Making Every Toilet Flush Count—Creating Electricity From Sewage

Treating sewage takes a lot of energy, but in the face of rising energy costs, creating electricity from wastewater is a near-ideal renewable energy option.

“Wastewater operators are asking themselves how to maximise energy recovery from wastewater treatment as well as minimising energy consumption in the treatment process,” Dr Paul Greenfield says.

Dr Greenfield, chair of the Australian Nuclear Science & Technology Organisation, addressed an international water congress in Korea about achieving improved sustainabilty in the urban water sector.

He says the two most valuable products from wastewater treatment are energy and clean water.

“As the price of energy goes up, that will encourage wastewater treatment operators to become more energy efficient and look for more efficient ways of generating energy from the wastewater processing.”

Sewage, or wastewater, needs to be cleaned of chemicals, organic matter, bacteria and viruses—and part of the process to achieve this clean-up can be used to generate electricity, fuel, heat, biogas and more.

Treatment plant operators are increasingly interested in using methane generated from wastewater to power their plants and, in some cases, feed electricity back to the grid.

The main drivers for mining energy from wastewater are rising electricity costs and, similarly, carbon prices in countries that have pollution taxes in place such as Europe and Australia. Modern cities are also turning to greener design and innovation.

Dr Greenfield points out that, with time, “there will be different ways of collecting water—recycled, rainwater, stormwater, desalination, reservoirs—and a myriad of uses—industry, agriculture, developing and old areas,” he says.

“We will end up with much more complex systems than we currently have, and see great advances in technology. Operators will certainly want to recover energy, because energy costs are only going to go one way in future.”

The International Water Association’s World Water Congress and Exhibition, in Busan (Korea), ran 16–21 September 2012.