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Application of Bioreactor Systems to Low-Concentration Contaminated WaterState College, PASource: American Water Works Association Research Foundation (AWWARF) Information, December 2000, and AWWARF website, available at http://www.awwarf.com/research/perch.htm. Liu, J., and J. Batista, 2000. "A Hybrid (Membrane/Biological) System to Remove Perchlorate from Drinking Waters" in Perchlorate Treatment Technology Workshop, 5th Annual Joint Services Pollution Prevention & Hazardous Waste Management Conference & Exhibition, August 21-24, 2000, Henry B. Gonzalez Convention Center, San Antonio, Texas. The Pennsylvania State University website of Dr. Bruce E. Logan - Ongoing research topics and topical webpage links, available at http://www.engr.psu.edu/ce/enve/logan.htm. Project Summary: The following text was excerpted from information supplied by American Water Works Association Research Foundation (AWWARF), December 2000, and AWWARF website, available at http://www.awwarf.com/research/perch.htm; and ongoing research topics and topical webpage links, Dr. Bruce E. Logan webpage, The Pennsylvania State University website, available at http://www.engr.psu.edu/ce/enve/logan.htm: This research will evaluate the efficiency of a biological process to reduce perchlorate concentrations of up to 1,000 ug/L to levels of 4-18 ug/L. The research will also evaluate the impact of co-contaminants on process performance, characterized process effluents, and define post treatment requirements. The research is to be completed in 2001. Objective Evaluate the efficiency of a biological process to reduce perchlorate concentrations of up to 1,000 micrograms per liter to drinking water action levels of 4-18 micrograms per liter, Evaluate the impact of co-contaminants, such as nitrate and volatile organic compounds (VOCs), on process performance, and Characterize process effluents and define post treatment requirements. Background A limited number of bioreactor systems have been successfully developed to treat water streams with high concentrations of perchlorate. Examples are the Aerojet process using a GAC/fluidized bed under anoxic conditions and the suspended growth reactor using W.succinogens HAP1 developed by Tyndall A.F.B. The ability of a bioreactor to reduce low concentrations of perchlorate, approximately 1,000 micrograms per liter or less, to drinking water action levels of 4-18 micrograms per liter, is an important knowledge gap. Another important knowledge gap is whether bioreactors developed for removal of nitrate (denitrification) can also be applied to removal of perchlorate. Perchlorate contamination of drinking water is currently impacting at least 12 million consumers. Effective treatment technologies for perchlorate removal or destruction are needed immediately. In order to expedite the research process, this project will be undertaken in two phases with the intent that one of the contractors selected for Phase I will continue as the contractor for Phase II. Phase II continuation of the project will be contingent upon several factors, including: success of Phase I, availability of funding for Phase II, and PAC and AWWARF approval of the detailed scope for Phase II work. The AWWA Research Foundation reserves the right to issue a Request for Proposals (RFP) for Phase II work if this is deemed appropriate. The Crafton-Redlands Plume in the Redlands, California area will be required to be investigated as a pilot-scale study site in Phase II. Research Approach Perchlorate has recently been detected in several surface waters and ground water wells used to supply drinking water at concentrations above the detection limit (0.4 ppb) to 0.37%. The California Department of Health Services (CDHS), based on EPA work, has established a provisional action level of 18 ppb for drinking water due to perchlorate's interference with iodine in the production of hormones in the thyroid. The presence of perchlorate at these high concentrations in the environment, coupled with a very low drinking water standard, has created a national water contamination crisis in the US potentially affecting 12 million people. Perchlorate is readily biodegradable, and under proper conditions, can be reduced to non-detectable levels by fixed and suspended cultures of microorganisms. Since 1993, the PI has been conducting research on microbes that can respire chlorate or perchlorate: that is, they can use either of these compounds as an electron acceptor in the oxidation of many common substrates such as acetate, simple sugars and amino acids. Phase I This project should begin with a brief literature review of potential bioreactor treatment systems potentially applicable to perchlorate contamination. This literature search should include bioreactor systems used for similar contaminants, such as nitrate. Based on this information, bench-scale experiments should be planned and conducted to evaluate several conditions pertinent to drinking water and low concentrations of perchlorate. Example factors to consider are:
