Treatment Processes
– Pump Operation
Version 1, Ref P10
January 2014
Citation: Ministry of Health. 2014. Water Safety Plan Guide: Treatment Processes – Pump Operation, Version 1, ref p10. Wellington: Ministry of Health.
Published in January 2014
by the Ministry of Health
PO Box 5013, Wellington, New Zealand
ISBN: 978-0-478-42758-5 (print)
ISBN: 978-0-478-42759-2 (online)
Previously published in 2002 as Public Health Risk Management Plan Guide: Treatment Processes – Pump Operation, Version 1, ref p10. 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.
Ref P10 Water Safety Plan Guide: iii
Version 1, January 2014 Treatment Processes – Pump Operation
Contents
Introduction 1
Risk Summary 2
Risk Information Table 3
Contingency Plans 7
Water Safety Plan Performance Assessment 9
Ref P10 Water Safety Plan Guide: iii
Version 1, January 2014 Treatment Processes – Pump Operation
Ref P10 Water Safety Plan Guide: iii
Version 1, January 2014 Treatment Processes – Pump Operation
Introduction
Pumps are used in a number of ways in a water supply: providing pressure; controlling pressure fluctuations; moving water and dosing chemicals. This Guide is concerned with the management and operation of the three main categories of pumps:
Transmission pumps: / These move water from the source through the supply system.Bore pumps: / These pumps draw water out of bores or wells; they may be down the bore hole or on the surface.
Process pumps: / These are used to dose chemicals and to pump water to equipment that checks water quality (monitoring).
If an event occurs during pump operation (ie, a pump doesn’t work properly), the following could happen:
· if there are fluctuations in water pressure because a transmission pump fails, or does not operate in a way that avoids water hammer, backflow can occur so that germs or chemicals may get into the water and cause sickness
· if there are fluctuations in water pressure because a bore pump fails, backflow can occur so that germs or chemicals may get into the water and cause sickness
· if chemicals or disinfectants are not dosed or monitored properly because a process pump fails, germs that are not killed or removed or chemicals that are incorrectly dosed may cause sickness.
The operation of pumps can present risks to the health of supply staff. These are acknowledged, but are not discussed further as such risks are the subject of health and safety in employment legislation.
Correct pump operation helps to reduce public health risk from a number of supply activities (see P1, P4, P5, P6, P7, P8, and D2 series of Guides, and Guides P3, P9 and D1).
For every pump in a supply, records should be kept of:
· pump identification number
· pump type
· condition factor
· maintenance schedule.
Risk Summary
The two events creating the greatest risk with pumps are the failure of a transmission pump which can lead to backflow and pipe failure caused by pressure fluctuations and water hammer (P10.1), and the failure of a dosing pump to dose chemicals at the correct rate (P10.2).
The most important preventive measures are:
· to have duplicate pumps for critical operations (P10.1.1, P10.2.1)
· to have devices in place to reduce water hammer (P10.1.1)
· to have preventive maintenance programmes (P10.1.1, P10.2.1).
(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; MAV – Maximum acceptable value – see DWSNZ:2000, FAC – free available chlorine.
Causes / Preventive measures / Checking preventive measures / Corrective action /What to check / Signs that action is needed /
Event: CHANGES IN PRESSURE, OR WATER HAMMER (PRESSURE SURGES), SUCK CONTAMINANTS INTO THE WATER
Possible hazards: Germs and chemical contaminants.
Level of risk: High
(See Guides P2 and D2.2 for additional causes of this event.)
P10.1.1
Transmission pump failure due to mechanical failure or overload.
In addition to the possibility of contaminants being sucked into the water by back flow, water hammer can also cause pipe failure. / · Preventive maintenance programme in place:
– regular inspections
– lubrication
– seal replacement
– leaks repaired
– corroded components replaced
– annual ammeter tests
– daily visual inspection, etc.
· Planned maintenance programme for replacement of components as per manufacturer’s recommendations.
· All pumps itemised and maintenance schedule followed.
· Duplicate pumps for critical applications.
· Use duplicate pumps alternately (provides a check that both are functioning and will not need to be overhauled at the same time).
