Registration Dossier

Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

In accordance with Column 2 of Annex IX Sections 9.2.1.2 and 9.2.1.4 of the REACH regulation, a water and sediment simulation study does not need to be conducted as the substance is readily biodegradable. However, two studies are available in which the behaviour of the structurally realted substance TMAC (see read-across justification in IUCLID section 13) was simulated. From the key study by Ripley and Hossain (1997), it can be concluded that an acclimated bench-scale activated sludge system that treats waste water containing TMACl at a concentration upto 100 mg/L can remove >98% of TMACl. 

Key value for chemical safety assessment

Additional information

Biodegradability study results of TMAC are also valid for TMAOH 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.

The biodegradation of TMACl and its effect on the operation of a municipal wastewater treatment plant were examined by Ripley and Hossain (1997) in a bench-scale activated sludge system. Based on the results, it can be concluded that an acclimated bench-scale activated sludge system that treats waste water containing TMACl at a concentration upto 100 mg/L can remove >98% of TMACl. Acclimation of the biomass to TMACl was critical. While some of the TMACl removal may have been due to physical adsorption, the primary mechanism was biological oxidation. This was demonstrated by increased oxygen uptake rates, increased production of nitrate+nitrite and decreased mixed liquor pH resulting from nitrification.

The degradation of components in TFT-LCD wastewater, which also contains a high concentration of TMAOH (which is structurally related to TMAC) was studied by Lei et al. (2008) in experiments with an anoxic/oxic sequence batch reactor with adapted sludge. It was concluded that an Anoxic/Oxic Sequencing Batch Reactor with adapted sludge can remove 99% of TMAOH at an influent concentration upto 190 mg/L.

Biodegradability study results of TMAC are also valid for TMAOH because both substances dissociate in water to tetramethylammonium and chloride or hydroxide ions and it is the tetramethylammonium cation that biodegrades. Further read-across justification is attached to IUCLID section 13.

The simulation study of Ripley and Hossain (1997) can be regarded as representative for a municipal waste water treatment plant treating a waste water stream with TMACl. The result (98% removal) was used in the risk assessment of TMAOH.

The study of Lei et al. are related to a very specific waste water stream (TFT-LCD waste water) and a specific reactor and can therefore only be regarded as indicative.