FILTEC FLUORIDE
SOLUTIONS
PROPOSAL PRESENTED BY FILTEC LTD. AUCKLAND
Rev
Date
Description
By
Checked
Approved
Steven
0
20/01/2022 Draft for discussion
Mark Hillman
Rumble
Steven
1
20/01/2022 Final Draft
Mark Hillman
Steven Rumble
Rumble

www.filtec.co.nz | 09 274 4223 | [email address]
PO Box 132-329, Sylvia Park, Auckland 1644
102A Carbine Road, Mt Wellington, Auckland 1060
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FLUORIDATION REPORT
SUMMARY
The Ministry of Health is expected to consider issuing directions to fluoridate from mid-2022. Local
Authorities with un-fluoridated water that service over 500 people are encouraged to start
fluoridation-related preparatory work now – especially those in areas with large populations or
have poor oral health outcomes.
The purpose of this report is to provide all Filtec customers with preliminary information on water
fluoridation to allow them to initiate discussions with Filtec on the most effective fluoride solution
for their drinking water supply.
1
FLUORIDATION CHEMICALS
There are currently 3 fluoridation chemicals available in New Zealand.

Sodium Fluoride – NaF

Sodium Fluorosilicate (SFS) – also known as SSF

Fluorosilicic Acid - (FSA) – also known as HFA
1.1
SODIUM FLUORIDE

Sodium Fluoride (NaF) is supplied as a white crystalline powder, comprising 45% w/w fluoride
ion.

classified as a Dangerous Good with a hazard class of 6.1 Toxic

NaF has an almost constant solubility in water of approximately 4%, regardless of water
temperature. This allows for automatic, continuous preparation of saturated solutions in a
saturator tank without the need for equipment to measure chemical addition, therefore
reducing the risk of overdosing fluoride.

Suitable for small WTPs supplying up to 5MLD

NaF is available from Ixom in 5kg bottles which are supplied for the Prominent patented bottle
unloader
1.2
SODIUM FLUOROSILICATE

Sodium Fluorosilicate (SFS – Na2SiF6) is supplied as a white pungent crystalline powder,
comprising 60% w/w fluoride ion.

classified as a Dangerous Good with a hazard class of 6.1 Toxic.

SFS has a variable solubility in water (unlike NaF) and therefore must be added at a
controlled rate to produce the saturated solution

Suitable for medium size WTPs supplying 5 – 50MLD.

Available in 25kg bags – minimum order of 1 tonne (Ixom)
Note – due to lack of information, Sodium Fluorosilicate is not considered from a cost
perspective in this report.
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FLUORIDATION REPORT
1.3
FLUOROSILICIC ACID

Fluorosilicic acid (FSA/HFA – H2SiF6) is a pale-yellow fuming corrosive acid with a pungent
odour.

currently delivered at a concentration of 16.8% – 18.4% (w/w) and has a pH of approximately
1.

classified as a Dangerous Good1 with a hazard class of 8 Corrosive

available in 200L drums, 1000L IBCs and bulk delivery (North Island only) – Ixom. Bulk
deliveries to the South Island would be considered if the demand warrants.
2
EQUIPMENT REQUIRED
2.1
SODIUM FLUORIDE
Typical sodium fluoride installations contain the following equipment:

Saturation tank – upflow saturation is preferred

stirrer

Dosing skid – pump/s, filters, piping, valves

Control panel

Analyser

Water softener – required if water hardness exceeds75mg/L as calcium carbonate
The main benefit of using sodium fluoride is that a constant 4% solution is produced thus
minimising the risk of over-dosing. Sodium fluoride powder is more expensive than the other 2
chemical options however the capital cost of the equipment is less.
2.2
SODIUM FLUOROSILICATE
Typical sodium fluorosilicate installations contain the following equipment:

Hopper containing the powder for a pre-determined dosing capacity

Vacuum loading facility – handheld or automated

Powder feed system flow paced to ensure an accurate measure of powder is added to the
solution tank

