AWWA WQTC64105

To meet the water demands for Phoenix's growing population, a future 80-million gallon per day (mgd) water treatment plant (WTP), the Western Canal Water Treatment Plant (WCWTP), is being master planned to include desalination of brackish surface and groundwater through a low-pressure reverse osmosis (RO) membrane system. This paper presents the development and evaluation of the membrane concentrate management and disposal alternatives, and the City's short-term and long-term concentrate management strategies. The study recommended that the City's membrane concentrate management and disposal strategy for the proposed WCWTP consist of two steps. In the short term, membrane concentrate can be pretreated to remove Selenium, pumped via a force main and blended with the 91st Avenue WWTP effluent prior to being reused at PVNGS. It is expected that the discharge of the concentrate, at the dilution ratio projected for the near future, would not cause significant deterioration in the reuse water quality. In the long term, a ZLD concentrate management and disposal option will be implemented either on the Western Canal WTP site or at a centralized regional concentrate management facility. The ZLD option is proposed to include an initial volume reduction step using HPRO with and without chemical precipitation pending pilot results. The two-step strategy sets the long-term goal but allows the City to handle the short-term needs within their planning budgets while protecting the environment and the sustainability of the water reuse program. The deferral of the ZLD requirements allows the City to capture the emergence of more cost-effective options with the evolution of technology, when ZLD becomes necessary. The additional benefit is that the concentrate is reused at the PVNGS that is expected to be a major power supplier to the Southwestern United States. Includes 7 references, tables.