污水处理外文翻译---污水的生物处理过程

生物法处理废水流程Biological wastewater treatment is an essential process that helps to clean contaminated water by using natural processes to degrade pollutants. 生物法处理废水是一种重要的过程，通过利用自然过程降解污染物来清洁污染水。

It is a sustainable and environmentally friendly method that is widely used in wastewater treatment plants around the world. 这是一种可持续且环保的方法，在全世界的污水处理厂广泛应用。

One of the main advantages of biological wastewater treatment is that it is cost-effective compared to other treatment methods. 生物法处理废水的主要优势之一是与其他处理方法相比成本效益高。

This is because it uses natural processes to break down contaminants, reducing the need for expensive chemicals or equipment. 这是因为它利用自然过程降解污染物，减少了对昂贵化学品或设备的需求。

Another benefit of biological wastewater treatment is that it is energy efficient. 生物法处理废水的另一个好处是它具有高效能。

Unlike some other treatment methods that require a large amount of energy, biological treatment relies on natural processes that requireless energy input. 与一些其他处理方法需要大量能源相比，生物处理依赖于需要较少能源投入的自然过程。

污水处理流程英文版Wastewater Treatment Process.Primary Treatment.The first step in wastewater treatment is primary treatment. This process removes settleable solids and floating materials from the wastewater. Primary treatment is typically accomplished through the use of sedimentation tanks, which allow the solids to settle out of the water. The settled solids are then removed from the tank and sent to a landfill or incinerated.Secondary Treatment.The second step in wastewater treatment is secondary treatment. This process removes dissolved organic matter from the wastewater. Secondary treatment is typically accomplished through the use of biological processes, such as activated sludge or trickling filters. In theseprocesses, bacteria consume the organic matter in the wastewater, converting it into carbon dioxide and water.Tertiary Treatment.The third step in wastewater treatment is tertiary treatment. This process removes nutrients, such as nitrogen and phosphorus, from the wastewater. Tertiary treatment is typically accomplished through the use of chemical processes, such as coagulation, flocculation, andfiltration. In these processes, chemicals are added to the wastewater to cause the nutrients to clump together. The clumps are then removed from the water through filtration.Disinfection.The final step in wastewater treatment is disinfection. This process destroys harmful bacteria and viruses in the wastewater. Disinfection is typically accomplished through the use of chlorine or ultraviolet light.中文回答：污水处理流程。

污水sewage 污水处理污水处理 sewage treatment 一级处理一级处理 primary treatment 二级处理二级处理 secondary treatment 生物处理生物处理 biological treatment 活性污泥法活性污泥法 activated sludge process 曝气池曝气池 aeration tank 曝气曝气 aeration 充氧oxygenation 好氧消化好氧消化 aerobic digestion 厌氧消化厌氧消化 anaerobic digestion 溶解氧dissolved oxygen 沉淀沉淀 sedimentation 搅拌agitation 氯化氯化 chlorination 余氯余氯 residual chlorine 污泥污泥 sludge 泥龄sludge age 回流污泥回流污泥 returned sludge 剩余污泥剩余污泥 surplus sludge 消化污泥消化污泥 digested sludge 活性污泥活性污泥 activated sludge 污泥浓缩污泥浓缩 sludge thickening 污泥脱水污泥脱水 sludge dehydrating 絮凝絮凝 flocculation 水头Flood peak 水头损失水头损失 head loss 液面负荷液面负荷 surface load、 工艺参数类工艺参数类设计流量流量 Design flow 泵流量pump flow 栅前水深栅前水深 water depth of ahead grille 过栅流速Crosses the grille speed of flow 栅条间隙Grille gap 过栅水头损失head loss of crosses the grille 格栅倾角格栅倾角 Grille inclination angle 过栅流量过栅流量 flow of grille 齿耙运行速度齿耙运行速度 rake speed 有效水深Effective water depth 水力停留时间HRT hydraulic residence time 水力表面负荷Hydraulic load surface 污泥浓度sludge concentration 污泥回流比sludge reflux ratio 机械设备类机械设备类粗格栅粗格栅 coarse screen 回转格栅除污机grille decontaminating equipment 无轴螺旋输送机shaftless screw conveyor 无轴螺旋压榨机无轴螺旋压榨机 shaftless screw compressor 潜污泵submersible sewage pump 细格栅fine screen 旋流沉砂器rotational sand processor 砂水分离器砂水分离器 grit-water separator 潜水搅拌器submersible agitator 潜水推流器潜水推流器 submersible water impeller 可调堰门adjustable weir 曝气转刷aeration brushes 吸刮泥机aspiration sludge scraper 离心脱水机Decanter Centrifuge 切碎机Macerator 转鼓浓缩机Drum thickener 絮凝剂投配单元polymer make-up & dosing unit 圆形闸门Circular gate 蝶阀蝶阀 butterfly valve 闸阀闸阀 gate valve 球阀球阀 Ball valve 止回阀止回阀 Check Valve 放空阀放空阀 Emptying valve 微阻缓闭止回阀微阻缓闭止回阀 Tiny Drag Slow Shut Check Valves 电磁阀电磁阀 Mgnetic valve 电动阀电动阀 Mortor operated valve 法兰法兰 Flange 主轴承main bearing 减速机gearbox 超声波流量计supersonic flow meter 电磁流量计electromagnetic flow meter 。

污水处理的过程英语作文Wastewater Treatment ProcessWastewater treatment is a crucial process that plays a vital role in maintaining the health and sustainability of our environment. It involves the removal of contaminants from wastewater, ensuring that the discharged water is safe for the ecosystem and human use. The process of wastewater treatment consists of several stages, each designed to address specific types of pollutants and ensure the final effluent meets the required standards.The first stage of wastewater treatment is known as the preliminary treatment. This stage aims to remove large, coarse, and floating materials from the wastewater. This includes items such as rags, sticks, and other debris that could potentially clog or damage the equipment used in the subsequent treatment stages. Preliminary treatment typically involves screening, grit removal, and sometimes oil and grease removal.Following the preliminary treatment, the wastewater undergoes primary treatment. This stage focuses on the removal of suspended solids and organic matter from the wastewater. The primarytreatment process involves sedimentation, where the wastewater is allowed to settle, allowing the heavier solids to sink to the bottom of the tank. The settled solids, known as primary sludge, are then removed and sent to further processing or disposal. The clarified liquid that remains is then ready for the next stage of treatment.The secondary treatment stage is the most crucial step in the wastewater treatment process. This stage is designed to remove the remaining organic matter and nutrients, such as nitrogen and phosphorus, from the wastewater. The secondary treatment typically involves biological processes, where microorganisms are used to break down the organic matter. The most common secondary treatment methods include activated sludge, trickling filters, and rotating biological contactors.In the activated sludge process, the wastewater is mixed with a population of microorganisms, typically bacteria and protozoa, in an aeration tank. The microorganisms consume the organic matter, converting it into carbon dioxide and new cellular material. The resulting mixture of wastewater and microorganisms is then sent to a clarifier, where the treated water is separated from the excess microorganisms, known as activated sludge. The activated sludge is then recycled back to the aeration tank to continue the treatment process.Trickling filters, on the other hand, use a fixed-film biological process. In this method, the wastewater is sprayed over a bed of media, such as rocks or plastic, where a layer of microorganisms grows. As the wastewater trickles through the media, the microorganisms break down the organic matter. The treated water is then collected and sent to the next stage of treatment.Rotating biological contactors (RBCs) are another type of secondary treatment method. RBCs consist of a series of large discs that are partially submerged in the wastewater. The discs are slowly rotated, allowing the microorganisms that grow on the discs to be alternately exposed to the wastewater and the air. This process enables the microorganisms to consume the organic matter in the wastewater.After the secondary treatment, the wastewater may undergo additional treatment steps, such as tertiary or advanced treatment, depending on the specific requirements of the receiving water body or the intended reuse of the treated water. Tertiary treatment can include processes like filtration, disinfection, and nutrient removal to further improve the quality of the effluent.The final stage of wastewater treatment is the sludge treatment and disposal. The sludge generated during the various treatment stages is processed to reduce its volume and stabilize the organic matter. This can involve thickening, dewatering, digestion, and sometimesincineration or landfilling. The treated sludge can then be used as a soil amendment or disposed of in an environmentally responsible manner.The wastewater treatment process is essential for protecting the environment and public health. By removing contaminants and ensuring the treated water meets the necessary standards, wastewater treatment helps to maintain the quality of our water resources, prevent the spread of waterborne diseases, and support the overall sustainability of our ecosystems. As the demand for clean water continues to grow, the importance of efficient and effective wastewater treatment will only become more critical in the years to come.。

污水处理流程英语介绍Wastewater treatment is a critical process that aims to remove contaminants from wastewater, primarily from household sewage and industrial effluents, to produce an effluent that can be safely returned to the environment. Here's an overview of the wastewater treatment process 英文版:Introduction to Wastewater Treatment ProcessWastewater treatment is an essential part of modern infrastructure, designed to protect the environment and human health. It involves a series of processes to removeimpurities and harmful substances from water that has been used in homes, businesses, and industries.1. Preliminary TreatmentThe first step in wastewater treatment is the preliminary treatment, which includes screening and grit removal. Large debris and grit are physically removed from the wastewater to prevent damage to the equipment and pipes downstream.2. Primary TreatmentFollowing preliminary treatment, the wastewater undergoes primary treatment, where it is allowed to settle in large tanks. This process, known as sedimentation, separates the heavier particles from the water, forming sludge that can beremoved and treated separately.3. Secondary TreatmentSecondary treatment involves the biological breakdown of organic matter in the wastewater. This is typically achieved through the use of activated sludge processes, trickling filters, or rotating biological contactors. Microorganisms consume the organic matter, converting it into carbon dioxide, water, and biomass.4. Tertiary TreatmentTertiary or advanced treatment is the final stage of the process, aimed at removing nutrients such as nitrogen and phosphorus, which can cause eutrophication in water bodies. This step may include filtration, disinfection, and the useof chemical processes to precipitate out remaining contaminants.5. Sludge TreatmentThe sludge produced during primary and secondarytreatment is not simply discarded. It undergoes further treatment to reduce its volume and stabilize it for disposalor reuse. This can involve processes such as anaerobic digestion, which produces biogas, or composting.6. DisinfectionBefore the treated water is released back into theenvironment, it is disinfected to kill any remaining pathogens. Common disinfection methods include chlorination, ultraviolet light, and ozonation.7. Discharge or ReuseFinally, the treated water, now considered effluent, is either discharged into rivers or oceans or treated furtherfor reuse in irrigation, industrial processes, or even as potable water in some cases.Wastewater treatment is a multifaceted process that requires careful management and advanced technology to ensure the protection of our water resources. As populations grow and water scarcity becomes more prevalent, the importance of efficient wastewater treatment will only increase.。

