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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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For the interpretation of the stp simulation tests the hydrolysis behaviour of EUF should be considered .

The results of the stp simulation test (Schülke & Mayr 2010) indicate that EUF will be removed in STPs by more than 62% based on DOC or more than 43% based on total formaldehyde. Further decrease of formaldehyde (and EUF) is expected within the clarification period, in the mixing zone of the effluent and in the environment. Finally, no persistent parts of EUF are expected. Elimination is predominantly due to hydrolysis following biodegradation, rather than volatilization or adsorption onto sludge. From the results of the algae growth inhibition test using the effluent of the present stp simulation test (Schülke & Mayr 2010), it can be concluded that EUF is considerably detoxified in treatment plants. The algae test indicates clearly that only free formaldehyde is toxic to algae, while toxicity of chemically bound formaldehyde is much lower.

As shown in the stp simulation test with urea derivatives (Garrido 2000) free formaldehyde is nearly quantitatively removed, while chemically bound formaldehyde is degradable to a lower rate.

In conclusion, EUF hydrolyses in aqueous media and thus biodegradability is affected by the biodegradability of the hydrolysis products. OECD criteria on ready biodegradability are not applicable on the studies using EUF as test substance. Ultimate biodegradation is expected for EUF.

In a test on biodegradation in seawater according to OECD 306 (Closed-Bottle-Method) BOD/COD ratios of 54 and 60% were obtained after 28 days at test substance concentrations of 4.5 and 5.5 mg/L. The test demonstrates that EUF has a potential for ultimate biodegradation in seawater.

Algal testing of the effluent revealed that the toxicity is low compared to the substance before treatment (Schülke & Mayr, 2010). Taking this into account, for exposure and risk assessment the biodegradability of 99% for formaldehyde is used, while the PNEC is related to EUF.