Energy Audit of Sewage Treatment Plants

The objective of this study is to conduct an energy audit of a sewage treatment plant,
analyze the energy consumption and efficiency of the STP and design energy
conservation measures to reduce energy consumption and cost It also serves as a
continuation and monitoring of Pantai Dalam SIP's previous energy audit 2008-2010.
At national level, IWK's total operating cost bas increased at a much higher rate than its
total revenue. In 2009, the company's loss amounts to RM33 million. From that total,
the energy cost contributes about 19%. At branch level, for 2008-2010, Pantai Dalam
STP' s energy cost contributes about 56% which is much higher. This shows that energy
has become one of the main contributors for their high cost, thus solutions should be
identified to optimize their energy efficiency and minimize the cost. The scope of study
is conducting an energy audit to analyze the energy usage of the plant. The
methodologies for the energy audit are the pre-site work: plant and utility data analysis,
site visit: walk-through survey and post-site work which comprises of baseline for
building energy use and evaluation of energy savings measures. Finally, the findings
indentifies that the largest energy user is the sewage lift pumps at the pump station,
followed by the blowers, clarifiers and aeration tank. It also identifies that the previous
energy audit still bas not achieved its goal of a I 0% reduction but already half-way
there. Thus, further initiatives and monitoring is required in achieving it. The sewage lift
pump is also identified to be inefficient and has a potential maximum savings of 34,815
kWh/month or RM8,024.86/month. Energy savings measures to achieve this is
changing the speed to 90"/o, which will increase its efficiency to 80.5% and yield a
saving of31,371 kWh/month or RM7,23l.02/month. Others include installing new
properly sized pumps, changing the pump impellers and replacing the motor.