management in wastewater treatment plants
3.4.4 Methodology for pAS application
The first step of PAS application is the definition of the objectives and of the assessment criteria for a given WWTP or a group of WWTPs. The PIs must then be selected and calculated accordingly, and analysed against the references values.
Further insights may require the use of complementary PIs.
The next step is the selection and calculation of PXs to complement the information provided by the homologous PIs. The latter assess the overall performance in the
2Applicable to conventional (with or without sludge return) and enhanced primary sedimentation.
3Variables applicable to several AS variants: complete mix; plug flow (conventional, extended aeration); oxidation ditch (C removal, C + N removal); A/O; MLE; Bardenpho (4-stage, 5-stage); A2/O;
UCT; VIP; SBR (C removal), SBR (C + N removal) and SBR (C + N + P removal). The performance functions are AS-type specific.
4Except for SBR.
5Variables applicable to different filter packing (mono and dual media) and height; performance functions are filter-type specific.
6Net treatment capacity accounts for the water filtered minus the water spent for cleaning and the filtration time plus the cleaning time.
7Excluding the g-force, the variables listed are applicable to gravity, dissolved air flotation, gravity belt and rotary drum thickening. The performance functions are thickener-type specific.
8Applicable only to anaerobic digestion.
9Applicable to centrifuge, belt filter press, recessed-plate filter press and sludge drying beds. The performance functions are dewatering-type specific.
10Applicable only to centrifuge.
table 3.5 State-variables relevant for assessing the WWTP energy performance (adapted from Silva et al. 2013) (Continued).
treatment unit or step (type)
State-variables relevant for energy performance [units]
UV disinfection UV dose [mJ/cm2]
Unit energy consumption [kWh/m3]
Thickening7 Daily operating hours of mechanical thickeners [hours/day]
Relative centrifugal force (g-force) [× g]
Unit energy consumption [kWh/m3] Stabilization
(aerobic and anaerobic digestion)
Solids retention time (without recirculation) [d]
Biogas production8 [m3/kg converted VSS]
Production of energy from biogas [kWh/m3] Unit energy consumption [kWh/m3]
Dewatering9 Daily operating hours [hours/day]
Rotational speed10 [rpm]
Relative centrifugal force (g-force)10 [× g]
Unit energy consumption [kWh/m3]
assessment period (usually, a calendar year) and the PXs assess ‘where’ (unit operations/processes and equipment) and ‘when’ the performance did satisfy or fail the pre-established objectives and the distance that remains to achieve these targets (Silva et al. 2014a), enabling the identification of improvement actions.
As introduced earlier, prior to WWTP energy efficiency one should verify the plant effectiveness and reliability, that is, the compliance over time with the quality requirements of the treated water (Silva et al. 2014a). One may then select the parameters and unit operations or processes for which one intends to assess and optimise the removal efficiency to enhance the treatment reliability (Silva et al. 2014b).
The continuous improvement of WWTP performance requires the verification and, eventually, the (re)definition of objectives and (re)selection of the corresponding PIs and PXs, which restarts the PDCA cycle of PAS application (Figure 3.10).
Figure 3.10 PDCA methodology for the continuous improvement of WWTP energy performance.
3.5 rEFErEncES
Alegre H., Baptista J. M., Cabrera Jr. E., Cubillo F., Duarte P., Hirner W., Merkel W. and Parena R. (2006). Performance Indicators for Water Supply Services. 2nd edn, Manual of Best Practices Series, IWA Publishing, London, ISBN: 1843390515.
Introduction to energy management in wastewater treatment plants 53
Alegre H. and Coelho S. T. (2012). Infrastructure Asset Management of Urban Water Systems. Chapter 3 of “Water Supply System Analysis”, Avi Ostfeld (ed.), Open access at: www.intechopen.com/books/water-supply-system-analysis-selected-topics, ISBN: 978-953-51-0889-4 (accessed March 11, 2014).
