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Environmental fate & pathways

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Betaine is readily biodegradable in water. Therefore, biodegradation studies in sediments and soil were considered to be unnecessary. Based on the physico-chemical test results, this substance is very soluble in water (160g/100g). According to the OECD guideline 301 B study results, betaine is readily biodegradable in water (mineralisation in 28 d is 88%). Also the BOD/COD -ratio (ratio 1) indicates ready biodegradability of the substance. The ratio was calculated based on an analysed BOD -value and theoretical COD calculations.

Theoretical COD-value was used instead of measured COD-value because the COD method is not technically feasible for betaine. Chemical oxygen demand determination (i.e. methods ISO DP 6060, SFS5504) is technically feasible for organic substances that can become oxidized fully to carbon dioxide and water. In this oxidation process, nitrogen present in substances remains in the form of ammonium. This COD determination is used to describe the oxygen demand of waste water effluents at WWTP. Therefore, it is also more suitable for waste water effluents than for certain organic substances. Betaine contains trimethylamine and organic acid (COOH) functional groups that cannot become oxidized in this COD determination. Therefore, theoretical COD value was considered to be more appropriate than measured COD value to evaluate the biodegradation of this substance based on BOD:COD-ratio.

However, the supportive information on substance degradation and migration studies in soil columns was evaluated for the chemical safety assessment. According to the supportive study presented by Salminen & Kalevi (2009), betaine rapidly biodegraded in the sand soil columns. Betaine or its organic degradation compounds were not likely to enter the groundwater. Ammonium and nitrite concentrations in the soil effluent indicated that ammonium was oxidised to nitrate. This resulted in very low concentrations of ammonium and in elevated concentrations of nitrate in the soil leachates. The results proved that this substance is degradable in soil, resulting in mainly ammonium and nitrate as decomposition products.

Exposure to sediments was also considered to be unlikely based on the information from the waste water treatment plant (WWTP) treating betaine containing influents. The results of the supportive study presented by Thalassoet al. (1999) from two full-scale anaerobic waste water treatment plants also indicated that this substance present in waste water influents appeared to be readily biodegradable in the anaerobic treatment. Waste water samples were collected from two industrial production processes using molasses as a substrate in citric acid fermentation and in yeast production. According to Thalassoet al. (1999) betaine was completely removed from waste waters during the anaerobic treatment. The substance concentration in the influents of 2.3-4.55 gdm-3 resulted in effluent concentrations of 0.02-0.09 gdm-3, respectively.

In addition, the field data of the manufacturer's WWTP indicated that betaine at average influent concentrations of 0.079 g/L is not inhibitory to activated sludge micro-organisms. Nitrogen present in the substance yielding mainly ammonium and nitrate as decomposition products can be efficiently removed during the treatment process. The removal efficiency of total nitrogen is 93 % and 95% for ammonium, respectively. After treatment, effluents can be discharged into the sea.

Based on the existing data on the substance ready biodegradability in water, the chemical safety assessment does not indicate the need to investigate further the biodegradation of the substance in sediment or the soil compartment.

 

References:

Thalasso F, Van der Burgt J, O’Flaherty V, and Colleran E (1999). Large-scale anaerobic degradation of betaine. J. Chem. Tech. Biotech., 74(12)1176-1182.