8.6.3 Specifications for the supply of drinking water treatment chemicals
Preparing specifications for a chemical supply contract can be a time-consuming and difficult task. Documents should be prepared in conjunction with a risk assessment and controls recommended in Sections 8.5.1 and 8.5.2.
To simplify the process for water authority staff preparing their own specifications, an example specification for the supply and delivery of liquid aluminium sulfate (Al₂SO₄) to a water authority is provided in Box 8.2.
The specification includes details on the required content of aluminium, which is often, but not always, expressed as equivalent aluminium oxide (Al₂O₃); product clarity; solids content; and pH, as well as specific impurity limits. The specification also details some delivery and acceptance criteria. Product strengths and basic characteristics of the chemicals can be obtained from the relevant fact sheets in Section V. The water authority may customise these specifications to suit their particular situations and risks.
The specification should also clearly define the arrangements and responsibilities for ensuring the treatment chemical is not contaminated during transport or storage prior to transport.
Example specification for the supply and delivery of liquid alum to a water authority
Aluminium Sulfate (ALUM)– Specification reference
This specification is for the supply and delivery of liquid aluminium sulfate (Al₂(SO₄)₃.14H₂O) to [Name of water authority] sites. This specification is based on the NHMRC Australian Drinking Water Guidelines (2010), the American Water Works Association Standard for Aluminium sulfate – liquid, ground or lump (ANSI/AWWA B403-93) and the Water Chemicals Codex (NRC 1982).
Liquid aluminium sulfate is not currently listed as Dangerous Goods.
REQUIREMENTS
Material Safety Data Sheets (MSDS)
The successful tenderer must supply a current MSDS with a review date not exceeding five (5) years. The MSDS must, as a minimum, comply with the requirements of the National Occupational Health and Safety Council (NOHSC) MSDS Guidelines. Whilst the NOHSC-MSDS format is preferred, alternative formats exceeding the level of information required by NOHSC-MSDS Guidelines are acceptable.
Liquid aluminium sulfate clarity
Liquid aluminium sulfate shall be of such clarity as to permit the reading of flow measuring devices without difficulty.
Content of aluminium
The water soluble aluminium content of liquid aluminium sulfate is expected to be greater than or equal to 4.23% of Al, or to fall within the range of 7.5 to 8.0 % as (Al₂(SO₄)₃.
Suspended solids
In liquid aluminium sulfate, it is expected that the level of suspended solids is below 0.2%.
pH
The pH of liquid aluminium sulfate is expected to fall within the range of 2.3 to 2.8 pH units.
Specific impurity limits
It is expected that the total water-soluble iron (expressed as Fe₂O₃) content of liquid aluminium sulfate shall be no more than 0.35%.
The level of contamination of the liquid aluminium sulfate shall be such that compliance with the recommended maximum impurity content (RMIC) values from Table 8.4 in the NHMRC Australian Drinking Water Guidelines is achieved. The RMICs, in mg/kg, for Al₂(SO₄)₃ are:
Arsenic
16.5
5.5
2.7
Cadmium
4.7
1.6
0.8
Chromium
117.5
39.2
19.6
Lead
23.5
7.8
3.9
Mercury
2.4
0.8
0.4
Selenium
23.5
7.8
3.9
Silver
235
78
39
VERIFICATION
Quality assurance
The supplier is expected to possess a Quality System that facilitates the tracking of product from raw material to delivery. [Name of water authority] may audit this Quality System to verify the correctness of information relating to the purchased product. In addition, [name of water authority] may sample the purchased product at the point of destination to verify the quality of the supplied product.
Liquid alum samples
If [name of water authority] elects to sample the product at the point of destination, the sampling procedure outlined in the American Water Works Association Standard for Aluminium Sulfate – Liquid, Ground, or Lump (ANSI/AWWA B403-93) will apply.
Nonconforming product
If [name of water authority] discovers that the aluminium sulfate delivered does not meet the requirements of this specification, a notice of nonconformance will be issued to the supplier through the [name of water authority] ’s Quality System, within ten working days of the receipt of the goods.
A nonconformance will also be issued if deficiencies are detected during any audit of the supplier’s Quality System.
DELIVERY
Liquid
Marking, packaging and shipping of aluminium sulfate shall comply with AS 3780:1994 The Storage and handling of corrosive substances, and current federal, state, territory, and local regulations.
The carrying vessel shall be in a suitable condition for hauling liquid aluminium sulfate and shall not contain any substances that might affect the use or usefulness of the liquid aluminium sulfate in treating potable water or in treating wastewater.
Contamination
Bulk or semi-bulk containers shall be carefully inspected prior to loading of the chemical by the supplier to ensure no contaminating material exists.
The supplier must have a system in place to ensure that liquid aluminium sulfate is not contaminated by any other product. This may involve implementing a specific cleaning regime between loads or the dedication of tankers or containers to only one type of product.
Certificate of weight
[Name of water authority] may require that weight certificates accompany bulk shipments from a certified weigher or [name of water authority] may check the weights on delivery.
Affidavit of compliance
[Name of water authority] requires an affidavit from the manufacturer or supplier that the aluminium sulfate furnished according to [name of water authority]’s order complies with all applicable requirements of this specification. [name of water authority] also requires that the supplier provide a certified analysis of the aluminium sulfate. [name of water authority] may also elect to use in-house analytical equipment to analyse the product to ensure compliance with this specification.
Documentation
A copy of the order, the delivery docket, and the affidavit of compliance and/or the record of certified analysis will accompany the delivery of aluminium sulfate. This documentation shall be left in an appropriate location at the delivery point.
Further, a copy of the delivery docket is to accompany the invoice (with references to the delivery docket number), and forwarded to [name of water authority]’s Accounts Department to facilitate timely payment of accounts.
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