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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Comparison of centralised and decentralised wastewater systems

Protection of public health and the environment from wastewater discharges is crucial to achieve and maintain. Developed countries, such as the UK, usually use conventional end-of-pipe wastewater systems to manage those discharges. However, many unsustainable features, such as high energy demand and complex treatment stages, are associated with the centralised wastewater systems initiating the investigation of alternative solutions aiming to achieve the regulatory standards and required performance levels with a simultaneous prevention of further contribution to climate change and the degradation of natural resources.

This research aims to compare centralised and decentralised strategies regarding their sustainable performance, having as a reference the new Ebbsfleet “Garden City”. A location appraisal is carried out and it rebounds to three different options: centralised, semi-centralised and decentralised that are further analysed regarding sustainability factors. A Life Cycle Assessment (LCA) analysis is conducted in order to quantify the environmental impacts of the different proposed options.

Findings concerning the environmental evaluation show that the decentralised option will perform better based on the values of the environmental impact indicators for the three options. Nevertheless, LCA analysis is very sensitive to data quality and system boundaries, and it is found that the above-mentioned result may vary in some investigated scenarios. The semi-centralised option seems to have less impacts in some environmental indicators, making the comparison a multivariate issue. Findings from cost evaluation show that decentralised and semi-centralised options are more cost-effective while the social criteria indicates that the centralised option is the preferable one. A final recommendation is produced after combining the three dimensions of sustainability by different weighting in an indicative multi-criteria analysis.

Consequently, after the analysis, the main conclusions reveal the opportunities in management optimisation of disposals’ transportation both in construction and operation phases irrespectively of the chosen wastewater treatment strategy. Recommendations and limitations of this research are specified, in order to set up the basis for future work.


Course Overview


The need to engage in better problem definition through careful dialogue with all stakeholder groups and a proper recognition of context.


An ability to work with specialists from other disciplines and professional groups acknowledging that technical innovation and business skills also must be understood, nurtured and combined as precursors to the successful implementation of sustainable solutions.


An understanding of mechanisms for managing change in organisations so future engineers are equipped to play a leadership role.


An awareness of a range of assessment frameworks, sustainability metrics and methodologies such as Life Cycle Analysis, Systems Dynamics, Multi-Criteria Decision making and Impact Assessment.