Monday, April 30, 2007

Selective enrichment of a methanol-utilizing consortium using pulp and paper mill waste streams

Gregory R. Mockos1, William A. Smith2, Frank J. Loge1, and David N. Thompson3. (1) Department of Civil and Environmental Engineering, University of California at Davis, 1 Shields Avenue, Davis, CA 95616, (2) Biological Systems Department, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203, (3) Biotechnology Department, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203

Efficient utilization of carbon inputs is critical to the economic viability of the current forest products sector. Input carbon losses occur in various locations within a pulp mill, including losses as volatile organics and losses in the wastewater treatment systems. Opportunities exist to capture much of this carbon in the form of value-added products such as biodegradable polymers. Activated sludge from a pulp and paper mill wastewater treatment plant was enriched over an 80 day period for a methanol-utilizing microbial consortium. Five enrichment conditions were tested: three high-methanol streams from the kraft mill foul condensate collection system, one stream from the wastewater treatment plant, and one methanol-only enrichment (2500 mg L-1). Enrichment reactors (160 mL working volume) were operated aerobically in sequencing batch mode at neutral pH and 25ºC with a hydraulic residence time (HRT) and a solids retention time (SRT) of four days. Enrichments were supplemented with a methanol-free nutrient medium that supplied micronutrients, nitrogen, and phosphorus in order to promote balanced growth. The COD reduction over a single feed/decant cycle (24 hours) ranged from 79 to 89 % while methanol concentrations dropped below method detection limits (100 mg L-1) in all treatments.  The results of this study indicate that it is possible to use aerobic treatment to degrade the methanol in pulp and paper mill foul condensate waste streams. Furthermore the enriched consortium will be tested for its ability to store the captured carbon in the form of biodegradable polymers such as polyhydroxyalkanoic acids (PHA).