An optimization model for green water and wastewater network redesign considering different quality of returned wastewater

Expansion of urbanization, increasing in the population of planet, excessive exploitation of water resources and wastewater release in nature have negative and irreversible impacts on the environment. The present research has been carried out in order to optimize the redesign model of the green water and wastewater network.

In this research, a bi-objective optimization model for the green redesign of the water and wastewater network is proposed. The model includes locating the optimal place of storage ponds and also optimally allocating the treated wastewater to agricultural areas and industrial settlements in order to mitigate the devastating effects of discharging industrial wastewater into the municipal wastewater treatment plants and eventually mitigating the entry of such pollutants into the environment. The proposed model, has been solved using the - constraint method.

Accordingly, the total system cost is minimized, the demand is met and simultaneously the environmental issues are met and the environmental pollution load of the network is minimized, because of network redesign. Also, a sensitivity analysis is performed on some important parameters.

The results showed that the proposed model can help the designers in this field to design the distribution network, because despite the increase in costs the environmental pollution is reduced by installing COD meters and performing environmental disinfection. In addition, in this model, it has been tried to compensate part of the increased costs by selling activated sludge.