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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Acetonitrile has been determined to be readily biodegadable in guideline studies (OECD 310; 301C) conducted under GLP conditions (Brixham, 2010; CITI of Japan, 1998), and by other supporting information.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In a guideline (OECD 310) and GLP study by Brixham Environmental Laboratories (2010) acetonitrile was determined to be readily biodegradable by non-acclimated activated sludge (> 60% degradation within 10 -days; 70% degradation after 21 days). The CITI of Japan (1998) reported a biodegration study of acetonitrile according to OECD guideline 301C (modified MITI test I) and under GLP conditions. Biodegradation results at a concentration of 100 mg/L after 28 days were 65%, 84% and 88% as measured by BOD, TOC, and GC, respectively. The BOD-curve was still on the upward trend after 28 days, therefore, additional testing was performed at a lower concentration of test substance (30 mg/L), and the degradation of the test substance measured by TOC and GC reached 100% after 14 days. Based on these results, acetonitrile is considered to be readily biodegradable.

Evidence for the biodegradation of acetonitrile by non-adapted bacterial populations has been reported by a number of other investigators. In a review, Sasaki (1978) characterized acetonitrile as “well- biodegradable”, which based on classification is understood as more than 30% of degradation (BOD/ThOD) in 14 days. In early work, Plack and Ruchhoft (1947) indicated 17% removal of acetonitrile in 1 day (based on oxygen demands) in a bench-scale fill and draw study with non-acclimated (< 1 day) activated sludge. US EPA BIOWIN software (v4.10) predicts that acetonitrile is ready biodegradable.

There is evidence of the rapid degradation of acetronitrile by adapted microbial populations. Ludzack and Ettinger (1960) reported previous works from Ludzack et al. indicating 100% removal (60% theoretical oxidation) after 4 days in acclimated river water, and more than 98% removal (more than 70% theoretical oxidation) in acclimated activated sludge in 28 days. In addition, Babeu and Vaishnav (1987) reported 57.5% of degradation (BOD/ThOD) in 5 days using mixed microbial cultures acclimated to several chemicals including acetonitrile.

The anaerobic degradation information available for acetonitrile suggest no digestion of acetonitrile in a 1-month study with digestion bottles (Ludzack, 1961) and an estimated half-life of 4-16 weeks under anaerobic conditions (Howard, 1991).

Biodegradation test results for acetonitrile

Type

Source of microorganisms

Method

Result

Detection

Ref


Aerobic

activated sludge

<1 day acclimation

Bench-scale fill and draw study

17%, 1day

O2 demand

Plack, 1947

Aerobic

river water, acclimated (19 days) population

Other

100%, 4day

O2 demand

Ludzack, 1960

Aerobic

Other

Other

98%, 28day

O2 demand

Ludzack. 1960

Aerobic

Acclimated mixed microbial cultures

Othera

>58%, 5day

BOD/ThOD

--

Babeu, 1987

Aerobic

Active sludge

Japanese methodb

30%, 14day

BOD/ThOD

--

Saski, 1978

 Aerobic  Activated sludgenon-adapted  OECD 301C  65%, 28dayBOD84%, 28dayTOC88%, 28dayGC --  CITI of Japan, 1998 
 Aerobic  Activated sludgenon-adapted  OECD 310  70%, 21dayCO2 evolution  --  Daniel, 2010

 

aAmerican Public Health Association 1980

bDirective 84/449/EEC.C7