Estimating oxygen transfer conefficients in the presence of surfactants using turbine aeration system

Abstract

Aeration plays an important role in the activate sludge process; it supplies enough oxygen to maintain the metabolic reactions of microorganisms and provide sufficient mixing in the aeration tank. During aeration, the presence of surfactants in watewater becomes one of the major obstacles for the process. Generally, the presence of surfactants reduced the oxygen transfer efficiency. Unsuitable Unsuitable estimation of the oxygen transfer rate (OTR) decreased the process efficiency and increased the cost of energy consumption. The optimum oxygen transfer rate was investigated in this study using oxygen transfer coefficient (KLa) in order to find the best transfer efficiency with suitable oper inputs in the presence of surfactant. Laboratoy-scale tests were performed in 300-L reactor equipped with a turbine aeration system in the absence and the presence of surfactants (5, 10 and 15 mg/L). Power inputs per unit volume were varied at 13.17, 26.33, 39.50 and 52.67 W/m3. Dissolved oxygen (DO) was measured during the tests under non-steady state under non-steady state condition and the data was calculated for overall oxygen transfer coefficient (KLa) using ASCE DO Parameter Estimation Program (DO_PAR) (Lee et al. 2002). According to the experimental results, the KLa increased linearly with increasing power inputs for clean water and 5 mg/L of the urfactant concentrations. But for 10 and 15 mg/L of the surfactants, the KLa seemed to decrease at 39.50 and 52.67 W/m3. The results from this sduty showed that at the lower power inputs (13.17 and 26.33 W/m3), with different surfactant concentrations (clean water, 5, 10 and 15 mg/L of surfactant concentrations), surfactant did not effect significantly on KLa values. This result contrast with what Stenstrom (1980) found. So, this turbine aeration system can handle the effect of surfactant concentrations to KLa values, practically.