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Activated sludge tank at Beckton sewage treatment plant, UK.The white bubbles are due to the diffused air aeration system. The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa.
Mesophilic anaerobic digestion (MAD) is also a common method for treating sludge produced at sewage treatment plants. The sludge is fed into large tanks and held for a minimum of 12 days to allow the digestion process to perform the four stages necessary to digest the sludge. These are hydrolysis, acidogenesis, acetogenesis, and methanogenesis.
The quantity or “age” of sludge within the tank is closely monitored, as this can have a marked effect on the treatment process. The sludge is allowed to settle until clear water is on the top 20 to 30 percent of the tank contents. The decanting stage most commonly involves the slow lowering of a scoop or “trough” into the basin.
Extended aeration agitates all incoming waste in the sludge from a single clarifier. The combined sludge starts with a higher concentration of inert solids than typical secondary sludge and the longer mixing time required for digestion of primary solids in addition to dissolved organics produces aged sludge requiring greater mixing energy input per unit of waste oxidized.
Upflow anaerobic sludge blanket (UASB) technology, normally referred to as UASB reactor, is a form of anaerobic digester that is used for wastewater treatment. The UASB reactor is a methanogenic (methane-producing) digester that evolved from the anaerobic clarigester .
The history of sewage treatment had the following developments: It began with land application (sewage farms) in the 1840s in England, followed by chemical treatment and sedimentation of sewage in tanks, then biological treatment in the late 19th century, which led to the development of the activated sludge process starting in 1912.
Sludge is continually drawn off as new sewage enters the tank and this sludge must then be settled so that the supernatant (the remaining liquid) can be separated to pass on to further stages of treatment. Sludge bulking occurs when the sludge fails to separate out in the sedimentation tanks. The main cause of sludge bulking is the growth of ...
Activated sludge tank at Beckton sewage treatment plant, UK. The white bubbles are due to the diffused air aeration system. The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa.