South West Water Limited – Knapp Mill Treatment Works, Disinfection Improvements

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

Reference: SWB-2020-00008

Version Number: 1

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): South West Water Limited, with registered number 02366665 (hereinafter called ‘the Company’).

Assets Affected:

• Knapp Mill WTW (T9200F)
• Knapp Mill Supply System (T9200)

Details of this Notice:

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 22 January 2020 and 20 October 2020, which state that there is or has been a significant risk of supplying water from Knapp Mill 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 (multiple hazards including but not limited to the following, by way of example):
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Colour	7797
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Total algae	7902
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Geosmin	7985
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Taste and odour	7825, 7826
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Total organic carbon (including dissolved organic carbon)	7811
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Disinfection by-products, including trihalomethanes	7976
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Pesticides	7986
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Oil / fuel	7904
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Cryptosporidium	7980
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Colony counts	7823
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Escherichia coli	7821
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Enterococci	7808
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Total coliforms	7982
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Clostridium perfringens	7834
Raw water risk and potential risks generated by the treatment process or inadequate treatment processes, including: SSF deficiencies; SSF operation and maintenance deficiencies; ultraviolet transmittance (UVT); and failure to comply with regulation 26.	Turbidity	7827

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.

3. 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.

Requirements:

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

1. Raw water continuous monitoring for ammonia, dissolved oxygen, conductivity, pH, turbidity, oil and colour at the point of abstraction, with suitable alarm triggers and response procedures in place.
   Date: Ongoing for the duration of this Notice.
2. Maintain contingency plans to protect human health in the event of a risk to human health associated with drinking water quality, which should include proactive liaison with local and regional public health officials.
   Date: Ongoing for the duration of this Notice.
3. Risk informed monitoring for chironomid larvae at a representative point post all slow sand filters (SSFs) at Knapp Mill Water Treatment Works (WTW).
   Date: Ongoing until all SSFs are no longer in supply.
4. Monthly inspection of hatch integrity and remediation of any identified issues for hatches over partially or fully treated water.
   Date: Ongoing for the duration of this Notice.
5. Ensure the partially treated water presented for ultraviolet (UV) disinfection is within the design envelope and capability of the installed UV units and subject to sufficient preliminary treatment. Ensure the effectiveness of UV disinfection is verified.
   Date: Ongoing for the duration of this Notice.
6. Weekly sampling for microbiological parameters from each individual SSF at Knapp Mill WTW.
   Date: Ongoing until all SSFs are no longer in supply.
7. Continuous monitoring and recording of UV intensity, UV dose and flow of water through the UV plant.
   Date: Ongoing for the duration of this Notice.
8. Continuous monitoring for Cryptosporidium from the point at which water leaves the treatment works (final water monitoring point).
   Date: Ongoing for the duration of this Notice.
9. Annual rapid gravity filters media assessments (including size and shape analysis) and implementation of any required measures identified.
   Date: Ongoing for the duration of this Notice
10. Undertake effective liaison with relevant stakeholders to allow appropriate response to upstream sewage events.
    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:

Slow sand filters (SSFs)and associated assets

1. Complete or implement the following as specified:
   1. Complete a critical review of the Knapp Mill WTW’s slow sand filter maintenance, operation and management procedures.
      Date: 30 September 2022
   2. Complete the revision of the Knapp Mill WTW’s SSF maintenance, operation and management procedures, following the findings of the critical review in (b)1.1. This revision must include the items listed in Annex 1 as a minimum standard.
      Date: 31 October 2022
   3. Implement the revised slow sand filter maintenance, operation and management procedures completed under (b)1.2. and operate all the Knapp Mill WTW’s slow sand filters in accordance with these procedures.
      Date: 31 October 2022
   4. Complete the training of all relevant personnel to achieve competency in the revised slow sand filter maintenance, operation and management procedures implemented under measure (b)1.3.
      Date: 31 October 2022
2. Remove or ensure the external pipework to the underdrains of the SSFs is water- and vermin- proof to prevent contamination from entering the filtered water stream.
   Date: Complete
3. Replace or regenerate the SSF media (granular activated carbon (GAC) and sand) and inspect the SSFs, in accordance with the dates set in Annex 2.
   Date: as specified in Annex 2
4. For the SSF filtrate collection chamber:
   1. Complete an internal inspection of the SSFs filtrate collection chamber.
      Date: 31 December 2022
   2. Implement appropriate mitigation to address any risks identified by the SSF filtrate collection chamber internal inspection, completed under (b)4.1. above.
      Date: 28 February 2023

Contact tank

5. Complete an internal inspection of the contact tank.
   Date: 31 December 2022
6. Implement appropriate mitigation to address any risks identified by the internal inspection of the contact tank, completed under measure (b)5. above.
   Date: 31 March 2023

Treated water tank – East

7. Complete an internal inspection of the Treated Water Tank – East.
   Date: 31 December 2022
8. Implement appropriate mitigation to address any risks identified by the internal inspection of the Treated Water Tank – East, completed under (b)7. above.
   Date: 28 February 2023