Researchers have proposed here to conduct bench scale experiments on three different fixed-film biological treatment processes that should be capable of being scaled up to treat large quantities of drinking water. These treatment systems are: a packed bed (slow sand filter) amended with soluble substrates (acetate, methanol, and ethanol); a hydrogen gas fed four-phase (hydrogen gas, water, biofilm, and support media), unsaturated trickle-type packed column; a membrane-bound biofilm reactor. The hydrogen gas-based systems offer an additional potential advantage of achieving chlorinated aliphatic reduction by hydrogen-oxidizing bacteria under highly reducing conditions. With information gained in this proposal, we will estimate the costs of treating waters using the reactors and feed substrates that successfully remove perchlorate down to drinking water levels (<18 ug/L). Based on the engineering and economic analysis, one of these treatment systems will be selected for further testing in Phase II at the Crafton-Redlands site in Redlands, CA. This project will involve researchers at Penn State University, the University of Nevada, Las Vegas, the City of Redlands, and Camp, Dresser and McKee (CDM) consulting Engineering. In order to assess the general nature of the findings, and to test the performance of the systems for Phase II work, water samples will be obtained from two sites: the Crafton-Redlands site, and a perchlorate contaminated areas in Nevada (the Nevada Wash area and Lake Mead). The purpose of the Phase I project was to evaluate three different fixed-film biological treatment processes at the bench scale in order to determine their feasibility for being scaled up to treat large quantities of perchlorate contaminated water to drinking water levels (<18 ug/L). These treatment systems were: a packed bed (slow sand or GAC filter) amended with soluble substrates (acetate, lactate, methanol, and ethanol); a hydrogen gas fed four-phase (hydrogen gas, water, biofilm, and support media), unsaturated trickle-type packed column; a membrane-bound biofilm reactor. Based on bench tests, we were to estimate the costs of treating waters using in full scale systems and to recommend one of these treatment systems for pilot-scale testing at the Crafton-Redlands site in Redlands, CA. All three systems successfully removed perchlorate at rates sufficient to achieve an acceptable level of perchlorate removal for subsequent treatment for potable use. Our economic and engineering analysis indicated that the least-expensive, most reliable system was an acetate-fed packed bed reactor. The packedbed sand reactor achieved the highest perchlorate removal rates of the three systems. In addition, there was a precedent for using an acetate-fed biological reactor for drinking water treatment in the U.S., making it likely that a reactor of this type would gain public acceptance. Nitrate has been treated using an acetate-fed packed bed reactor for drinking water pretreatment at a site in Coyle, Oklahoma. In addition, biological denitrifying systems have been successfully used in Europe for several years. The wider acceptance of biologically activated filters in the U.S. also points to new trends in the acceptance by water utilities to incorporate biological treatment into drinking water treatment trains. These factors, coupled with a national trend towards "green engineering" and sustainable technologies, suggests that an acetate fed bioreactor is a feasible perchlorate treatment technology. Phase II Following completion of the bench-scale work, a separate pilot-scale project should be initiated approximately two years from now. The pilot-scale work will further develop the most promising bench-scale biological treatment system. In general, the pilot-scale work should evaluate:
The Crafton-Redlands groundwater source contains necessary trace minerals for biological growth of perchlorate-reducing bacteria. However, in addition to perchlorate, it contains as competing electron acceptors, dissolved oxygen and nitrate-nitrogen. Dissolved oxygen is the preferred electron acceptor and the system is designed to biologically remove this first in the treatment system. As flow progresses through the reactor, nitrate and perchlorate will be simultaneous removed by the perchlorate-acclimated culture. All three electron acceptors will be removed in the fixed bed reactor by adding an electron donor (acetate) at sufficiently high concentrations to ensure their complete removal. A small amount of ammonia phosphate and ammonianitrogen may be needed to satisfy bacterial nutritional requirements. Residual electron donor in the effluent will be removed in a post treatment system (biological aerobic filter). The major questions, or outstanding issues, that will be addressed during this phase of the project are: What are the major design criteria for facilities to reliably remove perchlorate with the tested processes?
Additional Info Source: American Water Works Association Research Foundation (AWWARF) Information, December 2000, and AWWARF website, available at http://www.awwarf.com/research/perch.htm. Liu, J., and J. Batista, 2000. "A Hybrid (Membrane/Biological) System to Remove Perchlorate from Drinking Waters" in Perchlorate Treatment Technology Workshop, 5th Annual Joint Services Pollution Prevention & Hazardous Waste Management Conference & Exhibition, August 21-24, 2000, Henry B. Gonzalez Convention Center, San Antonio, Texas. The Pennsylvania State University website of Dr. Bruce E. Logan - Ongoing research topics and topical webpage links, available at http://www.engr.psu.edu/ce/enve/logan.htm. |
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