Download Evaluation of microbiological growth potential

Issue: Liquid products that contain a carbon source such as mineral oil will not pass the microbiological
growth potential test.
Question: Is the purpose of NSF/ANSI 60 to evaluate the health effect of the chemical or to evaluate
potential interactions of the chemical in drinking water, such as microbial growth.
Other products such as activated carbon filters are known to grow bacteria but do not have to pass a
microbial growth test.
Proposal:Change the criteria of the microbial test from pass / fail to a product literature requirement so
that the user can determine if the product is appropriate for use.
Use of Mineral Oil in well pumps
Background
Food grade petroleum hydrocarbon mineral oils have been historically used as drip well lubricants for
many years. A very rough estimate at usage volume would be around 200,000 gallons per year although
this number could be larger. At this time multiple companies’ products are failing the microbiological
testing portion of the NSF/ANSI 60 standard. These products are food grade and safe to consume,
therefore material safety even direct ingestion is not a problem. The failing test results are obtained
because these products provide a carbon source for bacteria to grow in drinking water and the current
test procedure does not allow bacterial growth.
While reviewing the current microbiological testing protocol there is concern that the G-22 predictor test
and confirmatory test used in the NSF/ANSI 60 standard are designed for solid materials and introduce
false positives when testing gel or liquid materials.
As the group considered if the current test protocol could be modified for liquid and gel materials there
was concern that all microbiological test protocols, which evaluate whether products can grow microbes
would cause a problem for this product category because they all supply a source of carbon for microbes
to grow. Before the task force spends considerable effort to determine if the microbiological test protocol
should be modified the group felt that the Joint Committee should review the intent (purpose and scope)
of NSF/ANSI 60 to determine if a microbiological test should be included in the standard and if it should
be a pass/fail requirement or a product literature requirement. Based on the current purpose and scope
of the NSF/ANSI 60 standard many people in the task force do not feel microbial growth was intended to
include as a testing parameter.
NSF/ANSI 60
1.1 Purpose
This Standard establishes minimum health effects requirements for the chemicals, the chemical
contaminants, and the impurities that are directly added to drinking water from drinking water treatment
chemicals. This Standard does not establish performance or taste and odor requirements for drinking
water treatment chemicals.
1.2 Scope
This Standard contains health effects requirements for drinking water treatment chemicals that are
directly added to water and are intended to be present in the finished water. This Standard also contains
health effects requirements for other chemical products that are directly added to water but are not
intended to be present in the finished water. Chemicals covered by this Standard include, but are not
limited to, coagulation and flocculation chemicals, softening, precipitation, sequestering, pH adjustment,
and corrosion/scale control chemicals, disinfection and oxidation chemicals, miscellaneous treatment
chemicals, and miscellaneous water supply chemicals. Contaminants produced as by-products through
reaction of the treatment chemical with a constituent of the treated water are not covered by this
Standard.
8 Miscellaneous water supply products
8.1 Coverage
This section covers products used in a variety of drinking water supply applications. These products are
not routinely used to produce a treatment effect in the water they may contact. The products can be fed
continuously, applied intermittently, or flushed from the water supply system prior to its return to use.
These products include, but are not limited to, antifoamers, separation process scale inhibitors and
cleaners, water well drilling aids, water well rehabilitation aids, well pump lubricating oils, backfill materials
for cathodic protection or electrical installations, and distribution system cleaning aids.
8.3.1.1 Well application products
All products used in well applications shall not support microbiological growth when evaluated in
accordance with annex C. Well cleaning aids used in conjunction with sodium hypochlorite, calcium
hypochlorite or chlorine are excluded from this requirement.
Evaluation of microbiological growth potential
C.1 Background
This annex contains the protocol for determining a product's potential to support microbiological growth.
The protocol presented in this section is a modification of American Society for Testing and Materials
(ASTM) Standard G22-76, Standard Practice for Determining Resistance of Plastics to Bacteria. The
protocol involves exposing a product to nutrient salts agar (lacking a carbon source for microbial growth
support) inoculated with a standard suspension of Pseudomonas aeruginosa. Following one week of
incubation, bacterial growth is visually assessed. This test is a qualitative assessment of microbiological
growth support propensity.
Issue: Liquid products that contain a carbon source such as mineral oil will not pass this microbiological
growth potential test.