Solution tank

Stirrer

Dosing skid – pump/s, filters, piping, valves

analyser
Sodium Fluorosilicate has a variable solubility and therefore it is good practice to provide a 10
minute detention time to ensure the powder is completely dissolved. If this cannot be met using
one tank then a second tank is required – one for dissolution, one for dosing.
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FLUORIDATION REPORT
2.3
FLUOROSILICIC ACID
Typical fluorosilicic acid installations contain the following equipment:

Bulk unloading system

Bulk tank storage

Transfer pump system

Day tank

Ventilation system

Bunding

Dosing skid – pump/s, piping, valves

Heating (if required)
3
FLUORIDE DOSING CONSIDERATIONS

Target concentration of fluoride in treated water is between 0.7 and 1.0 mg/L

Drinking water supplier should maintain an historical record of the fluoride concentration in
the raw water to ensure an appropriate allowance is made when determining the dosing
concentration

Fluoride concentration in the drinking water must never exceed 1.5 mg/L

Real time monitoring of the fluoride concentration is required

The system must be fully automated and operated by a control system based at the WTP

The Fluoride Code of Practice requires that a number of independent checks are met. For
water supply systems that serve more than 10,000 people, at least two of the three
following independent checks must be used. If the water supply system serves 10,000 or
fewer people, then at least one of the three independent checks is required.
o
Independent Check 1: Use of a day tank that can only be filled once a day and
is equipped with an online device to measure its contents
o
Independent Check 2: Use of a fluoride measuring flow meter on the fluoride
dosing line before the dosing point (only for (a) fluorosilicic acid, or (b) sodium
fluoride from a saturator)
o
Independent Check 3: Fluoride concentration analyser on the drinking-water
line after dosing point
Other design inputs which must be considered:

Existing water offtakes and their location in relation to the dosing point

Anti-siphonage and backflow prevention

Level of existing control

Corrosion and dust suppression

Existing building materials – high gloss moisture resistant finish walls for NaF and SFS
installations (Hardie Glaze or similar recommended)

handling and storage facilities

guaranteed chemical supply

environmental considerations - spill removal and clean up systems

Plant security

Continuous monitoring

Existing plant infrastructure

Operation and maintenance
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FLUORIDATION REPORT

Ventilation

Reporting and auditing
4
LAYOUT CONSIDERATIONS
4.1
SODIUM FLUORIDE

Minimum room size required – approx. 3m x 2.5m. This is based on a Prominent 5kg jar
system. System would fit into a 10’ container. No allowance for any NaF storage

Security of the site is required

The walls of the room to be high gloss
4.2
FLUOROSILICIC ACID

Bunded area of approx. 3m x 3m to house both the storage and day tanks (based on a
population of 10,000. Ideally storage tank to be placed external to the building.

Bunded chemical delivery area required

Safety shower required

Security of the site is required
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FLUORIDATION REPORT
5
ROOM LAYOUT
5.1
SODIUM FLUORIDE
Following is a typical layout of the Sodium Fluoride Prominent 5kg jar solution.
Figure 1 – Sodium Fluoride Typical Layout (Image courtesy from Prominent)
5.2
FLUOROSILICIC AID
No typical equipment layouts are available for the HFA installation. However, this would typically
show a chemical unloading system and storage tank mounted externally to the treatment building
with the day tank and dosing equipment inside. All areas would be bunded to suit.
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FLUORIDATION REPORT
6
COST SUMMARY
The costs below are indicative only. More detail design and information on the current treatment plant infrastructure would be required to provide more accurate estimates of the costs involved.
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FLUORIDATION REPORT
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P&IDS
Figure 2 - Sodium Fluoride Sheet 1 of 2
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FLUORIDATION REPORT
Figure 3 - Sodium Fluoride Sheet 2 of 2
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FLUORIDATION REPORT
Figure 4 - HFA Sheet 1 of 1
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