Treatment Processes
– Fluoridation
Version 1, Ref P9
January 2014
Citation: Ministry of Health. 2014. Water Safety Plan Guide: Treatment Processes – Fluoridation, Version 1, ref p9. Wellington: Ministry of Health.
Published in January 2014
by the Ministry of Health
PO Box 5013, Wellington, New Zealand
ISBN: 978-0-478-42756-1 (print)
ISBN: 978-0-478-42757-8 (online)
Previously published in 2001 as Public Health Risk Management Plan Guide: Treatment Processes – Fluoridation, Version 1, ref p9. This publication’s title and any reference within the text to ‘public health risk management plan’ were changed in January 2014 to reflect the December 2013 legislation change of the term ‘public health risk management plan’ to ‘water safety plan’. No other changes have been made to this document.
This document is available at: www.health.govt.nz
This work is licensed under the Creative Commons Attribution 4.0 International licence. In essence, you are free to: share ie, copy and redistribute the material in any medium or format; adapt ie, remix, transform and build upon the material. You must give appropriate credit, provide a link to the licence and indicate if changes were made.
Contents
Introduction 1
Risk Summary 2
Risk Information Table 3
Contingency Plan 6
Water Safety Plan Performance Assessment 7
Ref P9 Water Safety Plan Guide: iii
Version 1, January 2014 Treatment Processes – Fluoridation
Ref P9 Water Safety Plan Guide: iii
Version 1, January 2014 Treatment Processes – Fluoridation
Introduction
This Guide deals with the addition of fluoride to drinking-water to protect teeth against dental decay. It is not concerned with situations in which too little fluoride is dosed to protect teeth. To protect teeth, the target fluoride concentration is 0.7 to 1.0 mg of fluoride/L.
If an event occurs during fluoridation (ie, the process doesn’t work properly), concentrations of fluoride that are too high (more than 1.5 mg/L) for a long time can cause mottling of teeth and fluorosis.
The chemicals used in fluoridation present risks to the health of treatment plant staff. These are acknowledged, but are not discussed further as such risks are the subject of health and safety in employment legislation.
So long as the fluoride is added to the water after coagulation and filtration processes, and well away from the addition point of any calcium compounds, its effectiveness will not be reduced.
Risk Summary
The event creating the greatest risk involved in fluoridation is too much fluoride being added to the water (see P9.1).
The most important preventive measures are:
· regularly check that the dosing solution has been prepared at the right concentration using the right chemical (see P9.1.1)
· put an alarm on the fluoride concentration in the water to let you know when it is too high (see P9.1.3)
· make regular manual checks on the fluoride concentration in the treated water, and in some cases split the sample and send one portion to an external approved laboratory for analysis (see P9.1.1, P9.1.3, P9.1.4)
· make sure the treatment plant staff are properly trained (eg, in making fluoride dosing solutions, taking samples and calibration of the fluoride sensor) (see P9.1.1, P9.1.5–7).
(References in parentheses are to the Risk Information Table.)
Risk Information Table
Reliable information about water quality is essential for the proper management of a water supply. Knowledgeable and skilled staff are also essential for minimising the public health risks associated with water supplies. Please read the staff training (Guide G1) and the monitoring guides (Guide G2). While we haven’t pointed out every detail of how these documents are linked with the present document, the links are many and are important.
Abbreviations: DWSNZ – Drinking-Water Standards for New Zealand
Causes / Preventive measures / Checking preventive measures / Corrective action /What to check / Signs that action is needed /
Event: FLUORIDE CONCENTRATION GREATER THAN REQUIRED FOR DENTAL PROTECTION
Possible hazard: Fluoride
Level of risk: High
P9.1.1
Fluoride dosing solution (day tank) prepared at the wrong concentration, or using the wrong fluoride chemical, or spillage of fluoride chemical into solution preparation tank. / · Make sure chemicals supplied are delivered to the correct bins or containers; clearly label bins; ensure that operator is on site when chemicals are delivered.
· Make sure dosing solution concentration is cross checked (by a second person) after preparation and before use; check purity of chemicals supplied. / · Fluoride concentration.
· Supplier’s certificate of analysis. / · Fluoride concentration more than 1mg/L.
· Chemical bins not labelled.
· Checks show dosing solution concentration incorrect.
· Notification of spillage.
· Cross checks not signed off. / · Label chemical bins.
· Supplier is required to ensure that operator is present when chemicals are delivered.
· Instigate checks.
· Change supplier.
· Train staff in preparation of fluoride dosing solutions (including calculations).
· Schedule regular split samples of fluoridated finished water to be analysed by an external approved, laboratory. / · Identify staff training needs and provide training.
· Arrange for split sample analysis.
P9.1.2
Back-siphoning from day tank. / · Install a devise to prevent backflow into the water supply (see Guide D2.4). / · Absence of a backflow preventer. / · Install a backflow preventer.
Event: FLUORIDE CONCENTRATION GREATER THAN REQUIRED FOR DENTAL PROTECTION cont’d
P9.1.3
Dosing system malfunction. / · Routine maintenance schedule for dose controller, or flow proportional dosing system, (whichever is appropriate) and dosing pump (see Guide P10). / · Fluoride concentration.
