In a new report released in July, the European Environment Agency (EEA) recommends initiatives towards achieving circularity in wastewater treatment.
Urban wastewater treatment in Europe, the report notes, has focused on treating wastewater before returning it to the environment. However, there are significant opportunities for wastewater treatment facilities to become more resource efficient and more circular.
One aspect of urban wastewater treatment is the fact that it is highly energy intensive and, if the energy is sourced from fossil fuels or biomass, greenhouse gases are emitted in the process. Another key aspect is the release of persistent pollutants into wastewater which require advanced treatment to remove them from the water, resulting in these pollutants remaining in sewage sludge, diminishing its potential for reuse.
Rather, the EEA recommends that Urban Wastewater Treatment Plants (UWTPs) be more widely recognised as ‘resource hubs’ which offer the potential to recover elements and energy from the wastewater. This requires adaptation of existing legislation, as in many cases the (re)use of waste is restricted by law.
Also, at EU level, the regulation of UWTP’s focused on maintaining the quality of surface water and groundwater in Europe. The 1991 Urban Wastewater Treatment Directive does not cover greenhouse gases, whereas UWTP’s are a significant source of emissions. Also, the directive is outdated, listing a small range of controlled substances in comparison with the range of substances that are produced now - three decades later.
On the one hand, viewing UWTP’s as resource hubs, undertaking measures to reduce emissions and recover elements is key to the circular economy. On the other hand, ‘upstream’ measures such as limiting the substances that may be discharged into drains and pre-treating effluent before its release into the sewers can also contribute to circularity.