· Align and secure all pump-linked pipework, valves and fittings according to standard practice. / · Flows.
· System pressure.
· Reservoir levels.
· Pump maintenance log.
· E. coli.
· FAC. / · No water.
· Reservoir levels are difficult to maintain.
· Frequent pump breakdowns.
· Frequency of unacceptable pressure drops in the system.
· Maintenance log not kept.
· Non-compliance with DWSNZ:2000. / · Revise, or put in place maintenance schedule.
· Review service/ duty periods of duplicate pumps (time in operation: time on standby).
· Carry out residual disinfection in the distribution zone if not presently done.
Event: CHANGES IN PRESSURE, OR PRESSURE SURGES (WATER HAMMER) SUCK CONTAMINANTS INTO THE WATER cont’d
P10.1.1 cont’d / · Install devices to lessen water hammer should it occur, eg:
– surge tanks
– air chambers
– slow-closing check valves
– surge suppressors.
P10.1.2
No water because of pump failure due to power failure. / · Carry out biennial inspection of power source, connections and electrical equipment.
· Set up standby generator to cut in automatically when main power fails.
· Run standby generator monthly. / · Flows.
· System pressures.
· Reservoir levels.
· Pump maintenance log.
· E. coli.
· FAC. / · No water.
· Reservoir levels are difficult to maintain.
· Frequent pump breakdowns.
· Frequency of unacceptable pressure drops in the system.
· Maintenance log not kept.
· Non-compliance with DWSNZ:2000. / · Prepare and follow inspection schedule.
· Modify standby generator to allow automatic cut in.
· Carry out residual disinfection in the distribution zone if not presently done.
P10.1.3
No water because of pump failure due to flooding or other damage. / · Locate pumps above likely flood levels.
· Correctly align and bolt pumps to plinth.
· Protect pump(s) from the weather. / · Flows.
· System pressures.
· Reservoir levels.
· Pump maintenance log.
· E. coli.
· FAC. / · No water.
· Reservoir levels are difficult to maintain.
· Frequent pump breakdowns.
· Frequency of unacceptable pressure drops in the system.
· Maintenance log not kept.
· Non-compliance with DWSNZ:2000. / · Relocate pumps.
· Re-align pumps and secure.
· Provide cover for pump(s).
· Disinfect the distribution zone if not presently disinfected.
Event: INCORRECT CHEMICAL DOSING LEADS TO POOR TREATMENT
Possible hazards: Germs and chemical contaminants.
Level of risk: High
P10.2.1
Process pumps do not add the correct dose of chemical. / · Schedule preventive maintenance, particularly replacement of elastomeric parts: diaphragms; tubing etc., as per manufacturers recommendations.
· Calibrate dosing pumps for expected duty.
· Ensure pumps are fit for the purpose, eg., corrosion resistant.
· Provide duplicate pumps for critical functions.
· Daily check amount of chemical used.
· Use day tanks to reduce risk of overdosing.
· Visually check pumps daily.
· Check stroke and speed settings for manual pumps. / · Turbidity.
· E. coli.
· FAC.
· Chemical usage.
· Chemical type being dosed.
· Coagulation process (if appropriate). / · Non-compliance with DWSNZ:2000.
· Signs of ineffective coagulation.
· Difficulty maintaining a chlorine residual in the treated water.
· No maintenance programme in place. / · Put maintenance schedule in place.
· Review dosing programme.
· Replace pump(s) with one appropriate for the chemical being dosed and its concentration.
· Obtain standby pump (critical functions).
P10.2.2
Process pumps supplying water to monitoring instrumentation fail. / · Strainers on pump lines to remove debris.
· Clean strainers regularly.
· Ensure pumps are fit for the purpose.
· Check required flow rates are within the range recommended by the manufacturer.
· Schedule preventive pump maintenance. / · Flow rates to instrumentation.
· Condition of strainers.
· Turbidity.
· E. coli.
· FAC. / · No, or irregular, flow to instrumentation.
· Fluctuating readings from instrumentation.
· Non-compliance with DWSNZ:2000.
· Maintenance log not kept.
