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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.
Secondary treatment (mostly biological wastewater treatment) is the removal of biodegradable organic matter (in solution or suspension) from sewage or similar kinds of wastewater. [ 1 ] : 11 The aim is to achieve a certain degree of effluent quality in a sewage treatment plant suitable for the intended disposal or reuse option.
The Imhoff tank, named for German engineer Karl Imhoff (1876–1965), is a chamber suitable for the reception and processing of sewage. It may be used for the clarification of sewage by simple settling and sedimentation, along with anaerobic digestion of the settled sludge. [1]
Secondary sludge is sludge separated in secondary clarifiers that are used in secondary treatment bioreactors or processes using inorganic oxidizing agents. In intensive sewage treatment processes, the sludge produced needs to be removed from the liquid line on a continuous basis because the volumes of the tanks in the liquid line have ...
The aeration stage and the disinfecting stage are the primary differences from a traditional septic system; in fact, an aerobic treatment system can be used as a secondary treatment for septic tank effluent. [1] These stages increase the initial cost of the aerobic system, and also the maintenance requirements over the passive septic system.
The term sewage treatment plant (STP) (or sewage treatment works) is nowadays often replaced with the term wastewater treatment plant (WWTP). [7] [8] Strictly speaking, the latter is a broader term that can also refer to industrial wastewater treatment. The terms water recycling center or water reclamation plants are also in use as synonyms.
The basic national standard for U.S. municipal treatment plants is the Secondary Treatment Regulation. [2] Most plants in the U.S. must meet this secondary treatment standard. The permit authority (state agency or EPA) can compel a POTW to meet a higher standard, if there are applicable water quality standards for the receiving water body.
Larger centralized sewage treatment plants typically use many trickling filters in parallel. Systems can be configured for single-pass use where the treated water is applied to the trickling filter once before being disposed of, or for multi-pass use where a portion of the treated water is cycled back and re-treated via a closed loop .