Fixed-bed (FXB) Bioreactors and post-treatment (reoxygenation, biofiltration and disinfection)
- Two first-stage parallel FXB Bioreactors (F120 with a 3.9-ft bed depth and a 2-ft diameter, and F130 with a 4.7-ft bed depth and 2-ft diameter) were used to treat groundwater contaminated with perchlorate.
- Effluent from the bioreactors was dosed with hydrogen peroxide to reoxygenate and oxidize residual organics and hydrogen sulfide.
- Reoxygenated water was passed through a FXB Biofilter to oxidize any remaining organics and sulfide, and to reduce turbidity.
- Effluent from the biofilter was dosed with chlorine to disinfect the water.
Department of Defense (DoD)
Dr. Jess Brown, P.E.
401 North Cattlemen Road
Sarasota, FL 34232
Dr. Andrea Leeson
Environmental Restoration Project Manager
901 North Stuart Street, Suite 303
Arlington, VA 22203
Ms. Barbara Sugiyama
Contract Officer Representative
Naval Facilities Engineering Service Center
1100 23rd Avenue
Port Hueneme, CA 93043
The area around Rialto Well #2 was used by numerous companies for fireworks manufacturing and large-scale explosives disposal (both potential sources of perchlorate), ordnance and pyrotechnics manufacturing, and for the treatment, storage, and disposal of explosive waste containing perchlorate. The area surrounding Well #2 was formerly used as a citrus grove that used Chilean sodium nitrate fertilizer containing perchlorate.
Type/Quantity of Media Treated:
Groundwater (7.2 million gallons)
Purpose/Significance of Application:
This demonstration evaluated the efficacy of FXB Bioreactors to treat perchlorate-contaminated groundwater (in combination with post-treatment reoxygenation, biofiltration, and final disinfection processes) to treat the water to potable standards.
Regulatory Requirements/Cleanup Goals:
There is no federal maximum contaminant level (MCL) for perchlorate. The primary performance criteria for this demonstration include:
- Achieve sustained perchlorate removal. Sustained removal was defined as detecting no perchlorate (< 2.0 µg/L) in ≥ 95% of effluent directly from the FXB Bioreactor samples over the 6-week operation testing period.
- Achieve concentrations of system effluent with biodegradable organic carbon (BDOC) below 0.1 mg/L for ≥ 90% of effluent samples during a 6-week operation testing period.
Data from the demonstration site indicated the following:
- Using an empty-bed contact time (EBCT) of about 10 to 12 minutes, perchlorate concentration was reduced from <2.0 µg/L to 53.5µg/L. However, numerous samples contained perchlorate concentrations below 0.5 µg/L. An EBCT as low as 5 minutes also resulted in the steady removal of perchlorate to below detection limit concentrations. The detection limit for most perchlorate samples was 2 µg/L.
- BDOC concentrations were below 0.1 mg/L and BDOC was often undetected after the initial FXB Bioreactor treatment. However, after the final FXB Biofilter process was completed, effluent BDOC concentrations increased to 0.5 mg/L.
The estimated project costs for two system capacities (1,000 gallon per minute [gpm] and 2,000 gpm) are as follows:
- Total installation plus annual operation and maintenance costs;
- $4,368,000 for 1,000 gpm
- $7,743,000 for 2,000 gpm
During the 1940s, the Rialto Ammunition Storage Point, a 2,800-acre area in the City of Rialto, California, was used for storage of ordnance and explosives for World War II. This site was also used for the manufacturing of explosives, fireworks, and ammunition. Rialto Well #2 is located about 2 miles from a 160-acre parcel that was used for these manufacturing processes.
In February 2007, a 10 month study and demonstration was performed to evaluate the efficiency of using a FXB Bioreactors for the treatment of perchlorate-contaminated groundwater. The treatment system included two FXB Bioreactors, combined with post-treatment reoxygenation, biofiltration, and final disinfection processes to treat the water to potable standards. The general objectives of this study included: (1) demonstrate perchlorate removal capabilities, (2) identify and evaluate potential process limitations and points of failure, and (3) develop process designs and cost assessments for a full-scale application of this treatment process.
The results indicated that as FXB Bioreactor systems scale up, process efficiencies will increase. The results also showed that the two post-treatment processes (using hydrogen peroxide and chlorine) were effective for reoxygenating and disinfecting the contaminated groundwater. The process encountered few implementation issues and system operation required no specialized training. Cost assessment and projected costs for full-scale applications are included in this report. A cost comparison to other treatment methods is also included.