ANAEROBIC PHOTOCATALYSIS AS A SECONDARY TREATMENT FOLLOWING ANAEROBIC DIGESTION
Catherine M. Davis
An increased understanding of the impact of waste streams with high organic content on the environment and the large number of industries producing such waste has prompted more regulations requiring the reduction of biological oxygen demand (BOD) and chemical oxygen demand (COD) caused by organic materials in discharged water. Because waste water treatment plants (WWTP) charge customers based on the concentration of BOD in waste water, companies have an economic incentive to treat water with high organic content onsite prior to discharge to a WWTP. One treatment technique that is being considered in many industries is anaerobic digestion.
Three main drawbacks of anaerobic digestion are that the retention time and, hence, the required tank volume are very high; volatile solids concentrations and chemical oxygen demand are typically reduced by 50% or less; and the bacteria that convert volatile fatty acids to methane are very sensitive to changes in temperature and pH. This research project will replace the biological methane formation process with photocatalysis, a chemical process that can degrade volatile fatty acids into methane and carbon dioxide. The goals are to determine whether photocatalysis reduces the amount of volatile fatty acids and whether this chemical process produces bio gas more efficiently and more thoroughly than biological methane formation.