DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY ASSET MANAGEMENT WORK PROCEDURE SECONDARY DISINFECTION DESIGN AND INSTALLATION

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1 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY SECONDARY DISINFECTION DESIGN AND INSTALLATION Document Title: Document Reference: Work Procedure Secondary Disinfection Design and Installation Date: October 2013 Approved By: Asset Management Title: General Manager

2 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: Record of Changes and Amendments Amendment No. Document Section/ Reference Number Document / Section Title Version Number Amendment Date Archived Document / Section Text Affected 1 Section 3 Description A Oct 2013 Updated DOMS Training Guidelines Sheet i Archived Document / Section Replaced By

3 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: FOREWORD Summary DOMS stands for Distribution Operation & Maintenance Strategy and was introduced into Scottish Water to: safeguard the quality of water supplied to customers show that Scottish Water apply due diligence to operation and maintenance of their 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 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 and service to the customer; 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 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. Change Request A change to this document can be requested by completing a Change Request Form - refer to document DISTRIBUTION OPERATION and MAINTENANCE STRATEGY GOVERNANCE (DOM- WN-GOV ) for change request procedure. All employees are encouraged to submit Change Request Forms for consideration by the Document Authors, DOMS Champions and DOMS Working Group. Copyright Copyright of this document is owned by Scottish Water. The document may not be copied or reproduced in any way. Page i

4 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: CONTENTS FOREWORD... i CONTENTS... ii 1 PREAMBLE Procedure Objectives Related Parent Documents Related External Controlled Documents Related Internal Controlled Documents PROCEDURE SWIMLANE. 2 3 DESCRIPTION Introduction Design and Installation Considerations 5 Page ii

5 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: 1. PREAMBLE 1.1 Procedure Objectives This procedure outlines the key considerations, which must be considered when designing and installing secondary disinfection, where Sodium Hypochlorite (Chloros) is the dosing chemical. 1.2 Related Parent Documents None 1.3 Related External Controlled Documents SW Water Supply Hygiene Code of Practice (HCOP). SW Health and Safety COSHH assessment for Sodium Hypochlorite Solution > 10%. WRc A Guide to Chloramination, P6169. Manufacturer's Safety Data Sheet for Sodium Hypochlorite Solution > 10%. 1.4 Related Internal Controlled Documents DOM-WN-PRC Work Procedure Water Quality Failure Action Triggers DOM-WN-PRC Work Procedure Secondary Disinfection Maintenance, including Breakdown 2. PROCEDURE SWIMLANE One page swimlane of Functional Work Procedure for chlorination failure and High chlorine residual refer to page 2. Page 1 of 5

6 SW Security Section Customer Service Delivery Water Operations and Treatment Scientific Services Installation Designer Customer Service Delivery Operations Microbiological failures DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: Provide advice Provide feedback Provide advice Action Triggered Consultation Health and Safety Risk Assessment Design Installation Produce Impact Assessment and operating instructions Handover Preferred - connection to national grid. Preferred - connection to telemetry. Preferred - analyser + flow dosing control Page 2 of 5

7 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: 3. DESCRIPTION DOMS Training Guidelines Evidence of DOMS Training In 2007, Scottish Water set the goal that all staff working on the water network receives the relevant DOMS training by the end of the year. The result - over 9,000 people have currently completed DOMS training to support their network activities since it has been introduced within SW. All staff, both internal and external, who work on the water network, MUST complete the relevant Distribution, Operation and Maintenance Strategy (DOMS) training associated with their specific network activities and as a result MUST carry two cards which confirm their training. DOMS training is available through a number of approved Training Providers and the registration of the training units taken by individuals is administered through EU Skills. The first card relates to training given around the Hygiene Code of Practice (HCoP) and the card usually coloured light blue, confirms the cardholder has completed this element, which includes a health screening questionnaire. The second card, usually coloured white, relates to training given around DOMS and the training units shown on the back of the card detail the type of DOMS related site activities that the cardholder can undertake. Both cards detail the name of the cardholder, along with their picture, which will allow confirmation that the cardholder is the person holding the card. Scottish Water staff may and will challenge all internal and external staff working on the water network at anytime to produce both their cards to ensure that cardholder has the relevant training and understanding of DOMS Procedures and Work Instruction for the specific task that they are undertaking. The following guidelines should be followed for deciding the course of action to take when either internal of external staff were found to be working on the water network, or any infrastructure that will be connected to our network, without the requisite HCoP/DOMS cards confirming training 1) New starts - expectation that they will have their necessary HCoP/DOMS training organised by their employer within the first 4 weeks of them joining their company. They will not be allowed to work on the water network without the HCoP/DOMS training, even though they are being supervised by a person who has gone through the training. There is a minimal health risk here, which the health questionnaire, completed during the HCoP training, will confirm as acceptable or unacceptable. Page 3 of 7

