Direct water reuse: a hydraulic economic analysis of connecting the wastewater treatment effluent to water treatment influent

Abstract

Climate change is causing increased flooding and droughts. Droughts can cause drinking water sources to run dry. Therefore, recycling water from the wastewater plant effluent to the water treatment plant influent, also called ‘direct reuse’ is becoming necessary. A connection between a city's wastewater treatment plant (WWTP) effluent and water treatment plant (WTP) influent via pipe was simulated to provide an understanding of the capital costs and feasibility of execution. Hydraulic pipe-flow and pump equations were used to calculate the pipe and pump sizes needed for various flow rate and elevation head values. Various flow rate recycle rates were modeled by taking the WWTP effluent flow and in percentages ranging from 5 to 100% to estimate the pipe and pump requirements to send that amount to the WTP influent, including greenhouse gas emissions from pumping. The costs of installation were then determined using current market values for parts and trenching. Data analysis showed that the cost of this project is driven by the pump size requirements.