Enerwater Project Waste Water Treatment Plants


Waste Water Treatment Plants (WWTPs) is one of the most expensive public industries in terms of energy requirements accounting for more than 1% of consumption of electricity in Europe. EU Water Framework Directive (WFD) 91/271/CEE made obligatory waste water treatment for cities and towns. Now within the EU-27, the total number of WWTPs is estimated as 22.558, for which we can estimate a total energy consumption of 15,021 GWh/year. Although most of the objectives of the WFD in relation to water protection have been achieved, most of these aging plants show unsustainable energy consumption and must be optimized to the maximum and renovated accordingly. However, in Europe there is no legislation, norms or standards to be followed, and as consequence, a gigantic opportunity for reducing the public electric expense remains unregulated.


  • In the United Kingdom, where roughly 3% of generated electricity is used by the water industry alone, energy efficiency is also of growing interest1,2.Besides, some recent studies have highlighted the importance of greenhouse-gas (GHG) emissions from energy use in the water sector. They show that water-related energy use in the US accounts for nearly 5% of total GHG emissions, and the proportion is even higher in the UK3,4.
  • In Italy, the energy consumption of the integrated water service is about 7.5 billion of kWh/year5
  • In Spain the three major sources of consumption in the public sector are: 1. Street lighting, 2. Drinking water supply & waste water treatment, 3. Water desalination6.
  • Within the EU-27, the total number of Urban Wastewater Treatment plant are 22.558 (agglomerations > 2.000 pe7), where 96% of them include secondary, nutrient removal or more stringent treatment8. A similar ratio applies to wastewater in EU big cities, with 586 big cities that comprise 250.2 million pe9.
  • Taking into account that the total population in the EU-27 is around 500.7 million10 and assuming an energy intensity use from the urban wastewater treatment (Figure 1) of 30 kWh/pe·year11, we can estimate a total energy consumption associated to this sector of 15,021 GWh/year.

1 UK Water Industry Research Energy Efficiency in the UK Water Industry: A Compendium of Best Practices and Case Studies (UK WIR, 2010).

2 Ainger, C. et al. A Low Carbon Water Industry in 2050 (Environment Agency, 2009).

3 Department for Environment Food and Rural Affairs Future Water. The Government’s Water Strategy for England (Stationery Office, 2008).

4 Griffiths-Sattenspiel, B. & Wilson, W. The Carbon Footprint of Water (River Network, 2009).

5 Atti di Ecomondo 2012 (page 815 – Maggioli Editore 2012 [In Italian]

6 Spanish energy Efficiency Plan 2011 – 2020 http://idae.electura.es/libros/PAEE/

7 pe = population equivalent

8 http://www.eea.europa.eu/data-and-maps/uwwtd/interactive-maps/urban-waste-water-treatment-maps

9 http://www.eea.europa.eu/data-and-maps/indicators/urban-waste-water-treatment/urban-waste-water-treatment-assessment-3

10 http://appsso.eurostat.ec.europa.eu/nui/show.do?dataset=demo_gind&lang=en

11 See references on footnotes 35-38.


Therefore, ENERWATER´s objectives are next in chronological order:

  1. O1: To carry out a thorough study on the current energy status of existing WWTPs and to identify best case scenarios, best practices & best available technologies. (Base-line report)

  2. O2: To establish energy consumption benchmarks and record them in a publicly available database.

  3. O3: To define and validate a standard methodology for energy assessment and classification. The goal is to guide expert auditors on how to evaluate the energy performance of WWTP´s, allowing them to classify WWTPs in several categories (A, B, C, D, similar to Energy Performance Certificate for properties)

  4. O4: To develop and validate an online web application that automatizes the methodology, facilitating the process of energy diagnosis of a WWTP.

  5. O5: To foster the discussion and dialogue among member states, the water- energy sector and other stakeholders.

  6. O6: To address the main issues present for the creation of an EU directive.

  7. O7: To disseminate the methodology for a faster replication and market acceptance. Proposal and contribution to new European standardisation works.