8 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: 2) Completed HCoP/DOMS Training but no card issued by EU Skills - staff in this situation can work on the water network as long as they can demonstrate that they have a 'cover note' issued by training providers. If a 'cover note' is produced, then the person challenging can ensure that 'cover note' refers to the actual person by checking the EU Skills web site against name or reference number. This will be done in conjunction with the relevant DOMS Working Group representative. 3) Person challenged on site and person has no HCoP/DOMS relevant training - if this scenario occurs then the person who has made the challenge will remove the person from working on the water network and contact the relevant business unit DOMS Working Group representative as the first point of contact. Together, the site contact and the DOMS Working Group representative will make the decision on whether work can or cannot continue after discussions with the employee s relevant organisation. 4) Person challenged on site and cannot produce HCoP/DOMS relevant training cards, but claims to have undergone training - if no cards can be produced, then the person challenging can not confirm that the person has had the relevant training by checking the EU Skills web site against name or reference number. This will be done in conjunction with the relevant DOMS Working Group representative. 5) Person challenged on site; DOMS CARD EXPIRED. If a DOMS card has expired and the person is waiting to attend a SW DOMS training course, a signed and dated cover note, with the course reference confirmation number and Registration Status clearly shown, must be issued by the person s line manager, in order to allow access to the network. The person must present this cover note on site. (Failure to provide cover note will result in the individual being removed from working on the network until a cover note is issued, or the individual is retrained and re-registered with EUSR) The cover note will only be valid for 3 months after the original card expiry date. After 3 months has elapsed, if the person has not re-registered and is NOT in possession of a new card or a cover note stating the person is awaiting delivery of a new card, then access to work on the network will be refused. All internal and external staff working on the water network must have completed the relevant training. If the site challenges are made by SW staff (and on occasions the DWQR) for all those working on the network, the message will be sent clearly that 'IF YOU HAVEN T HAD THE TRAINING YOU CANNOT WORK ON OUR NETWORK OR ANY INFRASTRUCTURE THAT WILL BE CONNECTED TO OUR NETWORK. While we all want to balanced and professional in our company approach to this matter, water quality and customer satisfaction in our product is our paramount concern. Finally, can all Scottish Water staff note that for out-of-hours advice on public health issues, a representative from the Public Health Team can be contacted 24/7 through the ICC. Page 4 of 7

9 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: 3.1 Introduction This procedure covers the use of Sodium Hypochlorite (Chloros) at secondary disinfection installations. The need for additional disinfection will have been triggered by microbiological failures on the network. Refer to: Work Procedure Water Quality Failure Action Triggers (DOM-WN-PRC ) Before considering creating a Chloros secondary disinfection installation, consideration should be given to the advantages, disadvantages and costs associated with the introduction of chloramination at the Water Treatment Works. Chloramination is the process whereby ammonia and chlorine are added to produce monochloramine. Advantages: Reduce potential for Trihalomethanes (THMs) Significant reduction in chlorine taste complaints Maintenance of a potential disinfectant residual. Reduces the need for secondary disinfectant installations. Disadvantages: The process requires careful control. Mixing chloraminated water with chlorinated water within a supply zone should be avoided. The probability of a problem is high. The formation of nitrates must be monitored and controlled. The disinfection chemical used by SW is Sodium Hypochlorite Solution > 10%, S.D.S. No. S Design and Installation Considerations Consult with Scientific Services, who will advise on any potential THM problems, which may arise following the introduction of secondary chlorination. Scientific Services will determine any additional sample monitoring, which may initially be needed. Consult with Water Resources and Treatment, who will confirm any proposed changes to disinfection at the appropriate Treatment Works. Security of the installation - Consult with the SW Security section which will advise what the current government security guidelines are. Health and safety considerations Has chloramination at the source WTW been fully considered and other alternative disinfection methods? Refer to COSHH assessment for Sodium Hypochlorite Solution. Complete a health and Safety risk assessment for the installation. Refer to the Health and Safety Management System manual, which can be accessed via the SW intranet. Ensure good access to the installation. Chloros and at some sites batteries must be transported to the site regularly, in addition to regular site checks. Determine the optimum way of delivering the chloros to the site. Tanker deliveries should be considered for larger installations. Page 5 of 7

