GB/T 15818  Surfactant biodegradability test method

GB/T 15818 Biodegradation of surfactants is a process in which microorganisms are used to decompose surfactants and convert them into carbon dioxide and water.

This process can be divided into three stages: primary biodegradation that changes material properties; final biodegradation that transforms into inorganic substances such as carbon dioxide and water.

The World Organization for Economic Cooperation and Development stipulates that only surfactants with primary biodegradation >80% and final biodegradation >70% are allowed to be used.

Judging from the chemical structure of surfactants, aliphatic groups are easier to degrade than aryl groups, and straight chains are easier to degrade than branched chains; among polar groups, carboxyl groups, sulfonic acid groups, sulfate groups, and ethoxy groups are easier to degrade.

Therefore, linear alkyl compounds, alkyl alcohol polyoxyethylene compounds, alkyl polyglycosides and biosurfactants are easily degraded.

Surfactant biodegradation mechanisms vary. For linear sodium alkyl benzene sulfonate, the terminal methyl group and alkyl chain of the alkane are first gradually and continuously oxidized, then the sulfo group is removed, the benzene ring is broken, and finally it is degraded into products such as carbon dioxide, water, and sulfate radicals.

Alkyl alcohol polyoxyethylene compounds usually undergo the action of esterase, deoxygenase, etherase, etc.

GB/T 15818 testing reference standard documents

GB/T 5173 Determination of anionic active content of surfactants and detergents by direct two-phase titration method

GB/T 5174 Determination of cationic active content of surfactants and detergents by direct two-phase titration method

GB/T 6682 Analytical laboratory water specifications and test methods ,

GB/T 13173 Test methods for surfactant detergents

GB/T 19464 Alkyl glycosides

QB/T 2344 Amphoteric surfactant fatty alkyl dimethyl betaine

QB/T 2739 Common test methods for detergents Preparation of test solutions for titration analysis ( volume analysis )

1. Biodegradation requires the addition of high-concentration microbial solutions. The microorganisms must first be cultured. After reaching a certain concentration, they are recovered and concentrated. This 7- day period is indispensable. Then the microorganisms are added to the solution containing surfactant. According to the standard , it is necessary to calculate how much of the sample has been degraded by microorganisms 28 days after adding microorganisms. 

GB/T 15818 detection reagents

Unless otherwise stated , only reagents confirmed to be of analytical grade and grade three water specified in GB/T 6682 are used in the analysis .

5.1 Ammonium chloride.

5.2 Dipotassium hydrogen phosphate

5.3 Potassium dihydrogen phosphate.

5.4 Disodium hydrogen phosphate.

5.5 magnesium sulfate.

5.6 Potassium chloride.

5.7 Calcium chloride.

5.8 Ferrous sulfate

5.9 Ferric chloride.

5.10 Yeast extract ( biochemical reagent ) .

5.11 The content of linear sodium dodecyl benzene sulfonate is more than 95% , and the biodegradability is greater than 99%

5.12 Linear chain dodecanol polyoxyethylene ether CEO): content is more than 98% , and biodegradability is greater than 99% .

5.13 Microbial source : Activated sludge is taken from a sewage treatment plant that treats civil wastewater . The mass concentration of activated sludge suspended matter should be adjusted to 10 g/L~20 g/L, and it should be used within 5 hours after sampling .

5.14 Formaldehyde .

5.15 Hydrochloric acid.

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GB/T 15818 testing sample delivery specification :  500g

GB/T 15818 inspection cycle: Regular 50 working days ( 50 working days)