Generate electricity from garbage

Some types of bacteria that are active in wastewater treatment can help people generate electricity, scientists claim.

Special vehicle for garbage disposal at a waste treatment plant in Australia.Photo: theage.com.au.

Livescience said that in conventional waste treatment equipment, microorganisms decompose solid waste in 'activated sludge'. They turn organic matter into methane but leave waste water including ammonia and phosphates - substances that need to be removed before people pour water into the river.

Current waste treatment devices consume a lot of energy to remove ammonia. This process uses bacteria that convert ammonia into nitrates, and those bacteria need to be continuously oxygenated into tanks processed by electric pumps. Later, it is necessary to add nitrogen denitrification bacteria to convert nitrate to nitrogen. To work, these bacteria also need methanol added in the mixture.

The process consumes an average of 44 Wh of electricity per day for a person to add waste to the treatment system. In a big city, this number could reach MWh.

Eliminate intermediate bacteria

However, now Gijs Kuenen - a scientist at Delft University of Technology, the Netherlands - and his colleagues are developing a technology to eliminate these energy-consuming processes. The key is the recent discovery of a bacterium that can break down ammonia without oxygen. This bacterium called anammox shortens the nitrogen cycle by directly converting ammonia into nitrogen gas.

A by-product of this process is methane, a gas that Kuenen can collect and use as fuel. The team also calculated that this process does not consume energy but also generates electricity.

"This process will help the wastewater treatment equipment work sustainably, meaning that they can even produce energy, unlike current processing machines," Kuenen said.

In May the team will begin to build a pilot device to illustrate this technology in the Dokhaven wastewater treatment system in Rotterdam, the Netherlands. They will partner with Radboud University in Nijmegen and Paques water treatment company based in Balk city.

Microbiologist Michael Wagner of the University of Vienna, Austria, said anammox bacteria were discovered only 20 years ago and could lead to the creation of a generation of sustainable wastewater treatment equipment.

'The story of anammox bacteria shows how the basic discovery of microbiologists can revolutionize the process of waste treatment ,' Wagner commented.