German sewage plant cuts energy use by 40 percent, starts supplying power back to the grid
The sewage treatment plant in Bocholt, Germany, treats up to 108,000 cubic meters of wastewater every day. Cutting the country’s emissions by 65 percent by 2030 will require a collaborative effort, including improving energy efficiency in water and wastewater facilities – and the operators at Bocholt were keen to do their part.
In 2020, the facility needed to replace the motors for the back sludge pumping station II and the flocculation filtration system. The funding was provided by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety. To meet the requirements of the National Climate Protection Initiative, the upgrades would have to prioritize the efficiency of the wastewater treatment plant, as well as the reduction of CO2 emissions.
Before this investment, sludge pumping station II used six motors to power its pumps. The operator adjusted the impeller geometry and replaced these motors with four highly efficient SynRM models, resulting in significant energy savings.
The operator also paired the new motors with ACS880-31 ultra-low harmonic variable speed drives (VSDs). These drives enable the pumps to dynamically adjust to varying hydraulic loads and reduce the risk of disturbances on the power network, further improving the water treatment plant’s efficiency.
“The sewage treatment plant has its own power grid. Our ultra-low harmonic drives ensure that it is free of harmonics, so as not to impair the sensitive measurement technology,” explains Markus Flierdl, Sales Engineer Region North-West at ABB Motion Germany. “Due to reduced harmonics, there is also less heat generation. This protects all electrical components in the system and extends their service life.”
Three more motor-drive packages were used for the flocculation filtration system, delivering the same efficiency and control benefits. Collectively, these upgrades have reduced the plant’s power consumption by 40 percent.
The sewage treatment plant uses biomass, photovoltaics and wind energy to generate around 6.3 million kilowatt hours of renewable electricity per year on-site. Following these efficiency improvements, the plant now consumes less power than it generates. As a result, the project to improve energy efficiency in the water and wastewater facility has also resulted in a supply of additional renewable electricity to the local power grid.
Andreas Wehren has been Operations Manager for the past ten years and is dedicated to improving the efficiency of the sewage treatment plant. “Because of climate change, we want to become more and more energy efficient. When I took over the sewage treatment plant as manager, we still needed almost five million kilowatt hours to operate. Now we need an average of around three million, partly because we have invested a lot in energy-efficient technology,” he explains.
