MEMBRANE TREATMENT EE&T has a long history of membrane work and has on our staff a membrane specialist whose research in nannofiltration (NF) and reverse osmosis (RO) has been nationally and internationally presented. Active participation in the American Water Works Association (AWWA) Membrane Technology Research Commitee and membership in the International Desalination Association (IDA) , the American Membrane Technology Association (AMTA), and the North American Membrane Society (NAMS). There has been a global increase in membrane use in water/wastewater municipal treatment since its emergence in the 1960's. Membrane systems provide improved treatment for potable water and certainly one of the most appropriate technological responses to increasing regulatory pressure. Membranes provide a consistent finished water quality regardless of the influent water quality. Key membrane performance parameters are:  Contaminant rejection   Permeate flux Operation pressure   Recovery Reverse osmosis (RO) and nanofiltration (NF) provide a service not met by conventional water treament because they remove total dissolved solids (TDS). Other contaminants, such as DBP precursors, can be removed by both NF and RO. Pretreatment is very important because membranes can get damaged or blocked. Damage can be due to presence of acids, bases, free chlorine, or bacteria. Blocking can either result from fouling (e.g., colloids,metal oxides) or scaling (e.g., calcium carbonate, calcium sulfate, magnesium silica). EE&T is familiar with several physico-chemical techniques to alleviate such problems based on a mathematical model developed to optimize operating conditions by correlation permeate salinity, recover, flux, and antiscalant dosage. EE&T also knows how to polish RO/NF finished water in post-treatment to distribute water to customers. Microfiltration (MF) and ultrafiltration (UF) systems over conventional clarification/filtration are: No need for coagulant Residual disinfection only, depending on State requirements Effluent quality independent of influent quality   Process compactness and automation As examples of EE&T's versatility in membrane expertise, EE&T recently performed the value engineering of the proposed 5_mgd RO plant in James City Service and completed an American Water Works Association Research Foundation (AWWARF) project investigating the feasibility of recycling backwash from MF and UF treatment systems. EE&T has evaluated and designed many reverse osmosis (RO) systems as part of a five-year contract with the U.S. Department of State (DOS). The firm was responsible for evaluating, retrofitting, and designing new treatment systems for DOS posts all over the world. Another important example of EE&T's membrane experience is the extensive work done on the Newport News RO system. In that project, EE&T was responsible for: Overseeing the hydrogeology and groundwater development   Selection of aquifer for water supply   Management and operation of the RO pilot plants   Selection of the RO membrane process for the full-scale facility   All permitting associated with discharge of the RO concentrate   Impacts and treatment needs for corrosion control and DBP control   Development of preliminary RO design criteria EE&ampT evaluated the potential for using reverse osmosis or electrodialysis reversal (EDR) for well systems within the City of Suffolk, VA. Recommendations were based on initial capital cost, operation and maintenance costs, waste discharge, overall environmental impact, aesthetics, and finished water quality. The primary objective of this work was to develop cost-effective solutions to lowering fluoride and TDS concentrations in the groundwater that serves as the water supply for the seven community systems in the City. The City of Chesapeake, VA retained EE&T to evaluate the feasibility of membrane treatment to reduce raw water salinity and organics. The evaluation included bench-scale testing of membranes on filtered water to evaluate membrane fouling. The study resulted in the preliminary treatment plant layout, estimate of capital costs, and development O&M costs for the addition of membrane treatment to the 10-mgd conventional water plant that serves the City of Chesapeake. Costing included consideration of pretreatment requirements, membrane cleaning and replacement, operation pressures and membrane configuration, and discharge of reject water to receiving streams. EE&T also conducted a membrane project for organics reduction and hardness mitigation at the Hyde County Water System in Swan Quarter, NC. EE&T conducted the bench-scale membrane testing, determined the water quality objectives, and prepared bid specifications for the pilot-scale membrane equipment.