Technical and Economic Evaluation of WWTP Renovation Based on Applying Ultrafiltration Membrane

Nowadays, the standards of discharging are gradually becoming stricter, since much attention has been paid to the protection of natural water resources around the world. Therefore, it is urgent to upgrade the existing wastewater treatment plant (WWTP), to improve the effluent quality, and reduce the discharged pollutants to the natural environment. In this paper, taking the "Liaocheng UESH (UE Envirotech) WWTP in Shandong province of China" as an example, the existing problems and the detailed measures for a renovation were systemically discussed by technical and economic evaluation, before and after the renovation. During the renovation, the ultrafiltration membrane was added as the final stage of the designed process route, while upgrading the operation conditions of biochemical process at the same time. After the renovation, the removal rates of chemical oxygen demand (COD_cr), biochemical oxygen demand (BOD₅), total phosphorus (TP) and other major pollutants were improved greatly, and the results fully achieved the standards of surface water class IV. The ultrafiltration system performs a stable permeability around 1.5 LMH/kPa. Besides, the economic performance of the renovation was evaluated via the net present value (NPV) method. The result reveals that the NPV of the renovation of the WWTP within the 20 year life cycle is CNY 72.51 million and the overall investment cost can be recovered within the fourth year after the reoperation of the plant. This research does not only indicate that it is feasible to take an ultrafiltration membrane as the main technology, both from technical and economic perspectives, while upgrading the biochemical process section in the meantime, but also provides a new strategy for the renovation of existing WWTPs to achieve more stringent emission standards.