E-Andrew Sindt Creative Component S11.pdf

Chapter 5: Conclusion5.1 SummaryBiological nutrient removal is an important wastewater treatment process for removing nitrogen andphosphorus from wastewater before discharge and reducing eutrophication in our water bodies.Optimization of BNR processes may be achieved with the aid of wastewater treatment processsimulators. There is a need for more investigation of practical applications of wastewater simulators toreal world problems. This report proposed the application of the BioWin wastewater simulator to thewastewater treatment facility of the City of Grundy Center, Iowa. The following conclusions were made:• The RBCOD fraction as calculated by the influent specifier for the Grundy Center rawwastewater was greater than typical (default) values. The calculated acetate and non-colloidalslowly biodegradable COD fractions less than default values. A two week intensive samplegathering period should be conducted to ensure the accuracy of values used in the influentspecifier.• Sensitivity analysis on regular and BNR-S1 modes indicated that the three most sensitivesimulator parameters are OHO yield, AOB maximum specific growth rate, and the NOBmaximum specific growth rate. The BNR-S1 mode indicated two additional sensitive simulatorparameters: substrate (NH 4 + ) half-saturation concentration and the aerobic P/PHA uptake ratio.• The simulation of the regular mode did not accurately predict the reported processperformance. The predicted effluent TN and NO 3 - concentrations in the regular modesimulation were not to within 20% of the observed values.• Calibration of the BNR-S1 mode was successful in reducing deviation of effluent concentrationsfrom observed values to less than 20% (except NH 3 at 21.6% deviation).• Default simulator parameter values were found to better predict effluent concentrations thancalibrated simulator parameter values from one mode applied to a different mode, i.e., BNR-S2.Calibrated simulator parameters from one mode (regular mode) were adequate for predictingperformance in another mode (BNR-S1 mode). Recalibration of simulator parameters for thespecific operation mode was required.• COD fractions were determined to have a significant effect on effluent TP but have only minoreffects on other effluent parameter concentrations for the calibrated regular mode.• COD fractions were found to have a significant influence on effluent NH 3 -N, NO 2 - -N, NO 3 - -N, TP,and filtered COD concentrations for the calibrated BNR-S1 mode.• Variation of cycle phase duration was found to have a greater sensitivity in TP removalefficiencies for runs with calibrated simulator parameters than for default simulator parameters.• Variation of cycle phase duration showed improved predicted TN and TP removal efficiencies forincreasing anaerobic and anoxic phase length (decreasing oxic phase length). Based on theanalysis completed for this report, the optimum anaerobic/anoxic/oxic times is 140/90/40.The amount of data produced by a BioWin simulation run is astounding. The quality of the dataproduced needs to be verified before it is used to make any significant changes to processoperations or design.68