42 n WATER INDUSTRY October 2023 www.drivesncontrols.com German water plant goes off-grid Treating and processing wastewater to make it safe to return to watercourses needs a lot of energy. Wastewater plants consume up to 3% of global energy output, with modern facilities typically using 20-45kWh per population equivalent (PE) a year. Improving the processes using the latest technologies, with the aim of increasing productivity, reducing energy consumption, minimising losses and optimising the use of chemicals is therefore key to water utilities achieving their sustainability goals. For example, the German utility Schwarzachgruppe started to operate an “energy-intelligent” wastewater treatment plant in the Bavarian municipality of Schwarzenbruck in September 2022. The plant is an environmental showcase project, which balances energy-consumption and production automatically so that external power supplies are rarely needed. It is estimated that the plant will save about 300 tonnes of CO2 per year compared to conventional sites. The project received €3.9m of funding from the German government as part of its Environmental Innovation Programme. The site now includes a hydroelectric power plant on the wastewater treatment plant outlet, photovoltaic panels, and two combined-heat-and-power plants fuelled using the sewage gas. It also stores heat (in the form of hot water), sewage gas and electricity (in batteries). The various storage technologies are coupled to ensure the continuous provision of thermal or electrical energy, depending on demand. The wastewater treatment plant also operates in a grid-serving manner. In the event of an oversupply of electricity, for example, the battery storage system is charged. During low production, the battery can be discharged. The system calculates the optimum use of the various forms of storage, based on load and production forecasts. To monitor, control, regulate and optimise the complex energy system in an energyefficient way, the site is using ABB Ability’s Optimax energy management and optimisation technology. This allows energy efficiency potentials to be exploited and the various energy generation and storage options to be networked, controlled and optimised. n A German wastewater treatment plant is using a combination of energy technologies to drastically reduce the amount of energy it requires from the grid – eliminating it entirely at times. The Schwarzenbruck wastewater treatment plant is now largely powered using on-site energy resources The plant combines various sources of energy production and storage to minimise its need for external supplies
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