Yorkshire Water Services Limited – AMP7 Fixby Water Treatment Works, Disinfection By-products Risk

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

Reference: YKS-2018-00002

Version Number: 5

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Yorkshire Water Services Limited, with registered number 02366682 (hereinafter called ‘the Company’).

Assets Affected:

Asset Name


Fixby Water Treatment Works (Fixby No. 2 Cwt 1)


Fixby Water Treatment Works (Fixby No. 2 Cwt 2)


Fixby Water Supply System


Table 1: List of assets affected and associated reference numbers

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 06 December 2017 (with subsequent updates including those dated 20 November 2022, 01 February 2023 and 09 March 2023), which state that there is or has been a significant risk of supplying water from Fixby Water Treatment Works (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 I D

  • Risk to compliance with regulation 26(1) and 26(2)(a)
  • Deterioration of raw water quality, caused by total organic carbon (dissolved organic carbon specified), and associated colour risks.
  • Failure of treatment process to treat deteriorating raw water colour.
  • Water quality risk due to disinfection by-product formation.
  • Failure of treatment process to achieve final water turbidity within acceptable limits
  • Disinfection by-products, including trihalomethanes and haloacetic acid.
  • Failure of DAF processes (inc. compression & saturation).
  • Colour
  • Turbidity









Table 2: Table of the hazards, hazardous events, and/or parameters covered by this Notice, including the Hazard I D 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. Weekly samples for colour at the individual inlets (when in supply) for Fixby WTW. Ongoing review and appropriate response to colour trends.
    Date: Ongoing for the duration of this Notice
  2. Continuous monitoring of UV254 (dissolved organic carbon (DOC)) levels in the incoming combined raw water and of the rapid gravity filtered water, to ensure levels are appropriate for the treatment in place, with appropriate triggers and failsafes in place to prevent operation outside of the design envelope. Ongoing review and appropriate response to UV254 trends.
    Date: Ongoing for the duration of this Notice
  3. Carry out enhanced monitoring (sampling) of disinfection by-products (trihalomethanes (THMs) and haloacetic acids (HAA)), including as a minimum at:
    • the point the water leaves the treatment works (final water monitoring points);
    • Overton Service Reservoir;
    • West Bretton No.3 Service Reservoir; and
    • Brighouse Water Supply Zone
    • at a minimum frequency (at each of the above points) of:
    • Twice monthly for the months August to November; and
    • Once monthly for the months December to July.

Date: Ongoing for the duration of this Notice

  1. Continue to review opportunities for catchment management activities with stakeholders, and implement protective measures, where feasible, to improve raw water quality and reduce disinfection by-product precursors.
    Date: Ongoing for the duration of this Notice
  2. Regularly review the levels of DOC removed by the treatment processes and ensure treatment processes are optimised for DOC removal. Optimisation includes the optimisation of coagulation pH and coagulant dose, and the minimisation of post-rapid gravity filters (RGFs) turbidity.
    Date: Ongoing for the duration of this Notice
  3. Optimise the treatment processes at Fixby WTW to ensure continued compliance with regulatory standards and disinfection by-products are kept as low as possible without compromising the effectiveness of the disinfection.
    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. Confirm the chosen solution and establish the outline design to minimise the risk of disinfection by-product formation and to enhance turbidity removal following engineering and process reviews and, where required, pilot trials. The following should be considered at the outline design stage:
    • Refurbishment of the dissolved air flotation (DAF) treatment process;
    • RGF refurbishment and increased process capacity;
    • New Manganese contactor splitter tank;
    • New lamella dirty wash water system;
    • Coagulant dosing for the RGFs and new lamella;
    • Post-manganese contactor run to waste; and
    • Caustic dosing at the treatment works outlet.

Date: Complete (31 October 2021)

  1. Provide a detailed design of the proposed solution.
    Date: Complete (30 June 2022)
  2. Produce an up-to-date detailed design, including dates for delivery of each element.
    Date: Complete (31 March 2023)
  3. Install commission, and verify through testing, the chosen solution as detailed under measure (b)3.
    Date: 31 March 2025

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

  1. Update the audit strategy to monitor the effectiveness of the measures specified in sections (a) and (b).
    Date: 30 June 2023
  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 Fixby Water Treatment Works, 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. Confirm the chosen solution for disinfection by-product minimisation and provide the outline design for turbidity removal enhancements (measure (b)1).
    Date: Complete (30 November 2021)
  3. Provide a summary of the detailed design of the proposed solution (measure (b)2).
    Date: Complete (31 July 2022)
  4. Provide the up-to-date detailed design of the proposed solution (measure (b)3).
    Date: Complete (31 March 2023)
  5. Confirm installation and commissioning of the chosen solution (measure (b)4).
    Date: 30 April 2025
  6. Submit the updated audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: 31 July 2023
  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: 30 April 2026

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
31 May 2023
Reference: YKS-2018-00002 v5

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