sewage treatment

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sewage treatment

the treatment of raw sewage to make it harmless for discharge into rivers, seas and oceans. Treatment systems may involve
  1. (a) Primary treatment in which physical methods are used to remove solid matter (primary sludge) from the waste-water.
  2. (b) Secondary treatment in which biological methods, involving a range of aerobic bacteria, are used to degrade the organic matter in the waste-water. The treated sewage may then be disinfected before discharge from the sewage plant. The sludge that accumulates during both primary and secondary treatments is acted on by anaerobic bacteria in an anaerobic sludge digester. The methane produced can be used as a fuel for heating the digester, whilst the treated sludge is dried and may be used as a fertilizer.
  3. (c) Tertiary treatment in which chemical and physical methods are generally used to remove all the biochemical oxygen demand (BOD), nitrogen and phosphorus. After this treatment the water is disinfected and can be pumped direct into reservoirs. However, tertiary treatment is an expensive process, so water is often returned to the environment after secondary treatment.
References in periodicals archive ?
CARES, which is two-thirds owned by Casella Waste and one-third owned by Altela, has built a 100-by-200-foot building that houses storage tanks and treatment towers developed by Altela for the oil and gas wastewater cleaning.
To set optimal technological parameters of lipid-rich model wastewater cleaning, 4 series of factorial experiments with 16 parallel tests in each were done.
The new system has a number of advantages to wastewater cleaning including: energy efficiency, recycling water for reuse, improved performance and low capital costs.
It also manufactures an industrial wastewater cleaning system called the Clean Machine that cleans wastewater for direct disposal into a sewer.
It covers a wide range of applications including food, cosmetic, medical, lithography and ink jet printing, agricultural, wastewater cleaning, and oilfield chemicals.