“CATTLE SLAUGHTERHOUSE WASTEWATER CHARACTERIZATION AND ALTERNATIVE METHODS FOR TREATMENT AND ENERGY RECOVERY”

Advisors: Bruce I. Dvorak and Jeyamkondan Subbiah

Processing cattle produces a substantial amount of high strength wastewater that needs to be properly treated before discharge. The main objectives of this research were to characterize the wastewater of two cattle slaughterhouses and investigate dark fermentation (hydrolysis and acidogenesis) and microbial fuel cells (MFC) as alternative methods for treatment and energy recovery from wastewater.

Wastewater samples were collected from two cattle slaughterhouses located in the Midwest of the U.S. in three sampling events over six months, focusing one processes inside the slaughterhouse and the overall wastewater. The slaughterhouse wastewater concentrations were impacted by the water use, dilution, processes and wastewater pre-treatment that occurs within the slaughterhouse. Viscera and offal processing was the major wastewater load producer.

Dark fermentation was investigated as an alternative method for energy recovery. The highest hydrogen yield (0.85 mol H2/ mol lactate consumed) was achieved when fermenting lactic acid wastewater at 45°C and initial pH 7.5. 16s rRNA sequencing analysis revealed bacteria from the Clostridium and Pseudomonas genera were the most abundant at the end of experiments.

Tubular membrane and membrane-less MFCs were investigated as an alternative method for treatment and energy recovery for MFC for different slaughterhouse wastewater streams. The highest energy recovery was achieved when feeding the overall slaughterhouse wastewater to membrane MFC (0.26 kWh/ ?kg COD) and carcass wash wastewater membrane-less MFCs (0.36 kWh/ ?kg COD). Combining dark fermentation with MFC to treat lactic acid wastewater resulted in high overall organic removal and most of the energy was recovered by the dark fermentation.