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Project Appreciation and Objectives Past studies have shown that changes in Dissolved Oxygen (DO) concentrations can provide valuable information on: microbial growth; areas of active corrosion; and air ingress points, but maintenance requirements/calibration drift of conventional instruments has severely hindered this use from being exploited. However, new instruments with more accurate and reliable optical technology, is now available, and a recent Portfolio study (CP281) was able to demonstrate the enormous potential of using DO trends as a powerful multi-purpose networks monitoring tool; providing real-time information on significant microbial, chemical and physical water changes in distribution. Building on the work of CP281, this project is developing robust methodologies for key applications of DO: linking DO change to: network condition/water quality risk; estimating time-of-travel; and, mixing in networks. The feasibility of using DO to assess the condition of domestic systems and to evaluate the contribution of DO to the taste of water is also being examined. Benefits to Clients A highly cost-effective approach to: - Identify where network condition may put water quality at risk.
- Assess the effectiveness of interventions to address a quality issue.
- Determine residence time distribution in tanks.
- Validate existing hydraulic models and provide qualitative network information (eg identifying source changes, reverse flow).
Work Programme - Undertake comprehensive network monitoring programmes to demonstrate how DO trends can be used to identify risk areas, including ingress at service reservoirs/contact tanks. This will include monitoring DO trends “before” and “after” refurbishment to assess the effectiveness of a planned intervention (swabbing, lining, replacement).
- Develop a software tool and methodology for using DO trend data to provide information on time-of-travel and residence time distribution between network points.
- Assess the feasibility of using the DO trend of the “first-draw” of water to assess domestic pipework condition.
- Undertake taste panel tests to ascertain the contribution of DO to drinking water taste.
Project Outputs - Guidelines on the application of DO as a network monitoring tool.
- A spreadsheet tool for estimating residence time distributions from trends in DO.
- A workshop to review the outcome of the work and facilitate implementation of DO as a tool for monitoring networks.
Related WRc Work - Evaluation of DO instruments and development of mathematical technique to derive residence times, CP281, 2005-2006.
- Study of “white water” complaints including demonstration of the application of DO to identify air ingress during mains cleaning activity, major utility, 1999.
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