Does carbon reduction increase sustainability? A study in wastewater treatment. (15th December 2015)

• Record Type: Journal Article
• Authors: Sweetapple, Christine; Fu, Guangtao; Butler, David
• Is Part Of: Water research. Volume 87(2015)
• Page Start: 522
• Page End: 530
• Publication Date: 2015-12-15
• Subjects: Carbon neutral -- Control -- Energy -- Sustainability -- WWTP; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2015.06.047
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: This study investigates the relationships between carbon reduction and sustainability in the context of wastewater treatment, focussing on the impacts of control adjustments, and demonstrates that reducing energy use and/or increasing energy recovery to reduce net energy can be detrimental to sustainability. Factorial sampling is used to derive 315 control options, containing two different control strategies and a range of sludge wastage flow rates and dissolved oxygen setpoints, for evaluation. For each, sustainability indicators including operational costs, net energy and multiple environmental performance measures are calculated. This enables identification of trade-offs between different components of sustainability which must be considered before implementing energy reduction measures. In particular, it is found that the impacts of energy reduction measures on sludge production and nitrogen removal must be considered, as these are worsened in the lowest energy solutions. It also demonstrates that a sufficiently large range of indicators need to be assessed to capture trade-offs present within the environmental component of sustainability. This is because no solutions provided a move towards sustainability with respect to every indicator. Lastly, it is highlighted that improving the energy balance (as may be considered an approach to achieving carbon reduction) is not a reliable means of reducing total greenhouse gas emissions. Graphical abstract: Highlights: Changes to WWTP control to reduce net energy use can be detrimental to sustainability. Trade-offs between sustainability indicators, encompassing environmental and economic factors, are identified. Lowest energy solutions can increase sludge production and reduce nitrogen removal. Increased energy recovery does not necessarily result in a move towards sustainability. Improving the energy balance is not a reliable means of reducing total GHG emissions.