Assessing the scale of resource recovery for centralized and satellite wastewater treatment.

Wastewater treatment to recover water, energy, and other resources is largely carried out at centralized treatment facilities. An alternative is local treatment at satellite facilities where wastewater is removed from a collection system, resources are recovered locally, and the residuals are returned to the collection system. Satellite systems decrease the pipe and energy required for delivery of treated water and may decrease cost. But decisions regarding the geographic scale of resource recovery require consideration of many criteria. In this study, we rank water and energy recovery options for a simplified test case at three scale configurations: a centralized configuration and two hybrid configurations. We first choose criteria for decision-making. Quantitative performance metrics are defined for each criterion, weighted, and computed for each configuration. We then rank configurations. Rankings depend upon the decision-making strategy. For our test case, though, several strategies yield the same top-ranked configuration: a hybrid where communities close to the centralized facility use centralized resource recovery; communities far from the centralized facility use satellite resource recovery. Our ranking is sensitive to initial investment cost for satellite treatment. The results underscore the importance of cost-effective treatment systems and of an accurate and comprehensive analysis of design components.