Design of water network with internal mains for multi-contaminant wastewater regeneration recycle

Water networks incorporating a regeneration recycle can minimize freshwater consumption and wastewater discharge, to the extent of approaching the inherent minimum value. Based on the water network structure provided with internal water mains, this paper addresses the design methodology for water recycling with regeneration, and extends prior work to cases involving multi-contaminant systems. In such a structure water is supplied to each water-using process from freshwater main, regenerated water main, or regeneration water main according to water quality. How to determine the contaminant concentrations in the regeneration water main is the key in such a water network design. The regeneration concentrations should be the lowest compatible with the freshwater consumption of the system equal to its inherent minimum value. The corresponding design methodology focuses on how to determine which main to use as the water source and how much the water flow rate is to be for each water-using process, on the basis of mass balance and the inlet contaminant concentration condition of that process. Finally, an example is given to illustrate the design method.