Treated water tank – West:

9. Complete an internal inspection of the Treated Water Tank – West.
   Date: 28 February 2023
10. Implement appropriate mitigation to address any risks identified by the internal inspection of the Treated Water Tank – West, completed under (b)9. above.
    Date: 30 April 2023

Rapid gravity filters

11. For the rapid gravity filters backwash tank:
    1. Complete an external inspection of the rapid gravity filters backwash tank.
       Date: Complete
    2. Implement appropriate mitigation to address any risks identified from the external inspection of the rapid gravity filters backwash tank completed under (b)11.1. above.
       Date: Complete
    3. Complete an internal inspection of the rapid gravity filters backwash tank.
       Date: 31 December 2022
    4. Implement appropriate mitigation to address any risks identified from the internal inspection of the rapid gravity filters backwash tank completed under (b)11.3. above.
       Date: 31 March 2023
12. Create a suitable procedure and asset standard for the maintenance and operation of rapid gravity filters. This must include specifications of:
    • Media regeneration and replacement frequencies and external inspections;
    • Media size and type;
    • Flowrates through rapid gravity filters; and
    • Monitoring set points.
      Date: 31 July 2022

13. Complete a gap analysis between the created asset standard for rapid gravity filters (created under (b)12.) and the Knapp Mill WTW rapid gravity filters.
    Date: 28 February 2023
14. Implement measures to address the findings of the gap analysis completed under measure (b)13.
    Date: 30 April 2023

External maintenance checks of treated or partially treated water storage tanks

15. Review the suitability of the Company’s procedure for ongoing external maintenance checks of treated or partially treated water storage tanks at Knapp Mill WTW. This is to be reviewed against checks that are being completed on-site.
    Date: 30 June 2022
16. Following the review completed in (b)15., rectify any identified deficiencies within the procedure and then instigate appropriate ongoing maintenance checks for treated or partially treated water storage tanks at Knapp Mill WTW.
    Date: 30 June 2022

Water Fittings

17. Complete a water fittings inspection of Knapp Mill WTW.
    Date: Complete (25 January 2022)
18. Implement measures to address the findings of the water fittings inspection completed under measure (b)17.
    Date: 31 July 2022

(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). This must include:
   1. Detailed specification of enhanced monitoring to be undertaken (parameters and frequencies);
   2. Ownership of the audit strategy (roles and responsibilities); and
   3. Specified review of all monitoring data and resulting action.
      Date: 30 September 2022

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 Knapp Mill 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. Report summarising the outcome of the SSF maintenance, operation and management procedures review (measure (b)1.1.), accompanied by the revised procedures (measure (b)1.2.), confirmation of the implementation of the revised procedure and appropriate training (required under measure (b)1.3. and (b)1.4.).
   Date: 30 November 2022
3. Evidenced completion of measure (b)2.
   Date: Complete (30 June 2022)
4. Provide regular updates through South West Water Ltd-Drinking Water Inspectorate liaison meetings on compliance with measure (b)3.
   Date: Ongoing for the duration of the notice
5. Provide an annual confirmation of compliance with measure (b)3.
   Date: Annually by 31 January
6. Summary of the findings of the internal inspection of the SSFs filtrate collection chamber (measure (b)4.1.) and Treated Water Tank – East (measure (b)7.). Additionally, provide a summary of any mitigation implemented under measures (b)4.2. and (b)8.
   Date: 31 March 2023
7. Summary of the findings of the internal inspection of the contact tank (measure (b)5.) and the rapid gravity filters backwash tank (measure (b)11.3.). Additionally, provide a summary of any mitigation implemented under measures (b)6. and (b)11.4.
   Date: 30 April 2023
8. Summary of the findings of the internal inspection of Treated Water Tank – West (measure (b)9.). Additionally, provide a summary of any mitigation implemented under measures (b)10.).
   Date: 31 May 2023
9. Report summarising the findings of the external inspection of the rapid gravity filters backwash tank (measure (b)11.1.) and any required actions taken to address any risks (measure (b)11.2.
   Date: Complete (30 June 2022)
10. Submit the created rapid gravity filters procedure required under measure (b)12.
    Date: 31 August 2022
11. Submit a summary of the gap analysis completed under measure (b)13. and confirm the implementation of measures to address the gap analysis (measure (b)14.).
    Date: 31 May 2023
12. Report outlining the findings of the review completed under measure (b)15. and the measures taken to address any findings (measure (b)16.).
    Date: 31 August 2022
13. Report the findings of the water fittings inspection and confirm completion of any required measures to address any risks found (measures (b)17. and (b)18.).
    Date: 31 August 2022
14. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: 31 October 2022
15. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
16. 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.
17. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: One month after the current treatment process arrangement is no longer in supply.

Further Details of this Notice:

4. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
5. 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.
6. 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).

Signed

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
02 August 2022
Reference: SWB-2020-00008