Biodegradation of a Food Processing Wastewater UtilizingPhanerochaete Chrysosporium

Abstract

Soybean hulls are processed into soy flour in a method similar to paper mill production. During the process, the soybean hull wastewater (SHW) is discharged into an anaerobic lagoon and then into an aeration basin. From there, it passes to a facultative lagoon before discharge. Even after this conventional treatment, the SHW has extremely high amounts of Total Kjeldahl Nitrogen (TKN), Chemical Oxygen Demand (COD) and a high pH. We have developed an attached growth, packed-bed bioreactor (PBR) containing the white rot fungus (WRF), Phanerochaete chrysosporium . This fungus secretes enzymes that catalyze oxidation reactions that result in degradation of recalcitrant compounds such as PCB, PCP, and pesticides. Previous studies utilizing the fungus in a bioreactor found that it could decolorize a polymeric dye. We hypothesize that the WRF could degrade the SHW and reduce the TKN and COD. We also assessed the effectiveness of pH adjustment of the SHW before introduction into the bioreactor. The objectives were to evaluate the ability of P. chrysosporium grown in a PBR to degrade the SHW containing high concentrations of TKN and complex organic compounds and to investigate the effectiveness of pH adjustment of the SHW before treatment in the PBR. The WRF in the PBR was fed an N-limited media for 5 days before introduction of the SHW. The effluent was sampled daily and measure for TKN, COD and pH. The pH adjusted wastewater was recycled through the PBR and the effluent was sampled daily and measure for TKN, COD and pH. Within 48 hours, 63% of the TKN and 37% of the COD was degraded. The pH of the effluent increased steadily from an initial pH of 4.88 to 8.59 at 24 hours. Within 72 hours, the effluent pH was equal to the influent pH. At this point, degradation within the PBR ceased. Continuous adjustment of pH during recycling of the wastewater within the PBR resulted in an increase in the amount of TKN and COD degraded. Over 90% of the TKN and approximately 33% of the COD was removed during treatment within the PBR. The pH of the SHW in the PBR had a significant effect on fungal degradation. The reduction of COD was more sensitive to pH changes than the reduction of TKN. With the improved pH control in the PBR during recycling events, a greater amount of TKN and COD were removed from the wastewater. These positive results indicate that treatment of recalcitrant wastewater with the WRF deserves further investigation.