Enzymatic Treatment of a Modified Food Processing Wastewater

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The wastewater resulting from soy-processing is found to have 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 resulting in degradation of recalcitrant compounds. Previous studies utilizing the fungus in the bioreactor found that the high pH of the wastewater caused inhibition of TKN and COD degradation. Adjustment of the wastewater pH before introduction into the bioreactor resulted in a greater reduction of TKN and COD. However, complete degradation did not occur and pH adjustment was required continuously. Thus, we investigated the effectiveness of treating the wastewater with the enzyme culture solution obtained from the reactor instead of utilizing the fungal reactor itself in order to overcome the inhibitory effect of high pH on fungal activity within the reactor. The inorganic forms of nitrogen found in the pH adjusted wastewater were removed by treatment with both anion and cation exchange columns. Diluted wastewater (10% and 20%) was treated with enzyme solution (5% and 10%) and monitored for changes in TKN and COD for 24 hours. There was little change in pH over time for any of the treatments. The COD dropped 50 – 67% for all treatments over 24 hours. Removal of the inorganic nitrogen within the wastewater before treatment with the enzymes resulted in a greater reduction in COD. There was little change in TKN over time for any of the treatments. Treating the wastewater with fungal enzymes successfully reduced the COD concentration by approximately 60%. The results indicate that the use of the ligninolytic enzymes of the white rot fungi to degrade soy-processing wastewater could be a viable treatment technology.