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The United States Environmental Protection Agency (EPA) defined secondary treatment based on the performance observed at late 20th-century bioreactors treating typical United States municipal sewage. [31] Secondary treated sewage is expected to produce effluent with a monthly average of less than 30 mg/L BOD and less than 30 mg/L suspended ...
The RBC process allows the wastewater to come in contact with a biological film in order to remove pollutants in the wastewater before discharge of the treated wastewater to the environment, usually a body of water (river, lake or ocean). A rotating biological contactor is a type of secondary (biological) treatment process.
A 2006 study found detectable concentrations of 28 pharmaceutical compounds in sewage treatment plant effluents, surface water, and sediment. The therapeutic classes included antibiotics, analgesics and anti-inflammatories, lipid regulators, beta-blockers, anti-convulsant, and steroid hormones.
Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. The removal is achieved by dissolving air in the water or wastewater under pressure and then releasing the air at atmospheric pressure in a flotation tank basin. The released air forms ...
Sludge Volume Index (SVI) is a process control parameter used to describe the settling characteristics of sludge in the aeration tank of an activated sludge process. [1] It was introduced by Mohlman in 1934 and has become one of the standard measures of the physical characteristics of activated sludge processes.
Additionally, AOPs can be used to treat effluent of secondary treated wastewater which is then called tertiary treatment. [6] The contaminant materials are largely converted into stable inorganic compounds such as water, carbon dioxide and salts, i.e. they undergo mineralization.
Particles finer than 0.1 μm (10 −7 m) in water remain continuously in motion due to electrostatic charge (often negative) which causes them to repel each other. [citation needed] Once their electrostatic charge is neutralized by the use of a coagulant chemical, the finer particles start to collide and agglomerate (collect together) under the influence of Van der Waals forces.
Aerobic digestion is a process in sewage treatment designed to reduce the volume of sewage sludge and make it suitable [1] for subsequent use. [2] More recently, technology has been developed that allows the treatment and reduction of other [3] organic waste, such as food, cardboard and horticultural waste.