Current improvement programmes

Notice of Regulation: Oswestry Treatment Works




T229 – Oswestry WTW

DWI Reference: UUT-2020-00003


  1. has received reports from United Utilities Water Ltd (the “company”) dated 9 December 2019, 23 October 2019, 21 October 2019 (the “Reports”) which state that there is or has been a significant risk of supplying water from Oswestry WTW that could constitute a potential danger to human health.
  2. GIVES NOTICE to the company under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended) that it must satisfy the following requirements:

For risks associated with:

  • Iron
  • Manganese
  • Turbidity
  • Cryptosporidium
  • Taste and Odour
  • E. coli and total coliforms


(a) to maintain the following measures for the period specified:

Date: Ongoing for the duration of the Notice.

  1. Optimise existing treatment processes to ensure continuous compliance with regulation 26 and to minimise the risks from geosmin, iron and manganese.
  2. Continue raw water monitoring of geosmin and carry out treated water monitoring where required by company policy.
  3. Continuous monitoring for Cryptosporidium to ensure detections are within the validated range of the UV reactors.

(b) to review, revise and/or make operational the following measures, by the date specified below:

  1. Complete the design and procurement for capital works on site.
    Date: 31 March 2022
  2. Evaluate the raw water geosmin monitoring data and determine whether the efficacy of the treatment works will be sufficient to mitigate the risk based on long term trends.
    Date: Complete
  3. Complete the installation and commissioning of validated, ultra violet disinfection treatment, capable of treating full works flow (180 Ml/d).
    Date: Complete
  4. Conversion of first stage filters to GAC.
    Date: 31 July 2024
  5. Provision of new second stage manganese removal stage
    Date: 31 July 2024
  6. UV treatment capability on full flow
    Date: 31 July 2024
  7. Provision of a new chemical disinfection process, enabling the current contact tank and valve house to be abandoned
    Date: 31 July 2024
  8. Provision of automatic shutdown pre contact tank to prevent inadequately treated water entering supply
    Date: 31 July 2024
  9. Provision of manual start up to waste facilities for inadequately treated water
    Date: 31 July 2024

(c) to audit whether the measures have been effective by the following means:

  1. Define and keep under continuous review an audit strategy to monitor the effectiveness of the above measures.
    Date: 31 October 2020 and ongoing for duration of the Notice
  2. Implement the audit strategy defined in (c)1.
    Date: For the duration of the Notice.

(d) not to supply water for regulation 4(1) purposes from Oswestry WTW.

Not applicable

(e) to provide the following information in the time and manner specified below to enable monitoring of progress towards the mitigation of the risk of supplying water that would constitute a potential danger to human health:

  1. Provide a progress report annually by 31 January and against the following milestones:
    • Confirmation of UV installation and commissioning.
      Date: Complete
    • Details of the audit strategy.
      Date: 30 November 2020
    • Confirm completion and provide details of the design and procurement for the improvement works.
      Date: 30 April 2022
    • Produce a report detailing the analysis of geosmin trends and capability of the works to mitigate the risk.
      Date: Complete
    • Completion of construction work at Oswestry WTW.
      Date: 30 August 2024
  2. Review the risk assessment for Oswestry WTW as required by regulation 27(3) and subsequently submit a revised regulation 28 report accompanied by a signed board level declaration.
    Date: From time to time and by 21 August 2024
  3. Submit a satisfactory completion report.
    Date: 30 August 2025

Failure by the company to comply with this Notice may result in enforcement proceedings under section 18 of the Water Industry Act 1991.

Signed by authority of the Secretary of State
Nick Adjei
Deputy Chief Inspector
04 February 2022
DWI Reference: UUT-2020-00003
Version 2