10 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: A permanent eye-wash station must be fitted. Where practical to do so, pressurised chloros dosing lines should be contained behind a secure barrier e.g. Perspex. Determine how the chloros will be transferred to the on-site storage tank: - electric or battery drum pump or hand-operated bellow pump. Does the site have a power supply? A permanent power supply is more reliable than a battery installation. Does the site have telemetry? Connecting to an existing telemetry system will provide constant monitoring, provide immediate failure notification and reduce the need for frequent site visits. Controlling the dosing rate The preferred option for the optimum dose control is to install a meter on the dosed main and a sample analyser to monitor the residual in the dosed water. Both are then used to control the dose rate. The second option is to install a sample analyser to monitor the residual in the dosed water, and control the dosing rate. The third option is to install a meter on the dosed main, and flow control the dosing rate. The last option is to set the dosing rate to a pre-determined dosing rate, based on site specific tests combined with knowledge gained from similar installations. Produce an impact assessment for system failure Where a service reservoir is being secondary-chlorinated, what are the normal minimum and maximum hours' storage? What is the Service Reservoir outflow pattern? What customers are supplied? What is the recommended method of routinely operating the installation, including the frequency of site visits? Determine the servicing needs of the chlorination system. Ensure an adequate turnover of the chloros solution, which will prevent the potential for bromate formation. Site Specific actions to be taken, when the secondary chlorination fails. * Refer to Work Procedure Secondary Disinfection Maintenance, including Breakdown (DOM-WN-PRC ) Chloros Storage tank Consider the frequency of site visits, when determining the capacity of the tank. The chloros tank must be fitted with a level indicator. The chloros tank must be bunded. The bund must be sized to hold tank contents plus 10%. Provide a water mixing supply. Page 6 of 7

11 DISTRIBUTION, OPERATION and MAINTENANCE STRATEGY Ref: A normal installation will have a duty / standby pump arrangement. The duty pump shall be switched on a weekly basis. Where the pump is dosing directly into a pressurised main, the pump will be sized to accommodate the maximum mains pressure. The dosing pump shall be flexible in terms of pump turn down and dilution ratios, and should be capable of being varied to give 10 to 1 or 12 to 1 solution strengths. A non-return valve will be fitted on the pump outlet. The pump discharge pipe The pipe will be raised above the top of the chloros storage tank to prevent possible siphoning through the pump. An air-vent will be fitted at the top of the pump discharge pipe to reduce the possibility of air locks. Where the installation has a mains power supply, a back-up battery should be provided. Where a battery installation is the only option, the battery should be securely placed on a metal or wooden plinth above the concrete floor. Post installation monitoring Performance log books should be kept at each site, and all work activities should be recorded in these logs e.g. chlorine residuals (free and total), taste and odour checks, stock tank levels, calibration checks, pump speed and stroke, duty cycling of pumps and battery replacement and monitoring. Where dosing directly into a pressurised water main Saddle straps must be fitted to all non-ferrous mains. Staff must take the following precautions when working with chloros injection pencils: The correct PPE must be worn. All pipework systems, where pencils are fitted, must be designed such that the pressure within the chloros injection line can be vented and released prior to the removal of the pencil from its housing. A risk assessment, taking the above into account, must be carried out. Page 7 of 7