Date of Award
Master of Science
Food processing wastewater is commonly treated using conventional aerobic treatment such as activated sludge processes that produces excess bacterial biomass having a low economic value. On the other hand, the fungal biomass derived through wastewater purification of food processing wastewater, could be the source of valuable biochemicals, which has a high economic value. Moreover, the better settleability of the fungal filaments permits a low-cost separation and recovery of various fungal by-products. One of the most prevailing problems in utilizing food-processing wastewater as organic substrate for fungal cultivation is the bacterial contamination. Therefore, there is a need for cost-effective method to control bacterial growth under non-aseptic conditions. The selection mechanisms create an environment for the proliferation of fungi, making fungal cultivation much simpler during food processing wastewater treatment. This research focused mainly on improving fungal selection under non-aseptic conditions through selective disinfection in addition to microscreen for retaining fungi and pH adjustment to about 4. Ozone was used to limit bacterial competition and promote fungal growth. Different ozone dosages were continuously applied to continuous stirred tank reactors treating corn-processing wastewater from Archer Daniels Midland plants at Cedar Rapids. The effects of different ozone dosages on fungal biomass production, soluble chemical oxygen demand (SCOD) and bacterial contamination in the bioreactor were evaluated. Ozone dosage of about 57 mg/L provided maximum fungal biomass production and SCOD removal among the tested ozone dosages (from 0 to about 76 mg/L). Total biomass concentration (sum of fungal and bacterial biomass) increased from about 1,450 mg VSS/L (control reactor without ozonation) to about 1,750 mg VSS/L at around 57 mg/L ozone dosage. Maximum SCOD removal of about 90% was achieved at around 57 mg/L ozone dosage. Statistical analysis revealed that the SCOD removal, fungal biomass production and bacterial biomass at about 18 and 29 mg/L ozone dosage did not differ from that of control significantly. Bacterial population measurements using flow cytometry indicated that about one log reduction could be achieved at around 47 mg/L and greater ozone dosages.
Sankaran, Sindhuja, "Ozone as a selective disinfectant for nonaseptic fungal cultivation on corn-processing wastewater" (2006). Retrospective Theses and Dissertations. 19076.