Current improvement programmes

Notice of Regulation: Fixby Water Treatment Works – Disinfection By-products Risk


Yorkshire Water Services Limited: Fixby Water Treatment Works, Disinfection By-products Risk, AMP 7

Reference: YKS-2018-00002

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:

  • Fixby Water Treatment Works (T4692305 – Fixby No.2 WTW Cwt 1)
  • Fixby Water Treatment Works (T4692310- Fixby No.2 WTW Cwt 2)
  • Fixby Water Supply System (YSAI00130869)
  1. The Drinking Water Inspectorate (‘the Inspectorate’) has received multiple 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), which state that there is or has been a significant risk of supplying water from Fixby Water Treatment Works (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:

Hazard/Hazardous Event/Parameter

Hazard ID

Description of Risks

Disinfection by-products, including trihalomethanes and haloacetic acid

Failure of DAF processes (inc. compression & saturation).








Water quality issues due to Disinfection by-products levels.

Failure of treatment process to treat deteriorating raw water colour

Failure of treatment process to achieve final water turbidity within acceptable limits

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.

  1. The Company are required to satisfy the following:


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

Date: Ongoing for the duration of this Notice.

  1. Weekly samples for colour at the individual inlets for Fixby WTW. Ongoing review and appropriate response to colour trends.
  2. Continuous monitoring of UV254 (dissolved organic carbon (DOC)) levels in the incoming 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.
  3. Carry out enhanced monitoring (sampling) of disinfection by-products (trihalomethanes (THMs) and haloacetic acids (HAA)) at the point the water leaves the treatment works (final water monitoring point), in the key service reservoirs and zones supplied by Fixby WTW, at a minimum frequency of:
    • Twice monthly between August to November; and
    • Once monthly between December to July.
  4. Continue to review opportunities for catchment management activities with stakeholders to implement protective measures and reduce the risk of deterioration of raw water quality.
  5. Implementation of the AMP7 WINEP measures agreed with the Environment Agency.
  6. 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.
  7. 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.

(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:Date: 31 October 2021
    • 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.
  2. Provide a detailed design of the proposed solution. Date: 30 June 2022
  3. Install, commission, and verify through testing, the chosen solution.Date: 31 July 2023

(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 section (a) and (b).Complete
  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 WTW, or not to so supply unless the specified conditions below are satisfied:

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 by 31 January and against the following milestones:Date: Annually by 31 January
    • Confirm the chosen solution for disinfection by-product minimisation and provide the outline design for turbidity removal enhancements (measure (b)1.).Date: 30 November 2021
    • Provide a summary of the detailed design of the proposed solution (measure (b)2.).Date: 31 July 2022
    • Confirm installation and commissioning of the chosen solution(measure (b)3.).Date: 31 August 2023
  2. Submit the strategy for auditing the effectiveness of the measures, as specified in (c)1.Date: Complete
  3. Submit any revisions of the audit strategy produced under measure (c)2. Date: Within 1 month of a revision
  4. Submit a report in the event that any completed measure of this Notice needs to be altered in any way for any reason.Date: Ongoing for the duration of this Notice
  5. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.Date: 31 August 2024

  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).

Nick Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
05 November 2021
Reference: YKS-2018-00002
Version Number: 3