Triple bottom line assessment of raw water treatment: methodology and application to a case study in the municipality of Oppegård in south-eastern Norway

Abstract

There could be several options a water treatment plant (WTP) can select from, if an improvement in treated water quality (WQ) is desired. This paper outlines a methodology to test a variety of approaches to accomplish pre-set goals as regards WQ, while adopting a triple bottom line approach. This approach, in a nutshell, takes into consideration economic, environmental and social aspects in decision-making. The methodology has been applied to the Stangasen WTP in the town of Oppegård in south-eastern Norway. Among the seven alternative approaches compared were the use, as coagulant, of five different dosages of granulated aluminium sulphate, liquid aluminium sulphate (48%) and liquid ferric chloride (40%). Using the set of weighting factors obtained from experts, it was determined that increasing the dosage of granulated aluminium sulphate by 20% over the current one would be the most sustainable option from a triple bottom line point of view.

Keywords:

• chemicals
• energy
• water treatment sustainability
• triple bottom line
• water quality

Acknowledgements

The authors wish to acknowledge the help of Karl Olav Gjerstad (IVAR, Norway), Sveinung Lindland (Oppegård Municipality, Water and Wastewater Department, Norway), Halvard Kierulf (Municipality of Trondheim, Norway), Jon Mobråten (Asker and Bærum Waterworks IKS) and Arne Seim (Bergen Municipality, Norway) for their responses to queries sent regarding weighting factors. Thanks to Andreja Peternelj and Eva Mattsson from Kemira (Sweden) for their help with data on treatment of chemicals. Thanks also to Ida Johnsen of Oppegård for her kind help with data.

Funding

This work was supported by the European Union Seventh Framework Programme (FP7/2007–2013) [grant number 265122] (Project: TRansitions to the Urban Water Services of Tomorrow (TRUST).