Climatic Drivers of Wastewater Treatment Efficiency of Wastewater Treatment Facilities

Under current global warming, water resources management is a worldwide challenge. Wastewater treatment plants (WWTPs) recycle freshwater and protect the environment by reducing the discharged pollutant load into hydro-systems. The quality of treated wastewater depends on effluent physicochemical parameters and the efficiency of pollutant removal. However, the treatment process is vulnerable to climate change which can hinder wastewater treatment (WWT) efficiency. This study investigated the effect of climate parameters on the performance of WWTP based on total suspended solids (TSS) removal efficiency. Multi-scale temporal variations of chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD5), biodegradability index (COD:BOD5 ratio) and TSS removal were monitored during 2015–2022 at a semi-arid WWTP receiving exclusively municipal wastewater from Ain Beida City (NE Algeria). The removal efficiency of TSS was excellent, with 99.7% of samples yielding more than 80% of TSS reduction. The variation of COD, BOD5, TSS removal and effluent biodegradability index was significant among and within the studied years. The obtained results indicated that the correlations between TSS removal and the biodegradability index were statistically significant. The redundancy analysis examining the relationships between climate parameters and wastewater variables revealed that BOD5 was positively correlated with air temperatures and wind speed, whereas COD was inversely related to precipitation, air humidity, and rainy and snowy days. TSS removal seemed not to be affected by climatic factors as the WWT efficiency was excellent regardless of the quality of effluent sewage or local meteorological conditions. This study suggests that addressing the effects of weather events on effluent quality and WWT process helps improve the performance of municipal WWTPs for the proper functioning of the biological process of wastewater purification.