The effect of alternative detergent builders on the nutrient removal activated sludge sewage treatment process

Includes bibliography.Phosphate is an essential nutrient for photosynthetic plant growth. However if over-supplied in a water body, it leads to excessive algal growth, a condition is termed eutrophication. Eutrophication is not only unsightly, but renders the water less usable. Most of the highly eutrophied water bodies with a high phosphorus load still receive up to 90 of their phosphorus input from effluents discharged by sewage treatment works (Pretorius, 1983). The phosphorus content of domestic sewage originates from two main sources, namely human waste {±60) and detergents {±40) (Heynike and Wiechers, 1986). There is an argument for a ban on phosphate in detergents to reduce the phosphate load on sewage treatment plants and thereby limit phosphate discharges via treated municipal effluent. The removal of phosphate from detergent formulations has been an effective way in many countries of reducing the phosphorous load to receiving waters. In South Africa, detergent manufacturers are anticipating consumer pressure to reformulate their detergent products to eliminate phosphate. The two possible replacements for phosphates are zeolite 4A and high surface area {HSA) calcite. High surface area (SA) calcite is not yet being used as a detergent builder, but is being seriously considered as a potential replacement for phosphate in South African detergent formulations