污水处理流程英文版English:The wastewater treatment process involves several stages to remove impurities and contaminants from the sewage before it is released back into the environment. The first stage is screening, where large objects like sticks, rags, and debris are removed from the sewage using bar screens or fine screens. Then, the sewage goes through the primary treatment stage, where solid materials are settled and removed from the water. After that, the sewage undergoes secondary treatment, which uses biological processes to break down organic matter and remove pathogens. The final stage is disinfection, where chemicals or physical methods like UV radiation are used tokill any remaining bacteria and microorganisms in the water. Oncethe wastewater has gone through all these stages, it can be safely discharged into rivers, lakes, or oceans.中文翻译:污水处理过程包括几个阶段，以在将其排放回环境之前从污水中去除杂质和污染物。

外文原文：Wastewater Biological Treatment ProcessesThe objective of wastewater treatment is to reduce the concentration of specific pollutants to the level at which the discharge of the effluent will not adversely affect the environment or pose a health threat. Moreover , reduction of these constituents need only be to some required level.For any given wastewater in a specific location , the degree and type of treatment are variables that require engineering decisions . often the degree of treatment depends on the assimilative capacity of the receiving water . DO sag curves can indicate how much BOD must be removed from wastewater so that the DO of receiving water is not depressed too far . The amount of BOD that must be removed is an effluent standard and dictates in large part the type of wastewater treatment required .To facilitate the discussion of wastewater , assume a “ typical wastewater ”and assume further that the effluent from this wastewater treatment must meet the following effluent standards :BOD≤15mg/LSS≤15mg/LP≤1mg/LAdditional effluent standard could have been established , but for illustrative purposes we consider only these three . The treatment system selected to achieve these effluent standards includes1. Primary treatment : physical processes that nonhomogenizable solids and homogenize the remaining effluent .2. Secondary treatment : biological process that remove most of the biochemical demand for oxyen .3. Tertiary treatment : physical , biological , and chemical processes to remove nutrients like phosphorus and inorganic pollutants , to deodorize and decolorize effluent water , and to carry out further oxidation .Primary treatmentThe most objectionable aspect of discharging raw sewage into watercourses is the floating material . Thus screen were the first form of wastewater treatment used by communities , and they are used today as the first step in treatment plants .Typical screens consist of a series bars that might be about 2.5 cm apart . A screen in a modern treatment plant removes might damage equipment or hinder further treatment . in some older treatment plants are cleaned by hand , but mechanical cleaning equipment is used in almost all new plants . The cleaning rakes are activated when screens get sufficiently clogged to raise the water level in front of the bars .In many plants , the second treatment step is a comminutor , a circular grinder designed to grind the solids coming through the screen into pieces about 0.3 cm or less in diameter .The third treatment step is the removal of grit or sand from the wastewater . Grit and sand can damage equipment like pumps and flow meters and must be removed . The most common grit chamber is a wide place in the channel where the flow is slowed enough to allow the dense grit to settle out . Sand is about 2.5 times dense than most organic solids and thus settles much faster . The objective of a grit chamber is to remove sang and grit without removing organic material .Organic material must be treated further in the plant , but the separated sand may be used as fill without additional treatment .Most wastewater treatment plants have a settling tank after the grit chamber , to settle out as much material as possible . Accordingly , the retention time is long and turbulence is kept to a minimum .The solids settle to the bottom of the tank and are removed though a pipe , while the clarified liquid escapes over a V-notch weir that distributes the liquid discharge equally all the way around a tank . Settling tanks are also called sedimentation tank or clarifiers . The settling tank that immediately follows screening and grit removal is called the primary clarifier . The solids that drop to the bottom of a primary clarifier are removed as raw sludge .Raw sludge generally has a powerfully unpleasant odor , is full of pathogenic , and is wet , three characteristics that make its disposal difficult . It must be stabilized to retard further decomposition and dewatered for ease of disposal .The objective of primary treatment is the removal of solids , although some BOD is removed as a consequence of the removal of decomposable solids .A substantial fraction of the solids has been removed , as well as some BOD is a little P , as a consequence of the removal of raw sludge . After primary treatment the wastewater may move on to secondary treatment .Secondary TreatmentWater leaving the primary clarifier has not lose much of the solid organic matter but still contains high-energy molecules that decompose by microbial action , creating BOD . The demand for oxygen must be reduce (energy wasted ) or else the discharge may create unacceptable condition in the receiving waters . The objective of secondary treatment is to remove BOD , where the objective of primary treatment is to remove solids .The trickling filter consists of a filter bed of fist-sized rocks or corrugated plastic blocks over which the waste is trickled . The name is something of a misnomer since no filtration takes place . A very active biological growth forms on the rocks , and these organisms obtain their food from the waste stream dipping through the rock bed . Air either is forced through the rocks or circulates automatically because of the difference between the air temperature in the bed and ambient temperatures . Trickling filters use a rotating arm that moves under its own power , like a lawn sprinkler , distributing the waste evenly over the entire bed . often the flow is recirculated and a higher degree of treatment attained .Trickling filtration was a well-established treatment system at the beginning of the twentieth century . in 1914 , a pilot plant was built for a different system that bubbled air through free-floating aerobic microorganisms , a process which became known as the activated sludge system . The activated sludge process differs from trickling filtration in that the microorganisms are suspended in the liquid .An activated sludge system includes a tank full of waste liquid from the primary clarifier and a mass of microorganisms . Air bubbled into this aeration tank provides the necessary oxygen for survival of the aerobic organisms . The microorganisms come in contact with dissolved organic matter in the wastewater . adsorb this material , and ultimately decompose the organic material to CO2 , HO2 ,some stable compounds , and more microorganisms .When most of the organic material , that is , food for the microorganisms , has been used up , the microorganisms are separated from the liquid in a settling tank , sometimes called a secondary or clarifier . The microorganisms remaining in the settling tank have no food available , become hungry , and are thus activated-hence the term activated sludge . The clarified liquid escapes over a weir and may be discharged into the receiving water . The settle microorganisms , now called return activated sludge , are pumped back to the head of the aeration tank , where they find more food in the organic compounds in the liquid entering the aeration tank from the primary clarifier , and the process starts over again . Activated sludge treatment is a continuous process ,with continuous sludge pumping and clean-water discharge .Activated sludge treatment produces more microorganisms than necessary and if the microorganisms are not removed , their concentration will soon increase and clog the system with solids . Some of the microorganisms must therefore be wasted and the disposal of such waste activated sludge in one of the most difficult aspects of wastewater treatment .Activated sludge system are designed on the basis of loading , or the amount of organic matter , or food , added relative to the microorganisms available . The food-to-microorganisms (F/M) ratio is major design parameter . Both F and M are difficult to measure accurately , but may be approximated by influent BOD and SS in the aeration tank , respectively . The combination of liquid and microorganisms undergoing aeration is known as mixed liquor , and the SS in the aeration tank are mixed liquid suspended solids (MLSS) . The ratio of influent BOD to MLSS , the F/M ratio , is the loading on the system , calculated as pounds (or kg ) of BOD per day per pound or kg of MLSS .Relatively small F/M ,or little food for many microorganisms , and a long aeration period (long retention time in the tank ) result in a high degree of treatment because the microorganisms can make maximum use of available food . Systems with these features are called extended aeration systems and are widely used to treat isolated wastewater source , like small developments or resort hotels . Extended aeration systems create little excess biomass and little excess activated sludge to dispose of .The success of the activated sludge system also depends on the separation of the microorganisms in the final clarifier . when the microorganisms do not settle out asanticipated , the sludge is said to be a bulking sludge , Bulking is often characterized by a biomass composed almost totally of filamentous organisms that from a king of lattice structure within the sludge floes which prevents settling . A trend toward poor settling may be the forerunner of a badly upset and ineffective system . The settle ability of activated sludge is most often described by the sludge volume index (SVI) , which is reasoned by allowing the sludge to settle for minutes in a 1-Lcyliner . If the SVI is 100 or lower , the sludge solids settle rapidly and the sludge returned to the final clarifier can be expected at a high solids concentration . SVI is about 200 , however , indicate bulking sludge and can lead to poor treatment .Tertiary TreatmentThe effluent from secondary treatment meets the previously established effluent standards for BOD and SS . only phosphorus content remains high . The removal of inorganic compounds , including inorganic phosphorus and nitrogen compounds , requires advanced or tertiary wastewater treatment .Primary and secondary (biological) treatment are a part of conventional wastewater treatment plants . However , secondary treatment plant effluents are still significantly polluted . some BOD and suspended solids remain , and neither primary nor secondary treatment is effective in removing phosphorus and other nutrients or toxic substances . A popular advanced treatment for BOD removal is the polishing pond , or oxidation pond , commonly a large lagoon into which the secondary effluent flows . such ponds have a long retention time , often measured in weeks .BOD may also be removed by activated carbon adsorption , which has the added advantage of removing some is a completely enclosed tube , which dirty water is pumped into bottom and clear water exits at the top . microscopic crevices in the carbon catch and hold colloidal and smaller particles . As the carbon column becomes saturated , the pollutants must be removed from the carbon and the carbon reactivated , usually by heating it in the absence of oxygen . Reactivated or regenerated carbon is somewhat less efficient than using virgin carbon , some of which must always be added to ensure effective performance .中文译文：污水的生物处理过程物水处理的目的是降解特定污染物的浓度使其达到污水排放不影响环境或形成健康威胁的程度，而且降低这些成分仅仅需要达到要求大的水平即可。

aao污水处理工艺外文文献译文
AAO（Anaerobic, Anaerobic, Oxic）是一种污水处理工艺,主要用于处理含氮的污水。

该工艺结合了厌氧、厌氧、好氧三种生物学方法,可以有效降低污水中的氮、磷等有机物浓度,从而达到净化污水的目的。

在AAO工艺中,污水首先进入厌氧生物池进行处理,其中的微生物利用污水中的有机物作为食物,将其转化成氢气和二氧化碳。

接着,污水流入厌氧生物池,在这一步中,微生物利用氧气从空气中提取氧气作为能量来源,将污水中的有机物转化为二氧化碳和水。

最后,污水流入好氧生物池,在这一步中,微生物利用氧气将污水中剩余的有机物氧化成二氧化碳和水,最终达到净化污水的目的。

AAO工艺具有较高的厌氧氧化率和厌氧氧化率,能够有效降低污水中的氮、磷等有机物浓度,达到净化污水的目的。

同时,AAO工艺具有体积小、运行成本低、投资少的优点,是一种理想的污水处理方法。

污水处理外文翻译---污水的生物处理过程XXX to a level where the discharge of effluent will not harm the XXX only needs to be to a required level。

The degree andtype of treatment for a specific XXX。

The degree of treatment often depends on the XXX so that the DO of the receiving water is not depressed too far。

