Quantitative evaluation of A2O and reversed A2O processes for biological municipal wastewater treatment using a projection pursuit method

• A method was developed to quantitatively evaluate A2O and reversed A2O processes.
• In this approach PP and PSO methods are integrated.
• The results show A2O process is better than reversed A2O process for WWTP.

In this work, a new model was developed to quantitatively evaluate and compare anaerobic/anoxic/aerobic (A2O) and reversed A2O processes for municipal wastewater treatment using projection pursuit method based on particle swarm optimization (PSO). The optimal projection direction was obtained by optimizing the projection index function using the PSO algorithm. By fitting the logistic equation, the evaluation model was established. Then, the calculated ranks of the evaluation samples were computed. The overall performance of both A2O and reversed A2O processes were evaluated using the established model as a case study. The results show that the mean rank of the A2O process (1.79 ± 0.39) was lower than that of the reversed A2O process (1.97 ± 0.41), indicating that the former was better than the later under the same operating conditions. Through resolving multi-factor evaluation problems, such a PSO-based model is demonstrated to be effective to quantitatively assess wastewater treatment processes.

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