| Information on biodegradation kinetics is important for the design and operation of wastewater treatment systems. An extant respirometry test method was used to measure the kinetic parameters of activated sludge biomass degrading the aromatic hydrocarbons benzene, toluene and xylene.; The activated sludge biomass used for respirometric testing was obtained from a sequencing batch reactor. The reactor was primarily fed primary clarifier effluent as an organic source and target aromatic hydrocarbon substrates were fed to the reactor during respirometric testing to acclimate the seed biomass. A series of tests were conducted using each substrate during the testing period. The kinetic parameters for benzene and xylene were determined but there was no measurable response of the biomass to toluene. Subsequently, toluene was mixed with ethanol to determine its biodegradability in presence of ethanol. The kinetic parameters for the mixture of toluene and ethanol were determined as chemical oxygen demand (COD) mixtures of 80, 60, 40, and 20% toluene. The kinetic parameters found from each respirometric testing were yield (Y), half saturation coefficient (Ks), maximum specific growth rate (mu m) and maximum rate of substrate utilization (qm).; Benzene was found to have mean values for yield (Y), half saturation coefficient (Ks) and maximum specific growth rate (mum) of 0.99 mg COD/mg COD, 2.53 mg SCOD/L and 0.75/hr respectively. The 95% lower confidence interval (LCL) of Y, Ks and mum were 0.98 mg COD/mg COD, 1.75 mg SCOD/L and 0.59/hr respectively. The 95% upper confidence interval (UCL) of Y, Ks and mum were 0.99 mg COD/mg COD, 3.31 mg SCOD/L and 0.91/hr respectively.; Toluene (80%) + Ethanol (20%) was found to have mean values for yield (Y), half saturation coefficient (Ks) and maximum specific growth rate (mum) of 0.96 mg COD/mg COD, 0.88 mg SCOD/L and 1.00/hr respectively. The 95% lower confidence interval (LCL) of Y, Ks and mum were 0.95mg COD/mg COD, 0.85 mg SCOD/L and 0.74/hr respectively. The 95% upper confidence interval (UCL) of Y, Ks and mu m were 0.97 mg COD/mg COD, 0.91 mg SCOD/L and 1.26/hr respectively.; Xylene was found to have mean values for yield (Y), half saturation coefficient (Ks) and maximum specific growth rate (mum) of 0.97 mg COD/mg COD, 0.40 mg SCOD/L and 0.19/hr respectively. The 95% lower confidence interval (LCL) of Y, Ks and mum were 0.95 mg COD/mg COD, 0.28 mg SCOD/L and 0.17/hr respectively. The 95% upper confidence interval (UCL) of Y, Ks and mum were 0.98 mg COD/mg COD, 0.52 mg SCOD/L and 0.21/hr respectively.; The mean yield values for benzene, toluene (80%) + ethanol (20%) and xylene were nearly the same. Typical municipal wastewater has yield value lower than those of substrates tested in the laboratory. The Ks value of typical municipal wastewater was substantially higher than those of substrates tested in the laboratory. Benzene and toluene (80%) + ethanol (20%) exhibited higher mum values than those of typical municipal wastewater. Some of xylene mum values were in the range of typical municipal wastewater. |