The amount of BOD that must be XXX.XXX。

let's assume a "XXX: BOD ≤ 15mg/L。

SS ≤ 15mg/L。

and P ≤ 1mg/L.XXX-XXX。

Secondary treatment。

on the other hand。

is a logical process that XXX。

Finally。

XXX of physical。

logical。

and chemical XXX。

While there could have been nal effluent standards established。

we will focus on these three for XXX.The third step in XXX grit and sand。

These substances can cause damage to equipment such as pumps and flow meters。

so itis crucial to remove them。

The most common method for removing grit is through a grit chamber。

污水处理厂常见流程英文英文回答：Wastewater treatment is a process that aims to remove contaminants from wastewater before it is discharged back into the environment. The common flowchart of a wastewater treatment plant involves several stages:1. Preliminary Treatment: In this stage, large objects such as sticks, rags, and debris are removed from the wastewater using screens or grates. This helps to prevent damage to downstream equipment.2. Primary Treatment: During primary treatment, solid particles in the wastewater are settled and removed. This is typically done in large sedimentation tanks where gravity allows the heavier solids to settle at the bottom, forming a sludge layer. The clarified water, known as effluent, is then separated from the sludge.3. Secondary Treatment: The effluent from primary treatment still contains dissolved organic matter and nutrients that need to be further removed. Secondary treatment involves the use of microorganisms to break down and consume these contaminants. This can be achievedthrough various processes such as activated sludge,trickling filters, or rotating biological contactors.4. Tertiary Treatment: Sometimes, additional treatmentis required to meet specific water quality standards. Tertiary treatment processes include advanced filtration techniques such as sand filtration, membrane filtration, or disinfection methods like chlorination or ultraviolet (UV) radiation.5. Sludge Treatment: The sludge collected duringprimary and secondary treatment processes undergoes further treatment to reduce its volume and stabilize its content. This can be done through processes like anaerobic digestion, aerobic digestion, or mechanical dewatering. The treated sludge, known as biosolids, can then be used for land application or sent to a landfill.6. Disinfection: Before the treated wastewater is discharged into a receiving water body, it is often disinfected to eliminate any remaining pathogens. Chlorination, UV radiation, or ozonation are commonly used disinfection methods.7. Effluent Discharge: The final step in the wastewater treatment process is the discharge of the treated water, or effluent, into a river, lake, or ocean. Effluent quality must meet regulatory standards to ensure it does not harm the environment or public health.中文回答：污水处理是一种旨在在将废水排放回环境之前从废水中去除污染物的过程。

污水处理流程英语介绍Wastewater treatment is a crucial process for protecting the environment and public health by removing contaminants from sewage or industrial wastewater before it is released back into the environment. The wastewater treatment process typically involves several key steps:1. Preliminary Treatment: During this stage, large debris, such as sticks, leaves, and plastics, are removed from the wastewater through physical processes like screening and sedimentation.2. Primary Treatment: In the primary treatment stage, solids and organic matter are settled out of the wastewater through sedimentation. This process helps to remove a significant portion of the suspended solids and pollutants.3. Secondary Treatment: The secondary treatment stage involves biological processes where microorganisms break down organic matter in the wastewater. This step further reduces the concentration of organic pollutants and nutrients in the water.4. Tertiary Treatment: Tertiary treatment is the final stage of the wastewater treatment process, whereadditional treatment methods, such as filtration, disinfection, and nutrient removal, are employed to further improve the quality of the treated water.5. Discharge or Reuse: After undergoing the treatment process, the treated wastewater can be discharged into surface water bodies or reused for non-potable purposes like irrigation or industrial processes.Overall, the wastewater treatment process is essential for maintaining environmental sustainability and ensuring the safety of water resources. By effectively treating wastewater, we can protect ecosystems, prevent water pollution, and promote a healthier and cleaner environment.中文翻译：污水处理是一项关键的过程，通过将污水或工业废水中的污染物去除后再排放回环境中，以保护环境和公共卫生。

