Aarhus city: Use waste water to recycle clean water, provide electricity for people

A city in Denmark invests in a system to produce electricity from domestic waste water to bring water to households.

Every time I use clean water, few people think of . sewer water. But for people in Aarhus, Denmark's second largest city, the link between sewage and clean water is about to be present in their daily lives.

Marselisborg wastewater treatment plant in Aarhus has produced 150% of the electricity needed to operate the plant, bringing clean water to households. They sell excess electricity to the local electricity network.

To produce electricity, the pump pumps sewage into large tanks, with a constant temperature of 38 degrees C and contains bacteria.

Aarhus city.

Bacteria and temperature turn waste water into gas - a mixture of gases produced by decomposing organic compounds. The plant burns gas to generate energy in the form of heat and electricity.

Lars Schroder, general manager of Aarhus Water factory (which owns Marselisborg factory), confirmed the technicians did not add any organic materials to the sewage.

The investment cost for the electricity production system is up to 3.2 million USD, but Lars Schroder hopes the plant will pay back after 5 years. The factory's income consists of two sources: Revenue from selling electricity to the city electricity network and heating the heating system of households.

Producing electricity from sewage is not a new technology, but the city of Aarhus has made breakthroughs thanks to a combination of several factors: Strict environmental regulations, efforts to reduce phosphorus pollution and Nitrogen in waste water.

Eva Kjer Hansen, Danish Minister of Environment and Food, said that wastewater treatment plants should shed the image of " excessive electricity consumption" to become an electricity production facility.

'We have a good example in Aarhus,' she said.

Several Danish cities - including Copenhagen - are considering the possibility of mimicking the model in Aarhus. Many other cities in the world - like San Francisco or Chicago (USA) also learn the process of utilizing waste water to supply clean water to people.

Despite this, Molly Walton, an energy analyst with the International Energy Agency, warned that replicating Aarhus's model is a major challenge.

• Firstly , according to Molly Walton, in order for the system to function effectively, the wastewater treatment plant must be large enough to produce an abundance of gas.
• Second , if wastewater becomes diluted by storms or groundwater, electricity production becomes more difficult.