A wastewater treatment plant serves to process wastewater, removing any impurities or harmful substances in order for the wastewater to be ultimately recycled back to the river system. The focus of this study was on the nitrification process operating in activating sludge at wastewater treatment plants. Every biological system is at risk of being disrupted by toxins, with the nitrification process being no exception. Many chemicals used in industry may be inhibitory to microbial nitrification and thus, the difficulties – observed at many wastewater treatment plants – in achieving sufficient nitrification rates may result from the presence of trade effluent, which inhibits nitrification. The chief objective of this study was to evaluate the effects of trade effluent on the nitrification process at Amanzimtoti Wastewater Treatment plant and determine which types of industry, if any, had the most negative effects on the nitrification process of activated sludge at that plant. It was discovered that trade effluent from three of the four industries sampled had an inhibitory effect of up to 56% on the nitrification process, while trade effluent sampled from one industry stimulated the nitrification process. This stimulation was thought to be associated with the unusually high chemical oxygen demand (COD) of that particular trade effluent.

The theoretical implications and the possible practical applications of this study are discussed. These include enabling the relevant authorities to make informed decisions based on sound results, in order to control nitrification inhibition at all wastewater treatment plants in the future.