Study on Disinfection and Anti –microbial Technologies for Drinking WaterZHU Kun, FU Xiao Yong(Dept. of Environmental Engineering, LAN Zhou Railway University, LAN Zhou 730070, China)Abstract: Disinfection by-products produced by the reaction between chlorine and dissolved organic compounds and other chemicals are considered as a worrying problem in the drinking water treatment process since a series of mutagenic carcinogen substances are formed including trihalomethanes (THMs). Among the tested disinfectants(chlorine , ozone , chlorine dioxide , potassium permanganate , chloramines and hydrogen peroxide etc. ) , chlorine dioxide has proved to be the most feasible and effective oxidant for drinking water treatment and removal of pathogens due to its oxidation efficiency , low cost and simple way of utilization. A series of experiments indicate that chlorine dioxide can significantly restrain production of trihalomethanes (THMs) and control bacteria growth particularly for Cryptosporidium oocysts. The experiments verified that both ozone and chlorine dioxide are absolutely vital to ensure thtion of water storage are destroyed. The paper discusses oxidation capacity of chlorine dioxide, especially for removing petroleum compounds, which is affected by reaction time, gas injection way, and pH of treated water.Key words: disinfection; oxidants; water treatment; pathogens; chlorine dioxideCLC number: X523 Document code: A1 IntroductionChemical and filtration processes are two main methods used in China for treating drinking water meanwhile UV radiation has been used successfully for water treatment with relatively low flow rate. On the individual family level, usually chemical treatment is a feasible alternative. The following guidelines exist for the selection of suitablal of contaminants should be done by decomposition, evaporation or precipitation etc, to eliminate or decrease the toxicity, oxidants or reactionby-products should not be harmful to human health, and the purification processes should be practical and economical. The objective of this paper is to evaluate and discuss available disinfectants for drinking water treatment. The different disinfectants are compared regarding purification efficiencies and application approaches.2 Comparison ofO3 > ClO2 > HOCl > OCl - > NHCl2 > NH2ClReferring to Fiessinger′s [2] suggestion, the properties of these disinfectants are compared in Tab. 1. Chlorine is shown to be an excellent disinfectant to prevent waterborne diseases such as typhoid fever over long periods. Chlorine reacts not only within oxidation, but also by electrophilic substitution to produce a variety of chlorinated organic by - products, particularly trihalomethanes (THMs) and other mutagens. Here THMs mainly refer to chloroform, bromoform, dibromochloromathane and bromodichloromathane etc. Since the 1970`s, the usage of Cl2 in drinking water disinfection has been questioned with ozone being substituted as the preferred disinfectant in the water supply plants. But , ozone could not be introduced to the rural farmer community due to its high costs and short half - life (15～20 min. ) . As with other disinfectants, ozonation also leads to formation of organic by - product s such as aldehyde, ketones, and carboxylic acids, and also mutagenicity may be induced if bromic anion exists.Tab. 1 Comparison of various oxidants- no effect ; + little effect ; + + effect ; + + + largest effectMany studies have pointed out that disinfection is absolutely vital to ensure that any microorganisms arising from fecal contamination of water storage are destroyed. The selection of the available disinfectant s must concern to reduce risk from microbial contamination of drinking water and the potential increase in risk from chemical contamination that result from using any of the disinfectant s. The biocidal efficiency of commonly used disinfectants - ozone, chlorine dioxide, chlorine and chloramines are ranked almost with the same order as the oxidizing capacity, but the stability of those are following the order as [3]:Chloramines > Chlorine dioxide > Chlorine > Ozone3 Purification of organic pollutants by chlorine dioxideAccording to WHO guideline for drinking water quality, much consideration should be paid to benzene homologous compounds; therefore, the study on purification effect s of chlorine dioxide is focused on petrochemical pollutants. A series of experiment s were carried out to simulate the oxidation processes of contaminated water. The polluted solutions were prepared in a dark barrel (10L capacity) of seven kinds of benzene homologous compounds-Benzene , toluene , ethyl benzene , p-phenylmethane, o-phenylmethane, m-phenylmethane and styrene. Samples were taken to determine the initial concentration of the compounds prior to the test s. Standard chlorine dioxide solution was produced from sodium chlorite reacted with HCl solution of 10% [4]. The GR - 16A Gas - chromatograph with FID detector Shenyang LZ-2000 was used for measurement of Cl2, ClO2, ClO-2 and ClO-3[5]. Oil concentrations were determined with an UV -120-20 spectrophotometer (Shimadzu) following the procedure described by APHA [4]. Organic compounds in the water samples were measured with a GC-MS (QP-1000A). ClO2and O3were standardized by iodimetric titration at pH7.For the purpose of chemical disinfection for drinking water, chlorine was instantaneously ignored due to the formation of THMs and other mutagenic substances. The results indicated that potassium permanganate and hydrogen peroxide did not have enough oxidation capability to decompose petroleum contaminant s achieving only 46 %, and 5.7% decomposition of styrene, respectively. Ozone could not be selected due to it s high cost, complex operation and short half-life although it is an excellent oxidant for water treatment. Chlorine dioxide was the next most successful alternative for disinfection. The benefit s include-effective oxidation capacity, algicidal effect and negligible formation of halogenated by-products. Based on economic and operational requirement, the mixing gas method is easily used. The results obtained suggest that disinfection of drinking water with ozone and or chlorine dioxide seems to be a suitable alternatives to the use of NaClO for cont rolling the formation of non-volatile mutagens[6].In the laboratory experiments, the oxidants ozone, chlorine dioxide, potassium permanganate and the mixing gas (mainly contained ClO2 and a certain amount of Cl2, O3 and H2O2) were tested for removal of the petroleum compounds, and results are shown in Tab. 2.Tab. 2 Comparison of oxidation capacity for the various oxidantsA study was conducted to elucidate the decay pathway of monochloramine in thepresence and absence of natural organic matter (NOM) [7]. It was found that natural organic matter acted primarily as a reductant rather than catalyst. This conclusion was verified using a redox balance, and much of oxidizing capacity of monochloramine goes towards NOM oxidation. Cleaning agents and disinfectants from house keeping, hospitals, kitchens are sources of absorbable halogenated organic compounds (AOX) in municipal wastewater. The amount of AOX generated strongly depends on the nature and concentrations of dissolved and solid organic compounds, the concentration of active substances, temperature, pH and reaction time [8] When the mixing gases react with water molecules and organic micro-pollutants, hypochlorous acid is formed by chlorine, chlorite and chlorate ions are produced from chlorine dioxide in a series of redox reactions. The principal reactions are summarized as follows:ClO2+ organic →ClO -² + oxidized organic (1)2ClO -² + Cl2 = 2ClO2 + 2Cl - (2)2ClO -²+ HOCl = 2ClO2 + 2Cl - + OH- (3)2ClO2 + HOCl + H2O = 2ClO - ³ + HCl + 2H+ (4)The rate of chlorate yield can be described by Equation (5):d [ClO3]/ d t = 2 k [ClO2] [HOCl] (5)in which k = 1.28 M/ min at 25 ℃ [9].The stoichiometry of the undesirable reactions that form chlorate in low concentration of chlorite or presents of excess chlorine is given as:ClO -² + Cl2 + H2O = ClO - ³ + 2Cl - + 2H+ (6)ClO - ² + HOCl = ClO - ³ + Cl - + H+ (7)At alkaline conditions:ClO -² + HOCl + OH- = ClO - ³ + Cl - + H2O (8)Typically, chlorine dioxide is used in drinking water treatment and the concentrations are ranging from 0.1 to 2.0 mg/L [10]. However, the relevant by - products of chlorine dioxide treatment-chlorite and chlorate have been found to induce methemoglobinemia in the human body when concentrations are more than 100 mg/L [11]. The oxidation results of the organic contaminants were affected byreaction time. The initial concentrations and removal rate at different times are listed in Tab. 3. It is shown that chlorine dioxide has a very strong oxidation capability including the break down of the benzene ring. There are no other commonly used oxidants to do like this except for ozone.Tab. 3 Removal rate of tested organic compounds at different operating time (at pH7)The injecting method for chlorine dioxide gas into the solution also has an apparent influence on the removal rate. With the indirect method, the gas firstly was dissolved in a certain amount of distilled water, and then added to the tested organic solutions, as a result, removal rates appear lower than for the direct blowing method. The main reason for the difference is due to the conversion and decomposition of chlorine dioxide in the dissolving process before the reaction. It is confirmed from Tab. 3 that the removal rate was proportional to operating time. Since chlorine dioxide showed very strong oxidation capability for organic chemicals but was reduced to chlorite anion according to Equation (4), and the removal rate initially appeared quite high. Then, chlorite keeps the oxidation capacity at a level, which allows decomposition of the organic compounds to continue even though the oxidation reaction gradually became weaker with reaction time. The experiment indicated that pH values significantly influenced the removal rate of the organic compounds. The differences of degradation rates in a variety of pH through indirect input way areshown in Tab. 4.Tab. 4 Degradation rate of benzene homologous compounds with indirect method at different pH (after 15 min)There are, however, some disadvantages with ClO2, such as easy loss from solution due to volatilization, and disproportionation above pH 10 into chlorate and chlorite ions that are of certain oxidation capacity, but reported to be harmful to health if the concentration is too high. Chlorine dioxide was unstable in the solution even though it has a stronger oxidation capability than chlorite and chlorate as the two resulted in anions being dominant in the oxidation processes. The actual concentration of chlorine dioxide depended on the existence of chlorine, chlorite and chlorate whose concentrations were determined by pH values of the solution according to Equations (6) and (8) respectively. Consequently, the pH is the critical controlling factor in the concentrations of chlorine dioxide, chlorite and chlorate. The latter two harmful ions can be removed quite quickly by treatment with a reducing agent such as sulfur dioxide - sulfite ion at pH values of 5～7[10 ,12]. Fe (II) can be used to eliminate chlorite from the water , and the redox reaction is kinetically more rapid at pH 5～7 as well[13]. It was evident that the decomposition in acidic conditions was much better than that in alkaline conditions because a disproportional amount of chlorine dioxide was consumed by the reactions under alkaline conditions. For drinking water treatment, it has been suggested that the mixture of chlorine 0.8 mg/L and chlorinedioxide 0.5 mg/L will achieve disinfection and control THMs formation in preference to use of pure chlorine dioxide[14]. According to USEPA drinking water standard, the residue of ClO2 is limited as 0.8 mg/L that tends to the goal of 0.4 mg/L.4 Control of pathogens with disinfectantsHuman pathogens that are transmitted by water including bacteria, viruses and protozoa. Organisms transmitted by water usually grow in the intestinal tract and leave the body in the feces. Thus, they are infections. Fecal pollution of water supplies may then occur, and if the water is not properly treated, the pathogens enter a new host when the water is consumed, therefore, it may be infectious even if it contains only a small number of pathogenic organisms. Most outbreaks of waterborne diseases are due to breakdowns in treatment systems or are a result of post contamination in pipelines.The microorganisms of concern are those which can cause human discomfort, illness or diseases. These microbes are comprised of numerous pathogenic bacteria, viruses, certain algae and protozoa etc. The disinfection efficiency is typically measured as a specific level of cyst inactivation. Protozoan cysts are the most difficult to destroy. Bacteria and viral inactivation are considered adequate if the requirement for cyst inactivation is met. Therefore, water quality standard for the disinfection of water have been set at microorganisms, usually take the protozoan cysts as indicator, so viruses will be adequately controlled under the same operation conditions required for inactivation of protozoan cysts. The widely found drinking water contamination is caused by protozoan that is a significant intestinal pathogens in diary cattle, likely a source of this outbreak.There are two of the most important protozoa - Cryptosporidium and Giardia cysts those are known to outbreak diseases, frequently are found in nature and drinking water storage ponds. Protozoa form protective stages like oocysts that allow them to survive for long periods in water while waiting to be ingested by a host. Protozoa cysts are not effectively removed by storing water because of their small size and density. Cryptosporidium oocysts have a setting velocity of 0.5 um/s. Therefore, if the water tank is 2 m deep, it will take the oocyst 46 days to settle to thebottom. Giardia cysts are much large and have a great settling velocity of 5.5um/s. It was evident that chlorine and chloramines were ineffective against Cryptosporidium oocysts, which was discovered to be amazingly resistant to chlorine, and only ozone and chlorine dioxide may be suitable disinfectants [15]. The investigations have verified that Cryptosporidium is highly resistant to chorine, even up 14 times as resistant as the chlorine resistant Giardia, therefore methods for removing it in past rely on sedimentation and filtration. Watson′s Law to study protozoan disinfection, reads as follows:K = Cηt (9)In the formula:K ——constant for a given microorganism exposed to a disinfectant under a fixed set of pH and temperature conditions;C ——disinfectant concentration (mg/ L);η——empirical coefficient of dilution ;t ——time required to achieve the fixed percentage inactivation.For the preoxidation and reduction of organic pollutants , the recommended dosages are between 0. 5～2. 0 mg/ L with contact time as 15～30 min depending on the pollutants characteristics in the water. In the case of post - disinfection , the safe dosages of ClO2 are 0. 2～0.4 mg/L. At these dosages, the potential by - products chlorite and chlorate do not constitute any health hazard [16]. The relation between disinfectant concentration and contact time can be established by using Ct products based on the experimental data. From this the effectiveness of disinfectants can be evaluated based on temperature, pH value and contact time. Since Cryptosporidium has become a focus of regulatory agencies in the United States and United Kingdom, the prospects of controlling this pathogen show more considerable. The comparison of the Ct values by using ozone , chlorine dioxide , chlorine and chloramines for Giardia and Cryptosporidium cyst s are listed in Tab. 5[17 ,18 ] , and for some microorganisms disinfection are displayed in Tab. 6[19 ] .Tab. 5 Ct values (mg·min/ L.) for disinfection of Giardia and Cryptosporidium cysts by using 4 disinfectantsTab. 6 Comparison of value intervals for the product Ct (mg·min/ L) for the inactivation of various microorganisms by using 4 disinfectantsThe mean Ct value for ClO2 at pH 7 and 5 ℃was 11. 9 mg·min/ L, and dropped to 5.2 at pH 7 and 25 ℃. High temperatures normally enhance the efficiency of disinfectants while lower temperatures have opposite effects requiring additional contact time or extra quantity of disinfectants. The best performance for ClO2 is at pH 9 and 25 ℃, which yields a Ct product of 2.8 mg·min/ L [20]. Chlorine dioxide appears to be more efficient for Cryptosporidium oocysts than either chlorine or monochloramine. Exposure of oocysts to 1.3 mg·min/ L at pH 7 reduces excystation from 87 % to 5 % in a hour at 25 ℃. Based on this result, Ct product of 78 mg·min/ L was calculated. However, the Ct product for ozone to do this work was examined as 5 - 10 mg·min/ L from observation that excystation decreased from 84 % to 0 % after 5 minutes with the ozone concentration of 1 mg/ L [15]. As with other disinfectants, increasing temperature decreased the Ct values and improved the cysticidal action. Increasing temperature unexpectedly reduced the Ct values from a high of 6.35 mg·min/ L at pH5 to a low of 2.91 mg·min/ L at pH 9[20]. It is generally the rule, that for protozoa ozone is the best cysticide, chlorine dioxide is superior to chlorine andiodine, but chlorine, in overall, is much superior to chloramines [21].Although disinfection efficiency of ozone is higher than chlorine dioxide, this difference can be compensated by the contact time. The experiment indicated that chlorine dioxide could reach the same results for disinfection of coliform bacteria as ozone did if time lasted long enough, which can be seen in Fig. 1. The added concentrations of both of ozone and chlorine dioxide were 2 mg/ L.Control of Cryptosporidium oocysts in potable water requires an integrated multiple barrier approach. Coagulation is critical in the effective control of Cryptosporidium by clarification and filtration. Dissolved air floatation can achieve oocysts removal of 3 logs compared to about 1 log by sedimentation. Dissolved air floatation and filtration provide two effective barriers to Cryptosporidium oocysts with cumulative log removal of 4 to 5 compared to log removals of 3 to 4 by sedimentation and filtration [22].Fig. 1 Comparison of disinfection efficiency between ozone and chlorine dioxide on coliform bacteria5 Tendency of disinfection for drinking waterIn the future, the burden of producing water with low pathogen level and low tastes and odor will be allocated to a combination of steps, including source water protection, coagulation - flocculation - sedimentation, filtration, floatation, membrane processes and adsorption. Some form of terminal treatment with chlorine, chlorine dioxide, ozone, UV, or other agents will also be required. No single step can or should be expected to shoulder the entire burden to controlling a given contaminant. With the development of techniques, new chemical and physical agents will meet tests of practicability for use in water treatment and will reduce pathogens. These may include electromagnetic fields and other forms of treatment with light or sonic energy [23].In light of availability, efficacy, operability and costs, the priority should be given to ultraviolet method among all of the currently utilized disinfection technologies, particularly in developing countries. The medium and low - pressure UV extends tremendous potential promise for adaptation into various scale water supply plants. The researches have validated that extremely low dosage of UV can behighly effective for inactivate oocysts [24]. Furthermore, comparison of medium and low - pressure lamps demonstrated no significant differences. By using low - pressure UV at the dosage of 3 , 6 and 9 mJ/ cm2 , oocyst inactivation levels were yielded between 3.4 and 3.7 log. In the trials of UV in water with turbidity of more than 1 NTU, the ability of medium –pressure was not affected, and high level of oocysts inactivation could still be achieved.6 ConclusionsTo purify drinking water, chlorine dioxide can be chosen instead of chlorine, ozone and other disinfectants because of it s advantages of high efficiency of disinfection, competent stability, low cost and simple utilizing way etc. Both ozone and ClO2 are absolutely vital to ensure that any microorganisms arising from fecal contamination of water storage are destroyed. The utilization of chlorine dioxide has been found to efficiently restrict protozoa growth, to disinfect from bacteria and viruses. Taking the protozoan cysts as indicator in which Cryptosporidium oocysts were solidly resistant to chlorine, but chlorine dioxide may be suitable disinfectants to mutilate. Thus, viruses will be adequately controlled by chlorine dioxide under the same operation conditions required for inactivation of protozoan cysts. The experiment indicated that chlorine dioxide could reach the same results for disinfection of coliform bacteria as ozone did if time lasted long enough although disinfection efficiency of ozone is higher than chlorine dioxide.It is an obvious preference for chlorine dioxide to pragmatically remove oil and benzene homologous compounds in water treatment meanwhile the formation of mutagenic and toxic substances is limited. The degradation rate was proportional to input amount of oxidants and increase of operating time. The dosage input , in overall , is suggested to range between 0. 5～2.0 mg/ L. The effective pH at which reactions occur is in the slightly acid range of 5 to 7 at which formation of chlorite and chlorate is minimized. The chlorine dioxide gas should be injected directly into the treated water body, so that high concentrations of ClO2 can be kept in the solution. Under these conditions, the elimination rate for organic pollutants will be much higher. For the storage system, input dosage of chlorine dioxide concentration should be higherthan that in laboratory studies due to complex pollutants in treated water. References:[1 ] Katz J . Ozone and chlorine dioxide technology for disinfection of drinking water [M]. Noyes New Jersey: Data Corporation, 1980.[2] Fiessinger F. Organic micropollutants in drinking water and health [M] . Publisher, N. Y., U. S. A: Elsevier Sci., 1985.[3 ] Hoff J C , Geldreich E E. Comparison of the biocidal efficiency of alternative disinfectants [C] . In Proceedings AWWA seminar, Atlanta, Georgia, 1980.[4 ] APHA , American Public Health Association. American Water Works Association and Water Pollution Control Federation. Standard Methods for the Examination of Water and Wastewater. (16th Edition) [M]. Washington D. C., 1989.[5] Dietrich A M. Determination of chlorite and chlorate in chlorinated and chloraminated drinking water by flow injection analysis and ion chromatography[J ] .A nal. Chem., 1992, 64:496 - 502.[6] Monarca S. Mutagenicity of extracts of lake drinking water treated with different disinfectants in bacterial and plant tests[J ] . Water Res, 1998, (32):2 689 - 2 695.[7] Vikesland P , Ozekin K, Valentine R L. Effect of natural organic matter on monochloramine decomposition : pathway elucidation through the use of mass and redox balance[J ] . Envi ron. Sci. Tech., 1998, 32 (10):1 409 - 1 416.[8] Schulz S , Hahn H H. Generation of halogenated organic compounds in municipal wastewater [M] . Proc. 2nd Int. Assoc. Water Qual. Int. Conf. Sewer Phys. Chem. Bio. Reactor, Aalborg, Denmark, 1998.[9 ] Aieta E M. A review of chlorine dioxide in drinking water treatment [J]. J. A WWA, 1986, 78 (6): 62 - 72.[10 ] Gordon G Minimizing chlorine ion and chlorate ion in water treatment with chlorine dioxide[J ] . J. A WWA, 1990, 82 (4):160 - 165.[11] Kmorita J D , Snoeyink V L. Monochloramine removal from water by activated carbon[J ] . J. A WWA, 1985, (1):62 - 64.[12] Gordon G, Adam I , Bubnis B. Minimizing chlorate information[J ] . J. AWWA, 1995, 87, (6): 97 - 106.[13] Iatrou A. Removing chlorite by the addition of ferrous iron[J ] . J. A WWA, 1992, 84 (11): 63 - 68.[14 ] Schalekamp Maarten. Pre - and intermediate oxidation of drinking water with ozone, chlorine and chlorine dioxide [J]. J. Ozone Science and Engineering, 1986, 8: 151 - 186[15 ] Korich D G, Mead J R , Madore M S , et al . Effects of ozone, chlorine dioxide, chlorine and monochramine on Cryptosporidium parvum oosyst viability [J]. Applied and Environmental Microbiology, 1990, 56: 1 423 - 1 428.[16 ] AWWA Research Foundation. Chlorine dioxide; drinking water issues, 2nd International Symposium [R]. Houston, TX, 1992.[17] Lykins B W, Griese H G. Using chlorine dioxide for trihalomethane control[J ] . J, A WWA, 1986, 71 (6): 88 - 93.[18] Regli S. Chlorine dioxide , drinking water issues , 2nd International Symposium [ R ] . Houston, TX, AWWA Research Foundation, 1992.[19] Hoff J C. Inactivation of microbial agents by chemical disinfectants[J] . US EPA, 1986.[ 20 ] Rubin A , Evers D , Eyman C , et al . Interaction of gerbil - cultured Giardia lamblia cysts by free chlorine dioxide [J]. Applied and Envi ronmental Microbiology, 1989, 55: 2 592 - 2 594.[ 21 ] Rusell A D , Hugo WB , Ayliffe GA J . Principes and Practice of Disinfection [M]. Preservation and Sterilization. Blackwell Scientific Publications, Oxford, U K, 1992.[22 ] Edzwald J K, Kelley M B. Control of Cryptosporidium from reservoirs to clarifiers to filters [C] . Proc. 1st IAWQ –IWSA Joint Specialist Conf. Reservoir Manage. Water Supply, Prague, Czech, 1998.[23] Haas Charles N. Disinfection in the Twenty - first century[J ] . J. A WWA, 2000, 92 (2): 72 - 73.[24 ] Clancy L , Jenneifer , Bukhari Z , et al , Using UV to Inactivate Gryptosporidium[J ] . J. A WWA, 2000, 92: 97 - 104.饮用水的消毒及杀菌技术研究朱琨伏小勇(兰州铁道学院环境工程系, 甘肃兰州730070)摘要:饮用水处理消毒过程中可产生一系列致癌物质,主要是氯与水中的有机物和其它化学成分反应的结果,其中典型产物有三氯甲烷. 通过对常用消毒剂液氯,臭氧,二氧化氯,高锰酸钾,氯胺及过氧化氢的实验对比,证明二氧化氯是高效,方便,廉价的消毒剂. 它不仅对一般病原菌类有明显的抑制和杀菌作用,对清除难以灭杀的潜原性病毒也有理想的效果. 在净化水中石油类有机物时,二氧化氯的效果受到反应时间,注入方式和pH 值的影响.关键词:消毒;氧化剂;水处理;病原菌;二氧化氯中图分类号:X523 文献标识码:A中文译文：饮用水消毒和杀菌技术的研究朱琨伏小勇（兰州铁道学院环境工程系，甘肃兰州，730070 中国）在饮用水处理过程中，通过氯与溶解性有机物和其他化合物的反应所产生的消毒副产物被看作一个令人担忧的问题，因为一系列诱变致癌的物质组成包括总卤甲烷。

