Evaluation of the Methane Production Potential of Catfish Processing Wastewater Using Various Anaerobic Digestion Strategies

The U.S. catfish industry is a major industry that has been declining over the years due to imports competition and growing operational costs. Catfish processing wastewater management and high energy requirement put a large financial burden on catfish processing facilities. Recovered protein-based solids have provided some value-added co-products, however, more co-products are needed to offset processing costs. Anaerobic digestion is a proven waste treatment method that produces methane, which is an energetic co-product that can be used within the processing facilities. This study was conducted to evaluate the potential of anaerobic digestion as an alternative to the currently used aerobic biotreatment of catfish processing wastewater. Initial assessments indicated the recalcitrance of the full-strength wastewater to anaerobic digestion, yielding only similar to 4 m(3) per ton (U.S.) of input chemical oxygen demand (CODinput). Thus, several strategies were evaluated to improve the methane yield from the wastewater. These strategies include nutrient (nitrogen and sulfur) amendment, along with ozone, HCl, and NaOH pretreatment. The results showed that nutrient amendment was the most suitable strategy for improving the digestibility of the catfish processing wastewater. A methane yield of 121-236 m(3)/ton (U.S.) CODinput was obtained, with a purity of 67-80 vol.%. These results are similar to yields and purities of biogas from other feedstock, such as food waste, wastewater solids, and fish canning wastewater. This indicates that anaerobic digestion could be a viable alternative for simultaneous treatment and energetic co-product generation from catfish processing wastewater.