· Strainers clogged. / · Put strainers in place.
· Replace pump with a unit having specifications that match requirements.
· Prepare and follow maintenance schedule.
Event: CHANGES IN PRESSURE FROM THE BORE SUCK CONTAMINANTS INTO THE WATER
Possible hazards: Germs and chemical contaminants.
Level of risk: Moderate-high1
P10.3.1
Failure of the bore pump(s). / · Monitor bore performance either directly or using an observation bore.
· Schedule a preventive maintenance programme for bore pumps, and a planned maintenance programme for the overhaul of pumps.
· Monitor flow from the bore.
· Monitor system pressure. / · Bore flow.
· System pressure.
· E. coli. / · Bore pumps stop.
· Reduced, or no, flow from bore(s).
· Reduced pressure in distribution zone fed directly from the bore.
· Non-compliance with DWSNZ:2000.
· No maintenance log kept. / · Investigate bore pump performance.
· Put maintenance programme(s) in place.
· Disinfect the distribution zone if not presently disinfected.
1 If the water is disinfected after being drawn from the bore, or the water is pumped into a reservoir before reticulation, the consequences of the event will not be as severe as when the bore water is pumped directly into the distribution system.
Contingency Plans
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 – Contamination gets in the water because of pump failureIndicators: / · Reservoir levels difficult to maintain.
· Pump failure.
· Flow significantly reduced.
· Pressure decrease or fluctuations.
· Elevated levels of turbidity or chemical determinands.
· In 100 ml samples of water, E. coli is continually detectable, or is present at elevated levels (more than 10 per 100 ml).
· Increased chlorine demand.
· Widespread illness in the community linked to the water supply.
Required actions: / · Follow the actions given in Figure 3.2 or 3.3 (whichever is appropriate) of the DWSNZ:2000.
· If chemical contamination is suspected, monitor concentrations of the suspected determinand and follow the actions given in Section 4.4.1 of DWSNZ:2000.
· Identify the reason for pump failure, repair or use standby pump, and plan for long term preventive measures.
· Ensure that chlorine residuals of more than 0.2 mg/L can be maintained throughout the distribution system.
· Review laboratory results and take further samples if necessary.
· Record cause of system failure and steps taken to correct.
· Modify your water safety plan if necessary.
Responsibility: / Manager designated responsible for the water supply.
Event – Germs not killed or removed during treatment because of pump failure
Indicators: / · Visual observation of ineffective coagulation.
· No, or low, chlorine residual leaving the treatment plant.
· Pump failure.
· Elevated levels of turbidity or chemical determinands.
· In 100 ml samples of water, E. coli is continually detectable, or is present at elevated levels (more than 10 per 100 ml), in water leaving the treatment plant.
· Increased chlorine demand, which may not be met.
· Widespread illness in the community linked to water supply.
Required actions: / · Follow the actions given in Figure 3.2 or 3.3 (whichever is appropriate) of the DWSNZ:2000.
· Identify the reason for pump failure, repair or use standby pump, and plan for long term preventive measures.
· Ensure that chlorine residuals of more than 0.2 mg/L can be maintained throughout the distribution system.
· Review laboratory results and take further samples if necessary.
· Record cause of system failure and steps taken to correct.
· Modify your 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: / · System pressure and/or flow rates.· Pump maintenance log books.
· Determinands affected by the performance of treatment processes using process pumps.
· Consumption of treatment chemicals (no or little change may indicate pump failure).
· Faecal indicators (E. coli).
· FAC.
· Reservoir levels.
Follow the protocols set out in DWSNZ:2000 where appropriate.
A number of factors may affect these measurements or observations. A good understanding of the operation of the water supply will help in interpreting the results.
How often: / · For the monitoring frequencies for FAC and E. coli measurements see DWSNZ:2000 Section 3.3.2.
· System pressures, and maintenance logbooks should be checked at a frequency considered necessary by the manager responsible.
What to do with the results: / · Record results 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 review 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 the management and operation of pumps.
· 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 management and operation of pumps are recognised in the plan.
Responsibility: / Manager designated responsible for the water supply.
Ref P10 Water Safety Plan Guide: 9