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Evaluating The Resource Recovery Potential Of Dairy Processing Waste Through Anaerobic Digestion With Enhanced Microbial Retention
Brown, Kennedy Paige
Brown, Kennedy Paige
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Abstract
Agri-Mark is a farmer cooperative in the Northeast, known for its Cabot brand of award--winning dairy products. Agri-Mark’s creamery in Cabot, Vermont generates a large volume of production washwater which is currently land-applied on agricultural fields throughout the state. Washwater is rich in nitrogen and phosphorus, two beneficial nutrients that, in excess, can jeopardize freshwater ecosystems due to acidification and eutrophication. Agri-Mark is currently exploring alternative waste treatment solutions to remove and recycle nutrients. Anaerobic Digestion (AD) is an attractive alternative for organic waste management as it produces valuable products such as methane-rich biogas and nutrient-rich digestate. The applicability of AD is limited in the treatment of low-strength organic waste due to the low organic loading rates (OLR) and long retention times required to support a slow-growing methanogenic community. This study explores the development of an Anaerobic Sequencing Batch Reactor paired with Membrane Filtration (AnSBR-MF) for the treatment of low-strength dairy processing waste. Through passive retention using sedimentation and active retention using membrane filtration, biomass is retained within the reactor to promote contact between microorganisms and organic matter. Following a comprehensive characterization of Cabot Creamery’s washwater, the material was used as a feedstock for two bench-scale reactors simulating a conventional AD and an AnSBR- MF. When operated under a low OLR of 0.25 kg COD m-3 d-1, the conventional AD was unsuccessful and resulted in acidic conditions with a low methane content in the biogas. The enhanced biomass retention of the AnSBR-MF was operated at four stages of increasing OLR, with the most successful being an OLR of 2 kg COD m-3 d-1. Under these operating conditions, the reactor yielded 800 mL of biogas per day with a methane content average of 62%. The success of the AnSBR-MF system offers novel insights into the management of dairy production washwater and can expand the applicability of anaerobic digestion to low-strength organic wastes through enhanced biomass retention strategies.
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2024-01-01