GETTING THE SOLIDS OUT – OPTIMIZATION OF SOLIDS THICKENING AND DEWATERING PROCESSES INCREASES PLANT CAPACITY

Plant optimization has been used to enhance a plant's performance and demonstrate additional plant capacity. Often these projects concentrate on the liquid train of the wastewater treatment plant, where capacity increases in the clarification systems or biological reactors results in an overall plant capacity increase. However, solids handling systems are also key to an overall plant capacity, the performance of the facility and the end products (e.g. Biosolids). All biological systems require that the biosolids generated be stabilized and removed from the process.Tools are available to provide a detailed evaluation of a facility and devise ways to optimize its performance. For this project these tools were applied throughout the facility; however, their application to the thickening and dewatering centrifuge processes yielded the largest increase in capacity.The optimization project was undertaken at the Ottawa Robert O. Pickard Environmental Centre (ROPEC). Testing of the solids handling processes included a review of polymer use and stress testing units to demonstrate the available capacity in these processes. In addition, prior to the stress testing of the waste activated sludge (WAS) thickening centrifuges physical modifications to the units were undertaken to optimize their performance.The results of the work, in conjunction with a review of the liquid train, were very positive to the overall capacity of the ROPEC facility. The WAS thickening capacity was demonstrated at feed rates up to 24 L/s (380 gpm), well above the historical rates of between 10 and 12 L/s (160 to 190 gpm). Dewatering centrifuges were operated at rates of 15 L/s (240 gpm) with no deterioration in cake concentration or centrate quality.