Modelling and performance analysis of an urban wastewater treatment plant

The paper deals with modelling and performance analysis of an existent wastewater treatment plant which serves a town with a population ranged between 250000 and 300000 inhabitants, based on a complex mathematical model developed in SIMBA software. The model was simulated in all three characteristics regimes (dry, rain and storm) considering an influent proposed in BSM1 model (Benchmark Simulation Model). The analysis consisted in calculus of specific indicators of "limit" type (they belong to Romanian legislation in the field of the water quality) and of quality and cost indicators which are defined in BSM2 model, in open and closed loop. In closed loop regime two PI controllers were designed and implemented: the first controls the dissolved oxygen concentration in the tank T-4 and the second controls the nitrate concentration in the tank T-2 through the modification of the internal recycling flow.