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Environmental fate & pathways

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Betaine occurs in nature (plants) and is extracted from plant material (sugar beet). Based on the physico-chemical properties, it is not bioaccumulative and not expected to be persistent because the octanol-water partition coefficient is low (Log Kow is -3.1). The octanol-water coefficient also indicates that betaine has a low potential for adsorption. This substance is also very soluble in water (160g/100g), and readily biodegradable in water (mineralisation in 28 d is 88%). The BOD:COD -ratio (ratio 1) also indicates ready biodegradability. This ratio was calculated based on analysed BOD -values 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. method ISO DP 6060) is technically feasible for organic substances that can become oxidized fully to carbon dioxide and water. 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.

Betaine is also non volatile (vapour pressure 0.05 Pa at 25°C) therefore environmental emission considerations to the atmosphere can be disregarded.

Based on the additional information on degradation and migration studies presented by Salminen & Kalevi (2009), this substance was also rapidly biodegraded in sand soil columns. Betaine or its organic degradation compounds were not likely to enter groundwater. Ammonium and nitrite concentrations in 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.

Additional information from two full-scale anaerobic waste water treatment plants (WWTP) also indicated that this substance present in waste water influents appeared to be readily biodegradable during anaerobic treatment. The anaerobic degradation of betaine-containing waste waters were studied using field data from two full-scale treatment plants (Thalassoet al.1999). 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 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. The laboratory-scale biodegradation tests confirmed the results obtained from the field data. The substance was readily biodegradable using either acclimated or non-acclimated digester sludges. The biodegradation patterns of this study suggested that the degradation is a multistep process and nitrogen-containing intermediates are produced (e.g. N,N-dimethylglycine and trimethylamine) during the substance biodegradation process. Based on these laboratory tests, ammonia produced during complete anaerobic biodegradation could result in a maximum ammonia concentration of 35 mmoldm-3 to effluents when the concentration of this substance is between 2.3-4.55 gdm-3 in the influents.

The field data of the manufacturer's WWTP indicated that at average influent concentrations of 0.079 g/l betaine is not an inhibitory to activated sludge micro-organisms. Waste waters resulting from the manufacturing process of betaine are treated in a low-rate activated sludge treatment plant at the manufacturing site. In addition, nitrogen present in the substance can be efficiently removed during the treatment process. The removal efficiency of total nitrogen is 93 % and ammonium 95 %, respectively. After treatment, effluents can be discharged into the sea.

Based on the existing data on the physico-chemical properties, fate of the substance, and its degradation products in water, exposure to sediments or soil is unlikely. 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.