Research 255: Optimal design and operation of small-scale wastewater treatment plants: the Irish case

Authors: Lorna Fitzsimons, Greg McNamara, Edelle Doherty and Eoghan Clifford

Summary: There are many variables which must be considered when designing and operating a wastewater treatment system. The key objectives of this research were to develop software tools to assist in the selection and management of wastewater treatment systems, with a specific focus on small wastewater treatment plants in Ireland.

Published: 2018

ISBN: 978-1-84095-785-3

Pages: 63

Filesize: 2,631KB

Format: pdf

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Identify Pressures

Wastewater treatment plant managers are tasked with achieving emission limits values while simultaneously improving resource efficiency. Treatment plants vary considerably in terms of their emission limits values, scale, loading, technology and sludge management inter alia.

Benchmarking and life cycle cost assessment are two key approaches to (1) compare and improve the performance of wastewater treatment plants and (2) estimate the life cycle costs of a wastewater treatment system in given site-specific conditions. However, this research identified pressures in the adaptation and implementation of these approaches, for example limited and non-standardised data availability, and the need for effective sampling methodologies to accurately compare plant performance.

Inform Policy

The Urban Waste Water Treatment Directive (91/271/EEC) requires that wastewater is treated to designated standards before being discharged to the environment. Required effluent quality is largely driven by the sensitivity of the receiving water and the scale of the treatment plant. For example, nutrient removal is required in sensitive areas that are subject to eutrophication. Nutrient removal, as well as the predicted requirement to remove emerging contaminants of concern, is expected to increase wastewater treatment plant resource consumption. As a result, there are inherent trade-offs between the positive environmental benefits of higher quality wastewater and the negative environmental impacts associated with additional energy and chemical requirements to achieve those standards.

Using life cycle assessment (LCA) this research demonstrates that emission limits values, technology and operational choices have important consequences for environmental performance and therefore this should also be an important consideration for policymakers, as well as effluent quality.

Develop Solutions

The research team has developed benchmarking and life cycle cost/LCA methodologies and software tools (KPICalc and DST) that holistically consider both the economic and the environmental costs of wastewater treatment from a site-specific perspective (emission limits values, scale, loading, technology, sludge management). A DST was developed, which, given accurate local cost data, can be used to compare various wastewater treatment technologies under different user-defined operating scenarios, in terms of economic and environmental impact.

This research also developed software tools to assist key stakeholders to benchmark the performance of wastewater treatment plants. The tools developed facilitate the identification of suitable wastewater treatment plants for comparison purposes and appropriate sampling strategies.