Umeå Municipality has a total of 19 wastewater treatment plants. The largest handles waste water from households and various companies in the area. Every year, it receives about 13 million cubic metres of waste water, containing 3,000 tonnes of organic material and 80 tonnes of phosphorus. And every day it produces 23,000 kWh of biogas.
Umeå’s largest treatment plant manages the waste water of 166,000 inhabitants (including industrial load) and can purify up to 8,100 cubic metres of waste water an hour. There are mechanical, chemical and biological treatment stages, which remove 95–97 percent of phosphorus and organic material. The process of cleaning the water consumes a lot of energy, but the plant also produces 23,000 kWh of biogas every day.
Making use of nutritious sludge
Substances removed from the waste water form a nutritious sludge, which for the past 10 years has been made into fertiliser pellets. The sludge pellets were highly effective as fertiliser and soil conditioner, but, as demand declined, the pellet machines were removed and instead the sludge started to be used as a construction material in an industrial area where leachate is collected and treated.
Even with efficient wastewater treatment plants, it’s still vital to reduce the amount of polluting and hazardous substances and waste in the water. So the municipality runs information campaigns to increase people’s awareness of the importance of not disposing of any hazardous substances or rubbish down drains.
Biogas as a powerful energy source
The sludge is digested over about two weeks to obtain energy in the form of biogas. The biogas consists mostly of methane (65%) and is used in engines to produce electricity and heat. The gas production is 3,000–4,000 m3/day, equating to 23,000 kWh of energy a day (8.4 GWh a year).
Most important environmental facility
The treatment plant was built in the early 1970s but has since been modernised. In 2001, a digester and a pelleting plant was added for treatment of the sludge. Between 2012 and2015, the plant expanded further, extensively increasing its capacity. Two gas engines were installed for more efficient use of the biogas.
This makes Umeå Wastewater Treatment Plant the single most important environmental facility in Umeå, combining efficient treatment of water and the production of a considerable amount of energy.