  8. O8: To assess the impact on the society, economy and environment

Expected Goals

In this line ENERWATER will create an organized structure of collaboration to yield a methodology based on previous works and experiences. The methodology will be tested to reach an 11to 30% energy reduction in 65 WWTPs (15-20) WWTPs per country (preliminary selection has been done of total), and it will be also offered as an online tool to facilitate the work to WWTPs managers. ENERWATER will create an open benchmarking database to share energy data results. Discussion and networking with European stakeholders will be promoted. Finally, contribution of the project to the European standardisation system will propose and foster the elaboration of a new standardisation document.

Expected Results

The main result of the coordinated action will be a methodology, which will be suitably, assessed and tested in real case scenarios. Other results include: An automated tool reflecting the developed methodology, an energy benchmarking database, a guideline document on water treatment technologies and best practices for energy efficiency, proposal and contribution to a new standard and a set of recommendations to the EU commission towards a future directive. Results in chronological order and in relation to the project objectives are shown next:

  1. R1: Base-line report. A report on the current energy use of existing WWTPs will be compiled (O1) including:

    • R1.1: Study of published energy data. (At least 500 WWTPs).
    • R1.2: Selection of real case studies
    • R1.3: Pre-method. This document-guide will be used for carrying out energy diagnosis.
    • R1.4: Pre-diagnosis reports: a report will be drafted from each WWTP visited.
    • R1.5 Guideline on water treatment technologies and best practices for energy efficiency.
  1. R2: 65 WWTPs monitored in detail through an online energy monitoring system. (O1-O2).

  2. R3: Benchmarking database. (O2)

  3. R4: Main result. ENERWATER methodology. (O3)

  4. R5: Online method. An online web application that automatizes the methodology. (O4)

  5. R6: Test & Evaluation (O3-4)

  6. R7: Collaboration and contribution to the standardisation system. Proposal for standardisation of the method (O5-O7)

    • R7.1 Network of waste water stakeholders and Workshop
    • R7.2 Network for standardisation stakeholders and Workshop
  7. R7.2 Network of standardisation stakeholders

  8. R8: Recommendations for a future directive. One technical report addressing:

    • R8.1: WWTPs energy classification A,B,C,D…
    • R8.2: Minimum energy requirements.
    • R8.3: Minimum inspections schemes.
    • R8.4: Independent control systems. Auditor´s training and procedures.
    • R8.5: Recommendations guide.
    • R8.6: Challenges and difficulties report.
  9. R9: Dissemination actions. (O7)

    • R9.1 Dissemination Plan
    • R9.2 Present the project in 3 or more international events.
    • R9.3 ENERWATER Website
  10. R10: Assessment of socio-economical impacts.


The ENERWATER work‐plan has been divided into 6 work packages that will be carried out in 36 months.

waste water treatment plants project implementation

Expected Impact

Main impacts relate to:

  1. Decrease in the energy consumed in the water treatment processes: Due to the improved measurement of energy and the better understanding of the most important processes involved and their respective efficiencies expected, which one is behaving above average efficiency and which one can be improved. This advanced knowledge is likely to be translated in; the adoption of energy efficient operation practices and services, the renovation of equipment and the adaptation of present infrastructures.
    The energy related impact will depend on the outcome of the audits carried out on each of the plants, the possibilities of improvement and the decision to adopt the best practices and technologies recommended. Only by the ENERWATER services envisaged it is possible to obtain 11% reduction but if, as a final effort, an energy improvement action or ESCO service is adopted then the reduction can get to 20-30% depending on the effectiveness and appropriateness of the service adopted. The level of success on this expected reduction will be evaluated by means of a set of indicators that will be quantified within WP4 and communicate on WP6.
    Waste water treatment plants project impactsThe total annual consumption for only participating plants is 44,230 MWh/year which means that if we can get to achieve a 11% reduction as estimated in figure 4. We will achieve an energy reduction of 4.87 GWh-year of FINAL ENERGY (12.3 GWh-year of PRIMARY ENERGY) with only the application of the envisaged ENERWATER services to the participating plants.
  2. Subsequent impacts of energy reduction: public money savings, CO2 reduction and a more secure energy supply.
  3. Increase of competitiveness in the global sector of European WWTPs constructors and equipment manufacturers.
  4. The rise of new business models based on this standard methodology that may follow the model of energy performance contracting.