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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable (according to OECD criteria).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The available experimental data on the biodegradation potential of morpholine (CAS 110-91-8) show that the substance is readily biodegradable in 28 d but has a relatively long lag phase:

 

Biodegradation of morpholine was determined to be 93 % after 28 days in a guideline study following protocol OECD 301 E (modified OECD screening test; 10 -d window kept; inoculum: effluent from municipal wwtp; BASF AG 1990, Report No. 1901337). This result was selected as key data.

 

The result of the key study is supported by several studies performed with morpholine:

- In an OECD 301 E test with industrial activated sludge, a degradation of 95% (DOC) was found after 27 d (BASF AG, 1989).

- In two inherent biodegradability tests, performed according to OECD 302 B, performed with industrial and municipal sludge, degradation rates of 97% after 21 d (industrial) and 92% after 28 d (domestic) were found (BASF AG, 1990).

- In two further inherent biodegradability tests according to OECD 302 B, biodegradation was found to be 96 - 98% after 16 days using adapted activated sludge as inoculum, and <= 15% after 20 days using non-adapted activated sludge, respectively (BASF AG, 1976).

- Knapp & Whytell (1990) performed several DOC-Die-Away tests according to Alexander & Lustigmann (1966), using municipal and/or industrial activated sludge as inoculum. Degradation of Morpholine was: 100% after 10 days (municipal + industrial activated sludge; lag phase: 6 d); 100% after 18 days (solely municipal or industrial activated sludge; lag phases: 12 d for municipal sludge, 14 d for industrial sludge), and 100% after 30 days (activated sludge from wwtp treating solely sewage from breweries; lag phase: 24 d).

Calamari et al. (1980) performed a respirometric test (Sapromat) with a mixture of non-adapted bacteria from river mud, municipal activated sludge and pre-adapted bacteria as inoculum. After 14 days no biodegradation was observed under test conditions.

In a further study according to OECD 301 C (CITI, 1992), with a mixture of sludge, soil and natural water used as inoculum, no biodegradation (O2 consumption) was detected after 14 d.

However, a test period of 14 d may not generally cover the occurring lag phase.

 

In addition, Eide-Haugmo et al. (2012/2009) performed two guideline studies according to OECD 306 using natural seawater as inoculum. In the study from 2009 biodegradation was determined to be < 20% after 28 days (O2 -consumption). In the study from 2012 biodegradation was 22.4% after 28 days (O2 -consumption).

 

In conclusion, the substance is assessed to be readily biodegradable (according to OECD criteria).