This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.
This document is Part 12 of GB/T 5750 Standard examination methods for drinking water. The following parts of GB/T 5750 have been issued:
——Part 1: General principles;
——Part 2: Collection and preservation of water samples;
——Part 3: Water analysis quality control;
——Part 4: Organoleptic and physical indices;
——Part 5: Inorganic nonmetallic indices;
——Part 6: Metal and metalloid indices;
——Part 7: Aggregate organic indices;
——Part 8: Organic indices;
——Part 9: Pesticides indices;
——Part 10: Disinfection by-products indices;
——Part 11: Disinfectants indices;
——Part 12: Microbiological indices;
——Part 13: Radiological indices.
Standard examination methods for drinking water - Part 12: Microbiological indices
1 Scope
This document describes the methods for determination of standard plate-count bacteria, total coliforms, thermotolerant coliform bacteria, Escherichia coli, Giardia, Cryptosporidium, Enterococcus and Clostridium perfringens in drinking water and source water.
This document is applicable to the determination of microbiological indices in drinking water and source water.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 4789.28 National food safety standard - Food microbiological examination - Quality requirements for medium and reagents
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB 19489 Laboratories - General requirements for biosafety
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
standard plate-count bacteria
number of microbial colonies in 1 mL of water sample after incubation for a certain period of time under certain conditions
3.2
total coliforms
group of aerobic or facultative anaerobic, non-spore-forming, Gram-negative bacillus capable of fermenting lactose, producing acid and gas within 24 h of incubation at 37°C
3.3
thermotolerant coliform bacteria
group of aerobic or facultative anaerobic, non-spore-forming, Gram-negative bacillus capable of fermenting lactose, producing acid and gas within 24 h of incubation at 44.5°C
3.4
Escherichia coli
group of non-spore-forming, Gram-negative brevibacterium capable of fermenting various sugars, producing acid and gas, with flagella distributed over the entire surface and motile, which is usually found in the intestines and feces of humans and warm-blooded animals
3.5
Giardia
protozoan parasite found in water or other media, which can infect humans and cause diseases
Note: Giardia cysts are elliptical, with a length of 8–14 μm and a width of 7–10 μm. There are two nuclei in initial cysts, and four in mature cysts.
3.6
Cryptosporidium
protozoan parasite found in water or other media, which can infect humans and cause diseases
Note: Cryptosporidium oocysts are slightly elliptical and round, with a diameter of 4–8 μm. There are four nuclei in mature oocysts.
3.7
Enterococcus
type of facultative anaerobic non-spore and non-capsule-forming Gram-positive cocci in pairs or in chains, belonging to Group D Streptococci, typically present in the intestines and feces of humans and warm-blooded animals
3.8
Clostridium perfringens
type of anaerobic spore-forming Gram-positive bacilli capable of reducing sulfite, typically present in the intestines and feces of humans and warm-blooded animals
3.9
most probable number; MPN
number of target microorganisms present in a certain volume of samples, i.e., the most probable number of target microorganisms per unit volume, estimated based on the number of positive target microorganisms produced by incubation of a certain volume of samples with different degrees of dilution, using the principle of statistics and according to the Poisson distribution
4 Standard plate-count bacteria
4.1 Petri dish counting method
4.1.1 Principle
After culturing 1 mL of water sample on nutrient agar medium at 36±1°C under aerobic conditions for 48 h, the standard plate-count bacteria in 1 mL of water sample can be determined.
4.1.2 Nutrient agar medium
4.1.2.1 Composition
It can be prepared according to the following composition:
a) Peptone 10.0 g
b) Beef extract 3.0 g
c) Sodium chloride 5.0 g
d) Agar 10.0–20.0 g
e) Pure water 1,000 mL
4.1.2.2 Preparation method
Mix the above ingredients, heat to dissolve, adjust the pH to 7.4–7.6, dispense into glass containers, autoclave at 121°C for 20 min , and store the solutions at 0–4°C.
4.1.3 Instruments and apparatus
4.1.3.1 Autoclave sterilizer.
4.1.3.2 Incubator: 36±1°C.
4.1.3.3 Electric furnace.
4.1.3.4 Electronic balance.
Foreword I Introduction III 1 Scope 2 Normative references 3 Terms and definitions 4 Standard plate-count bacteria 5 Total coliforms 6 Thermotolerant coliform bacteria 7 Escherichia coli 8 Giardia 9 Cryptosporidium 10 Enterococcus 11 Clostridium perfringens
Foreword
This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.
