Modeling and Visualizing Energy for Water and Wastewater Services to Urban Communities in Hong Kong

Urban water and wastewater services are critical for liveable cities and communities at the cost of high energy dependence. To explore strategies for reducing energy dependence, it is essential to first explicitly reveal how much energy is used to provide water and wastewater services to various urban communities. So far, there is no study offering such spatial analytic solutions. To fill this gap, we created a mathematical model that can quantify energy consumption across different stages from withdrawing raw water from reservoirs to discharging the treated water for providing these services to urban communities. Using Hong Kong as the study case, our mathematical model includes 1) estimation of water demand and wastewater generation in urban communities based on water consumption surveys of residential, commercial, and industrial water use; 2) energy pumping calculation based on water transfer statistics from reservoirs to treatment works, and to communities; wastewater collection from communities to sewage treatment works; and seawater transfer from coastal extraction points to communities and storage tanks; and 3) energy consumption for treating water and wastewater. Our mathematical model was validated by comparing our calculated energy intensity for different waters with the observed values in Hong Kong. Our results include: 1) energy for different stages of water, wastewater, and seawater of Hong Kong water system; 2) spatial visualization of energy for urban communities to highlight regions with energy-intensive water services. Overall, our mathematical model provides a critical step to offering a systematic understanding of energy use for the urban water system.