Example of water treatment in Denmark: sewage plant transformed into power plant

Investment in new technologies between 2003 and 2016 helped reduce electricity consumption by 33% at the marselisborg wastewater treatment plant.

Last year, Denmark's wastewater treatment plant exceeded its own energy consumption and became a veritable "green power station". Engineers from Serbia to China have lined up to learn how to turn wastewater into valuable energy.

Most water treatment plants - which convert waste water and sewage into something that can enter the water cycle - consume a lot of energy and strive to use new technologies in order to save power costs and protect the environment.

The marlisburg sewage treatment plant, located in Aarhus, the second largest city in Denmark, has invested 3 million euros in upgrading, and its energy production in 2016 exceeded its energy consumption by nearly 70%, which has attracted the attention of the international community.

This makes Aarhus the first city in the world to provide fresh water to all citizens by treating domestic sewage and waste water to produce energy, which greatly increases people's interest in how to turn waste water into resources.

"We're just harnessing the potential of waste water," per overaard Pedersen, chief engineer at Aarhus water, said in a telephone interview. "We don't use heat pumps and wind turbines like anywhere else."

According to mallisburg plant, they are self-sufficient in energy by extracting carbon from waste water and sludge and transferring it to a decomposition tank with bacteria to produce biogas, mainly methane, and then burning it to produce heat and electricity. Although this treatment process is not novel, the final effect is very good, which is attributed to their investment in new technology and customized equipment to prevent leakage and reduce maintenance costs.

Pedersen said investment in new technologies between 2003 and 2016 helped reduce electricity consumption by 33% at the marlisburg wastewater treatment plant. "It's very important for a treatment plant like ours," he said.

International concern

Mallisburg sewage treatment plant is regarded as an example of wastewater transformation, which has attracted the attention of the international community. In its world energy outlook 2016, the International Energy Agency in Paris has identified marlisburg as a typical example of energy neutralization through wastewater treatment in the future.

In last month's World Water Development Report 2017, the United Nations said that wastewater should not be regarded as a problem, but a valuable resource that can meet our needs for water, energy and nutrition. Energy efficiency is important for utilities like Aarhus water because it reduces costs and helps protect the environment.

According to the EPA, electricity accounts for 25 to 40 per cent of water companies' budgets, and 24-hour machines may be one of the biggest contributors to community greenhouse gas emissions.

Every year, more than 30 million cubic meters of waste water generated by 300000 customers are treated in marlisburg. The energy produced by marlisburg is used to run the waste water pump and provide clean water for customers. Excess heat and energy - equivalent to the energy consumption of 500 households - are being sold to the local grid, creating additional revenue.

The plant produces 2.5 gigabytes of grid heat per year, delivered to the local district heating system, plus the remaining electricity, which is equivalent to 99% of the total energy required for wastewater treatment and water supply. "Taking this into account, we can reduce our operating costs by about 3% to 4%," Pedersen said.

Visitors to marlisburg to learn from experience come from all over the world, as far as South Africa, but Pedersen said that our factory model does not necessarily apply to all places, especially small-scale processing plants, with a small population equivalent. "It's very difficult for small plants because it requires an expensive investment in the decomposition pool," he said. Based on our situation in Denmark, it is estimated that with a population equivalent of 100000, investment is feasible, but it also depends on the facilities of the factory and the local environment. "