AWWA ACE63133

The Sonoma County Water Agency (SCWA) initiated a 4-month pilot study in conjunction with the California Energy Commission to evaluate the effectiveness of microfiltration (MF) and reverse-osmosis (RO) processes, in series, following tertiary wastewater filtration. Specifically, the study examined the extent of PPCP and EDC contamination of tertiary-treated wastewater at the project site, and the removal of these compounds through the two membrane processes. Additionally, the study targeted the transition from dry weather flows to wet weather flows in an effort to expose the study to a concentration variable presented by these operational norms. The water quality objectives for the MF/RO permeate water were: to provide preliminary indications of plant performance for the specific wastewater tested, such as operating pressures, cleaning frequencies, and membrane fluxes; to meet primary and secondary drinking water regulations for compliance with California Title 22 water reuse standards; and, to remove representative PPCPs and EDCs to below detection limits. A suite of analytes was selected for this project to represent a broad range of the most prominent PPCPs and EDCs in wastewater, based on scientific literature and the results from an initial characterization of the tertiary-treated wastewater. Sampling throughout the study was conducted on the MF feed, MF filtrate, RO permeate, and RO concentrate. The data collected throughout the study strongly indicate that the membranes tested can meet the objectives set forth. Although biofouling caused some initial operational challenges, successful process improvements indicated that biofouling issues could be minimized. The membranes otherwise ran at typical operating pressures and fluxes. All primary and most secondary drinking water standards were met or exceeded under both wet- and dry-weather flows. Of the 47 PPCPs and EDCs that were analyzed, about half were present in the tertiary-treated wastewater effluent and the MF filtrate, including caffeine, nicotine, and estrogen. Only one compound (the fire retardant TBEP) was present above detection limits in the RO permeate in naturally occurring influent concentrations. Under spiked influent concentrations, only NDMA and 1,4-Dioxane were present above detection limits in the RO permeate. This paper presents results and conclusions from the pilot study. Includes 20 references, tables, figure.