aao污水处理工艺外文文献译文Recent Upgrades to Aerobic Activated Sludge Treatment for Sewage (AAO)最近污水激活液体处理技术(AAO)的升级近年来，汉语激活液体处理技术(AAO)被广泛地应用于各种废水污水处理系统，特别是在有机物的分解过程中发挥了重要作用。

这种处理技术根据有机化合物的溶解及二氧化碳的气态收集，能够有效地帮助减少污染物的总量和质量。

而近些年来随着现代技术的发展，AAO处理技术也开始得到改良和更新。

Firstly, the science and technology surrounding AAO has been subject to a numberof improvements. For instance, there have been updates to the wastewater treatment process which have resulted in a more efficient removal of nitrogen and phosphorus with fewer risks of sludge build-up. This means that AAO systems can now be applied to a wider range of wastewater applications. In addition, new measuring systems have been developed to monitor the performance of AAO systems more precisely. This has opened up the possibility of making adjustments to the optimal parameters, which can help to ensure that the outcome of the process is as effective as possible.RR先后，AAO 技术围绕的科学技术也被进行了一系列的改进。

Biological Wastewater TreatmentThis is a brief summary of the various techniques that have been developed to treatwastewater by biological means. They accomplish what is generally called secondary treatment.Purpose:The idea behind all biological methods of wastewater treatment is to introduce contactwith bacteria (cells), which feed on the organic materials in the wastewater, therebyreducing its BOD content. In other words, the purpose of biological treatment is BODreduction.Typically, wastewater enters the treatment plant with a BOD higher than 200 mg/L, but primary settling has already reduced it to about 150 mg/L by the time it enters thebiological component of the system. It needs to exit with a BOD content no higher than about 20-30 mg/L, so that after dilution in the nearby receiving water body (river, lake), the BOD is less than 2-3 mg/L. Thus, the biological treatment needs to accomplish a 6-fold decrease in BOD.Principle:Simple bacteria (cells) eat the organic material prese nt in the wastewater. Through their metabolism, the organic material is transformed into cellular mass, which is no longer in solution but can be precipitated at the bottom of a settling tank or retained as slime on solid surfaces or vegetation in the system. The water exiting the system is then much clearer than it entered it.A key factor is the operation of any biological system is an adequate supply of oxygen.Indeed, cells need not only organic material as food but also oxygen to breathe, just like humans. Without an adequate supply of oxygen, the biological degradation of the waste is slowed down, thereby requiring a longer residency time of the water in the system. For a given flowrate of water to be treated, this translates into a system with a larger volume and thus taking more space. Advantages:Like all biological systems, operation takes place at ambient temperature. There is noneed to heat or cool the water, which saves on energy consumption. Because wastewater treatment operations take much space, they are located outdoor, and this implies that the system must be able to operate at seasonally varying temperatures. Cells come in a mix of many types, and accommodation to a temperature change is simply accomplished by self adaptation of the cell population.Similarly, a change in composition of the organic material (due to people’s changingactivities) leads to a spontaneous change in cell population, with the types best suited to digest the new material growing in larger numbers than other cell types.Types of equipment for biological treatment:There are two broad types of biological wastewater treatment: those that includemechanical means to create contact between wastewater, cells and oxygen, and those than don’t.a) With mechanical means:1. Activated sludge: This is the most common type. It consists in a set of two basins. In the first, air is pumped through perforated pipes at the bottom of the basin, air rises through the water in the form of many small bubbles. These bubbles accomplish two things: they provide oxygen form the air to the water and create highly turbulent conditions that favor intimate contact between cells, the organic material in the water and oxygen. The second basin is a settling tank, where water flow is made to be very quiet so that the cellular material may be removed by gravitational settling. Some of the cell material collected at the bottom is captured and fed back into the first basin to seed the process. The rest is treated anaerobically (= without oxygen) until it is transformed into a compost-type material (like soil).The cost of an activated-sludge system is chiefly due to the energy required to pump air at high pressure at the bottom of the aerator tank (to overcome the hydrostatic pressure of the water). Another disadvantage is that the operation is accomplished in two separate basins, thereby occupying a substantial amount of real estate.2. Trickling filter: A trickling filter consists in a bed of fist-size rocks over which thewastewater is gently sprayed by a rotating arm. Slime (fungi, algae) develops on the rock surface, growing by intercepting organic material from the water as it trickles down. Since the water layer passing over the rocks makes thin sheets, there is good contact with air and cells are effectively oxygenated.Worms and insects living in this “ecosystem” also contribute to removal of organic material from the water. The slime periodically slides off the rocks and is collected at the bottom of the system, where it is removed. Water needs to be trickled several times over the rocks before it is sufficiently cleaned. Multiple spraying also provides a way to keep the biological slimes from drying out in hours of low-flow conditions (ex. at night). Plastic nets are gradually replacing rocks in newer versions of this system, providing more surface area per volume, thereby reducing the size of the equipment.3. Biological contactor: This is essentially a variation on the trickling filter, with thedifference being that solid material on which slime grows is brought to the water rather than water being brought to it. Rotating disks alternate exposure between air and water.b) Without mechanical means:The wastewater is made to flow by gravity through a specially constructed wetland.There, the water is brought into close contact with vegetation (ex. reeds), which acts as a biological filter to the water. The organic material in the wastewater is used as nutrient by the plants. Oxygen supply is passively accomplished by surface aeration (contact with oxygen of the atmosphere). Since water flow is slow in such system, to give ample time for the biological activity to take place, there is almost no turbulence in the water and reaeration is weak. Compared to mechanical systems, constructed wetlands occupy far more real estate, but they may be aesthetically pleasing, especially if they are well integrated in the local landscape. They emit no odor, but people should stay away because of the danger posed by pathogens. Constructed wetlands have also the least energy requirement. Energy is only needed to pump the wastewater to the entrance of the system, from where gravity and biology do the rest. A major disadvantage, however, is the highly reduced performance during winter, especially in regions where ground freezes during some of the winter months.。

