An evaluation of treatment process options for the retrofit of an existing urban wastewater treatment plant with a focus on energy efficiency

Abstract

The wastewater treatment industry faces severe challenges due to sudden increases in populations and hence increased sewage flows to the plants along with harsher regulations from the EU and other regulatory bodies to meet effluent quality requirements. In addition to this, is also the reduction in the specific energy which is becoming more of a concern as time passes, and plants are looking for ways to decrease the energy and carbon footprint. This report describes retrofit options for extended aeration activated sludge process in IĊ-Ċumnija wastewater treatment plant. The main aim of this research was to establish a process that will allow the treatment of an increased influent flow. The two main constraints were to use the existing plant footprint without extensive additional civil works that will result in downtime and to use the existing electrical power usage or less. The processes were narrowed down to Moving Bed Biological Reactor (MBBR) and Integrated Fixed-Film Activated Sludge (IFAS) as both meet the mentioned constraints and show good improvement potential. The evaluation of the MBBR and IFAS processes with respect to the current extended aeration process was performed through BioWin by EnviroSim, a wastewater simulation software. The model was configured and calibrated based on drawings and data of the plant, meetings with engineers and operators, and site visits involving onsite measurements and tests along with observations. This preliminary study gives a good insight of the potential effluent quality for the technological solution that was the preferred option of the plant engineer. However, Integrated Fixed Film Activated Sludge (IFAS) process is not eliminated by this option. The simulation was done using different media surface areas and reactor media fill factors. The effluent parameters BOD, COD and N improved by 4% with a reduction of 0.093 kWh per m3of effluent. The MBBR upgrade will allow a 50% increase in the influent flow while still meeting the BOD, COD and N values of the current process at 10000m3/day of influent.