AWWA MTC64599

The 40-mgd Nick C. DeGroot Water Treatment Plant, operated by South San Joaquin Irrigation District (SSJID) of Manteca, is the largest existing membrane drinking water treatment plant in California to date. The SSJID treatment plant, dedicated on July 14, 2005, employs the processes of coagulation, flocculation, high-rate dissolved air flotation (AquaDAF™), stabilization with lime and carbon dioxide, submerged ultrafiltration (ZeeWeed® 1000 membrane), and disinfection with sodium hypochlorite. This is the first low-pressure membrane plant using the high-rate AquaDAF™ process as pretreatment. The AquaDAF™ process can operate at surface overflow rate as high as 18 gpm/ft², which is super-high when compared to conventional clarification. A 4-month pilot testing program was conducted prior to the design of the treatment plant to verify design assumptions of the pretreatment (coagulation, AquaDAF™, and stabilization) and membrane filtration systems, and to seek regulatory approval for permitting. The full scale plant has been operating satisfactorily for more than a year. This paper compares the performances of the pilot- and full-scale plants. Water quality, chemical coagulant (ferric chloride) dosages, surface overflow rates, turbidity and total organic carbon (TOC) removal of the AquaDAF™ and ZeeWeed® 1000 systems, fluxes, backwash frequencies, recovery rates, etc., will be reviewed and compared. Operating problems encountered and suggestions for design improvements are discussed. Includes tables, figures.