RESULTS FROM INITIAL TESTING OF THE INTEGRATED MEMBRANE ANAEROBIC STABILIZATION (IMANS™) PROCESS FOR WASTEWATER TREATMENT AND WATER RECLAMATION

Treated wastewater offers an excellent source of water for reclamation and reuse. In response to increasing demands for potable water in Southern California, the Orange County Water District and Sanitation District have developed a joint Groundwater Replenishment (GWR) System. This project will treat secondary wastewater effluent, currently discharged to the ocean, to produce high-quality water for recharge of the Orange County groundwater basin and injection into a seawater intrusion barrier. To address the special challenges of the future phases of the 130 mgd GWR project, such as a shortage of land, high costs associated with additional secondary wastewater treatment facilities, and the disposal of additional biosolids, a new treatment approach is being tested. The new approach called the Integrated Membrane Anaerobic Stabilization (IMANS™) process utilizes membrane processes in combination with anaerobic biological treatment. The system utilizes the microfiltration (MF) process to treat primary effluent followed by reverse osmosis (RO), or nanofiltration (NF), to concentrate soluble BOD and produce a high-quality effluent for reuse. The RO concentrate, which is free of suspended material, is then treated in a high-rate anaerobic digestion process that eliminates the need for conventional secondary activated sludge treatment.An IMANS™ pilot plant was set up at the Orange County Sanitation District treating 15 gpm of primary effluent. Operation of the MF unit began in August 1999. Preliminary results indicate good performance by the MF and RO processes, with little evidence of permanent membrane fouling occurring. The high rate UASB process is in an acclimation phase. Estimates show that the new process combination has the potential of a lower overall power requirement and substantially less biosolids production. The pilot testing is planned to be complete in October 2000.