Design of distributed wastewater treatment systems with multiple contaminants

Abstract

In design of a distributed wastewater treatment system, wastewater degradation caused by unreasoning stream-mixing will increase the total treatment flowrate, and this will often increase treatment cost. Therefore, it is necessary to reduce unreasoning stream-mixing as much as possible in the design procedure. This paper proposes a new method to reduce unreasoning stream-mixing in the design of distributed wastewater treatment networks. The design procedure includes following steps: (1) the main function of each treatment unit is identified; (2) the minimum treatment amount of each unit for its main contaminant, without considering other contaminants, is obtained with pinch method; (3) for the systems with many treatment units, a three-unit-group is selected and the precedence order of the units in the group is determined with the heuristic rules proposed in this paper. The above procedure will continue till the number of the units left is equal to or less than three. Some literature examples are investigated, and the results obtained in this work are compared to that obtained in the literature. It is shown that the design method proposed is simple and effective.