This document is Part 12 of GB/T 5750 Standard examination methods for drinking water. The following parts of GB/T 5750 have been issued:
——Part 1: General principles;
——Part 2: Collection and preservation of water samples;
——Part 3: Water analysis quality control;
——Part 4: Organoleptic and physical indices;
——Part 5: Inorganic nonmetallic indices;
——Part 6: Metal and metalloid indices;
——Part 7: Aggregate organic indices;
——Part 8: Organic indices;
——Part 9: Pesticides indices;
——Part 10: Disinfection by-products indices;
——Part 11: Disinfectants indices;
——Part 12: Microbiological indices;
——Part 13: Radiological indices.
Standard examination methods for drinking water - Part 12: Microbiological indices
1 Scope
This document describes the methods for determination of standard plate-count bacteria, total coliforms, thermotolerant coliform bacteria, Escherichia coli, Giardia, Cryptosporidium, Enterococcus and Clostridium perfringens in drinking water and source water.
This document is applicable to the determination of microbiological indices in drinking water and source water.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB 4789.28 National food safety standard - Food microbiological examination - Quality requirements for medium and reagents
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB 19489 Laboratories - General requirements for biosafety
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
standard plate-count bacteria
number of microbial colonies in 1 mL of water sample after incubation for a certain period of time under certain conditions
3.2
total coliforms
group of aerobic or facultative anaerobic, non-spore-forming, Gram-negative bacillus capable of fermenting lactose, producing acid and gas within 24 h of incubation at 37°C
3.3
thermotolerant coliform bacteria
group of aerobic or facultative anaerobic, non-spore-forming, Gram-negative bacillus capable of fermenting lactose, producing acid and gas within 24 h of incubation at 44.5°C
3.4
Escherichia coli
group of non-spore-forming, Gram-negative brevibacterium capable of fermenting various sugars, producing acid and gas, with flagella distributed over the entire surface and motile, which is usually found in the intestines and feces of humans and warm-blooded animals
3.5
Giardia
protozoan parasite found in water or other media, which can infect humans and cause diseases
Note: Giardia cysts are elliptical, with a length of 8–14 μm and a width of 7–10 μm. There are two nuclei in initial cysts, and four in mature cysts.
3.6
Cryptosporidium
protozoan parasite found in water or other media, which can infect humans and cause diseases
Note: Cryptosporidium oocysts are slightly elliptical and round, with a diameter of 4–8 μm. There are four nuclei in mature oocysts.
3.7
Enterococcus
type of facultative anaerobic non-spore and non-capsule-forming Gram-positive cocci in pairs or in chains, belonging to Group D Streptococci, typically present in the intestines and feces of humans and warm-blooded animals
3.8
Clostridium perfringens
type of anaerobic spore-forming Gram-positive bacilli capable of reducing sulfite, typically present in the intestines and feces of humans and warm-blooded animals
3.9
most probable number; MPN
number of target microorganisms present in a certain volume of samples, i.e., the most probable number of target microorganisms per unit volume, estimated based on the number of positive target microorganisms produced by incubation of a certain volume of samples with different degrees of dilution, using the principle of statistics and according to the Poisson distribution
4 Standard plate-count bacteria
4.1 Petri dish counting method
4.1.1 Principle
After culturing 1 mL of water sample on nutrient agar medium at 36±1°C under aerobic conditions for 48 h, the standard plate-count bacteria in 1 mL of water sample can be determined.
4.1.2 Nutrient agar medium
4.1.2.1 Composition
It can be prepared according to the following composition:
a) Peptone 10.0 g
b) Beef extract 3.0 g
c) Sodium chloride 5.0 g
d) Agar 10.0–20.0 g
e) Pure water 1,000 mL
4.1.2.2 Preparation method
Mix the above ingredients, heat to dissolve, adjust the pH to 7.4–7.6, dispense into glass containers, autoclave at 121°C for 20 min , and store the solutions at 0–4°C.
4.1.3 Instruments and apparatus
4.1.3.1 Autoclave sterilizer.
4.1.3.2 Incubator: 36±1°C.
4.1.3.3 Electric furnace.
4.1.3.4 Electronic balance.
Contents of GB/T 5750.12-2023
Foreword I
Introduction III
1 Scope
2 Normative references
3 Terms and definitions
4 Standard plate-count bacteria
5 Total coliforms
6 Thermotolerant coliform bacteria
7 Escherichia coli
8 Giardia
9 Cryptosporidium
10 Enterococcus
11 Clostridium perfringens
