Toxicity of lead to biodegradability of organic wastes

The effects of lead on biodegradation rate of organic wastes were investigated at lead concentrations of O, 5, IO, 20, 30, 40, 50, 75, 100, 125, 150, 200 mg/l in batch cultures. Several runs were performed at various temperatures in order to determine the effect of lead at various temperatures. A model was proposed which enables prediction of deoxygenation rate for different concentrations of lead at different temperatures. The model parameters namely the ultimate biochemical oxygen demand, reaction rate constant and lag time were optimized by ordinary least squares (OLS) technique using modified Gompertz model. The results indicate that modified Gompertz model may be used suitably to predict deoxygenation curve. In general, the ultimate biochemical oxygen demand and lag time increased as lead dose was increased. However, the deoxygenation rate decreased as lead concentration was increased. These model parameters were further modelled for the influence of temperature. It was observed that lag time increased as temperature was increased or decreased from the optimum temperature. The deoxygenation rate and ultimate biochemical oxygen demand, however, had maximum values at optimum temperature of about 30. l to 33.s0 c. It was proposed that further study must be done in order to modify the proposed model so that it may incorporate other environmental factors such as pH, which is also known to influence biodegradation rate. The study recommended The use of synthetic waste water so as to maintain the consistent organic source in all samples.