Service reservoirs (SRs) are crucial components in drinking water distribution systems (DWDSs). These assets are often associated with water quality issues, including significant waterborne disease

outbreaks. To ensure safety of supply, monitoring is conducted at SR outlets for disinfectant residual and bacteriological indicators. Older SRs are often believed to be a source of bacteriological failures as old or poorly constructed SRs can be prone to structural issues, which can lead to ingress and contamination of the stored water. However, there is a lack of evidence to support the existence of a genuine relationship between SR age and risk of failure. In this study, historical bacteriological failure data at SR outlets and company-wide SR construction age data collected from three large UK water utilities was used to assess the potential relationship between the duration of time a SR has been in service and the likelihood of bacteriological failure. Findings showed that there was no relationship between the two parameters. Analysis also revealed instances where newer SRs, no older than twenty

years old, experienced one or more bacteriological failures, challenging the ingrained association that older SRs are at a higher risk of ingress and bacteriological contamination

Boxall, J.

Doronina, A.

Husband, P.

Speight, V.

White Rose Research Online

This is a repository copy of Influence of service reservoir construction age on the likelihood of bacteriological failure occurrence.White Rose Research Online URL for this paper:https://eprints.whiterose.ac.uk/196768/Version: Accepted VersionArticle:Doronina, A., Husband, P., Boxall, J. orcid.org/0000-0002-4681-6895 et al. (1 more author)(2023) Influence of service reservoir construction age on the likelihood of bacteriological failure occurrence. Institute of Water Journal (8). pp. 22-25. © 2023 Institute of Water. This is an author-produced version of a paper subsequently published in Institute of Water Journal. Uploaded with permission from the copyright holder.eprints@whiterose.ac.ukhttps://eprints.whiterose.ac.uk/Reuse Items deposited in White Rose Research Online are protected by copyright, with all rights reserved unless indicated otherwise. They may be downloaded and/or printed for private study, or other acts as permitted by national copyright laws. The publisher or other rights holders may allow further reproduction and re-use of the full text version. This is indicated by the licence information on the White Rose Research Online record for the item. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. 1 | Page  Influence of Service Reservoir Construction Age on the Likelihood of Bacteriological Failure Occurrence  A.V. Doroninaa, S. P. Husbandb, J. B. Boxallb, and V. L. Speightb aPanton McLeod, Unit 4B, Tweed Mills, Dunsdale Road, Selkirk, TD7 5DZ bDepartment of Civil and Structural Engineering, The University of Sheffield, Sheffield, S1 3JD, UK Abstract  Service reservoirs (SRs) are crucial components in drinking water distribution systems (DWDSs). These assets are often associated with water quality issues, including significant waterborne disease outbreaks. To ensure safety of supply, monitoring is conducted at SR outlets for disinfectant residual and bacteriological indicators. Older SRs are often believed to be a source of bacteriological failures as old or poorly constructed SRs can be prone to structural issues, which can lead to ingress and contamination of the stored water. However, there is a lack of evidence to support the existence of a genuine relationship between SR age and risk of failure. In this study, historical bacteriological failure data at SR outlets and company-wide SR construction age data collected from three large UK water utilities was used to assess the potential relationship between the duration of time a SR has been in service and the likelihood of bacteriological failure. Findings showed that there was no relationship between the two parameters. Analysis also revealed instances where newer SRs, no older than twenty years old, experienced one or more bacteriological failures, challenging the ingrained association that older SRs are at a higher risk of ingress and bacteriological contamination. Keywords  Service reservoir, water quality, bacteriological failures, construction age, contamination, risk Introduction  Service reservoirs (SRs) store treated water and balance supply to continuously meet demands in the drinking water distribution system (DWDS); they are crucial and integral components of the system. 