Notice of Regulation: South West Water Limited – AMP7 Stithians Water Treatment Works
Notice under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended)
Reference: SWT-2018-00006
Version Number: 4
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:
- Stithians WTW, T08033F
- Stithians Supply System, Y0833
Details of this Notice:
- 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 2018, which states that there is or has been a significant risk of supplying water from Stithians Water Treatment Works (and associated assets as applicable) that could constitute a potential danger to human health or could be unwholesome.
- 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 |
|---|---|---|
|
Earthy and musty taste and odour metabolite |
Geosmin |
1125 |
|
Earthy and musty taste and odour metabolite |
2-methylisoborneol |
1214 |
|
Disinfection by-products |
Trihalomethanes (Total by calculation) |
1764 |
|
Earthy and musty taste and odour (and any related taste and odour descriptors) |
Taste (Taste Quant) |
1771 |
|
Earthy and musty taste and odour (and any related taste and odour descriptors) |
Odour |
1772 |
- 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:
- Enhanced operational monitoring of the raw and final water and the supply area. Parameters including disinfection by-products and their pre-cursors, taste and odour should be included along with any other relevant parameters as appropriate. Algology should also be included within the raw and final water monitoring programmes.
Date: Ongoing for the duration of this Notice - Intermittent powdered activated carbon dosing as required.
Date: Ongoing for the duration of this Notice - Optimisation of current treatment processes to minimise disinfection by-products and reduce levels to as low as possible.
Date: Ongoing for the duration of this Notice - Manage the network to minimise the risk of disinfection by-product formation.
Date: Ongoing for the duration of this Notice - Continue to assess raw water risks and hazards as part of DWSP approach.
Date: Ongoing for the duration of this Notice - Continue to operate reservoir management/destratification in accordance with company procedures.
Date: Ongoing for the duration of this Notice - Catchment management and stakeholder engagement to implement wider company and industry aims to reduce nutrient inputs and reduce the risk from pesticides.
Date: Ongoing for the duration of this Notice - Inform on-going raw water risk assessment by enhanced monitoring during ‘high risk’ periods to be defined by the company by 31 January 2019.
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:
- Optimise powdered activated carbon (PAC) application and dosing to achieve the best practicable dose and maximum contact time prior to coagulation within the current constraints of the site.
Date: Complete - Investigate options to reduce the risks from taste and odour, geosmin, 2-methylisoborneol, dissolved organic carbon and disinfection by-products. This will include optimisation of existing processes and investigation of technical solutions.
Date: Complete - Confirm the required activated carbon treatment in terms of empty bed contact time, dose, contact time and regeneration regime, as appropriate, for the raw water quality.
Date: Complete - Confirm the rationale regarding the use of ultraviolet (UV) disinfection in combination with other treatment and hygienic barriers on the site to assure they are suitable for the raw water quality.
Date: Complete - Plan and develop the outline design of the long-term solution. Award the full contract for the construction of the chosen solution.
Date: Complete - Develop the detailed design of the chosen solution.
Date: Complete - Complete the construction, installation, and commissioning of the preferred solutions identified in (b)3, 4, and 5.
Date: 30 April 2024
(c) To audit whether the measures have been effective by the following means:
- Define an audit strategy to monitor the effectiveness of the measures specified in sections (a) and (b).
Date: Complete - 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 Stithians Water Treatment Works, 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:
- Provide a progress report annually.
Date: by 31 January each year. - Completion of review of medium-term measures (b) 3, 4 and 5, to confirm the long-term solution.
Date: Complete - Complete the outline design of the final solution proposed. Confirm and evidence the award of the full contract for the scheme.
Date: Complete - Provide the detailed design of the chosen solution.
Date: Complete - Completion of construction, installation, and commissioning of the long-term solution.
Date: 31 May 2024 - Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
Date: Complete - Submit any revisions of the audit strategy produced under measure (c)2.
Date: Within 1 month of a revision - 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 - Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
Date: 31 May 2025
Further Details of this Notice:
- Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
- 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.
- 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
30 November 2023
Reference: SWT-2018-00006 v4