污水处理流程(中英文)修改污水处理流程Wastewater Treatment Process引言概述：污水处理是一项重要的环境保护工作，通过对污水进行处理，可以有效减少对环境的污染，保护水资源的可持续利用。

本文将详细介绍污水处理的流程，包括五个大点，每个大点下分3-5个小点进行详细阐述。

正文内容：一、预处理阶段1.1 污水收集：收集来自居民区、工业区和商业区的污水。

1.2 筛选：通过格栅筛选，去除大颗粒的固体物质，如树叶、纸张等。

二、初级处理阶段2.1 沉淀：将污水放置在沉淀池中，通过重力作用，固体颗粒沉淀到污泥层。

2.2 气浮：利用气体的浮力原理，将浮性固体物质从污水中分离出来。

2.3 沉淀池：将沉淀后的污泥与污水分离，使得污泥沉淀到底部，清水上升到上层。

三、中级处理阶段3.1 活性污泥法：将污水与含有微生物的活性污泥混合，微生物分解有机物质，减少水中的污染物。

3.2 厌氧消化：将污泥暴露在无氧环境中，通过细菌分解污泥中的有机物质，产生沼气。

3.3 植物处理：利用植物的吸收作用，将水中的营养物质吸收，净化水质。

四、高级处理阶段4.1 活性炭吸附：利用活性炭对水中的有机物质进行吸附，进一步净化水质。

4.2 膜过滤：通过微孔膜过滤，去除水中的微小颗粒和细菌。

4.3 紫外线消毒：利用紫外线照射，杀灭水中的细菌和病毒，确保水质安全。

五、终级处理阶段5.1 除磷除氮：通过化学反应，去除水中的磷和氮，减少对水体的富营养化。

5.2 脱盐：利用逆渗透等技术，去除水中的盐分，使其适合特定用途，如工业用水或饮用水。

5.3 水体深度处理：将处理后的水体排放到河流或海洋中，经过水体深度处理，确保对环境没有二次污染。

总结：通过预处理、初级处理、中级处理、高级处理和终级处理等阶段，污水处理流程能够有效去除水中的固体颗粒、有机物质和细菌等污染物，保护水资源的可持续利用。

污水处理是一项重要的环境保护工作，对于维护生态平衡和保护人类健康具有重要意义。

污水处理流程(中英文)修改Title: Wastewater Treatment ProcessIntroduction:Wastewater treatment is an essential process to protect the environment and public health. It involves a series of steps to remove pollutants from wastewater before it is discharged back into the environment. In this article, we will discuss the wastewater treatment process in detail.正文内容：一、 Preliminary Treatment1.1 Screening: The first step in wastewater treatment is screening, where large objects such as sticks, rocks, and plastics are removed from the wastewater.1.2 Grit Removal: After screening, the wastewater goes through a grit chamber where sand, gravel, and other heavy particles are settled out.1.3 Primary Sedimentation: In this step, the wastewater is held in a tank where suspended solids settle to the bottom and fats, oils, and grease float to the surface.二、 Secondary Treatment2.1 Biological Treatment: In the secondary treatment process, microorganisms are used to break down organic matter in the wastewater.2.2 Aeration: Aeration tanks are used to provide oxygen to the microorganisms, allowing them to thrive and continue breaking down pollutants.2.3 Clarification: After the biological treatment, the wastewater is passed through a clarifier where the remaining solids settle out.三、 Tertiary Treatment3.1 Filtration: In the tertiary treatment process, the wastewater is passed through filters to remove any remaining suspended solids.3.2 Disinfection: To kill any remaining pathogens in the wastewater, disinfection methods such as chlorination or ultraviolet light are used.3.3 Nutrient Removal: Some wastewater treatment plants also remove excess nutrients such as nitrogen and phosphorus to prevent eutrophication in receiving waters.四、 Sludge Treatment4.1 Thickening: The sludge produced during the treatment process is thickened to reduce its volume.4.2 Digestion: The thickened sludge is then anaerobically digested to break down organic matter and reduce pathogens.4.3 Dewatering: The digested sludge is dewatered using centrifuges or filter presses to remove excess water before disposal.五、 Discharge and Reuse5.1 Discharge: After the treatment process is complete, the treated wastewater is discharged back into the environment through a designated outfall.5.2 Reuse: In some cases, treated wastewater can be reused for irrigation, industrial processes, or even drinking water after additional treatment.5.3 Monitoring: Wastewater treatment plants continuously monitor the quality of the treated effluent to ensure it meets regulatory standards before discharge.Conclusion:The wastewater treatment process is a complex series of steps designed to remove pollutants from wastewater and protect the environment. By following these steps carefully, wastewater treatment plants can ensure that the water they discharge back into the environment is clean and safe for both humans and wildlife.。

