DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY ASSET MANAGEMENT WORK PROCEDURE WATER QUALITY FAILURE ACTION TRIGGERS

Transcription

1 Document Title: Work Procedure Water Quality Failure Action Triggers Document Reference: DOM-WN-PRC Approved By: Public Health Team Title: Public Health Manager

2 Ref: DOM-WN-PRC Record of Changes and Amendments Amendment. Document Section/ Reference Number Document / Section Title Version Number Amendment Date Archived Document / Section Text Affected Archived Document / Section Replaced By Sheet i

3 FOREWORD Background DOMS stands for Distribution Operation & Maintenance Strategy and is being used by Scottish Water to: Safeguard the quality of water to customers. Ensure that Scottish Water apply due diligence to their Scottish Water distribution network. The DOMS procedures and work instructions affect all functional staff who work on the network, which includes internal employees and employees of external organisations (i.e. planners, operators, delivery teams, Framework Contractors, or any other contractors). Through the application of the DOMS principles in day-to-day network activities, Scottish Water and their approved contractors will operate and maintain their water distribution networks through operational best practice. This will allow Scottish Water to meet the following objectives: to maintain water quality. to maintain continuity of supply. to maintain water supply hygiene. to undertake water quality incident management. to maintain a cost-effective water supply. to ensure a course of action for timely network intervention (Capex and/or Opex) to maintain statutory obligations and customer satisfaction. Responsibility The responsibility for adoption and implementation of all DOMS procedures and work instructions rest with Scottish Water General Managers and senior managers of external organisations. It is the responsibility of all Scottish Water employees and those of external organisations to comply with DOMS procedures and work instructions. Document Control This document is a CONTROLLED DOCUMENT when viewed on Wavelength. The document becomes UNCONTROLLED if printed or downloaded from Wavelength or any other source. Refer to the Wavelength site for the latest version of this document. Page i

4 Change Request A change to this document can be requested by completing a Change Request Form - refer to document DISTRIBUTION OPERATION and MAINTENANCE GOVERNANCE (DOM- WN-GOV ) for change request procedure. Copyright Copyright of this document is owned by Scottish Water. The document may not be copied or reproduced in any way. Page ii

5 CONTENTS FOREWORD. i CONTENTS... iii 1 PREAMBLE Procedure Objectives Related Parent Documents Related External Controlled Documents Related Internal Controlled Documents PROCEDURE FLOW CHART DESCRIPTION Water Quality Procedure Flow Diagram Water Quality Values Flow charts 3-6 Page iii

6 1. PREAMBLE 1.1 Procedure Objectives Scottish Water is committed to delivering the Ministerial Directions and other regulatory targets, within the financial limits set out in the Final Determination. To ensure that the risk of contamination of water in the distribution system is minimised we have produced a Water Supply Hygiene Code of Practice. This sets out the health and hygiene standards required of Scottish Water s employees and its Contractors/Consultants. This procedure is designed to give Scottish Water staff and Contractors an awareness of the Hygiene Code, its content and the steps they should take in their daily duties to ensure compliance.. Staff should refer to the Hygiene Code on a regular basis to ensure that they are working to the up to date requirements. Follow this file path on WaveLength to view the latest version of the Hygiene Code of Practice: Directorates > Asset Management > Scientific Services > Public Health Team > Useful Public Health & Scientific Links > SW Hygiene Code of Practice 1.2 Related Parent Documents ne 1.3 Related External Controlled Documents ne 1.4 Related Internal Controlled Documents SW Hygiene Code of Practice Water Supply (Water Quality) (Scotland) Regulations 2001 Scottish Waterborne Hazard Plan 2. PROCEDURE FLOW CHART Flow charts on pages 3, 4, 5 & 6 of this procedure. 3. DESCRIPTION The Water Supply (Water Quality) (Scotland) Regulations 2001 sets down legislation to ensure that water supplied to customers is both safe and wholesome. To determine whether water satisfies the criteria, monitoring shall be carried out at the water treatment works and associated zones. A suite of parameters needs to be analysed and the frequency of sampling is determined on the capacity of the works and the number of customers it supplies. In all, approximately 60 parameters can be analysed, each with their own PCV Page 1 of 6

