Vasstelling van die bakteriese profiel van 'n rietbedding op die terrein van 'n industriele aanleg

Abstract

A reedbed installed on the premises of Naschem near Potchefstroom to serve as a tertiary treatment of an effluent was the subject of this study. The effluent consists mainly of sewage water and water from a laundry where the clothes of the employees of the explosive plant are washed. This study is part of a more comprehensive programme to determine the bacterial profile of a constructed reedbed and to identify the factors influencing it, to determine possible tendencies and to make a contribution towards optimalising the use of reedbeds as a system for treating various effluents. The emphasis in this study was to determine the number of bacteria, the number of nitrifying and denitrifying bacteria of the four seasons of a year. Different zones - stagnant, slow and fast moving water - were distinguished in the first ten meters of the reedbed and analyzed with regard to the above-mentioned bacteria. Total bacterial counts were done at 20°C and 37°C on plate count agar (PCA). Nitrifiers were isolated on ammonia agar and nitrite agar and denitrifiers in nitrate broth. Representative isolated bacteria were grouped according to primary identification tests. According to "Bergeys's Manual of Systematic Bacteriology" the majority of the bacteria belongs to Sections 4 and 5 and the rest to Section 3 (Krieg et al., 1984) and Sections 12 and 14 (Sneath et al., 1986). The expected relationship between temperature and bacterial numbers counted at 20°C and 37°C on PCA was observed. At 37°C an increase in numbers was observed with increase in temperature while the opposite was true at 20°C. In agreement with the literature it was observed that the numbers of nitrifying bacteria was the lowest during winter. A clear relationship between the numbers of nitrifying bacteria and the ammonia concentration was, however, not observed. A more significant correlation was observed between the number of denitrifying bacteria and the nitrate concentration in the water. It was shown with the aid of a cross-streak procedure that most probably mainly heterotrophic nitrifying bacteria was observed in this study. Parts ofthis work was presented at the following meeting: Van der Walt, AM., Pieterse, A.J.H., Wood, A, Vermeulen, T., & Pretorius, P.J. A Reedbed System for Secondary Treatment of Domestic Wastewater with an Industrial Component. Biotechnology for Africa 95 : All African Conference on Biotechnology, University of Pretoria, November 1995.