WWTP’s struggle with quaternary treatment and energy neutrality

Wastewater Treatment Plants (WWTPs) struggle with reaching two objectives in the Urban Wastewater Treatment Directive. Implementing energy-intensive additional treatment technologies and heading for energy neutral WWTP’s seems contradictory. Two technical managers from wastewater treatment plants in Romania and Greece explained how they deal with this during a webinar about the implementation of the Urban Wastewater Treatment Directive (UWWTD) organised by the European Water Association (EWA) and Xylem.

Ioannis Mandilaras from EYDAP is responsible for one of Europe’s biggest wastewater treatment plant. The Psyttalia WWTP is the main wastewater treatment plant in the greater Athens area, receiving an average wastewater flow of approximately 730,000 m³/d. “The new UWWTD requirements increase our energy demand. It means we need to revise the whole system”, said Mandilaras during the webinar. He added that such a transition is extremely difficult because you cannot pause the treatment of wastewater. “Big WWTPs cannot produce enough biogas from their own sources, so you have to find extra energy sources and compete with other industries that demand energy.”

Deadline 2045

The Urban Wastewater Treatment Directive (UWWTD) sets a national energy neutrality target for urban wastewater treatment plants of 10,000 p.e. and above to produce energy from renewable sources by 2045, based on regular energy audits, with progressive intermediate targets. Another objective requires wastewater treatment plants of 150,000 p.e. and above to meet the requirements for quaternary treatment before 31 December 2045.

No audit organisation available

Csaba Bauer is the technical manager for wastewater treatment at Aquaserv, a water company in Romania. They serve 300,000 people and 5,000 companies. Bauer also identifies the high energy costs as one of the main challenges of the new rules. “We know that quaternary treatment requires 10-30% extra energy. This is at odds with energy neutrality. To evaluate how much energy you will need, you have to do energy audits, but we have no wastewater experts in Romanian audit organisations that can take that on. You need experts for WWTPs and these audits should be applied in the same way across the whole of Europe.” Arthur Guischet, EWA Secretary General, mentioned that based on members’ input in the EWA quaternary treatment working groups, additional treatment methods represent between 3 and 16% of a plant’s total energy consumption when implemented properly.

Intelligent pumps might be the solution

Tania Pentcheva from Xylem does not see a conflict between quaternary treatment and energy neutrality. “We are convinced it is possible to implement both objectives. The most important thing is to invest in energy efficiency and start looking at the pumping facilities. Most of the pumps in the industry are really old, because they were installed 30 years ago. Intelligent pumps can deliver huge benefits, cutting 50-60% of the energy costs.” She added that it differs how much energy is needed for quaternary treatment. This depends on the technology. In Denmark there are examples of energy positive WWTPs.”

Moving CAPEX to OPEX

Pentcheva emphasizes that water technology companies are willing to help wastewater treatment plants achieve the objectives. “We are also thinking of moving capital expenditures (CAPEX) to operational expenditures (OPEX), so we will own the assets and pumps. The water companies will pay for the m³ of water moved.” According to Pentcheva UWWTD-implementation requires high investment costs. We need to make sure funding for the water transition is included in of the Multiannual Financial Framework 2028-2034.