Investigations into the Dynamic Behaviour of a Full Scale Municipal Activated Sludge Waste Water Treatment Plant

Abstract

<p> Although both steady state and dynamic simulation studies of the activated sludge process are available, the data bases employed have traditionally been: derived from bench scale studies, derived from historical monitoring data, synthetic based on mathematical functions. Actual plant operating data, if available, would reflect full scale operation and would provide a much better data base to judge existing or future process models. This study was designed to provide a more comprehensive data base than presently existed on a full scale municipal activated sludge system. Both flow and component concentrations were continuously measured on two hour intervals for two periods of 10 days and 5 days duration. Streams sampled included the plant influent, the primary clarifier effluent, the aeration tank effluent, the secondary clarifier effluent, the activated sludge recycle and the waste sludge line. Based on total nitrogen and total phosphorus, the data were examined for mass flow closure around the aeration tank. A time dependent mixing model based on two unequal volume stirred tank reactors in series was found to adequately describe the observed variation in aeration tank input-output data. The measured aeration tank inflow and outflow was corrected to give a hydraulic balance using a statistical procedure which generates flow corrections based on expected measurement error. The resulting total nitrogen and total phosphorus material balances were found to improve based on a reduction of the residual sum of squares.</p>