Current sewage treatment systems consume between 1% and 3% of global energy output and make up over 20% of energy use on public utilities, but some countries are now using wastewater to their advantage
Considering wastewater as a resource is a relatively new perspective. The organic content in the wastewater can be used as a resource for energy production and phosphorus can be used for fertiliser production with several advantages compared to the application of sewage sludge on agricultural land.
More than 50% of a standard wastewater treatment plant’s energy consumption occurs during the process of aerobic activated sludge treatment by aeration. An alternative technology involves untapping the intrinsic energy content of wastewater and converting this to gas, producing heat and power.
Improving a wastewater treatment plant’s energy self-sufficiency and selling surplus energy to the grid can reduce costs for wastewater utilities.
Copenhagen (Denmark) and Turku (Finland) are two examples of energy-positive wastewater treatment plants, which use systems for harvesting the intrinsic thermal and chemical power of wastewater.
These real-life cases show that just by converting the chemical energy, twice as much energy can be supplied than consumed. While by utilising both the thermal and chemical energy, energy supply can be nine times higher than consumption.
A shift towards these technologies is becoming increasingly urgent.
Currently one third of the global population has no access to toilets or latrines, while six in 10 do not have access to safely managed sanitation facilities. Furthermore, 80% of wastewater from human activities is discharged into rivers and seas without any pollution removal, according to the latest data.
Yet by 2030, for compliance with SDG6, access to safely managed sanitation should be made available for all (target 6.2) and the volume of untreated, discharged wastewater should be halved (target 6.3).
Full implementation of currently prevailing technologies would significantly increase the negative climate impacts of wastewater treatment, with a notable rise in energy consumption.
Consequently, research efforts are underway globally to reduce the energy consumption of wastewater treatment.
For more information, watch the International Water Association’s webinar: Circular Economy: Tapping the Power of Wastewater