Chemical treatment of dairy wastewater was studied, using dissolved air flotation for solids separation. Four different combinations of coagulants were tested. Total COD removal was very dependent on the influent CODF/CODT ratio, with the bigbest removal efficiencies at the lowest CODF/CODT ratios. About 60% removal of total COD could be achieved at a CODF/CODT ratio of 0.6. JKL (FeClSO4) removed 2-3% more COD than H2SO4 plus CMC (carboxy methyl cellulose), and 4-6% more COD than lactic acid plus CMC. H2SO4 plus LSA (lignosulphonic acid) bad the poorest removal efficiencies. Use of lactic acid plus CMC is a novel and promising approach. Further studies of the lactic acid plus CMC process is recommended, especially with regard to the feed value of the sludge.

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