A simple sequential approach for designing industrial wastewater treatment networks

This paper addresses design of wastewater treatment network (WWTN) by hybrid approach. This is a sequential method applying insight-based techniques followed by mathematical programming. The water pinch analysis and wastewater degradation concepts are employed to develop an initial structure. Based on this solution a superstructure is created. The superstructure is the starting point for nonlinear optimisation. The decision variables are both structure of junctions (mixers and splitters) and flow rates. The optimisation model is solved by a simple but robust optimisation algorithm. The design approach can be used for synthesis and also, under some conditions, for retrofit of wastewater treatment networks. The efficiency and robustness of the approach is illustrated using literature examples and industrial cases.