Alternative Solutions for a Sustainable Future

April 12, 2006

About the author: Mark W. LeChevallier, Ph.D. is director, innovation and environmental stewardship for American Water. To find out more, contact American Water at 856/346-8200 and ask for business development.

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According to a recent World Bank report, 300 million people live in areas with serious to severe water shortages, and this number could reach three billion within 25 years. The option of tapping into alternative water resources continues to be explored as the demand for water increases. Population growth, environmental pollution, infiltration of saltwater into aquifers and the increased cost of wastewater disposal are some of the key reasons why membrane technology is being utilized to resolve these complex issues.

An increasing number of water and wastewater treatment facility managers are incorporating membrane filtration technologies into their treatment systems because of the many advantages of membranes. These advantages include greater automation, smaller facility requirements, reduced chemical use and environmental impact, and high-quality results. For drinking water, membranes provide a high level of treatment that often can’t be attained by other technologies.

American Water is investigating new ways of supplementing traditional treatment approaches with efficient, cost-effective and advanced technologies to meet its customers’ needs.

For example, membrane treatment is being applied in small community developments to provide high-quality, decentralized water and wastewater treatment utilizing automated, computer-controlled systems. Wastewater treated by such membrane processes is increasingly being reused for irrigation, sanitation and groundwater replenishment.

The brief case studies that follow illustrate the various applications of membrane filtration technology for treatment of potable water and wastewater, and for water reuse.

Potable water treatment

Four Seasons, Chester, N.J.

At Four Seasons at Chester, a senior community in Chester, N.J., treated water is discharged into the aquifer. This helps maintain a plentiful groundwater supply in the local environment. The Applied Water Management Group of American Water designed and built the facilities and now owns and operates them for this community.

Potable water plant, Anthem, Ariz.

The Anthem Water Treatment

Plant receives water from the Waddell Canal, which connects the Central Arizona Project Canal and Lake Pleasant. Surface water from the Waddell Canal is drawn through a trash rack and pumped to the Anthem Water Campus through a 30-in. diameter pipeline that is approximately 8.8 miles long.

At the water campus, the flow is directed into the raw water storage reservoir. From the reservoir, the water enters the raw water pump station wet well where submersible pumps convey the water through a strainer and influent meter to the membrane filtration (MF) process tanks. The MF system has a maximum design capacity of 7 mgd and utilizes ZeeWeed membrane technology by Zenon Environmental, Inc.

After treatment by the MF system, the permeate pumps deliver the water through a treated-water meter and into two finished water storage reservoirs. A UV disinfection system, followed by chlorine contact tanks, serves as the primary disinfection process for the plant.

Wastewater treatment and reuse

Wastewater plant, Anthem, Ariz.

Arizona American Water’s Anthem wastewater treatment facility is a 3-mgd membrane process plant that began operation in 1999. It produces an extremely high quality Class A+ effluent for reuse—the highest standard designated by the Arizona Department of Environmental Quality.

Plant effluent is used for irrigation at a local park, two golf courses, highway medians, community landscaping, aquifer recharge, and it is sold to contractors for spray application to control dust. The plant has been constructed in three distinct stages to meet the needs of a growing community, and it is in the planning stages of a fourth expansion.

At its headworks, the plant is equipped with a screenings grinder followed by a perforated 2-mm screen with screw conveyor and vortex grit removal system. The biological treatment design is similar to a normal wastewater plant design, except that the anoxic zone is increased. This is done to account for the long sludge age of the system based on a biological nutrient removal process that will nitrify and denitrify the wastewater to meet the permit effluent criteria. The purpose of the membrane system is to filter the water from the bioreactor mixed liquor suspended solids.

The membrane treatment process is capable of producing a filtrate meeting the permit requirements for suspended solids, turbidity and total nitrogen in a smaller space than other conventional alternatives. The system utilizes a ZenoGem system, which incorporates hollow, fine-fiber membranes in an “outside-in” flow configuration. The flow, provided by suction through the membranes induced by the permeate pumps, draws the clear water through the membranes at pressures ranging from -0 to -9 psi. The filtrate from the membrane bioreactor system is sent to the chlorine contact basin or an inline UV system and then to the storage reservoir. From the storage reservoir, the effluent is pumped to the reuse distribution system.

Sustainable water management

Membrane technology has helped American Water prepare for a future when freshwater supplies across the country and the world will be less readily available. It is critical that alternative solutions are investigated today for a sustainable future.

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