2 | Page  SRs have been documented to have an effect on water quality, with associated problems ranging from the degradation of disinfectant residual to significant waterborne disease outbreaks, which have resulted in serious illness and even death (Craun and Calderon, 2001). For example, a 1993 Salmonella typhimurium outbreak in Gideon, Missouri, which stemmed from a SR, resulted in 15 hospitalisations, and 7 deaths (Clark et al., 1996). To ensure the safety of supply and to assess SR performance, water utilities in the UK are required to monitor water quality at the outlet of SRs on a weekly basis (DWI, 2018). The water quality parameters stipulated by regulation to be monitored at SR outlets are disinfectant residual and bacteriological indicators (DWI, 2018). The current UK SR monitoring programme is considered good practice in comparison to other countries, like the US, where there is no specific regulatory requirement for routine sampling at SRs at all, although some utilities still carry out sampling at SRs (Kirmeyer et al., 1999). However, the lack of inlet monitoring at SRs in the UK makes it difficult to attribute any observed changes in water quality directly to the SR, as it lies between the previous upstream sampling point and the outlet. One study found that over 66% of bacteriological failures in water quality samples collected at SR outlets in the UK have not been directly attributed to the SR (UKWIR, 2019), potentially because the source of failure was actually upstream of the asset. It can be argued that to successfully assess SR performance, pinpoint the location of water quality problems, predict and prevent potential future issues, and avoid costly repeat errors, routine sampling at SRs should include both inlet and outlet monitoring (Kirmeyer et al., 1999; UKWIR, 2019; Doronina et al., 2020).  There is an assumption in the water industry that the likelihood of occurrence of bacteriological failures is higher in older SRs. Old or poorly constructed SRs can be prone to structural issues, which can lead to ingress and contamination of the stored water with pollutants and bacteria (Craun and Calderton, 2001; Brandt et al., 2016). For example, a Salmonella outbreak in Alamosa, Colorado, which resulted in 434 cases, 20 hospitalisations, and 1 death, was linked to animal contamination of a SR that had numerous cracks and inadequately protected entry points (Ailes et al., 2013). Washouts, drainage, overflows, and access hatches in particular present a high contamination risk as they are exposed to the outside environment (DWI, 2018). Protective entry mesh and sealants can become damaged through excessive hydrostatic pressure, corrosion, poor workmanship, age related deterioration, and vermin (UKWIR, 2019). Ensuring water tightness of the SR is difficult and SR components such as roof membranes and wall and floor joints are often the sources of ingress (Hope, 2016). Cracks can form in the walls, roof, and floor of concrete SRs as a result of structural and operational defects like corrosion, thermal contraction, overloading, and poor construction (UKWIR, 2019). Some examples of the aforementioned issues and defects can be seen in Figure 1. 3 | Page   Figure 1 – A collection of photos showing some common issues seen in service reservoirs: A broken and corroded air vent (A), corrosion of internal structures (B), staining on walls and cracks in the roof (C), and ingress through the seam of an access hatch (D). Despite the association of increased contamination risk with older SRs, there is a lack of evidence to suggest that there is a genuine relationship between the two. Although water quality deterioration is often associated with older and more stressed systems, problems also arise in new or recently improved ones (Brandt et al., 2016). Additionally, age does not always correlate with structural issues, which is evidenced by a significant number of SRs built in the 19th century that are still fully functional to this day. Another, non-structural, cause for bacteriological failures in SRs can be related to the presence of bacteria in biofilm and SR accumulated material (LeChevallier and Au, 2002; Speight et al., 2008). Both processes are prevalent in SRs, primarily due to low velocities in these assets, which allow suspended material to settle and allow biofilm to grow undisturbed (Grayman and Kirmeyer, 2000). If regularly inspected and well maintained, many SRs will remain operational long after their original design life expiration, with limited water quality issues (UKWIR, 2019).  4 | Page  This paper presents results from a comparison analysis carried out on company-wide operational SR construction age data against the number of SRs with one or more bacteriological failures at the outlet. Analysis was conducted on data collected from three UK water utilities to assess whether there is a relationship between the duration of time a SR has been in service against the likelihood of it experiencing a bacteriological failure, to test the hypothesis that older SRs are more likely to fail. Results provide a quantifiable measure of the relationship between asset age and risk of bacteriological contamination.  