Aerobic treatment of dairy wastewater with sequencing batch reactor systemsXiujin Li,Ruihong ZhangAbstract Performances of single-stage and two-stage se-quencing batch reactor(SBR)systems were investigated for treating dairy wastewater.A single-stage SBR system was tested with10,000mg/l chemical oxygen demand (COD)influent at three hydraulic retention times(HRTs) of1,2,and3days and20,000mg/l COD influent at four HRTs of1,2,3,and4days.A1-day HRT was foundsufficient for treating10,000-mg/l COD wastewater,with the removal efficiency of80.2%COD,63.4%total solids, 66.2%volatile solids,75%total Kjeldahl nitrogen,and 38.3%total nitrogen from the liquid effluent.Two-day HRT was believed sufficient for treating20,000-mg/l COD dairy wastewater if complete ammonia oxidation is not desired.However,4-day HRT needs to be used for achieving complete ammonia oxidation.A two-stage sys-tem consisting of an SBR and a complete-mix biofilm re-actor was capable of achieving complete ammonia oxidation and comparable carbon,solids,and nitrogen removal while using at least1/3less HRT as compared to the single SBR system.Keywords Aerobic,dairy,wastewater,sequencing batch reactor1IntroductionDairy wastewater is currently disposed of mainly through land application with little or no pretreatment in Califor-nia in the United States.Due to increasing awareness of the general public about potential adverse impact of ani-mal wastes on environmental quality and recent develop-ments in environmental regulations for gaseous-emission control and nutrient management,alternative wastewater treatment methods become attractive options for dairy producers.A sequencing batch reactor(SBR)is a biolog-ical treatment reactor that uses aerobic bacteria to degrade organic carbon and remove nitrogen present in the wastewater.If designed and operated properly,it maybecome a promising alternative for treating animal wastewater to control odors and reduce solids and nutrient contents.The SBR treats wastewater in small batches andfits wellwith most animal wastewater collection systems.It is atime-oriented system and operates over repeated cycles offive phases–fill,react,settle,decant,and idle.The major factors that control the performance of SBRs include or-ganic loading rate,hydraulic retention time(HRT),solids retention time(SRT),dissolved oxygen(DO),and influent characteristics such as chemical oxygen demand(COD),solids content,and carbon-to-nitrogen ratio(C/N),etc. Depending on how these parameters are controlled,theSBR can be designed to have one or more of these func-tions:carbon oxidation,nitrification,and denitrification[1,2].Carbon oxidation and denitrification are carried outby heterotrophic bacteria and nitrification is by auto-trophic bacteria.The SBR has been successfully used in the treatment of municipal and industrial wastewater,wherethe high treatment performance resulted in excellent ef-fluent quality[3,4].It is considered to be a suitable systemfor wastewater treatment applications in small communi-ties[5].The SBR is a relatively new technology for agri-cultural applications.Previous research on the SBR foranimal waste was primarily concentrated on swine wastewater treatment.Several researchers[6,7,8]re-ported the performance of SBR in treating swine waste-water with COD and suspended solids(SS)in the range of1,614–2,826mg/l and175–3,824mg/l,respectively.Satis-factory removal of COD and SS from the wastewater was achieved with HRTs of22–30h.Fernades et al.[9]studiedthe SBR for treating highly concentrated swine manurewith about4%total solids(TS).The influent COD,NH3-N,and total Kjeldahl nitrogen(TKN)were as high as31,175mg/l,1,265mg/l,and2,580mg/l,respectively.Their results indicated that above97%COD,99%NH3-N,and93%TKN removal efficiencies were achieved in theliquid effluent at HRTs of6and9days and SRT of over20days.Tam et al.[10]researched SBR for treatment of wastewater from a milking center and reported that the wastewater with919–1,330mg/l COD and15–37mg/lNH3-N could be successfully treated with a HRT of20h. Bioprocess Biosyst Eng25(2002)103–109DOI10.1007/s00449-002-0286-9103Received:2October2001/Accepted:6February2002 Published online:5April2002ÓSpringer-Verlag2002X.Li(&)Department of Environmental Engineering,Beijing University of Chemical Technology,100029,Beijing,ChinaE-mail:lxiujin@Tel.:+86-010-********Fax:+86-010-********R.ZhangBiological and Agricultural Engineering Department, University of California at Davis,CA95616,USAThis research was supported in part by the California Energy Commission and the Agricultural Experiment Station of the University of California,Davis,USA.Studies on the SBR for treating dairy manure are not well documented in the literature.Previous researchfindings about the SBR for treatment of swine manure and other types of wastewater provide valuable references for the treatment of dairy wastewater.However,due to the dif-ferences in the characteristics of dairy wastewater from other types of wastewater,research is needed to develop design and operational guidelines for the SBR in treating dairy wastewater of various characteristics.The objectives of this study are to investigate the effects of wastewater characteristics,HRT,SRT,and organic loading rate on the performance of the SBR system in treating dairy wastewater for carbon and solids removal and nitrogen conversion,and develop design and opera-tional guidelines for the SBR system in single-and mul-tiple-stage configurations.2Materials and methods2.1Dairy manure collection and preparationDairy manure was collected on the Dairy Research Farm of the University of California at Davis.Due to runoff of urine on the feedlot,the collected manure was mainly feces and contained a relatively low content of ammonia nitro-gen.The manure was slurried with addition of water and then screened twice with two sieves with openings of4·4 and2·2mm,respectively,to remove large particles.The screened manure was transported immediately to the laboratory and stored in a freezer at–20°C until use.The TS and COD of the screened manure were30,000–40,000mg/l and35,000–50,000mg/l,respectively.When needed,the stored manure was thawed and then diluted with tap water to obtain a desired COD concentration.Due to relatively low ammonia content of the raw manure as compared to typical levels in the manure collected on dairy farms,urea was added to increase the NH3-N in the prepared manure from100–125mg/l to500–550mg/l.The prepared manure was then put into a50-l feeding tank housed in a refrigerator at4°C for daily use.The feeding tank had an agitator to mix the wastewater during the feeding of the reactors.2.2Experimental setup and operationBoth single-stage and two-stage treatment systems were tested.The single-stage SBR system consisted of an SBR and a solids-settling tank in series.The wastewater wasfirst fed into the SBR for treatment and the effluent of the SBR, including both sludge and liquid,was then discharged into a settling tank,where liquid was separated from sludge by gravity settling and characterized as liquid effluent of the system.The two-stage system consisted of an SBR(first-stage reactor),a solids-settling tank,and a complete-mix biofilm reactor(CMBR)(second-stage reactor)connected in series.The liquid effluent obtained from the solids-set-tling tank was used as influent of CMBR and further treated in the CMBR for achieving complete nitrification.The two-stage SBR-CMBR system is shown in Fig.1.Each system was fed and decanted twice a day for12h in each treatment cycle.All the peristaltic pumps used for feeding and decanting were operated automatically with a digital time controller.The time sequence for different operations during each treatment cycle of the SBR was1–3minfill,11h and4–8min react,40min settle,1–3min decant,and10min idle.The CMBR was operated as a complete-mix reactor and had long SRT provided by the attached growth on the polyethylene pellets placed in the reactor.The plastic pellets had light density(920kg/ m3)and were keptfluidized with the airflow.Each pellet was10mm in diameter and10mm in height,with a cross inside the cylinder and longitudinalfins on the outside, providing a large surface area for bacterial attachment. Thefilling volume of the pellets in total occupied ap-proximately18%of liquid volume(3l)in the reactor.The SBR and CMBR reactors were made from trans-parent acrylic and had a total volume of6l each,with51cm height and12cm diameter.During testing,the liquid vol-ume of each reactor was3l.Each reactor was aerated using pressurized air at a controlledflow rate.In order to mini-mize the water evaporation in the reactor,the air was hu-midified by traveling through water contained in a15-l jar prior to entering the reactor.The air was evenly distributed into the wastewater through four air stone diffusers in-stalled near the bottom of the reactor.All the reactors were initially seeded with the activated sludge obtained from the UC Davis Wastewater Treatment Plant and allowed to ac-climate for about2months before formal experiments were started.It normally took about4weeks for each SBR re-actor to reach a steady state when a new operating condi-tion was introduced.The steady state was defined to be a state when the weekly variations of effluent COD,TS,NH3-N,and pH were less than5%.These parameters were monitored twice a week.The CMBR had been fully accli-mated with dilute dairy wastewater for about6months and had nitrification bacteria well established before being connected with the SBR.The mixed liquor suspended solids (MLSS)in the CMBR was about10,000mg/l,which was calculated from both suspended growth and attached growth solids.In order to determine the ammonia emission from SBR due to aeration,ammonia in the exiting air of SBR was collected by absorbing it in0.3N boric acid solution for 24h under each testing condition.2.3Experimental plan and system performance evaluation The experiment was carried out in two phases.Thefirst phase was for studying the effects of influent characteris-tics,HRT,and corresponding SRT and loading rate on the performance of the single-stage SBR system.The second phase was to evaluate the performance of a two-stage SBR-CMBR system.The two systems were then compared in terms of carbon and solids removal and nitrogen conver-sion efficiencies.With the single-stage SBR system,three HRTs(1,2and 3days)were tested for wastewater of10,000mg/l COD and four HRTs(1,2,3and4days)for wastewater of20,000mg/l COD.For the wastewater of10,000mg/l COD, the corresponding loading rate and SRT for the three HRTs were10,5,and3.3g COD/l/day and8,12,andBioprocess Biosyst Eng25(2002) 10415days,respectively.For the wastewater of 20,000mg/l COD,the corresponding loading rate and SRT for the four HRTs were 20,10,6.7,and 5g COD/l/day and 1.5,3,4,and 6days,respectively.With the two-stage SBR system,2days was used first as the system HRT,with 1day for the first-stage and 1day for the second-stage for both in flu-ents,and then 2.5days was used with 2days for the first stage and 0.5days for the second stage.An air flow rate of 4l/min was applied for all runs,which was able to main-tain dissolved oxygen (DO)in the SBR and CMBR above 3mg/l.The performance of the treatment systems was evalu-ated in terms of carbon and solids removal and nitrogen conversion ef ficiencies.The parameters analyzed included TS,volatile solids (VS),COD,SCOD (soluble COD),TKN,NH 3-N,NO 2-N,and NO 3-N.Two kinds of removal/con-version ef ficiencies were used to interpret the results for carbon and solids removal and nitrogen oxidation.One ef ficiency,E t ,is based on the removal from total ef fluent (including both sludge and liquid ef fluent generated),re-flecting the removal ef ficiency through biological process alone.The other ef ficiency,E l ,was based on the removal from liquid ef fluent,i.e.,supernatant,representing the removal ef ficiency through both biological process and sludge separation.For the single-stage SBR system,the total ef fluent was the ef fluent from the SBR and the liquid ef fluent was the supernatant decanted from the solids settling tank.For the two-stage SBR-CMBR system,the total ef fluent was the combination of sludge from the settling tank and the final ef fluent from CMBR,and the liquid ef fluent was the liquid ef fluent of CMBR.Most of previous research only reports removal ef ficiency from liquid ef fluent (E l ).Actually,E l does not re flect the real capability of a system for removing various constituents from wastewater,because part of these constituents are contained in the sludge that is separated from the liquid ef fluent and discharged as a separate sludge stream.Therefore,E t needs to be used in order to assess the real capability of a system for removing various constituents from wastewater.2.4Sampling and analytical methodsAfter each reactor reached steady state under testing conditions,samples were taken from the in fluent,mixed liquor,total ef fluent,and liquid ef fluent of the reactor three times a week (every other day)for analyses of COD,SCOD,TS,VS,NH 3-N,NO 2-N,NO 3-N,and TKN.The re-moval ef ficiencies,E l and E t ,were calculated based on the data from in fluent,liquid ef fluent,and total ef fluent of the systems.The separation of sludge and liquid in the total ef fluent of the SBR was performed by settling the ef fluent in a 1-l graduated cylinder for 2h and then decanting the liquid fraction above the sludge-liquid interface line.The COD,SCOD,TS,VS,and TKN were measured according to APHA standard methods [11].The COD measured in this study was COD Cr .The pH was measured with an Accumet pH meter (Fisher Scienti fic,Pittsburgh,Pa.).The NH 3-N was measured with a gas-sensing elec-trode and the pH meter.The DO in the reactors wasmonitored on a daily basis with a DO meter (YSI Mode158,Fisher Scienti fic,Pittsburgh,Pa.).The NO 2-N was analyzed with the HACH method,using a DR/2000spectropho-tometer [12].The NO 3-N was measured with a diffusion –conductivity analyzer [13].3Results and discussion3.1Performance of the single-stage SBR system3.1.1Removal of carbon and solidsThe performance data of the SBR for 10,000mg/l COD in fluent COD of 10,000are shown in Table 1.With the increase of HRT from 1to 3days,the COD,SCOD,TS,and VS in the liquid ef fluent became lower,yielding better ef fluent quality due to increased biological conversion and improved sludge settleability,as indicated by the increased removal ef ficiencies (E l and E t ).However,there wasnoboratory setup for a two-stage SBR-CMBR system for dairy wastewater treatmentX.Li,R.Zhang:Aerobic treatment of dairy wastewater with sequencing batch reactor systems105signi ficant difference in terms of carbon and solids rem-ovals and liquid ef fluent quality for the three HRTs.For example,the increase of COD and TS removal ef ficiency E l was 5.1%and 0.3%,and E t was 5.7%and 2.0%,respec-tively,when HRT increased from 1to 3days.Therefore,1-day HRT was believed to be suf ficient for treating the dairy wastewater with 10,000mg/l COD for its satisfactory removal