Alegre H., Coelho S. T., Covas D., Almeida M. C. and Cardoso M. A. (2013). A utility-tailored methodology for integrated asset management of urban water infrastructure.
Water Science & Technology: Water Supply, 13(6), 1444–1451.
Alegre H. and Covas D. (2010). Infrastructure Asset Management of Water Services. An Aproach Based on Rehabilitation. Technical Guide 16. ERSAR, LNEC, IST, Lisbon, 472 pp. (in Portuguese) ISBN: 978-989-8360-04-5.
Almeida M. C. and Cardoso M. A. (2010). Infrastructure Asset Management of Wastewater and Stormwater Services. An Approach Based on Rehabilitation (in Portuguese). Technical Guide 17. ERSAR, LNEC, IST, Lisboa (in Portuguese) ISBN:
978-989-8360-05-2.
Burton F. L. (1996). Water and Wastewater Industries: Characteristics and Energy Management Opportunities. Burton Environmental Engineering, Los Altos, CA.
Prepared for the Electric Power Research Institute. Palo Alto, California. Report CR106941. September.
CEC & AWWA RF (2003). Water and Wastewater Industry Energy Efficiency: A Research Roadmap. California Energy Commission and American Water Works Association Research Foundation. Prepared by Means E., McGuire Environmental Consultants, Newport Beach, CA.
Guimet V., Kelly R., Doung F., Rosina M., Audic J. M. and Terry J. M. (2010). Green energy resource: research and learning experiences from wastewater treatment plants.
Proceedings of IWA World Water Congress, Montreal (Canada).
Hernández-Sancho F., Molinos-Senante M. and Sala-Garrido R. (2011). Energy efficiency in Spanish wastewater treatment plants: a non-radial DEA approach. Science of the Total Environment, 409, 2693–2699.
ISO 24510: 2007(E) – Activities Relating to Drinking Water and Wastewater Services – Guidelines for the Assessment and for the Improvement of the Service to Users. 1st edn, International Organization for Standardization, Geneva.
ISO 24511: 2007(E) – Activities Relating to Drinking Water and Wastewater Services – Guidelines for the Management of Wastewater Utilities and for the Assessment of Wastewater Services. 1st edn, International Organization for Standardization, Geneva.
ISO 24512: 2007(E) – Activities Relating to Drinking Water and Wastewater Services – Guidelines for the Management of Drinking Water Utilities and for the Assessment of Drinking Water Services. 1st edn, International Organization for Standardization, Geneva.
ISO 50001: 2011. Energy Management Systems. Requirements with Guidance for Use.
1st edn, International Organization for Standardization, Geneva.
ISO 55000: 2014. Asset Management — Overview, Principles and Terminology. 1st edn, International Organization for Standardization, Geneva.
ISO 55001: 2014. Asset Management — Management Systems — Requirements. 1st edn, International Organization for Standardization, Geneva.
ISO 55002: 2014. Asset Management Guidelines for the Application of ISO 55001. 1st edn, International Organization for Standardization, Geneva.
Lingsten A. and Lundkvist M. (2008). Description of the Current Energy Use in Water and Wastewater Systems in Sweden (in Swedish). The Swedish Water & Wastewater Association, SWWA.
Matos R., Cardoso A., Ashley R., Duarte P., Molinari A. and Schulz A. (2003). Performance Indicators for Wastewater Services. Manual of Best Practices Series, IWA Publishing, London, ISBN: 19002229006.
Mizuta K. and Shimada M. (2010). Benchmarking energy consumption in municipal wastewater treatment plants in Japan. Water Science and Technology, 65(10), 2256–2262.
NREL (2012). Energy Efficiency Strategies for Municipal Wastewater Treatment Facilities.
National Renewable Energy Laboratory, Technical Report NREL/TP-7A30-53341.
Colorado, January.
PG&E (2003). Municipal Wastewater Treatment Plant Energy Baseline Study. Pacific Gas and Electric Company (PG&E). San Francisco, CA, June.
