Abstract
Modern wastewater treatment plants (WWTP) often make use a combination of multiple interrelated physical, biological and chemical treatment processes, making performance predictions difficult. The advent of computer modeling software has given engineers and operators a potential tool to aid in WWTP analysis. In this project, BioWin™ was used to examine the performance of the City of Dunsmuir (City) existing WWTP and the performance resulting from proposed WWTP improvements. Two independent numerical models were created to simulate both the existing conditions and the conditions after the proposed improvements are constructed. The primary focus of the improvements is nitrogen removal in its various forms, specifically ammonia, nitrate, and nitrite. The City’s influent wastewater and plant operations were characterized using available data collected for its National Pollutant Discharge Elimination System (NPDES) permit, for internal process control, and for special studies. Typical mass concentration ratios (e.g., cBOD/BOD, NH4/TKN, etc.) were used to convert available data into the form required by the modeling software. Where no data existed for a given constituent of concern, literature values were employed. According to model results, the proposed WWTP improvements will yield minimal improvement in effluent quality. The effluent quality achieved at the actual plant, however, may differ from model predictions because the model was unable to fully simulate the actual plant’s control scheme. Furthermore, the models’ ability to depict process improvements may have been limited by the assumptions made in creating the influent wastewater and plant operations data set. More accurate simulations of the existing and planned WWTP improvements may be realized if constituent and process data expressly tailored to the software’s required inputs are collected.