Objective:

The objective of this project is to demonstrate and validate that a membrane biofilm reactor (MBfR) coupled with downstream ultrafiltration (UF) is capable of destroying nitrate and perchlorate in extracted groundwater as well as producing water that is potable. Specific technical objectives include demonstrating that (1) nitrate and perchlorate concentrations consistently can be reduced to analytical method reporting limits at a flow rate of 25 gallons per minute; (2) biofilm growth and chemical scaling of the MBfR and UF fibers is controllable, stable, and does not require unusual maintenance requirements; (3) produced water meets California Department of Health Services and U.S. Safe Drinking Water Act chemistry requirements for potable water and other relevant requirements such as maximum tolerable dissolved organic carbon; (4) produced water does not contain sulfide or objectionable taste/odor; and (5) system is responsive to possible operational upsets, normal maintenance procedures, and normal temporal variations in water quality. The demonstration will be conducted in a well located in the East Valley Water District in California.

Technology Description:

The MBfR includes numerous hollow fiber membranes onto which anaerobic nitrate- and perchlorate-reducing bacteria grow as a biofilm. Hydrogen gas is delivered to the lumen of these hollow fibers and used by these bacteria as an electron donor. Carbon dioxide naturally present in groundwater is used as a carbon source by the nitrate- and perchlorate-reducing bacteria. The bacteria biologically reduce nitrate and perchlorate present in the groundwater to harmless nitrogen gas, water, and chloride ions. The MBfR is designed with three stages operated in series to promote flow and first-order kinetics to increase process efficiency. Aerobic stabilization and conventional UF are used downstream of the MBfR to remove residual dissolved organic carbon, suspended solids, and bacteria, thereby producing potable water.

Expected Benefits:

The MBfR technology is capable of nitrate and perchlorate destruction and does not generate a brine requiring further treatment. Use of hydrogen as an electron donor as opposed to carbon sources such as ethanol and acetic acid results in less sludge production compared to conventional bioreactor technologies. The use of UF membranes downstream of the bioreactor offers a distinct advantage over fluidized bed and packed bed bioreactor technologies since it provides a barrier between the bacteria and the potable water supply. Membrane technologies are being used extensively in drinking water plants across the United States, thus the MBfR is also more consistent with existing potable water production processes. The overall process is expected to be cost effective with operating costs anticipated at $100 per acre-foot. (Anticipated Project Completion - 2008)

Principal Investigator:
Dr. Patrick Evans
CDM
P.O. Box 3885
Bellevue, WA 98009
Telephone: (425) 453-8383
Fax: (425) 646-9523
E-mail: evanspj@cdm.com

DoD Liaison:
Mrs. Barbara Sugiyama
Naval Facilities Engineering Service Center
1100 23rd Avenue, Code ESC 411
Port Hueneme, CA 93043
Telephone: (805) 982-1668
Fax: (805) 982-1668
E-mail: barbara.sugiyama@navy.mil