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Input1=Blackwater|Input2=Greywater |Input3= Brownwater | Input4= Effluent |Input5=|Output1= Effluent | Output2= Treated Sludge | Output3= | Output4= | Output5=

 '''Activated Sludge is An activated sludge process refers to a multi-chamber reactor unit that makes use of (mostly) aerobic highly concentrated microorganisms to degrade organics in andremove nutrients from wastewater and to produce a high-quality effluent. To maintain aerobic conditions and to the keep the active biomass activated sludge suspended, a constant continuous and well-timed supply of oxygen is required.'''

Different configurations of the Activated Sludge activated sludge process can be employed to ensure that the wastewater is mixed and aerated (with either in an aeration tank. Aeration and mixing can be provided by pumping air or pure oxygen) in an aeration into the tankor by using surface aerators. The microorganisms oxidize the organic carbon in the wastewater to produce new cells, carbon dioxide and water. Although aerobic bacteria are the most common organisms, aerobic, anaerobic, and/or nitrifying facultative bacteria along with higher organisms can be present. The exact composition depends on the reactor design, environment, and wastewater characteristics. During aeration and mixing, the bacteria form small clusters, or flocs. When the aeration stops, the mixture is transferred to a secondary clarifier where the flocs are allowed to settle out and the effluent moves on for further treatment or discharge. The sludge is then recycled back to the aeration tank, where the process is repeated.

The exact composition depends on the reactor design, environment, and wastewater characteristics. The flocs (agglomerations of sludge particles), which form in the aerated tank, can be removed in the secondary clarifier by gravity settling. Some of this sludge is recycled from the clarifier back to the reactor. The effluent can be discharged or treated in a tertiary treatment facility if necessary for further use. ===Design Considerations=== Activated sludge processes are one part of a complex treatment system. They are usually used after primary treatment (that removes settleable solids) and are sometimes followed by a final polishing step (see POST, p.136). The biological processes that occur are effective at removing soluble, colloidal and particulate materials. The reactor can be designed for biological nitrification and denitrification, as well as for biological phosphorus removal. The design must be based on an accurate estimation of the wastewater composition and volume. Treatment efficiency can be severely compromised if the plant is under- or over-dimensioned. Depending on the temperature, the solids retention time (SRT) in the reactor ranges from 3 to 5 days for BOD removal, to 3 to 18 days for nitrification. The excess sludge requires treatment to reduce its water and organic content and to obtain a stabilized product suitable for end-use or final disposal. It isimportant to consider this step in the planning phase of the treatment plant. To achieve specific effluent goals for BOD, nitrogen and phosphorus, different adaptations and modifications have been made to the basic Activated Sludge activated sludge design. Aerobic conditions, nutrient-specific organisms Well known modifications include sequencing batch reactors (especially for phosphorusSBR), recycle design and carbon dosingoxidation ditches, among othersextended aeration, have successfully allowed Activated Sludge processes to achieve high treatment efficienciesmoving beds and membrane bioreactors.

- Good resistance against Resistant to organic and hydraulic shock loading. loads <br> - Can be operated at a range of organic and hydraulic loading rates. <br>- High reduction of BOD and pathogens (up to 99%). <br> - High nutrient removal possible <br>- Can be modified to meet specific discharge limits. | con=- High energy consumption, a constant source of electricity is required <br>- High capital and operating costs <br>- Requires operation and maintenance by skilled personnel <br>- Prone to complicated chemical and microbiological problems. <br> - Effluent might require further treatment/ disinfection before discharge. <br> - Not all parts and materials may be locally available locally. <br> - Requires expert design and supervision. <br> - High Capital cost; high operation cost. construction <br> - Constant source of electricity is required. <br> - Effluent Sludge and sludge possibly effluent require secondary further treatment and/or appropriate discharge.

===AdequacyAppropriateness=== Activated Sludge An activated sludge process is only appropriate for a centralized treatment Centralized Treatment facility with a well-trained staff, constant electricity and a highly developed centralized management system to ensure that ensures that the facility is correctly operated and maintained correctly. Activated Sludge processes are one part Because of economies of a complex treatment system. They are used following primary treatment (that removes settleable solids) scale and before a final polishing step. The biological processes that occur are effective at removing solubleless fluctuating influent characteristics, colloidal and particulate organic materials for biological nitrification and denitrification and for biological phosphorus removal. This this technology is more effective for the treatment of large volumes of flows: 10,000 to 1,000,000 people. Highly trained staff An activated sludge process is required for maintenance and trouble-shootingappropriate in almost every climate. The design must be based on an accurate estimation of the wastewater composition and volumeHowever, treatment capacity is reduced in colder environments.

===Health Aspects/Acceptance=== Because of space requirements and odours, Centralized Treatment efficiency can be severely compromised if facilities are generally located in the periphery of densely populated areas. Although the plant effluent produced is under- or over- designedof high quality, it still poses a health risk and should not be directly handled. An Activated Sludge process is appropriate for almost every climateIn the excess sludge pathogens are substantially reduced, but not eliminated.

===Health Aspects/AcceptanceOperation & Maintenance=== Because of space requirements, Centralized treatment facilities are generally located away from the densely populated areas that they serve. Although the effluent produced Highly trained staff is of high quality, it still poses a health risk required for maintenance and should not be handled directlytroubleshooting. ===Maintenance=== The mechanical equipment (mixers, aerators and pumps) must be constantly maintained constantly. As well, the influent and effluent must be constantly monitored constantly and the control parameters adjusted, if necessary, to ensure that there are no avoid abnormalities that could kill the active biomass and to ensure that the development of detrimental organisms have not developed that which could impair the process (e.g. , filamentous bacteria).

* CritesLudwig, R. and Tchobanoglous, G. (1998). [http://books.google.com/books/about/Small_and_decentralized_wastewater_managH.html?id=yx9SAAAAMAAJ Small and Decentralized Wastewater Management Systems]. WCB and McGraw-Hill, New York, USA. pp 451–504. Comprehensive summary including solved problems. * Ludwig, HFF. and Mohit, K. (2000). [http://link.springer.com/article/10.1023%2FA%3A1006751714180?LI=true Appropriate technology Technology for municipal sewerageMunicipal Sewerage/Excreta management Management in developing countriesDeveloping Countries, Thailand case study]Case Study. The Environmentalist 20(3): 215–219215-219. (Assessment of the appropriateness of Activated Sludge activated sludge for Thailand.)

* von Sperling, M. and de Lemos Chernicharo, CAC. A. (2005). [http://www.iwapublishing.com/template.cfm?name=isbn1843390027 Biological Wastewater Treatment in Warm Climate Regions, Volume Two]. IWAPublishing, London, UK.:Available at: [http://www.iwawaterwiki.org iwawaterwiki.org]

* Tchobanoglous, G., Burton, FLF. L. and Stensel, HDH. D. (20032004). [http://books.google.com/books/about/Wastewater_Engineering_Treatment_and_Reu.html?id=L1MAXTAkL-QC Wastewater Engineering: Treatment and Reuse, 4th Edition]. Metcalf & Eddy, 4th Ed. (Internat. Ed.). McGraw-Hill, New York, US.(Detailed design information)