Investigation on bio kinetic coefficients for making biological treatment of wastewater treatment plants in cold region

Selection of bio kinetic coefficients, as local conditions, is necessary for proper designing of wastewater biological treatment processes and meeting to effluent discharge standards. This research was performed in order to determination of the bio kinetic coefficients of sewage in cold regions of Iran.
This study is a semi-empirical research that was done as interventional using an extended aeration activated sludge process in pilot-plant scale. Research variables were measured daily in order to calculate cell yield coefficient(Y), endogenous decay coefficient(kd), saturation constant(ks) and maximum specific growth rate(µm). The pilot was operated with three concentrations of Mixed Liquor Suspended Solids(MLSS) of 2000, 3000 and 4000 mg/l, a Sludge Retention Time(SRT) of 20-30 days and a range of hydraulic retention time(HRT) of 20-30 hours. The coefficients were calculated according to Chemical Oxygen Demand(COD), Biochemical Oxygen Demand(BOD5). Achieved data were analyzed using Pearson correlation coefficient.
The results showed that the Y, K, Kd, Ks and µm coefficients based on the COD, were equal to 0.142–0.4915 mg/mg, 0.72–1.091 day−1, 0.0021–0.0153 day−1, 178.99–251.16 mg /l, and 0.15-0.35 day−1, respectively. The rate of these coefficients based on the BOD5, were equal to 0.2174–0.4915 mg/mg, 0.53–1.05 day−1, 0.008–0.0197 day−1, 102.38–214.6 mg /l, and 0.12-0.69 day−1, respectively. Achieved bio kinetic coefficients in this research, except to low range of the Y and kd that were less than those in the same studies, were fitted in range of reported amounts in the same studies. The results also showed that removal efficiency of COD and BOD5 was in range of 85.15 – 93.6% and 88.2- 94.85%, respectively.
The obtained coefficients in this study could be useful for designing of activated sludge processes in other regions with similar climate and culture.