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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Two reliable ready biodegradability tests are available for TMAOH, which is structurally related to TMAC. In both tests, TMAOH was ready biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Two reliable ready biodegradability tests are available for TMAOH, which is structurally related to TMAC.

A ready biodegradability test was carried out with 25% TMAOH according to to OECD301 B and GLP (Noack, 2001).

The concentration of the test substance at the beginning of the test was 90 mg/L (corresponding with 22.5 mg TMAOH/L).

Based on the results, it can be concluded that TMAOH is readily biodegradable.

A ready biodegradability test was carried out with 27.5% TMAOH according to to OECD301 B and GLP (CERI, 2002).

The concentration of the test substance at the beginning of the test was 100 mg/L (corresponding with 27.5 mg TMAOH/L).

Based on the data in the SIDS, the test substance shows more than 90% degradation within 14 days, measured according to different methods. The substance TMAOH is therefore considered to be ready biodegradable

Based on the results for TMAOH, it can be concluded that TMAC is ready biodegradable.

Under anaerobic conditions a rapid biodegradation is possible as well:

TMAOH biodegradation was studied in a batch test with sludge from an Upflow Anaerobic Sludge Blanket (UASB) treating TFT-LCD waste water at concentrations varying from 500 - 2000 mg/L. The TMAOH concentrations were determined by ion chromatography at regular intervals. For all concentrations 100% biodegradation was observed within 10 hours. The total volume of accumulated methane gas production was proportional to the amount of TMAOH added, indicating that the anaerobic sludge was able to completely convert TMAH to methane gas and ammonium. Based on these results, it can be concluded that TMAOH is rapidly biodegradable by adapted sludge under anaerobic methanogenic conditions.

Although both ready biodegradability studies were carried out in accordance with OECD guidelines and GLP and have similar results, the study from Noack (2001) was selected as a key study because the original study report was available and thus more details could be evaluated, whereas the study from CERI (2002) had to be summarised and evaluated based on the IUCLID summary from the OECD SIDS of TMAOH (CERI, 2006). Furthermore, in the study from Noack (2001) a toxicity control was included, whereas in the study from CERI (2002), this was not the case.

Biodegradability study results of TMAOH are also valid for TMAC because both substances dissociate in water to tetramethylammonium and hydroxide or chloride ions and it is the tetramethylammonium cation that biodegrades. Further justification is given in the attached Read Across document.