Cost analysis and effects of various coagulants used for sludge treatment at the full-scale wastewater treatment plant

Abstract

The economic potential of poly-aluminum chloride (PAC) at full-scale sludge treatment plant and its impact on sludge production was explored in this study. The effect of recycling water on major parameters of wastewater treatment plant (WWTP) such as chemical oxygen demand (COD), suspended solids (SS), total nitrogen (TN) and total phosphorus (TP) was investigated. Comparative cost-analysis for powdered polymer coagulant (PPC), liquid polymer coagulant (LPC) and PAC was made for the period of 2016-2019 while the impact of recycling water from the sludge treatment section on to the effluent characteristics was conducted for six months before and after PAC application. Coagulants cost per ton of sludge treatment was dropped by 15% without increasing sludge production after PAC application in combining with PPC instead of LPC. TN removal efficiency of the WWTP was about 6% while TP 1% that can be attributed to the mixing of PAC loaded recycling water from sludge treatment section with the influent. COD and SS removal were slightly dropped throughout the period of 2016-2019. After PAC application, mixing of recycling water from the sludge treatment section with the influent significantly decreased the fluctuation in TP concentration of the effluent. Therefore, PAC can be an economical and environmentally sustainable option for sludge treatment at full-scale WWTP.