Transformation of an energy consumer into an energy producer - is it possible?

Wastewater and water treatment plants are usually the largest single electric energy consumers in each town and city.Wastewater and water treatment processes are usually responsible for 25-40% of the total electric energy consumption in the city as it is associated with energy-consuming processes and a continuous operation cycle (24h, 365 days a year).The changes introduced in Marselisborg / Aarhus, Denmark consisting in the replacement of conventional blowers with high-speed units brought about a 100% surplus energy production - it was achieved without adding any external organic waste or coal and with no additional investments.Currently, the plant produces a net surplus of both electric and heat energy, supplying it to the district heating system in Denmark's second largest city, Aarhus.The carbon footprint was reduced by 35%.https://www.youtube.com/watch?v=XHOmBV4js_E