Performance Evaluation and Mathematical Modeling of Nitrogen Reduction in Waste Stabilization Ponds in Conjunction with Other Treatment Systems

Abstract

In this study, a widely-recognized nitrogen reduction model of waste stabilization ponds (WSPs) was tested for its universal utility in four different cases including shallow algal ponds (SAPs), WSPs followed by SAPs and water hyacinth ponds, respectively, and WSPs upgrading a secondary effluent. A goodness-of-fit study between measurements and calculated values indicates that it provides a satisfactory description of nitrogen reduction for all three cases except the WSPs treating the effluent from SAPs. This is due to the inherent structure of the model underestimating an effect of pH and hydraulic residence time for ponds system operated in series. However, when original model equation was modified as a form having a linear-relationship between reduction rate constant and pH values, it showed much better ability to reflect the process effluent. Finally, all the measured and calculated values were plotted to assess the overall performance of both models. Again, these results support an universal utility of original model, although it shows more robustness at a high range of nitrogen concentration. Meanwhile, the new approach tends to underestimate the effluent concentration at high concentrations but gives better performance at lower range.