chlorine dioxide, potassium permanganate are all possible oxidants in this type of process. the choice is primarily determined by which is the cheapest at the point of use. a secondary consideration is how effective is the oxidant. possibly the most researched catalytic area is the generation and use of _oh as a very active oxidant (advanced oxidation processes) 8. there are a variety of ways of doing this but the most usual is with photons and a photocatalyst. the photocatalyst is normally tio2 but other materials with a suitable band gap can be used 9,10. the processes can be very active however the engineering difficulties of getting light, a catalyst and the effluent efficiently contacted is not easy. in fact the poor efficiency of light usage by the catalyst (either through contacting problems or inherent to the catalyst) make this process only suitable for light from solar sources. photons derived from electrical power that comes from fossil fuels are not acceptable because the carbon dioxide emission this implies far outweighs and cod abatement. hydroelectric power (and nuclear power) are possible sources but the basic inefficiency is not being avoided. hydrogen peroxide and ozone have been used with photocatalysis but they can be used separately or together with catalysts to effect cod oxidation. for ozone there is the problem of the manufacturing route, corona discharge, which is a capital intensive process often limits its application and better route to ozone would be very useful. it is important to note at this point that the oxidants discussed do not have sufficient inherent reactivity to be use without promotion. thus, catalysis is central to their effective use against both simple organics (often solvents) or complex recalcitrant cod. hence, the use of fentons catalyst (fe) for hydrogen peroxide 11. in terms of catalysis these oxidants together with hypochlorite form a set of materials that can act has active oxygen transfer (aot) oxidants in the presence of a suitable catalyst. if the aot oxidant is hypochlorite or hydrogen peroxide then