LIFE Project Cover Photo

Two-Stage Autotrophic N-remoVal for maINstream sewaGe trEatment

Reference: LIFE14 ENV/ES/000633 | Acronym: LIFE SAVING-E



Currently, urban wastewater treatment plants (WWTPs) consume at least 8-15 kilowatt hours/inhabitant/year of energy in order to meet legal requirements on discharges of organic matter, nitrogen and phosphorus. Meeting these requirements incurs a significant economic cost and produces substantial greenhouse gas emissions.


The SAVING-E project aimed to demonstrate how urban WWTPs can be redesigned so that they become energy producers rather than energy consumers. The performance of the redesigned WWTP would compare favourably to current standards.

SAVING-E technology works by using most of the organic matter that enters the WWTP for biogas production. Wastewater passes through a biological treatment step with low oxygen consumption and high biomass production. The biomass produced in this step has very favourable methane production potential, greater than that achieved by the current generation of urban WWTPs.

In a second step, SAVING-E technology biologically removes nitrogen from wastewater without the need for organic matter. SAVING-E uses the autotrophic biological nitrogen removal (BNR) process for this step, but with a novel two-step approach comprising two reactors: an aerobic partial nitritation reactor followed by an Anammox (anaerobic ammonium oxidation) reactor. The application of autotrophic BNR significantly cuts aeration costs compared to current urban WWTPs. The novel two-step approach to autotrophic BNR represents an improvement compared to one-step autotrophic BNR because it can work stably at very low temperatures (10 ºC).

The SAVING-E technology was scheduled to be tested at pilot scale. The pilot plant would be installed in the Rubí (Barcelona) urban WWTP. The pilot plant would operate for 30 months at different temperatures, including 10 ºC to demonstrate the stability of the process. A technical and economic analysis of the impact of the implementation of the technology in different types of urban WWTPs was planned.


The SAVING-E project demonstrated, on a pilot scale and with real urban wastewater, that the energy balance of an urban WWTP can be greatly improved at both high and low temperatures, thanks to the implementation of autotrophic biological nitrogen removal (BNR) in the mainstream. The project designed and constructed the plant to operate with a total volume of the three reactors and the settler of 1.7 m3 for treating a maximum inflow of 3 m3/day. After the launch, the three biological reactors were connected in order to achieve the long-term treatment of real urban wastewater. The process operated for 800 days up to March 2019.

Tests carried out at mild temperature showed that the system was working well. When decreasing the temperature, however, some problems were encountered in the second reactor. The project team redesigned several parts of the reactor and further tested provided valuable information for a scaling-up the system.

Results moreover showed that applying the SAVING-E technology has significant positive impacts, including energy savings and a reduction of overall operational costs compared to current technologies for treating urban wastewater. Implementing the project’s solution for removing nitrogen in a WWTP increases the production of methane by up to 35%, while also lowering oxygen consumption by up to 35%.

Furthermore, the project carried out a simulation at the Rubí WWTP whereby only 50% of the total influent would be treated using the SAVING-E technology. The tests showed that using the project solution reduces electrical energy consumption from grid by 73%, falling from 0.22 kWh/m3 for the current configuration of Rubí WWTP to 0.06 kWh/m3 with the SAVING-E technology. This decrease results from improved biogas production (0.20 kWh/m3 can be obtained from cogeneration compared to 0.11 kWh/m3 under the current scenario). Also 50% of the influent flow rate is treated by a technology with very low aeration needs (biological treatment consumes 0.15 kWh/m3 compared to 0.20 kWh/m3 of the current scenario). Overall, if WWTPs with a capacity of 100,000 PE were to adopt the project technology, 647 tones CO2 eq. per year could be avoided in Spain, and 2,640 tones CO2 eq. per year would be avoided at European level (EU28).

The dissemination activities focused on the general public as well as the industrial sector. Apart from the usual channels (website, articles in the technical press, conferences, social media etc.) the project trained staff from the wastewater treatment sector in order to encourage the replication of the strategies developed. The beneficiary plans to continue to develop the project technology in order to resolve some remaining technical difficulties and ensure its effective working.

Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).


Reference: LIFE14 ENV/ES/000633
Start Date: 01/10/2015
End Date: 31/03/2019
Total Eligible Budget: 1,165,306 €
EU Contribution: 672,645 €
Project Location:


Coordinating Beneficiary: Universitat Autnoma de Barcelona
Legal Status: PAT
Address: Edifici Q - Escola d'Enginyeria. Campus UAB, 08193, Cerdanyola del Valls/Barcelona, España
Contact Person: Julian Carrera
Email: Send Email
Website: Visit Website

LIFE Project Map



  • Waste water treatment


  • waste water treatment
  • biomass energy
  • biogas


  • Directive 91/271 - Urban waste water treatment (21.05.1991)
  • Directive 2009/28 - Promotion of the use of energy from renewable sources (23.04.2009)


Name Type
Universitat Autnoma de Barcelona Coordinator
WssTP(European Water Supply and Sanitation Tecnology Platform), Belgium Participant
DAM(Depuración de Aguas del Mediterraneo), Spain Participant