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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

- Modified OECD Screening Test according to OECD Guideline 301 E: 98% of DOC removal after 28 days
- Degradation of peracetic acid during an activated sludge, respiration inhibition test according to OECD 209:
Half-life <3 min. at 0.3; 1.0; 3.0; 10; 30 mg/L;
Half-life ca. 30 min. at 100 mg PAA/L

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

From the results of the Modified OECD Screening Test (Richterich and Gode, 1986), it is concluded that peracetic acid is ready biodegradable when applied at concentrations which are not inhibitory to the microorganisms in the sludge or after adaptation of microorganisms to inhibitory concentrations has taken place, e. g. after stepwise addition of peracetic acid to the sludge. The test, conducted according to OECD guideline 301 E, revealed strong inhibition of the degrading organisms. Poor degradation of a well biodegradable reference substance was observed in the presence of the test substance. However, a modification of the test procedure, i. e. stepwise addition of the test substance until the required test concentration had been reached within 2 weeks, showed unequivocally that peracetic acid is readily biodegradable. This is confirmed by the results from an activated sludge respiration inhibition test (De Groot and Van Dijk, 2001), which provides relevant information on the primary degradation of peracetic acid followed analytically by HPLC. It was shown that peracetic acid disappeared rapidly with a DT50 of < 3 minutes when applied at concentrations <30 mg/L. At higher concentration of 100 mg/L, the degradation in activated sludge respiration inhibition test was retarded resulting in a DT50 of 15 minutes. The degradation product acetic acid is readily biodegradable.

The results from two other studies (Gerike and Gode, 1990; L'Haridon, 2003) were disregarded, because the test systems used (i. e. closed bottle test) are not considered suitable for a reliable biodegradation assessment of peracetic acid, which itself evolves oxygen upon decomposition. Moreover production of oxygen is also due to hydrogen peroxide decomposition.

However, the available data consequently show, that peracetic acid can be considered as readily biodegradable.