Methods  Historical data for bacteriological failures at SR outlets between 2012-2018, alongside company-wide data on the construction age of operational SRs, was collected from three large UK water utilities and used to assess the potential relationship between the duration of time a SR has been in service against the likelihood of it experiencing a bacteriological failure. Table 1 presents the raw data used for analysis, showing the number of operational SRs categorised by construction age and the quantity of those SRs that had one or more identified bacteriological failures between 2012 to 2018. The water utilities are located across various geographical regions of the country, with data from Company B split into two categories (1 and 2) as there are two distinct geographical regions covered by this utility, with highly varying topographies. Some SRs were without a known construction age and were omitted from the analysis. The biggest omittance was for Company C, with 654 SRs out of which 466 experienced one or more failures, followed by 15 SRs for Company B with 8 experiencing one of more failures (across both regions), and 5 SRs for Company A (Table 1).    5 | Page   Table 1 – Operational service reservoir data, 2012 to 2018 1841-1850 NA NA NA 2 2 NA NA NA 0 01851-1860 NA 1 0 NA 1 NA 0 0 NA 01861-1870 NA 1 0 1 2 NA 1 0 0 11871-1880 2 0 1 1 4 0 0 1 1 21881-1890 2 2 1 3 8 0 0 1 1 21891-1900 3 4 1 2 10 1 2 0 1 41901-1910 11 1 0 9 21 0 0 0 1 11911-1920 3 7 0 5 15 0 3 0 0 31921-1930 11 5 7 14 37 1 1 3 3 81931-1940 22 8 11 19 60 3 2 1 6 121941-1950 23 15 4 54 96 0 6 1 13 201951-1960 99 33 21 154 307 11 8 2 26 471961-1970 79 45 27 179 330 11 20 8 50 891971-1980 31 32 6 106 175 5 13 1 30 491981-1990 16 20 5 87 128 3 12 2 27 441991-2000 11 18 6 128 163 1 10 3 30 442001-2010 3 5 6 46 60 1 0 0 7 82011+ 1 1 0 NA 2 0 1 0 NA 1Total 317 198 96 810 37 79 23 196No known construction age 5 13 2 654 0 6 2 466Year built Company A Company B (1) Company B (2) Company C Company CNumber of operational service reservoirsTotalNo. of service reservoirs with 1≥ bacteriological failures 2012-2018TotalCompany A Company B (1) Company B (2)6 | Page   Results  Figure 2 shows the percentage of operational service reservoirs with a known construction age that had one or more bacteriological failures at the outlet between 2012-2018 for data collected from three water utilities.7 | Page   Figure 2 – The percentage of operational service reservoirs with one or more bacteriological failures at the outlet between 2012-2018 8 | Page  Results in Figure 2 show that a number of failures have occurred in most SR age bands, with no clear trends in the relationship between the duration of time an operational SR (with a known construction age) has been in service and the occurrence of bacteriological failures. It is important to highlight that there were some operational SRs that experienced one or more bacteriological failures between 2012-2018, but as they were without a known construction age, they were not included in the analysis above. For Company C data, the inclusion of these SRs could affect observations made in Figure 2, as the number of Company C SRs without a known age was 654, out of which 466 had experienced a bacteriological failure between 2012-2018. However, the inclusion of this data for Company B (both regions) is unlikely to influence above observations as there were only 2 SRs in region 2 and 13 in region 1, out of which 2 and 6 experienced bacteriological failures respectively. Company A had only 5 SRs without a known age, none of which has experienced a bacteriological failure between 2012-2018 (Table 1).  Also of interest is that records show only 4% of operational SRs with a known construction age are older than 100 years old and it is likely that many older SRs are no longer in operation or have been rebuilt (Table 1). Based on the data collected for this study, it appears that there was either an increase in construction of SRs or improved record keeping from the 1950’s onwards, predominantly between 1950’s to 1970’s for the studied water utilities (Table 1). This observation is supported by UKWIR (2019), who highlight that there is a peak in the number of SRs constructed between 1950 and 1980, with nearly 60% of those currently in operation constructed by 1970. Discussion and Conclusions  In this study, the association between older SRs and the increased likelihood of them experiencing a bacteriological failure was assessed. The analysis showed that there was no relationship between the duration of time an operational SR has been in service and the occurrence of bacteriological failures (Figure 2). Analysis also revealed instances where newer SRs, no older than 20 years old, had experienced one or more bacteriological failures. A similar observation was made in a 2016 assessment of bacteriological failure rates in Severn Trent SRs, which uncovered that the highest probability of failure occurs at SRs an average 28 years after construction (Hope, 2016).  