Portsmouth Water Limited – Itchen Water Treatment Works

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

Reference: PRT-2023-00012

Version Number: 1

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Portsmouth Water Limited, with registered number 02536455 (hereinafter called ‘the Company’).

Assets Affected:

  • TITCH – Itchen Water Treatment Works
  • YWSP-HSH – WSP-HSH Supply System

Details of this Notice:

  1. The Drinking Water Inspectorate (‘the Inspectorate’) has received a regulation 28(1) report of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated 18 October 2021, which states that there is or has been a significant risk of supplying water from Itchen 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

Failure to optimise poly-aluminium chloride dosing resulting in excessive carry over into downstream assets.

Chemical Dosing – Failure to administer the correct dose – Aluminium


Failure to operate the treatment works in accordance with the recommendations of the Badenoch and Boucher reports.



Failure to operate treatment works in accordance with regulation 26

Disinfection – Equipment Failure – Microbiological


Table 1: 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. Continuous on-line monitoring of aluminium post clarifiers and post rapid gravity filtration.
    Date: Ongoing for the duration of this Notice.
  2. Maintain an effective procedure for the communication of any pollution events from the upstream Southern Water Limited wastewater treatment plant.
    Date: Ongoing for the duration of this Notice.
  3. Enhanced (continuous) Cryptosporidium monitoring of Itchen treatment works final water.
    Date: Ongoing for the duration of this Notice.
  4. Continuous and representative pH monitoring in the raw and post pH corrected water.
    Date: Ongoing for the duration of this Notice
  5. Subject the water to sufficient preliminary treatment to prepare it for disinfection, including pH correction, as required.
    Date: Ongoing for the duration of this Notice
  6. Record the completion of daily, weekly and monthly required operational site maintenance checks.
    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 an investigation into the excessive carryover of aluminium from the treatment processes at Itchen WTW, to understand why this is occurring and the resulting impact. The investigation must include the following:
  • Clarification of what the Company define as optimisation of the coagulant dose for the Itchen WTW, stipulating what this means with regards to turbidity, pH and residual aluminium levels;
  • The procedure for manual restarts of the dosing system following electrical power failures, including any water quality safeguards, how it is ensured this takes place and how it is evidenced;
  • The total aluminium concentration post-clarification, post-rapid gravity filters (RGF) and post ultrafiltration; and
  • Review of aluminium levels throughout an RGF cycle (pre- and post- washes), to ensure removal of any carry-over from the clarification process.
    Date: Complete (30 June 2022)
  1. Complete a full process hazard review to identify the performance capabilities of the existing processes to treat all aspects of the raw water quality under all conditions and including (but not restricted to) the following elements:
  • A review of current asset performance and efficacy against catchment hazards and raw water challenge.
  • A review of site arrangements in respect of compliance with the recommendations of the Expert Group on Cryptosporidium “Badenoch and Bouchier”. In particular, the arrangements for the return of wash water to the head of the works and RGF flow changes.
  • A full review of the disinfection process, chemicals used, and the parameters monitored and used to control the process.
  • Review compliance with the requirements of regulation 31 throughout the treatment processes.
  • A review of site pipework, valving, drainage and sanitary disposal facilities.
  • An end-to-end review of operational and maintenance tasks (frequency and appropriateness).
  • A review of asset criticality, including single points of failure.
  • An assessment of hazard containment and recovery requirements, including run to waste, automated shutdown and alarm facilities.
  • A full review of all sampling and online monitoring against industry good practice, to ensure sampling locations are correct, frequencies are appropriate and that results are representative.
  • A review of contingency planning for the site.
  • Review the GAC regeneration frequency.
  • A review of the use of all consumable materials (e.g., chemicals, filtration media, membranes and cartridge filters) used on site, which are approved under regulation 31(4)a to ensure the manufacturer’s instructions for use, or the national conditions of use (as applicable) are complied with.
  • The general condition and operational lifetime of the treatment assets.
    Date: Complete (30 June 2022)
  1. Develop an action plan to address any deficiencies identified in measures (b)1 and (b)2.
    Date: Complete (30 September 2022)
  2. Deliver the action plan, developed under measure (b)3 as detailed in the document ‘Items that are considered included within the measure (b)3 action plan, Itchen Water Treatment Works, Treatment Process Risks, PRT-2021-00003’.
  • Phase 1 Date: 31 March 2024
  • Phase 2 Date: 31 December 2024
  1. Optimise the coagulation and put in place ongoing and regular optimisation through appropriate documented controls. Investigate automated coagulant dose control systems.
    Date: Complete (31 August 2022)
  2. Complete an investigation to ensure the requirements of regulation 26(2)(a) are being delivered, to keep disinfection by products as low as possible.
    Date: Complete (30 June 2022)
  3. Complete a review and update of site documentation, on a risk prioritisation basis.
    Date: 31 December 2024
  4. Complete an internal inspection of the Itchen WTW contact tank. Determine the plug flow efficiency of the contact tank.
    Date: 31 December 2023
  5. Complete any required mitigation measures to address any risk identified under measure (b)8.
    Date: 31 March 2024
  6. Complete an investigation into the condition of the Itchen WTW wastewater tanks.
    Date: Complete (30 June 2022)
  7. Complete any necessary remediation identified under measure (b)10.
    Date: Complete (30 September 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 sections (a) and (b).
    Date: 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 Itchen 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. Provide a report on the inspection of the Itchen contact tank and plug flow efficiency as delivered under measure (b)8.
    Date: 31 January 2024
  3. Confirm delivery of the action plan as required under measure (b) 4.
    Phase 1 Date: 30 April 2024
    Phase 2 Date: 31 January 2025
  1. Confirm completion of remedial measures required to address risks associated with the contact tank (as delivered under measure (b)9).
    Date: 30 April 2024
  2. Confirm the completion of the review and update of site documentation, as required by measure (b)7.
    Date: 31 January 2025
  3. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: Complete
  4. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  5. 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.
  6. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 30 April 2025

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
11 December 2023
Reference: PRT-2023-00012

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