Characterization of the inhibitory effects of recreational vehicle holding tank additive on an activated sludge system

This dissertation characterized the effects of shock loading recreational vehicle (RV) waste, applied as step function additions, on an aerobic, activated sludge system. The study was conducted using a bench-scale system that included three separate biological treatment units each with one-gallon aeration basins and 0.23-gallon clarifiers and a dosing system for treating each unit with a commercially available RV holding tank additive. A synthetic wastewater solution comparable to typical domestic wastewater was developed and used as the wastewater source. The units were operated at four different solids retention times (SRTs) of 4, 5.5, 6.9, and 10 days. The units were loaded with RV holding tank additive continuously for five consecutive days to simulate influent wastewater containing 0%, 10%, 25%, and 50% RV wastewater. Influent soluble COD concentrations were: 463 mg/l at 0%, 542 mg/l at 10%, 659 mg/l at 25%, and 854 mg/l at 50%.; The biological reaction rate was demonstrated to follow first order kinetics, and the reaction order models exhibited coefficient of determination of no less than 0.91. Kinetic coefficients were determined using data collected before introduction of the holding tank additive. The coefficients were: Y _max = 0.50 mg VSS/mg COD-day; k_d = 0.0725 mg VSS/mg VSS-day; k = 0.75 mg COD/mg VSS-day; and K_s = 25.9 mg/l COD.; A contingency table analysis showed significance greater than 99.9% in the COD removal performances. Comparisons of treatment means for COD removal, nitrification/nitrogen utilization, and oxygen uptake rates were all significant to at least 95% with the following exceptions: oxygen uptake rate at ten days SRT and 10% RV wastewater (less than 90%, greater than 80%), TKN reduction at four days SRT and 10% RV wastewater (less than 80%), and TKN reduction at 5.5 days SRT and 25% and 50% RV wastewater (both less than 80%). Effluent concentrations of soluble COD and solids increased during dosing with the holding tank additive regardless of SRT. As SRT and the dosage rate increased, nitrogen utilization increased. As the dosage rate increased, nitrate-nitrogen effluent concentrations decreased and TKN effluent concentrations increased. The reason was suspected to be reduced nitrification due to presence of the holding tank additive.