Nitrate and Perchlorate Bioremediation in Ground Water
In Situ Bioremediation Eliminated Pump and Treat and Ion-Exhange Treatment Cost
Site closure reached in less than half the time and at less than half the cost
CL-Out bioremediation was implemented at a confidential manufacturing site to remediate nitrate and perchlorate concentrations in soil and ground water. A pump and treatment system was installed and operated for years in immediate response to the discovery of contamination. While perchlorate was considered the primary contaminant, the ion-exchange resin became quickly saturated with nitrate, which was present at much higher concentrations than the perchlorate. In situ bioremediation was implemented to reduce the on-going cost of ground water extraction and treatment.
One of the key factors in CL-Out cometabolism of perchlorate at this site was that CL-Out organisms were able to reduce sequentially the oxygen and nitrate prior to perchlorate. The initial nitrate concentrations were typically much higher than the perchlorate concentrations. The perchlorate concentration did not decrease until the nitrate concentration decreased to less than the perchlorate concentration. One of the benefits of the CL-Out organisms was this ability to utilize these different electron acceptors.
In eight months, the perchlorate concentration in the unconsolidated aquifer was reduced from 128 mg/L to 3.4 mg/L immediately down gradient of the source area and from 220 mg/L to 39 mg/L farther down gradient.
Simultaneously, the CL-Out microbes also removed the nitrate. Down gradient of the source area the nitrate concentration decreased from 105 mg/L to The in situ bioremediation provided immediate risk reduction and mitigated potential off-site migration. The contaminant levels were reduced to the remediation target in 3 years, saving 5 years of projected treatment time and millions of dollars in OM & M costs. The property sold without environmental impairment upon completion of bioremediation.