A limitation in the study data used was that some operational SRs that had experienced a bacteriological failure did not have a known construction age, inclusion of which could have altered some of the results. Nevertheless, results indicating that SR age does not link directly to bacteriological failure occurrence were in agreement across data from all water utilities in this project. 9 | Page  In industry, the ingrained association of older SRs with ingress and risk of bacteriological contamination could be a consequence of most bacteriological failures being detected at SR outlets. For example, in 2020, there were 112 bacteriological failures at SR outlets, in comparison to 77 at WTW outlets and 15 at customer taps in England (DWI, 2020). At present, SR outlets are a convenient sampling point for bacteriological indicators in the DWDS but just because a failure is identified at the SR outlet, it does not necessarily mean that the root cause of the issue is the SR itself as opposed to the upstream network. Additionally, the source of bacteriological failure in SRs may not be related to the structural condition of the asset, but to other processes that can exacerbate bacteriological growth, such as the presence of biofilm and accumulated material. Acknowledgements and Funding  This work was funded by the Engineering and Physical Sciences Research Council (EPSRC) [National Productivity Fund Scholarship EP/R512175/1] and by Anglian Water, Dwr Cymru Welsh Water, Northumbrian Water, and Scottish Water to whom the authors extend their thanks for their input and support, both financial and otherwise. Disclosure statement  No potential conflict of interest was reported by the authors. ORCID  A. V. Doronina http://orcid.org/0000-0001-9240-1992  S. P. Husband https://orcid.org/0000-0002-2771-1166  J. B. Boxall http://orcid.org/0000-0002-4681-6895  V. L. Speight http://orcid.org/0000-0001-7780-7863   References  • Ailes, E., Budge, P., Shankar, M., Collier, S., Brinton, W., Cronquist, A., Chen, M., Thornton, A., Beach, M.J., Brunkard, J.M., 2013. Economic and health impacts associated with a Salmonella typhimurium drinking water outbreak − Alamosa, CO, 2008. PLoS One 8(3):p.e57439. 10 | Page  • Brandt, M. J., Johnson, K. M., Elphinston, A. J., Ratnayaka, D. D. 2016. Twort’s Water Supply (7th ed.). Oxford: Elsevier Science, Butterworth-Heinemann. • Craun, G. F., Calderon, R. L. 2001. Waterborne Disease Outbreaks Caused by Distribution System Deficiencies. Journal AWWA 93(9):64-75. • Clark, R.M., Geldreich, E.E., Fox, K.R., Rice, E.W., Johnson, C.H., Goodrich, J.A., Barnick, J.A., Abdesaken, F., Hill, J.E., Angulo, F.J. 1996. A waterborne Salmonella typhimurium outbreak in Gideon, Missouri: results from a field investigation. International Journal of Environmental Health Research 6(3):187-193. • Doronina, A.V., Husband, S.P., Boxall, J.B., Speight, V.L. 2020. The operational value of inlet monitoring at service reservoirs. Urban Water Journal 17(8):735-744. • DWI. 2018. Public water supplies for England and Wales – Quarter 1 – January-March 2018 – A report by the Chief Inspector of drinking water. London: Drinking Water Inspectorate. • DWI. 2020. Summary of the Chief Inspector’s report for drinking water in England. A report by the Chief Inspector of drinking water. London: Drinking Water Inspectorate. • Hope, I. 2016. Ageing Service Reservoirs—an increasing burden or scope for innovation? In Dams–Benefits and Disbenefits; Assets or Liabilities? Proceedings of the 19th Biennial Conference of the British Dam Society held at Lancaster University from 7–10 September 2016 (pp. 427-441). ICE Publishing. • Grayman, W.M., Kirmeyer, G.J. 2000. Quality of water in storage. Water distribution systems handbook, 11-1. New York: McGraw-Hill. • Kirmeyer, G. J., Kirby, R., Murphy, B. M., Noran, P. F., Martel, K. D., Lund, T. W., Anderson, J. L., Medhurst, R. 1999. Maintaining Water Quality in Finished Water Storage Facilities. Denver, CO: AwwaRF and AWWA. • LeChevallier, M. W., Au, K. K. 2002. Water Treatment for Microbial Control. World Health Organization, Geneva, Switzerland. • Speight, V. 2008. Water-distribution systems: The next frontier. The Bridge 38(3):31-37. • UKWIR. 2019. Treated water storage assets: good practice for operation and management version 2. London, UK: UKWIR. 

Influence of service reservoir construction age on the likelihood of bacteriological failure occurrence

https://eprints.whiterose.ac.uk/196768/1/Influence%20of%20Service%20Reservoir%20Construction%20Age%20on%20the%20Likelihood%20of%20Bacteriological%20Failure%20Occurrence%20A.%20Doronina.pdf

Influence of service reservoir construction age on the likelihood of bacteriological failure occurrence

Abstract

Similar works

Full text

Available Versions

White Rose Research Online