Application Of Bioaugmentation To Improve Nitrification At The Gammams Wastewater Treatment Plant

Abstract

Namibia is among the driest countries in the world, and with the current drought that the country is experiencing, there is a greater need to provide drinking water not only to Windhoek, but the greater Nation at large. The Gammams Wastewater Treatment Plant, which is responsible for treating domestic and some industrial wastewater, regularly experiences toxic pluses that result in the inhibition of nitrification in the activated sludge process, leading to poor removal of ammonia. This is of great concern as the final effluent of the plant is used downstream for the production of potable water. The aims of this study were firstly to isolate and identify the nitrifying bacteria in the activated sludge system. Secondly, it was to test the inhibition capabilities of three test chemicals and thirdly to test the percentage recovery attainable by bioremediation using a fresh sample of activated sludge and by bioaugmentation using pure strains of Nitrosomonas and Nitrobacter. Sampling was performed once off for the growing on culture media, which was then used for molecular experimentation. Samples were then collected once a week for a duration of 9 weeks for the inhibition experiments, and then once off for the remediation and bioaugmentation experiments. Inhibition was carried out using acetone, toluene and brake fluid at concentrations of 5 ml/L, 10 ml/L and 50 ml/L, respectively. The test chemical that produced the highest inhibition percentage was then used in the remediation and bioaugmentation experiments. Pure cultures of Nitrosomonas and Nitrobacter were used in the bioaugmentation experiment, whereas the remediation experiment used a fresh sample from the aerated basins. Toluene at 50 ml/L produced the highest inhibition percentage (484%), while acetone at 5 ml/L produced the lowest inhibition percentage (17%). Culturing on solid media resulted in little growth, compared to growth that was obtained on the samples that were cultured on broth, which produced visible growth in suspension.