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STAGES OF WASTEWATER TREATMENT PRE-TREATMENT Pre-treatment consists in removing the coarsest solid pollutants from the raw wastewater (screening, sand and oil removal) before it reaches the treatment plant.
SOLID REMOVAL
The largest solids in the water are removed by allowing them to settle at the bottom of the primary treatment tank. Mechanical scrapers in this tank continually drive all the sludge.
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BACTERIAL DECOMPOSITION Any remaining biological content is substantially degraded to purify the wastewater further. This is either done through biofiltration, aeration, or in oxidation ponds.
EXTRA FILTRATION The aim is to bring the quality of the water to industrial and domestic standards. Pathogens may also be removed at this stage, to ensure that the water is safe for drinking.
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