ef ficiency and relatively short HRT.At 1-day HRT,the removal ef ficiency from the liquid ef fluent (E l )was 80.2%for COD,63.4%for TS,and 66.2%for VS.These removals were due to both biological conversion in the SBR and sludge separation in the solids-settling tank.The removal due to biological conversion alone in the SBR,as measured by E t ,was 45.0%for COD,21.4%for TS,and 34.2%for VS.E t was signi ficantly greater than E l ,sug-gesting that the sludge separation after SBR treatment is necessary for achieving signi ficant carbon and solids re-moval from the dairy wastewater.It was found that aerobic treatment greatly enhanced the flocculation and settlea-bility of the solids in the wastewater.Good settleability of sludge was important for achieving high carbon and solids removal ef ficiency.The performance data of the SBR for 20,000mg/l COD in fluent are shown in Table 2.The 1-day HRT was tested first.It was found that it was impossible to control the SRT at a desired level due to fast solids buildup in the reactor and poor solids settleability.When the HRT was increased to 2days,there was signi ficant improvement in the ef fluent quality and increase of removal ef ficiencies.However,when the HRT was further increased to 3days,the changes in the ef fluent quality,COD,and solids removals were not signif-icant.Therefore,2-day HRT was considered enough for COD and solids removal for 20,000mg/l COD in fluent due to its relatively short retention time and high removal ef fi-ciency.At 2-day HRT,the removal ef ficiency E l of COD,SCOD,TS,and VS was 85.7%,67.1%,71.0%,and 70.6%,respectively,and E t was 35.9%,67.1%,22.8%,and 25.6%,respectively.The 4-day HRT was tested for achieving com-plete ammonia conversion.Since ammonia was not com-pletely converted at 2-day and 3-day HRT,longer HRT was needed when complete nitri fication was desired.This will be further discussed in the following nitrogen removal section.The sludge separated from the ef fluent of the SBR contained 4.1–5.9%TS.The lower in fluent COD(10,000mg/l)resulted in better sludge settleability than the higher in fluent COD (20,000mg/l).The sludge volume as the fraction of total ef fluent volume was 5–6%and 13–16%for the lower and higher levels of in fluent COD,respectively.The sludge was composed of not-degraded solids in the wastewater and newly formed bacterial cells.It can be further processed into organic soil amendment through dewatering and composting.Table 1.Ef fluent quality and treatment ef ficiencies of SBR for 10,000mg/l COD in fluentParametersIn fluent (mg/l)1-day HRT 2-day HRT3-day HRT Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)COD 10,0001,9806,50080.245.01,5805,13084.248.71,4704,93085.350.7SCOD 2,9141,4571,45750.050.01,4511,45150.250.21,4281,42851.051.0TS 6,6562,4365,23263.421.42,4765,07962.823.72,4165,09863.723.4VS 5,1081,7243,36166.234.21,5323,24970.036.41,4003,16772.638.0TKN 7801953657553.218535476.354.616533878.856.7TN 78048160738.322.248059838.523.447459639.223.6NH 3-N 51012012076.576.510510579.479.4707086.386.3NO 3-N 0375545NO 2-N 024*******pH8.16.86.76.7Table 2.Ef fluent quality and treatment ef ficiencies of SBR for 20,000mg/l COD in fluentPara-meters In fluent (mg/l)1-day HRT 2-day HRT 3-day HRT 4-day HRTLiquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)COD 20,0004,30013,92078.530.42,87012,82085.735.92,66012,32086.738.4167010,90091.743.3SCOD 6,6603,1973,19752.052.02,1902,19067.167.12,0052,00569.969.912151,21581.881.8TS 12,4424,36710,11564.918.73,6129,60571.022.83,4989,58071.923.033509,19573.124.3VS 10,1043,1427,92268.921.62,9727,51770.625.62,8097,33672.227.424607,05375.729.5TKN 1,14054089952.621.118063884.244.017060085.147.48550092.552.3TN 1,14057393349.718.248491857.519.548891857.219.538888863.020.5NH 3-N 54031031042.642.6828284.884.8808085.285.200100100NO 3-N 020*********NO 2-N 01314013010pH8.08.77.97.87.6Bioprocess Biosyst Eng 25(2002)1063.1.2Nitrogen conversionWith the influent of10,000mg/l COD and1-to3-day HRT,22.2–23.6%of total nitrogen(TN)was lost in the treatment process as indicated by the E t.The losses of TN for the three HRTs were not significantly different.The ammonia collection results showed that the amount of NH3-N volatilized accounted for only2–3%of TN,indi-cating that the ammonia loss through volatilization was small under these operating conditions.The rest of TN loss (approximately20%)might be due to the emission of other nitrogenous gases,such as nitrous oxides(NO and NO2)formed in the nitrification process,and nitrogen gas (N2)formed in the denitrification process.The TKN removal was53.2–56.7%from the total effluent and75–78.8%from the liquid effluent,respectively.The TKN removal mainly resulted from ammonia oxidation.With the influent of20,000mg/l COD and1-to4-day HRTs,the loss of TN was18.2–20.5%.For the1-day HRT, the ammonia collection results showed that ammonia volatilization accounted for16%of TN,indicating that most of TN loss was due to ammonia volatilization.This occurred with the low nitrification rate in the SBR.But ammonia volatilization was insignificant at2-to4-day HRTs,at which the SBR had high nitrification activities. These results might imply that ammonia volatilization could be related to nitrification activity.Little nitrification occurrence at1-day HRT was due to the short SRT of 1.5days.This agrees with thefindings of Prakasam and Loehr[14],who stated that2-day SRT was the minimum for nitrification of poultry wastes.Therefore,HRT was increased to2days and3days,and corresponding SRT were3days and4days.It was found that nitrification was able to sustain in the SBR at both HRTs.At2-day and3-day HRT,the TN and TKN removals were19.5%and44.0–47.4%from the total effluent,and57.5–57.2%and84.2–85.1%from the liquid effluent,respectively.Significant NH3-N was removed,as indicated by removal efficiency of 84.8%for2-day HRT and85.2%for3-day HRT,although there was still80–82mg/l residual NH3-N present in the effluent.It can be seen that there was no significant dif-ference between two HRTs in terms of TN,TKN,and NH3-N removal.Therefore,if complete ammonia oxidation is not required,2-day HRT would be considered efficient for treating20,000mg/l COD influent in terms of both nitrogen removal discussed here and COD and solids removal as mentioned in Sect.3.1.1.Certain amounts of residual ammonia were present in the effluent from20,000mg/l COD influent at2-day and 3-day HRT.This indicates that the nitrification process might have been inhibited in both operation conditions. Nitrification inhibition might be due to possible inhibitions of nitrification bacteria by free ammonia(FA)and free nitrous acids(FNA)and suppression of nitrification bac-teria by more competitive heterotrophic bacteria[15].NH3 was undesirable because of its odor and toxicity to aquatic lives;thus,it needed to be removed from the wastewater. Shammas[16]studied the interaction of temperature,pH, and biomass on the nitrification process and concluded that high nitrification efficiency can only be obtained with either very long detention time or a combination of highsolids concentration and elevated temperature.Therefore,HRT was further increased to4days in order to obtain complete ammonia conversion.It was found that4-dayHRT,corresponding6-day SRT,was enough for complete ammonia conversion,as indicated by zero ammonia pre-sent in the effluent(see Table2).Therefore,it could be concluded that if complete ammonia conversion is desired,4-day HRT would be needed for treating20,000mg/l COD wastewater with540mg/l NH3-N.A track study was conducted in order to further un-derstand the nitrification process in the SBR.The varia-tions of NH3-N,NO2-N,and NO3-N in the SBR during a12-h operating cycle in treating the wastewater of10,000mg/l COD at2-day HRT are shown in Fig.2.Am-monia oxidation mostly occurred in thefirst5h,as indi-cated by the increase of NO2-N and decrease of NH3-N.Since a large amount of ammonia was oxidized in the earlystage of one cycle with high nitrification,the amount of ammonia volatilization may be decreased in contrast tothe condition when nitrification is small as mentionedabove.The relationship between ammonia volatilizationand nitrification activity needs to be further investigated infuture study.The pH could be another factor related to ammonia volatilization.Since higher medium pH in-creased the gas fraction of total ammonia dissolved in the medium,ammonia volatilization could have been highwhen there was little nitrification and pH maintained rel-atively high(approximately8.0),but small when there wasgood nitrification and the pH was decreased(Fig.2).TheNO2-N increased to the peak value about5h later after feeding and then started to decrease,while NO3-N startedto increase slightly.Generally speaking,the variations ofNH3-N,NO2-N,NO3-N,and pH in the SBR during the operating cycle depends on the bioconversion dynamics inthe reactor,initial ammonia concentration,and alkalinityin the wastewater.3.2Performance of the two-stage SBR-CMBR systemAs stated above,a4-day HRT is needed for achieving complete oxidation of ammonia in the dairy wastewaterin107the single-stage SBR.It appears that increasing HRT to achieve complete nitri fication is not cost effective.This led us to explore a two-stage treatment system.Research showed that nitrifying in a separate second-stage aeration system would increase nitri fication rate,due to the more suitable environment provided by a two-stage system than a single-stage system [17].In aerobic treatment,carbon oxidation is carried out by heterotrophic bacteria,while nitri fication is carried out by autotrophic bacteria.The two groups of bacteria are signi ficantly different in physiology,substrate requirement,metabolic characteristics,and growth kinetics.In a single-stage system,both carbon oxidation and nitri fication proceed in one reactor.This forces two groups of bacteria to coexist within the same physical and chemical environment,which is not optimal for either autotrophic or heterotrophic bacteria and makes it dif ficult to achieve optimum carbon and ammonia ually,longer HRT is applied in a single-stage system to balance the slow-growing autotrophic bacteria responsible for nitri fication and fast-growing he-terotrophic bacteria for carbon oxidation.But this is not economical,as mentioned above.A two-stage system could separate carbon oxidation and the nitri fication process and make each process proceed in a separate re-actor.The first-stage reactor is intended mainly for carbon oxidation and enhancement of solids settleability,and the second-stage reactor for providing suitable conditions fornitri fication.Since carbon could be oxidized quickly by fast-growing heterotrophic bacteria,the first-stage reactorcould use a relatively shorter HRT.After the first-stage SBR treatment,the solids settleability is improved as well,the sludge generated is separated and the liquid ef fluent is used as in fluent for the second-stage reactor.Sludge sep-aration would signi ficantly increase the system removal ef ficiency and reduce concentrations of constituents such as COD,TS,and NH 3-N in the in fluent,making it possible to use a shorter HRT,while maintaining a longer SRT for nitri fication in the second-stage reactor.With the opti-mization of environmental conditions and substratecharacteristics for heterotrophic and autotrophic bacteria in separate stages as mentioned above,the overall per-formance of the two-stage system can be improved and overall HRT reduced,as indicated from the performance data presented below.The two-stage system consisted of one SBR as the first stage and one CMBR as the second stage.The CMBR was selected to be the second-stage reactor,because the at-tached bacteria growth supported by the polyethylene pellets were believed to be favorable for nitri fication bac-teria by providing a long SRT.The CMBR was used to treat the liquid ef fluent from the SBR.Both SBR and CMBR were first operated at 1-day HRT,with the system HRT being 2days for treating 10,000mg COD/l and 20,000mg COD/l in fluent,respectively.The 1-day HRT in the CMBR was determined to be the appropriate level,based on preliminary test results.The performance data of the two-stage system are shown in Tables 3and 4.It can be seen that the liquid ef fluent quality and removal ef ficiencies of carbon,solids,and nitrogen from the two-stage system at 2-day HRT were comparable to those from the single-stage SBR at 3-day HRT for both in fluents.This suggests that,based on the HRT,the two-stage system would require 1/3less reactor volume than the single-stage system and therefore appears to have more favorable economics.In addition,the two-stage system allows complete ammonia oxidation in the wastewater as indicated by zero NH 3-N present in the two-stage system ef fluent at 2-day HRT as compared to 70mg/l NH 3-N in the one-stage ef fluent at 3-day HRT.Because with the in fluent of 20,000mg/l COD ammonia volatilization was high in the first-stage SBR at 1-day HRT,Table 3.Performance of two-stage SBR-CMBR system for 10,000mg/l COD in fluent In fluent (mg/l)Stage I:SBR(1-day HRT)Stage II:CMBR (1-day HRT)E l (%)E t (%)Liquid ef fluent Liquid ef fluent (mg/l)(mg/l)COD 10,0001,9801,37486.351.1SCOD 2,9141,4571,01465.265.2TS 6,6562,4362,07668.824.8VS 5,1081,7241,47271.239.1TKN 7801956092.358.0TN 78048143544.224.7NH 3-N 510120 2.599.599.5NO 3-N 037195NO 2-N 0249180pH 8.16.87.9Table 4.Performance of the two-stage SBR-CMBR system for 20,000mg/l COD in fluentIn fluent (mg/l)stage I:SBR (1-day HRT)stage II:CMBR (1-day HRT)E l (%)E t (%)stage I:SBR (2-day HRT)stage II:CMBR (0.5-day HRT)E l (%)E t (%)Liquid ef fluent Liquid ef fluent Liquid ef fluent Liquid ef fluent (mg/l)(mg/l)(mg/l)(mg/l)COD 20,0004,3002,67686.637.028********.543.8SCOD 6,6603,1972,02069.769.7219089086.686.6TS 12,4424,3673,43272.421.83612267078.526.4VS 10,1043,1422,15278.727.029********.532.5TKN 1,14054018084.246.11804096.556.2TN 1,14057350455.823.248443062.321.5NH 3-N 540310 3.099.499.4820100100NO 3-N 020*********NO 2-N 0131341400pH 8.08.77.87.97.4Bioprocess Biosyst Eng 25(2002)108。

请简要介绍污水生物处理的原理和流程The principle of sewage biological treatment is to use microorganisms to biologically decompose and transform the organic matter in the sewage into stable, harmless substances. 污水生物处理的原理是利用微生物将污水中的有机物生物分解和转化为稳定、无害的物质。

This process is based on the natural biological processes that occur in bodies of water and soil. 这个过程是基于水体和土壤中自然发生的生物过程。

Sewage treatment plants use a combination of physical, chemical, and biological processes to remove contaminants from the water. 污水处理厂利用物理、化学和生物过程的组合来去除水中的污染物质。

The biological treatment component is crucial for effectively removing organic contaminants from the sewage. 生物处理部分对于有效去除污水中的有机污染物至关重要。

The first step in the biological treatment process is the removal of large debris and solids from the sewage. The sewage is then introduced into an aeration tank, where it undergoes aeration and agitation. This helps to create an environment suitable for the growth of microorganisms. 生物处理过程的第一步是从污水中去除大块垃圾和固体。