Quadros S. (2010). Desenvolvimento de um sistema de avaliação de desempenho de estações de tratamento de Águas residuais urbanas. PhDThesis, Azores University, Angra do Heroísmo, p. 286 (in Portuguese).
Quadros S., Rosa M. J., Alegre H. and Silva C. (2010). A performance indicators system for urban wastewater treatment plants. Water Science and Technology, 62(10), 2398–2407.
Rodriguez-Garcia G., Molinos-Senante M., Hospido A., Hernández-Sancho F., Moreira M. T. and Feijoo G. (2011). Environmental and economic profile of six typologies of wastewater treatment plants. Water Research, 45, 5997–6010.
Rosa M. J., Ramalho P., Silva C., Vieira P., Quadros S. and Alegre H. (2010). PASt21 – Iniciativa Nacional de Avaliação de Desempenho de ETA e ETAR Urbanas (‘PASt21’ – the Portuguese initiative for performance assessment of water and wastewater treatment plants). In: Proc. 10.° Congresso de Água. Alvor (Algarve). March, p. 14 (in Portuguese).
Silva C. (2008). Aplicação de medidas de avaliação de desempenho a estações de tratamento de Água da Águas do Algarve (Application of performance assessment measures to Águas do Algarve water treatment plants). MSc Thesis. Algarve University, Faro, p. 286 (in Portuguese).
Silva C. and Rosa M. J. (2014). Energy Performance Indicators of Wastewater Treatment – A Field Study with 17 Portuguese Plants. IWA World Water Congress, Lisbon, September.
Silva C., Ramalho P., Quadros S., Alegre H. and Rosa M. J. (2012). Results of ‘PASt21’ – the portuguese initiative for performance assessment of water and wastewater treatment plants. Water Science and Technology – Water Supply, 12(3), 372–386.
Silva C., Ramalho P. and Rosa M. J. (2013). Curative actions in wastewater treatment systems. Chapter 2 of PART I of report D43.1 – Results from Overall Exploration of Potential for Sustainability Improvements. TRUST Project.
Silva C., Quadros S., Ramalho P. and Rosa M. J. (2014a). A tool for assessing treated wastewater quality in urban WWTPs. Journal of Environmental Management, 146, 400–406.
Silva C., Quadros S., Ramalho P., Alegre H. and Rosa M. J. (2014b). Translating removal efficiencies into operational performance indices of wastewater treatment plants.
Water Research, 57, 202–214.
UNESCO (2014). The United Nations World Water Development Report 2014: Vol. 1 – Water and energy (WWDR 2014). United Nations Educational, Scientific and Cultural Organization, UNESCO 2014. ISBN 978-92-3-104259-1.
Introduction to energy management in wastewater treatment plants 55
USEPA (2008). Ensuring a Sustainable Future: An Energy Management Guidebook for Wastewater and Water Utilities. US Environmental Protection Agency, January.
Vieira P. (2009). Avaliação de desempenho de estações de tratamento de água para consumo humano (Performance assessment of drinking water treatment plants).
PhDThesis, Algarve University. Lisboa: Teses e Programas de Investigação LNEC, p.
451, ISBN 978-972-49-2186-0 (in Portuguese).
Vieira P., Alegre H., Rosa M. J. and Lucas H. (2008). Drinking water treatment plants assessment through performance indicators. Water Science and Technology – Water Supply, 8(3), 245–253.
WERF (2010). Overview of State Energy Reduction Programs and Guidelines for the Wastewater Sector. Water Environment Research Foundation. Co-published by IWA Publishing, Alexandria, VA.
WERF (2011). Energy Management. Exploratory Team Report Executive Summary. Water Environment Research Foundation, Alexandria, VA.
Yang L., Zeng S., Chen J., He M. and Yang W. (2010). Operational energy performance assessment system of municipal wastewater treatment plants. Water Science and Technology, 62(6), 1361–1370.