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Biodegradation in water: screening tests

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Description of key information

The substance is readily biodegradable (according to OECD criteria)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradability of formaldehyde was investigated in 3 tests on ready biodegradability according to the OECD guidelines 301 A (Fraunhofer IME, 2011) 301 C (MITI, 1989) and 301 D (Gericke & Gode, 1990).

In the DOC Die-Away Test (OECD 301 A), conducted in compliance with the principles of Good Laboratory Practice (GLP) and therefore selected as key-study, the degradation of Formaldehyde (30 - 55 % W/W aqueous solution) was found to be 99 % after 28 days. The degradation within the 10-day-window, which started at day 2, was 102 %. No inhibitory effects of the test item were observed (more than 35 % degradation occurred within 14 days) in the toxicity control.

In the MITI-I-Test (OECD 301 C) degradation after 14 days was found to be 91% of BOD/ThOD and 97% of TOC. Although the test substance concentration indicates that toxic effects can not be excluded (c.f. Section 6.1.7), the degradation was nearly complete. In a Closed-Bottle-Test (OECD 301 D), the substance degraded to 90% of ThOD after 28 days. No data are reported referring to the 14-days window criteria.

Overall, due to the results of the available tests according to OECD 301 A, C and D formaldehyde can be identified as readily biodegradable under enviromental conditions. This is in agreement with the OECD evaluation (OECD, 2004).

Mechanism of biodegradation: The mechanism of formaldehyde degradation by Pseudomonas putida is initiated by a dismutation reaction, yielding formic acid and methanol as products. Degradation of the products began after exhaustion of formaldehyde in the medium.

The anaerobic degradation of formaldehyde was studied in a non-guideline batch test (Eiroa et al., 2006). Sludge from the anoxic chamber of the full-scale wastewater treatment plant of a resin-producing factory was used as inoculum. An initial formaldehyde concentration of 1360 mg/L was applied. The formaldehyde concentration decreased rapidly in the test medium, after 4 days the test substance was completely biodegraded. Simultaneously to formaldehyde removal, methanol and formic acid were formed as intermediate products. Degradation of both metabolites began after the exhaustion of formaldehyde in the medium. From the results of this test it can be concluded that formaldehyde is rapidly removed in anaerobic digester sludge.