AWWA REUSE52125

The realization of the value of reclaimed water as a substitute for potable water for reuse applications such as turf irrigation has changed the wastewater management philosophy of the Sub-Regional Operating Group (SROG) Cities in the greater metropolitan Phoenix, Arizona area. This philosophy has shifted from each SROG city sending all their wastewater for treatment at the regional SROG-owned 91st Avenue Wastewater Treatment Plant (WWTP) to treating a greater quantity of their wastewater at smaller, decentralized water reclamation plants (WRPs) located near the point of reuse. A number of small to medium size WRPs have been constructed and more are planned in the next 10 years by the SROG members. For reasons of economics and/or aesthetics, these WRPs do not have on-site facilities to treat the residuals from the wastewater treatment process. The WRPs presently discharge concentrated residual streams to the SROG sewer interceptors discharging to the 91st Avenue WWTP. Regional planning indicates the practice of WRP residuals conveyance to the 91st Avenue WWTP will continue and increase. SROG realized that the potential adverse impacts of these residuals on the existing treatment processes at the 91st Avenue WWTP needed to be considered. In 1995, SROG retained Greeley and Hansen to perform a study to quantify the impact of WRP residuals on the 91st Avenue WWTP. The study investigated the impacts of WRP residuals on 91st Avenue WWTP wastewater treatability, treatment plant capacity, and treatment costs associated with flow and strength. The results of the study showed that there are additional costs that need to be taken into consideration when implementing a large scale water reclamation system. Those additional cost considerations are presented and discussed. Another important aspect of the study was the capital cost apportionment to the SROG cities to meet their WRP residual impact and treatment needs. Prior to the study, capital cost apportionment for improvements at the treatment plant were based solely on flow capacity. The study recommended that a new cost apportionment methodology based on flow and strength loading be adopted. Includes reference, tables, figure.