Paper Implementation of Biological Treatment for Cod/Bod Reduction of High-Strength Industrial Wastewater

This manuscript describes studies performed to identify and implement the most effective means of reducing dissolved COD/BOD in high-strength industrial wastewater with variable Oil and Grease (O&G) present for compliance with BOD and TSS discharge standards. Pre-treated wastewater effluent is discharged at a daily rate of approximately 60,000 gpd to the sewer and ultimately treated by the local Publicly Owned Treatment Works (POTW). The industrial wastewater discharge permit contains BOD standards for wastewater parameters that are subject to surcharges for BOD exceedances greater than 250 mg/L. A characterization of the wastewater effluent for COD/BOD levels shows that COD averages 8,000 mg/L; the COD:BOD ratio averages 1.67; and O&G ranges from 10 to 25 mg/L. Maximum values for COD and O&G exceed 12,000 mg/L and 100 mg/L, respectively The COD/BOD ratio indicates that the organic load could be reduced via biological treatment. The various treatment options for such high-strength wastewater were identified, screened, and the most appropriate and readily tested were bench or field pilot tested. Other site constraints and limitations include, limited space available for treatment, highly variable facility inputs that lead to variable effluent composition, facility operation is 5 days per week, future planned facility growth that will create the need to treat 108,000 gpd of high-strength wastewater within 5 years of the start of facility operation, and a future need for biosolids residual management options other than landfill disposal. The treatment options and bench top/pilot test results are summarized, and, where appropriate, full-scale design and operations with total cost comparisons, are also discussed. Field tests of IFAS treatment for 8 weeks of operation using a slipstream of wastewater proved problematic and underperformed as a result of nutrient deficiencies, low pH, exhibited excessive foaming and O&G slime deposit build up. A subsequent MBBR bench lab test showed significant COD/BOD reductions using shipped samples of wastewater. Hence, the bench top unit was reconstructed in the field and testing continued in continuous mode. The most important ranked criteria for selection of the most appropriate treatment options that meet the performance criteria is impact on project IRR. A summary matrix table of treatment options vs. indexed IRR enables the facility operator to rank the viable treatment options by capital cost and operating savings and select those that have the most positive IRR impacts. MBBR/IFAS treatment technology has been selected for the biological treatment system implementation as a result of bench top test results, its lowest impact on project IRR, small footprint, and modular design for readily implementable future expansion.