United Utilities Water Limited – Oswestry Treatment Works

Notice under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended)

Reference: UUT-2022-00003

Version Number: 3

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): United Utilities Water Limited, with registered number 02366678 (hereinafter called ‘the Company’).

Assets Affected:

  • T198 Oswestry WTW (At Hindford)

Details of this Notice:

  1. The Drinking Water Inspectorate (‘the Inspectorate’) has received a set of regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 12 July 2019, 16 July 2019, 09 December 2019, 21 October 2019, 23 October 2019 which states that there is or has been a significant risk of supplying water from Oswestry WTW(and associated assets as applicable) that could constitute a potential danger to human health or could be unwholesome.
  2. Consequently, this Notice is served on the Company by the Inspectorate on behalf of the Secretary of State, under regulation 28(4) for the assets listed above, for risks associated with:

Description of Risk 

Hazard/ Hazardous Event/ Parameter 

Hazard ID 

Underperformance of first stage filters


T198 A022240742

Underperformance of first stage filters


 T198 A002A240742

Underperformance of second stage filters


 T198 C111239069

Contact tank bacteriological risk from external factors


 T198 C111239069

Taste and odour risk from geosmin or 2MIB compounds

Taste and Odour

T198 A004305622

T198 A004245388

Contact tank bacteriological risk from external factors

E. coli

T198 C002239069

Contact tank bacteriological risk from external factors

Total coliforms

T198 C001239069

Table 1: Table of the hazards, hazardous events, and/or parameters covered by this Notice, including the Hazard ID numbers and the description of risks.
  1. The Company are required to satisfy the following requirements.

The date given is that until or by which the requirements must be maintained or satisfied, as appropriate.


(a) To maintain the following measures for the period specified in each case:

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

(b) To review, revise or make operational the following measures, by the dates specified in each case:

  1. Complete the design and procurement for capital works on site.
    Date: Complete
  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 2026
  5. Provision of new second stage manganese removal stage
    Date: 31 July 2026
  6. UV treatment capability on full flow
    Date: 31 July 2026
  7. Provision of a new chemical disinfection process, enabling the current contact tank and valve house to be abandoned
    Date: 31 July 2026
  8. Provision of automatic shutdown pre contact tank to prevent inadequately treated water entering supply
    Date: 31 July 2026
  9. Provision of manual start up to waste facilities for inadequately treated water Date: 31 July 2026

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

  1. Define an audit strategy to monitor the effectiveness of the measures specified in sections (a) and (b).
    Date: 31 October 2020
  2. Implement, and keep under continuous review, the audit strategy defined in measure (c)1.
    Date: Following completion of measure (c)1. onwards.

(d) Not to supply water for regulation 4(1) purposes from Oswestry WTW, or not to so supply unless the specified conditions below are satisfied:

  1. 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 risks:

  1. Provide a progress report annually.
    Date: by 31 January each year.
  2. Confirmation of UV installation and commissioning.
    Date: Complete
  3. Details of the audit strategy
    Date: 30 November 2020
  4. Confirm completion and provide details of the design and procurement for the improvement works.
    Date: 31 October 2022
  5. Produce a report detailing the analysis of geosmin trends and capability of the works to mitigate the risk.
    Date: Complete
  6. Completion of construction work at Oswestry WTW.
    Date: 31 August 2026
  7. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  8. Submit a report in the event that any completed measures of this Notice need to be altered in any way, for any reason.
    Date: Ongoing for the duration of this Notice
  9. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 31 August 2027

Further Details of this Notice:

  1. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
  2. Under regulation 28(6) the Inspectorate, on behalf of the Secretary of State, may by notice served on the Company, revoke or vary this Notice.
  3. Failure by the Company to comply with this Notice may result in enforcement proceedings under section 18 of the Water Industry Act 1991 (as amended).


Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
06 October 2022
Reference: UUT-2022-00003

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