Sustainability assessment of advanced wastewater treatment technologies L. Høibye, J. Clauson-Kaas, H. Wenzel, H. F. Larsen, B. N. Jacobsen and O. Dalgaard ABSTRACT L. Høibye COWI, Havneparken 1, DK-7100 Vejle, Denmark E-mail: lan@cowi.dk J. Clauson-Kaas O. Dalgaard COWI, Parallelvej 2, DK-2800 Kgs Lyngby, Denmark E-mail: jck@cowi.dk; oda@cowi.dk H. Wenzel H. F. Larsen IPU, The Technical University of Denmark, Produktionstorvet, Bygning 425, DK-2800 Kgs, Lyngby, Denmark E-mail: hw@ipl.dtu.dk; hfl@ipu.dk B. N. Jacobsen Avedoere Wastewater Services, Kanalholmen 26, DK-2650 Hvidovre, Denmark E-mail: bnj@spvand.dk As a consequence of the EU Water Framework Directive more focus is now on discharges of hazardous substances from wastewater treatment plants and sewers. Thus, many municipalities in Denmark may have to adopt to future advanced treatment technologies. This paper describes a holistic assessment, which includes technical, economical and environmental aspects. The technical and economical assessment is performed on 5 advanced treatment technologies: sand filtration, ozone treatment, UV exclusively for disinfection of pathogenic microorganisms, membrane bioreactor (MBR) and UV in combination with advanced oxidation. The technical assessment is based on 12 hazardous substances comprising heavy metals, organic pollutants, endocrine disruptors as well as pathogenic microorganisms. The environmental assessment is performed by life cycle assessment (LCA) comprising 9 of the specific hazardous substances and three advanced treatment methods; sand filtration, ozone treatment and MBR. The technical and economic assessment showed that UV solely for disinfection purposes or ozone treatment is the most advantageous advanced treatment methods if the demands are restricted to pathogenic microorganisms. In terms of sustainability, sand filtration is the most advantageous method based on the technical and environmental assessment due to the low energy consumption and high efficiency with regards to removal of heavy metals. Key words | advanced wastewater treatment, life cycle assessment, MBR, ozone treatment, sand filtration, UV treatment INTRODUCTION In 2000 the EU Water Framework Directive (WFC) (2000/60/EF) came into force with the aim to protect and improve the quality of EU waters. It is expected that new environmental quality standards (EQS) for specific com- pounds and sum parameters will be formulated in a future daughter directive to the WFC. Effluents from wastewater treatment plants (WWTP), etc. must result in compliance with these EQS so this may entail new requirements for existing WWTP in the form of advanced wastewater treatment technologies. There are many aspects that must be assessed before the optimal advanced treatment technology is chosen at a specific WWTP. These include technical, economic and environmental aspects which can play a major role in the selection process. All these aspects are included in the study described here, which is based on a Danish project on advanced treatment technologies for municipal wastewater (Clauson-Kaas et al. 2006). Another technical and econ- omical assessment was conducted in a Dutch study (STOWA 2005). The study also entails a tool for environmental assess- ment of various WWTP with specific outlet concentrations of selected hazardous substances. The tool can be used as a decision supporting tool in the screening process when doi: 10.2166/wst.2008.450 963 Q IWA Publishing 2008 Water Science & Technology—WST | 58.5 | 2008