Water -energy -carbon nexus approach for sustainable large-scale drinking water treatment operation

Abstract

Sustainability of energy and water are inextricably linked with each other. Over-utilization/degradation of these resources may occur due to changing climate, growing population, and increasing pollution including carbon emissions due to the burning of fossil fuels. Drinking water treatment is essential for safeguarding public health; however, it is an energy-intensive process. The purpose of the current study is to study the energy -water -carbon nexus of a large-scale drinking water treatment plant (DWTP) that treats 1 Mm3 of raw Colorado River water per day by using direct filtration process and utilizes fossil fuel as energy source. Energy consumption of each treatment process was determined and then validated against DWTP data. Energy intensity was found for the processes of ozonation (19.6 Wh m−3), coagulation (1.3 Wh m−3), flocculation (1.22 Wh m−3), filtration (1.24 Wh m−3), the sodium hypochlorite generation system (31.7 Wh m−3), chlorination feed pumps (1.27 Wh m−3), and residual management (0.07 Wh m−3). Further, a modeling study was conducted to offset the energy consumption of the DWTP and thus reduce carbon emissions, by utilizing PV system, considering both the existing land-holdings of the plant and cost-effectiveness of the PV system. Comparison of PV system performance and the effects of incentives and electric rates on cost effectiveness were analyzed for the locations of Nevada, New York and Massachusetts. Net reduction in carbon emissions was estimated in the range of 980–11000 and 480–5200 metric tons CO₂eq year−1, by using PV with and without battery storage, respectively.