7 (prescribed concentration and value) that must be met. In the event of a parameter failing various actions should be taken and will be specific to that parameter. The PCV is the initial Water Quality Action Trigger Point. Should the failure be far in excess of the PCV then a SHRAV (Short-term Health Risk Action Value) will be considered and the Scottish Waterborne Hazard Plan will be initiated. Contact the Public Health Team for further information on SHRAVs. Within the distribution system some parameters are significant such as iron, aluminium, Tri halomethanes (THMs) etc and in the event of a failure, relevant procedures should be followed. Water Quality Procedure Flow Diagrams: Iron and manganese failure of a sample in distribution Aluminium failure of a sample in distribution THM failure of a sample in distribution Turbidity exceedence Bacteriology failure of a sample in distribution 3.2 Water Quality Values Medical risk guidelines and risk values (refer to Scottish Waterborne Hazard Plan - Annex G). Follow this file path on WaveLength to view the latest version of the Hygiene Code of Practice: Directorates > Asset Management > Scientific Services > Public Health Team > Useful Public Health & Scientific Links > SW Hygiene Code of Practice The Public Health Team will assess the failures and inform the relevant personnel of any additional actions that should be taken. te: - If there are any doubts with any of the procedures or flow diagrams please contact your Manager who will advise you who to contact. Page 2 of 6

8 Iron or Manganese Failure Iron or Manganese exceedance at laboratory Instigate laboratory investigation to ensure failure is valid Inform Scientific Services, Public Health Team Refer to Scottish Waterborne Hazard Plan, Appendix 5 & 20 For information and advice. Contact CPHM for advice and complete Event form and circulate to CPHM, EHO, SE and SW Internally. Investigate to determine whether failure is due to one of the following:- * Treatment works * Service reservoir performance - raw water quality - results history - treatment performance - cleaning - flow changes - outwith design flow - coagulant dose - trends on SCADA system * Customer plumbing - service pipe * Network - storage tank - asset material & condition - internal plumbing - planned or unplanned work * Customer complaint history Resample at original sample point plus additional samples requested by PHT Instigate appropriate remedial action, eg:- * Treatment improvements * Service reservoir cleaning * Mains flushing * Increased monitoring Follow procedure for authorised departures Continue investigation Resamples satisfactory Inform CPHM, EHO, SE and SW of outcome Record in Promise further action Page 3 of 6

9 Aluminium Failure Aluminum exceedance at Laboratory Inform Scientific Services, Public Health Team Failure >200 ug/l Contact CPHM for advice and complete Event form and circulate to CPHM, EHO, SE and SW Internally. Initiate Scottish Waterborne Hazard Plan, if required, by Problem Assessment group Investigate failure, including:- * Treatment performance - filter performance - ph - coagulant dose - trends on SCADA system Arrange resamples from WTW and in distribution. Resamples satisfactory Inform personnel involved with SWHP of outcome Await further instructions Page 4 of 6

10 THM Failure THM exceedance at laboratory Inform Scientific Services, Public Health Team Refer to Scottish Waterborne Hazard Plan For information and advice. Complete Event form and circulate to CPHM, EHO, SE and SW Internally Arrange resamples from WTW and Zone * resamples need to be taken as soon as possible to ensure that 30 day rule for authorised departures is met. Are resamples satifactory ie. below the PCV Can treatment be improved further action is required Adjust treatment Increase monitoring Monitor effects at WTW and throughout the Zone Follow procedure for authorised departure Record actions on Promise system Page 5 of 6

11 Turbidity Exceedance Turbidity exceedance from laboratory or at WTW Instigate laboratory investigation to ensure failure is valid Inform Scientific Services, Public Health Team Refer to Scottish Waterborne Hazard Plan, Appendix 21 For information and advice. Is exceedance from WTW Arrange cryptosporidium sampling and advise laboratory that a quick turnaround is required Investigate cause, these should include:- * Iron and manganese * Aluminium * Network activity (planned or unplanned ie. bursts) * Service Reservoirs * Customers Internal pipework Investigate causes, these should include:- * Assessment of raw water quality * Filter Operation * Coagulant control * Flow changes * Pump control Are there health implications Inform CPHM, EHO and act on advice given. Complete Event form and notify CPHM, EHO, SE and SW. Adjust treatment as appropriate. Consider shutdown or rezoning Decide on advice Severe Instigate SWHP Low Complete Event form and notify CPHM, EHO, SE and SW. Arrange samples and consider what sampling and parameters are required. Page 6 of 6