AWWA MTC57616

Gwinnett County, Georgia is expanding an existing water reclamation plant by 40 mgd (maximum monthly flow). The expansion includes 50 mgd (feed flow) of membrane filtration equipment using Zenon ZeeWeed ZW500c ultrafiltration membranes, selected after a competitive procurement process. A four-month pilot test was conducted to verify proposed design and operation criteria while treating chemically-clarified secondary effluent. Testing was successful and performance met the manufacturer-guaranteed flux, recovery, transmembrane pressure (TMP) and cleaning frequency. Short maintenance cleans every 42 hours and periodic recovery cleans (greater than 30 days) maintained hydraulic performance. Permeate water quality met all treatment goals during the testing. At times during the test program, iron fouling from excessive ferric chloride feed carrying over from the clarifier was observed. The iron fouling was controlled by maintenance cleans with citric acid, instead of normal sodium hypochlorite cleans, and by periodic membrane "relaxation" which simulates actual operating conditions during backwash valve movement in the full-scale facility. The full-scale system has been designed and the general construction contract is expected to bid and be awarded in early 2003. The contract allows for the membrane process facilities to be commissioned in 25% capacity increments. The first increment of membrane capacity is expected to be operational in 2005 and the full facility completed in 2006. Includes 4 references, tables, figures.