· Maintenance log.
· Fluoride weight/ volume calculations. / · Fluoride concentration more than 1mg/L.
· Frequent repair needed.
· Maintenance log not signed off.
· No automatic shut off in event of fault.
· No evidence of dose cross checks having been carried out. / · Identify cause of fault and rectify.
· Replacement of controller if suspect.
· Ensure that all metering and dosing equipment is fail-safe and shuts off automatically on fault.
· Perform cross-checks each day of amount of fluoride dosed against the volume of water produced.
· Install an alarm to indicate when the fluoride concentration exceeds to the target level. / · Replace controller.
· Install equipment with required safeguards.
· Instigate weight/ volume cross checks.
· Regular manual checks on fluoride concentration in treated water, with these samples being periodically split and sent for independent analysis. / · Manual sampling and analysis.
P9.1.4
Dose rate set incorrectly. / · Periodic checks on fluoride concentration using an independent method of fluoride measurement. / · Fluoride concentration.
· Calibration schedule. / · Fluoride concentration more than 1mg/L.
· Monitoring checks show deviations from expected fluoride concentration. / · Adjust controller set point.
Event: FLUORIDE CONCENTRATION GREATER THAN REQUIRED FOR DENTAL PROTECTION cont’d
P9.1.5
Controller’s fluoride sensor out of calibration or malfunctioning (if dose controlled by feedback from in-line probe). / · Regular checks on fluoride sensor calibration using independent calibration solutions. / · Fluoride concentration.
· Calibration schedule. / · Fluoride concentration more than 1mg/L.
· Calibration checks show fluoride sensor out of calibration.
· Monitoring shows fluoride concentration out of control range. / · Recalibrate fluoride sensor.
· Determine reason for poor calibration and rectify.
· Train staff in fluoride sensor calibration.
· Regular manual checks on fluoride concentration in treated water, with these samples being periodically split and sent for independent analysis.
· Use more that one fluoride sensor so that any malfunction in one will become apparent from mismatch with readings from others. / · Identify staff training needs and provide training.
· Instigate monitoring.
P9.1.6
Monitoring samples not taken, or results incorrectly recorded. / · Provide staff training in sampling, and record keeping.
· Develop monitoring schedule, with checks on data entry. / · Fluoride concentration.
· Monitoring schedule.
· Monitoring records. / · Fluoride concentration more than 1mg/L.
· Monitoring schedule not followed.
· Errors in records. / · Identify staff training needs and provide training.
P9.1.7
Monitoring method incorrectly calibrated, performed incorrectly, or analysis reagents deteriorated. / · Provide staff training in sample analysis.
· Develop and use a quality control programme, including periodic split-sample measurement checks using an external approved laboratory. / · Fluoride concentration.
· Quality control checks. / · Fluoride concentration more than 1mg/L.
· Duplicate checks show errors in measurements. / · Identify staff training needs and provide training.
· Instigate quality control programme.
Contingency Plan
If an event happens despite preventive and corrective actions you have taken, you may need to consult with the Medical Officer of Health to assess how serious a problem is.
Event – Fluoride concentration is higher than maximum acceptable valueIndicators: / · Elevated fluoride concentrations evident from monitoring samples.
· Marked drop in pH (if the fluoride compound is acidic).
· Knowledge of a chemical spillage or overdose that may have led to a high fluoride concentration being produced in the water.
Required actions: / · Notify the MOH and shut down the plant if necessary. Provide another source of potable water until water of acceptable quality can again be supplied.
· Identify the cause of the problem and rectify.
· Dump the reservoir water if this is necessary and possible; flush the distribution system.
· Warn consumers to flush their taps thoroughly before resuming the supply of water.
· Record cause of system failure and steps taken to correct.
· Modify water safety plan if necessary.
Responsibility: / Manager designated responsible for the water supply.
Water Safety Plan Performance Assessment
To make sure that your supply’s water safety plan (formerly known as a Public Health Risk Management Plan, PHRMP) is working properly, periodic checks are needed. The overview document outlines what needs to be done. The following table provides the detailed information for checking this particular supply element.
What to measure or observe: / · Fluoride concentration.How often: / · DWSNZ:2000 Table 4.1 requires a minimum sampling frequency of 13/quarter for the purposes of P2 monitoring, but other regulations may require more frequent monitoring.
What to do with the results: / · Results need to be recorded to meet legislative requirements or to allow water safety plan performance assessment. The WINZ database is good for this.
· The collected data need to be periodically reviewed to see whether problems with this supply element are developing. This should be done as frequently as the manager responsible considers necessary to minimise risk to public health arising from this supply element.
· Should this view show any unusual incidents, indicate that proper procedures are not being carried out, highlight poor laboratory results or indicate that poor water quality is reaching customers, then review the procedures for managing the fluoridation process.
· Evaluate the monitoring results, and any actions taken as the result of having to implement a contingency plan, to see if the water safety plan needs modification – eg, preventive measures are up to date; the contingency plan steps are still adequate; and changes to the fluoridation process are recognised in the plan.
Responsibility: / Manager designated responsible for the water supply.
Ref P9 Water Safety Plan Guide: 7
Version 1, January 2014 Treatment Processes – Fluoridation