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Research publications

The following research projects have been published throughout 2024. 

Dual pipe water recycling systems and risks to water quality

Published 20 February 2024 Ref: DWI 70/2/346 

This report comprises of the outputs of a study conducted on behalf of Defra and the Drinking Water Inspectorate to gather current knowledge on dual pipe water recycling systems at both national and international levels. The aim of this research is to review the current risks from such systems and the suitability of English and Welsh regulation to manage these risks and evolving systems.  

The research project found that many large scale dual pipe systems in the UK have either been mothballed or have never become operational.  The reasons for this are unclear, but international experience suggests cost, maintenance, and inconsistent public support for recycling are factors.  

The research suggests some actions for further evaluation, to reduce the risks and enable the safe expansion of dual pipe systems and water recycling schemes, including:- 

  • Separate regulations for dual supplies and drinking water regulations, to provide a coherent governance framework for recycling schemes.  
  • Comprehensive types of dual pipe schemes (in terms of both source water and end uses)  
  • Targets for water quality based on the source water and the intended use.  
  • A single source of updated guidance for scheme designers, installers, and operators.   

The research project has highlighted opportunities to resolve guidance differences between regulators and legislators. Water quality legislation does not currently distinguish between water for bathing or consumption and water for other domestic purposes (such as toilet flushing). Currently, all water used for domestic purposes must be wholesome (i.e. of a drinking water standard) as per the relevant water quality legislation.   

Impact and future of the regulatory model and legislative framework surrounding private water supplies in England and Wales

Published 15 May 2024 Ref: DWI 70/2/352 

The Drinking Water Inspectorate commissioned research on the regulatory framework and regulation of private water supplies (PWS) to understand its impact and how this framework could be improved to safeguard consumers of PWS. This research was undertaken by WRc, and they have produced separate reports for England and Wales. 

Although public and private water supplies are subject to the same water quality standards, the risk assessment and monitoring of PWS and resulting enforcement is less rigorous. Current water quality legislation does not safeguard the health of all consumers equitably. A significant legislative gap means that single dwellings with a PWS, which constitute a significant proportion of the total, are not subject to regular risk assessment and monitoring. The number of water quality tests which fail the standard for total coliforms and E. coli is around one hundred times greater from private sources than from the public water supply.   

While there has been an improvement in compliance with standards since 2010, most likely due to regulatory activities being focused on prioritised regulation 9 supplies (large, plus any used for commercial or public activity) progress from 2020 onwards has stalled. Due to the variability, inconsistency, and an inadequate mechanism for collecting and collating PWS water quality data, it is not possible to demonstrate an evidential link between the introduction of risk assessment activities and its impact on water quality.  

There are economic barriers to connecting PWS to public water supplies where it is feasible, resulting in public supply connections being a non-viable option, even when a PWS poses a risk to health.   

Local authorities are the regulators of private water supplies, but the availability and funding of sufficient experienced practitioners in local authorities (LAs) results in the regulations not always being enforced, water quality sampling sometimes being inadequate and mandatory risk assessments not always being in place. None of the LAs interviewed as part of the research, commented that they routinely enforce based upon risk assessment alone in the absence of failed test results.  

Progress is recommended in areas including legislative harmonisation, a review of risk assessment and sampling practices, and the provision of additional powers to regulate and audit. The evidence from the review and stakeholder engagement suggests that a revised regulatory framework would deliver significant benefits in the medium term, without the need for centralised regulation. To resolve the uneven application of the legislation by LAs, training and toolkits should be provided, and the sharing of good practice and collaboration should be facilitated. 

The report made a number of recommendations for areas including the creation of an overseeing body with the powers to enforce and audit. The relevant legislation should be harmonised and modernised, additional resources should be found for Local Authority Private Water Supply teams and additional independent research should be commissioned. 

Cyanotoxins in raw surface waters

Published 13 August 2024 Ref: DWI 70/2/343 

This project aimed to determine the scientific relevance of any prescribed standard for Microcystin-LR (MC-LR), its occurrence in raw surface waters, treated water concentrations, risks to consumers, and the suitability of analysis methods for cyanotoxin monitoring. 

Cyanobacteria produce a wide range of cyanotoxins that are potentially hazardous to health. A health Guideline Value (GV) of 1.0 µg/L of total (intra + extra cellular) microcystin-LR in drinking water has been proposed by the World Health Organisation (WHO) and has been adopted by the Scottish government. However, this compound only needs monitoring “in the event of a potential bloom”.  

The need to understand the occurrence of cyanotoxins and their potential risk is exacerbated by the increasing frequency of bloom occurrence as a result of climate change and accelerated rates of eutrophication due to human activities such as farming and (treated) wastewater effluent. Consequently, there are a wide range of policies that could have an impact on cyanotoxin occurrence.  

A survey of water companies found that whilst cyanobacteria were commonly detected in UK drinking water sources, microcystins (the only cyanotoxin monitored) were infrequently detected and at low concentrations. A review of current literature also demonstrated that there is no universal definition for an algal bloom, which undermines any proposed requirement  that microcystin-LR (MC-LR) only needs monitoring in the event of a potential algal bloom. 

A single analytical method was developed for the detection of MC-LR, MC-RR, MC-YR, MC-LA, cylindrospermopsin, anatoxin-a (nodularin) by reverse phased LC-MS (liquid chromatography-mass spectrometry). A separate method using HILIC (hydrophilic interaction liquid chromatography) LC-MS was developed for the detection of saxitoxin. 

Cyanotoxins were monitored throughout 2023 in raw and final waters at five sites in England and Scotland. Microcystins were detected in raw water at two out of the five sites and concentrations were mostly <1.0 µg/L (< 0.2 µg/L outside of the summer months and generally < 0.5 µg/L during the ‘peak’ season). 

No cyanotoxins were detected in the final waters indicating that the risk to consumers is low. 

It is recognised that the data generated in this study is only representative of one year. Risk from cyanotoxins should remain under review given that the frequency of algal blooms are expected to increase with climate change. 

Prevalence of viruses and somatic coliphage in UK waters – method development and data gathering

Published 13 August 2024 Ref: DWI 70/2/339 

The main aim of this work was to enhance risk-based preventative strategies for maintaining drinking water safety by providing precise data on the prevalence and elimination of enteric pathogenic viruses at Drinking Water Treatment Plants in the UK. Given the current data deficiency regarding virus prevalence in UK drinking water sources, this research offers a novel perspective through appraisal of UK drinking water sources providing baseline measurement of somatic coliphage levels.  

This research accomplished two key objectives:  

  • optimized procedures for viral concentration and extraction from both surface and groundwater sources.  
  • quantified the presence of somatic coliphages across 13 different drinking water sources, documenting their removal at different treatment stages based on 96 sample analyses.  

Notably, no somatic coliphages were detected in the final treated drinking water samples, validating the efficacy of most current drinking Water Treatment Plants procedures in adhering to the EU’s requirement of nil plaque forming units (PFU)/100 ml. The study provides insights into drinking water sources with the identification of sources of historical risk for human enteric viruses (when somatic coliphages exceed 50 PFU/100ml), indicating the necessity for proof of viral log reductions across the treatment process. Future integration of this study’s catchment-specific data into a hybrid quantitative microbial risk assessment model could greatly assist in evaluating drinking Water Treatment Plants operation, ultimately contributing to the reduction of exposure to viral risk and regulatory non-compliance 

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