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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Data taken from phenol dossier for read-across (phenol content in the substance up to 50% (w/w).
Several biodegradation tests were performed following or according to standard methods. Aerobic degradation in waste water, freshwater, seawater and anaerobic degradation was investigated.
Following concentrations were applied:
waste water, activated sludge - MITI I test: 100 mg/L
fresh water - BOD test: 3 - 10 mg/L
salt water - BOD test: 3 - 10 mg/L
anaerobic degradation - 1 - 5 mM
In all aerobic tests degradation rates > 70 % were achieved within a short period (< 10 d). In the anaerobic test 100 % biodegradation was achieved up to a concentration of 4 mM.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Data on biodegradation of phenol in water is presented in the EU-RAR (2006) in Section 3.1.2.1.1 (page 11ff).

It is stated that only two standardised tests for ready biodegradability are available. In these MITI-I-tests, levels of degradation amounting to between 60 and 70 % (after 4 days) and to 85 % (after 14 days) were determined (Urano & Kato, 1986; MITI, 1992). With these results phenol can be classified as readily biodegradable. The results from the other available tests also point toward ready biodegradability. On account of the ubiquitous occurrence of phenol, adaptation is to be assumed in the case of all of the inocula. Since this also applies to WWTPs, a degradation rate constant of k = 1 h-1 can be used for them.

In various degradation studies employing adapted microbial inocula (e.g. activated sludge from industrial wwtp) removal rates in the range of 98.5-100 % were demonstrated (BUA, 1997).

Due to the high degradation rates within a period of < 10 days phenol is ready biodegradable in waste water, freshwater, sea water, and at anaerobic conditions with inoculum created from activated sludge.