Coagulation or precipitation followed by settling and/or filtration has proven effective in treating laundromat wastes. Alum alone at a pH of 4-5 may result in a 75% reduction in ABS and an 85% reduction in phosphate content of the waste. Iron salts effect a similar reduction, whereas calcium chloride can reduce ABS by 85%, but this results in only a 50% reduction in phosphate content at high doses.
In addition, ABS may be completely neutralized, using a cationic detergent. Tests must be performed to provide exact equalization with no excess of either detergent. Substances to perform this are commercially available. Phosphates are effectively removed by precipitation techniques. Alum, iron salts, and calcium salts at high pH offer a high degree of phosphate removal. Better than 90% phosphate removal can be obtained by calcium chloride combined with adjusting the pH to 10, or by lime, both followed by filtration in a diatomaceous earth filter.
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