Understanding the costs of investigating coliform and E. coli detections during routine drinking water quality monitoring

Abstract

Bacteriological failure investigations are crucial in the provision of safe, clean drinking water as part of a process of quality assurance and continual improvement. However, the financial implications of investigating coliform and Escherichia coli failures during routine water quality monitoring are poorly understood in the industry. The investigations for 737 coliform and E. coli failures across five UK water companies were analysed in this paper. The principal components of investigation costs were staff hours worked, re-samples collected, transportation, and special investigatory activities related to the sample collection location. The average investigation costs ranged from £575 for a customer tap failure to £4,775 for a water treatment works finished water failure. These costs were compared to predictions for US utilities under the Revised Total Coliform Rule. Improved understanding of the financial and staffing implications of investigating bacteriological failures can be used to budget operational expenditures and justify increased funding for preventive strategies.

A primer on emerging field-deployable synthetic biology tools for global water quality monitoring

“…Current gold-standard methods for assessing water quality, however, do not fulfill these criteria. Most technologies require expensive equipment and reagents, reliable electricity sources, technically skilled operators, and transportation infrastructure 15 . For example, the equipment to run qPCR (a DNA amplification technique for pathogen detection) and mass spectrometry (a molecular analysis technique for chemical detection) costs tens of thousands of dollars excluding operational expenses, must be operated by a trained technician, and cannot be brought into the field, thus necessitating sample transport for centralized analysis.…”

The operational value of inlet monitoring at service reservoirs

“…As site-specific factors and water quality characteristics will play a significant role in fouling rates, incorporating diagnostic sampling at service reservoirs can help determine a more appropriate maintenance frequency based on past performance, which could eliminate the repeat of costly errors (Kirmeyer et al 1999). This is especially important, as the impact of service reservoirs on water quality is not always negative as demonstrated here, despite the association with water quality deterioration and regulatory failures (NRC 2006;Ellis et al 2018). For example, site B was shown to be removing material from the water supply, improving water quality (Figure 3) and this will continue until the material is remobilised.…”

“…Routine cleaning of service reservoirs is recommended at different frequencies in different jurisdictions, typically every three to five years (Lambertini et al 2011;Brandt et al 2016), but these recommendations are not based on actual performance data. This can lead to unnecessary investigations, which can incur significant costs per investigation (Ellis et al 2018). A reactive response to an outlet bacteriological sample failure at a storage tank will also lead to an investigation (Environment Agency 2010).…”

“…Only disinfectant residual, colony counts, and Escherichia coli and coliform bacteria have UK regulatory sampling at service reservoir outlets (DWQR 2018; DWI 2020). Nevertheless, bacteriological failures have been shown to be double the rates at service reservoir outlets in comparison to their supplying water treatment works (Ellis et al 2018), indicating a risk to water quality from these water storage facilities. However, the results from this service reservoir outlet sampling do not necessarily confirm the true cause and location of the contamination, because the issue could be related to the network between treatment and the service reservoir, the service reservoir itself, or both.…”

“…It would be of value for water utilities to proactively identify the true causes and locations of water quality deterioration, thereby saving the effort, time, and expense of unhelpful investigations. Average costs per investigation, not including time, inconvenience or negative publicity, can be up to £4200 at service reservoirs, £4900 at water treatment works, and £1200 at customer taps (Ellis et al 2018).…”