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<!{|style="float: left;"|{{Language-- table at top of page with logo, picture, Application level, Management level, and input-output tables -->box|english_link=Activated_Sludge|french_link=Boues_activés|spanish_link=Lodo_Activado|hindi_link=coming soon|malayalam_link=coming soon|tamil_link=coming soon | korean_link=coming soon chinese_link=Coming soon | indonesian_link=Coming soon | japanese_link=Coming soon }}|}

sys2=[[Blackwater Treatment System with Infiltration|56]]|sys3=[[Blackwater Treatment System with SewerageEffluent Transport|67]]|sys4=[[Blackwater Transport to (Semi-) Centralized Treatment System |78]]|sys5=[[Sewerage System with Urine Diversion|9]]|

Input1=Blackwater|Input2=Greywater |Input3= Brownwater | Input4= Effluent |Input5=|Output1= Effluent | Output2= Treated Sludge | Output3= | Output4= | Output5=|english_link=Activated_Sludge|french_link=Boues_activés|spanish_link=Lodo_Activado

|[[Image:Activated_sludge.png |right|300px500px]]

[[Image:Icon_activated_sludge.png |right|95px80px]]'''Activated Sludge is a multi-chamber reactor unit that makes use of (mostly) aerobic microorganisms to degrade organics in wastewater and to produce a high-quality effluent. To maintain aerobic conditions and to the keep the active biomass suspended, a constant and well-timed supply of oxygen is required.'''

Different configurations of the Activated Sludge '''An activated sludge process can be employed refers to ensure a multi-chamber reactor unit that the wastewater is mixed makes use of highly concentrated microorganisms to degrade organics and aerated (with either air or pure oxygen) in an aeration tank. The microorganisms oxidize the organic carbon in the remove nutrients from wastewater to produce new cells, carbon dioxide and watera high-quality effluent. Although aerobic bacteria are the most common organisms, To maintain aerobic, anaerobic, conditions and/or nitrifying bacteria along with higher organisms can be present. The exact composition depends on to keep the reactor designactivated sludge suspended, 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 continuous and the effluent moves on for further treatment or discharge. The sludge is then recycled back to the aeration tank, where the process well-timed supply of oxygen is repeatedrequired.'''

To achieve specific effluent goals for BOD, nitrogen <br>Different configurations of the activated sludge process can be employed to ensure that the wastewater is mixed and phosphorus, different adaptations aerated in an aeration tank. Aeration and modifications have been made to mixing can be provided by pumping air or oxygen into the basic Activated Sludge designtank or by using surface aerators. Aerobic conditionsThe microorganisms oxidize the organic carbon in the wastewater to produce new cells, nutrient-specific carbon dioxide and water. Although aerobic bacteria are the most common organisms (especially for phosphorus), recycle design and carbon dosing, among others, have successfully allowed Activated Sludge processes to achieve high treatment efficienciesfacultative bacteria along with higher organisms can be present.

{{procontable | pro=- Good resistance against shock loading. <br> - Can be operated at a range of organic The exact composition depends on the reactor design, environment, and hydraulic loading rateswastewater characteristics. High reduction The flocs (agglomerations of BOD and pathogens (up to 99%sludge particles). <br> - Can , which form in the aerated tank, can be modified to meet specific discharge limitsremoved in the secondary clarifier by gravity settling. | con=- Prone Some of this sludge is recycled from the clarifier back to complicated chemical and microbiological problemsthe reactor. <br> - Effluent might require further treatment/ disinfection before discharge. <br> - Not all parts and materials may The effluent can be available locally. <br> - Requires expert design and supervision. <br> - High Capital cost; high operation cost. <br> - Constant source of electricity is required. <br> - Effluent and sludge require secondary discharged or treated in a tertiary treatment and/or appropriate dischargefacility if necessary for further use.}}

==Adequacy=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.

Activated Sludge is only appropriate for a centralized The excess sludge requires treatment facility with to reduce its water and organic content and to obtain a wellstabilized product suitable for end-trained staffuse 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, constant electricity different adaptations and a highly developed centralized management system modifications have been made to ensure that the facility is operated basic activated sludge design. Well known modifications include sequencing batch reactors (SBR), oxidation ditches, extended aeration, moving beds and maintained correctlymembrane bioreactors.

Activated Sludge processes are one part of a complex treatment system. They are used following primary treatment (that removes settleable solids) <br>{{procontable | pro=- Resistant to organic and before hydraulic shock loads <br>- Can be operated at a final polishing step. The biological processes that occur are effective at removing soluble, colloidal and particulate range of organic materials for biological nitrification and denitrification hydraulic loading rates <br>- High reduction of BOD and for biological phosphorus pathogens (up to 99%) <br>- High nutrient removal. This technology is effective for the treatment of large volumes of flows: 10,000 possible <br>- Can be modified to 1,000,000 people.meet specific discharge limits| con=Highly trained staff - High energy consumption, a constant source of electricity is required for maintenance <br>- High capital and troubleoperating costs <br>-shooting. The design must be based on an accurate estimation of the wastewater composition Requires operation and volume.maintenance by skilled personnel <br>- Prone to complicated chemical and microbiological problems <br>Treatment efficiency can - Not all parts and materials may be severely compromised if the plant is underlocally available <br>- or overRequires expert design and construction <br>- designed. An Activated Sludge process is and possibly effluent require further treatment and/or appropriate for almost every climate. ==Health Aspects/Acceptance==dischargeBecause of space requirements, Centralized treatment facilities are generally located away from the densely populated areas that they serve. Although the effluent produced is of high quality, it still poses a health risk and should not be handled directly.}}

==Maintenance=Appropriateness=== An activated sludge process is only appropriate for a Centralized Treatment facility with a well-trained staff, constant electricity and a highly developed management system that ensures that the facility is correctly operated and maintained. Because of economies of scale and less fluctuating influent characteristics, this technology is more effective for the treatment of large volumes of flows. An activated sludge process is appropriate in almost every climate. However, treatment capacity is reduced in colder environments.

The mechanical equipment (mixers===Health Aspects/Acceptance=== Because of space requirements and odours, aerators Centralized Treatment facilities are generally located in the periphery of densely populated areas. Although the effluent produced is of high quality, it still poses a health risk and pumps) must should not be maintained constantlydirectly handled. As well, In the influent and effluent must be monitored constantly to ensure that there excess sludge pathogens are no abnormalities that could kill the active biomass and to ensure that detrimental organisms have substantially reduced, but not developed that could impair the process (e.g. filamentous bacteria)eliminated.

==References=Operation & Maintenance=== Highly trained staff is required for maintenance and troubleshooting. The mechanical equipment (mixers, aerators and pumps) must be constantly maintained. As well, the influent and effluent must be constantly monitored and the control parameters adjusted, if necessary, to avoid abnormalities that could kill the active biomass and the development of detrimental organisms which could impair the process (e.g., filamentous bacteria).

===References===* Crites, R. and Tchobanoglous, G. (1998). [http://books.google.com/books/about/Small_and_decentralized_wastewater_manag.html?id=yx9SAAAAMAAJ Small and Decentralized Wastewater Management Systems]. WCB and /McGraw-Hill, New York, USAUS. pp 451–504. 451-504. (Book; Comprehensive summary including solved problems.)

* Ludwig, HFH. F. 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). [httphttps://www.iwapublishing.com/templatesites/default/files/ebooks/9781780402734.cfm?name=isbn1843390027 pdf Biological Wastewater Treatment in Warm Climate Regions, Volume Two]. IWAPublishing, London, UK.

* 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)

===Acknowledgements===