Evaluation of biodegradation kinetics of specific organic constituents at full-scale facilities

The present work was aimed at determining the feasibility of applying the extant kinetic technique to evaluate the ability of the biomass to degrade specific organic pollutants at full scale facilities and to determine the ability of these kinetic parameters to predict effluent concentrations of the target compounds. Biodegradation of acetate, ethylene glycol, acetone, and furfural was studied at two full scale facilities, the Cedar Rapids Water Pollution Control facility and the Boone Water Pollution Control Plant. Acetone and ethylene glycol biodegradation at Cedar Rapids exhibited fairly stable kinetic parameters over the entire period of observation. The mean values of the kinetic parameters were calculated at three month intervals, and those mean values varied within a 20% range. Three month mean values for furfural at Cedar rapids and ethylene glycol at Boone varied within a range of 300 % and 100 %, respectively. Standard deviations of the mean values within each of the 3 months period were used to evaluate short term variability. Standard deviations within 3 month periods were less than 60 % for KS and less than 50 % for the rest of parameters. Observed standard deviations were similar to those reported for laboratory scale reactors operated at steady-state in previous studies. Based on the results of extant kinetic tests and measured effluent concentrations during a calibration period, the competent biomass fractions for furfural and acetone were estimated in the mixed liquor from the Cedar Rapids WPCF as 2.3 % and 1.8 %, respectively. These values were more than an order of magnitude higher than the fraction of influent COD contributed by respective compounds. Consequently, it was evident that the competent biomass derived a significant portion of their carbon and energy requirements from other substrates. As a result, the concentration of the biomass with the enzymatic ability to degrade certain compounds was greater than would be predicted based on the influent concentrations of those compounds. After the calibration period, the extant kinetic parameters and estimated competent fractions were used to predict the effluent concentrations of furfural and acetone. The results indicated that the extant kinetic parameters provided a fairly good prediction of the effluent furfural concentration (e.g., within 13% on average). The prediction of the effluent acetone concentration was not as consistent, possibly due to the fact that the treatment facility was not at steady state and the influent concentrations of acetone varied more widely than furfural.