PLANNING FOR REUSE: TOTAL WATER MANAGEMENT

As communities begin to recycle more wastewater treatment plant (WWTP) effluent, new problems can arise. Reuse water that is used for irrigation will typically not be returned to the WWTP for treatment. However, reclaimed water that is used as make-up water for industrial processes is often returned to the WWTP where it originated creating a partially closed recycle system and leading to the accumulation of Total Dissolved Solids (TDS) in the WWTP effluent.Elevated concentrations of TDS can cause a WWTP effluent to fail its acute aquatic toxicity test. Elevated concentrations of sulfates and chlorides can corrode concrete in the wastewater collection system. Elevated concentrations of TDS or specific ions that comprise TDS can cause failure of the WWTP to meet water quality standards.Increased reuse of treated wastewater can conflict with regulatory compliance. A comprehensive or Total Water Management (TWM) plan can help define the regulatory pitfalls while still enabling the community to reuse treated wastewater. TWM is a water management approach that examines all uses and all sources of water, including the potential of reusing wastewater, to develop a long-term plan for meeting all of the community's water needs. TWM also includes examination of wastewater treatment options for compliance with the increasingly stringent discharge criteria. By thoroughly examining all possible water use and reuse alternatives, municipalities can move forward with water conservation and wastewater reuse projects with the confidence that they can manage future regulatory concerns and water capacity issues.This paper is confined to the technical aspects of TWM; it will not address rate structures or financial planning. Two case studies will re reviewed to show how critical TWM is to the planning effort.