EFFECTS OF CHEMICAL-ADDITION ION AEROBIC BIOLOGICAL TREATMENT OF MUNICIPAL WASTE-WATER

Chemical wastewater treatment is a commonly used and highly effective process. Chemicals can be dosed at a series of different points during the full treatment process. As addition directly to the biological sy stem, or 'co-precipitation', becomes increasingly popular, the direct effect of the chemicals on the biomass becomes of interest. The two ma jor reasons for dosing chemicals in this manner are for phosphorus rem oval and the prevention of sludge bulking/foaming. Another possible us e for chemicals at this point is for enhancement of biological treatme nt via micronutrient addition. This paper demonstrates the effectivene ss of the use of chemicals for these three functions as well as explor ing their effect on the biomass. The possibility of chemical dosing to achieve good phosphorus removal, sludge bulking control and biologica l treatment enhancement is also considered. Certain vitamins and trace metals were found to benefit aerobic biological treatment and other a dvantages of their use were improved sludge bulking control and altern ative sludge disposal routes. However, some toxic effects have been re ported if overdosed and the required concentration is difficult to det ermine. Chemicals used for phosphorus removal during co-precipitation have been found to control sludge bulking problems, increase BOD and s uspended solids removal and enhance the removal of trace metals amongs t other benefits. Drawbacks included nitrification/denitrification inh ibition and increased sludge volume. Beneficial effects of chemicals u sed primarily for sludge bulking control included phosphorus removal, increased BOD and suspended solids removal and biological treatment en hancement. Detrimental effects included increased sludge production an d increased costs.