Detergent Phosphorus in South Africa: Impact on Eutrophication with Specific Reference

The contribution of detergent phosphorus to eutrophication and the economic and water quality consequences of eliminating detergent phosphorus were assessed in the Umgeni catchment, in KwaZulu-Natal, South Africa. The following computations and investigations formed part of the assessment: • calculation of the phosphorus loading arising from urban and rural detergent consumptions, • quantification of phosphorus loadings on the four major impoundments in the Umgeni catchment and the contribution made by detergent phosphorus, • development of a predictive equation relating phosphorus loading to algal production in the impoundment and using it to determine the impact of detergent phosphorus elimination on algal production, • investigation of the fate of phosphorus compounds in an impoundment, using the MINTEQA2 geochemical equilibrium speciation model, • a cost-benefit assessment of detergent reformulation. The results indicated that detergents contributed significantly to the environmenta