Understanding the influence of energy and chemical use on water treatment plants carbon emissions accounting

Abstract

Urban drinking water treatment plants (DWTPs) depend on energy-chemical-intensive processes to treat drinking water, leading to carbon emissions during their operations. Variations in water quality parameters during these treatments may influence the emissions and efficiency of these plants. Thus, this study conducted a systematic assessment of carbon emissions accounting through the emission factor method in two urban DWTPs. Subsequently, multivariate and regression analyses were conducted to better understand the statistical relationships between energy, chemicals, and water quality parameters. Results show that the total carbon emissions intensity for both plants amounted to 0.328 kgCO₂-eq/m³, with treatment systems, chemicals, sludge, and facilities responsible for 60 %, 35.6 %, 2.5 %, and 1.9 %, respectively. Chemicals like polyaluminium chloride (PAC) were significant contributors to both plants, emitting 0.089 kgCO₂-eq/m³ of the total carbon emissions. The emissions intensity for both plants varies due to the continuous pumping and the chemicals used for treatment. However, the addition of CO₂ significantly reduces carbon emissions for the conventional treatment stages in one of the DWTPs. The regression and relative importance analysis conducted on carbon emission intensity, water quality parameters, and chemicals showed that the model is a good fit for understanding the variations in chemical and carbon emissions. Factors such as water temperature, turbidity, alkalinity, and permanganate were found to significantly influence the DWTPs. Conclusions of previous energy versus water supply studies, combined with findings from this research, indicate that the influence of climate change on DWTPs may vary depending on the location and individual processes involved.