Wastewater treatment and energy : an analysis on the feasibility of using renewable energy to power wastewater treatment plants in Singapore

Abstract

Wastewater treatment is a very energy intensive industry. Singapore has a state-of-the-art wastewater treatment system that uses a number of sustainable techniques that greatly improve its overall efficiency. The centralized Changi Water Reclamation Plant is one of the most advanced treatment facilities in the world. However, there are smaller, less efficient wastewater treatment plants still in use in Singapore. One of those is located in the Kranji Catchment region adjacent to the Lim Chu Kang Air Force Base. Called BJ725, this facility consists of a primary settler and a trickling filter. The purpose of this study is to determine the feasibility of using wind power, solar power, or methane gas combustion to meet the treatment facility's energy requirement. As the first part of this feasibility study, BJ725's energy requirement was analyzed. Additionally, wind and solar output was computed given historical meteorological conditions in Singapore, and the amount of power produced during methane gas combustion was computed given sludge output at BJ725. The outcome of these calculations showed mixed results. There was not one day of wind strong enough to produce usable energy in the 33-year meteorological dataset analyzed. Thus, there is essentially no potential for wind energy to be used in Singapore. Solar energy proved to be economically viable, but only with at least a 63 percent rebate. Sludge digestion and methane gas combustion proved to be by far the most economically viable option for wastewater treatment plants in Singapore. In the case of BJ725, approximately S$8,000 of yearly income can be generated if sludge digestion and methane gas combustion is utilized. Overall, sludge digestion seems to be the best option for wastewater treatment plants throughout the rest of the world. However, the three options studied are site specific and should be analyzed on a location-specific basis.