Diisopropyl ether

Biodegradation in water: screening tests

Description of key information

The substance exhibited little or no degradation when tested for ready biodegradability according to OECD 301 D, but did not exert an inhibitory effect in the toxicity control.  This result is consistent with an earlier BOD/COD study which also found little degradation.  

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Ready biodegradability was tested according to the Closed Bottle test (OECD 301 D, EC C.4-E) and in compliance with GLP (Shell Biosciences Laboratory, 1983, for Royal Dutch Shell). Nominal initial test substance concentration was 3.3 mg/L. The test was performed with inoculum collected from the Sittingbourne sewage works. The test substance showed no degradation by the end of the test. The viability of the inoculum and validity of the test were supported by the results of the reference substance, sodium benzoate, which degraded 65% to 73% by the end of the test, and achieved greater than 60% biodegradation by day 14. A toxicity control containing both test and reference substances showed that any inhibition of microbial activity caused by the presence of the test substance was negligible under the test conditions. The substance was not readily biodegradable under the conditions of the test.

A supporting study by Bridié et al. (1979) reports the BOD5 and COD of the substance to be 0.19 g O2/g and 1.75 g O2/g, respectively.  The BOD test was conducted in accordance with the standard dilution method (APHA "Standard Methods" No. 219 (1971)) at 20 ±1 ºC for a period of 5 days. The only deviation from the APHA standard was the addition of 0.5 mg/l allylthiourea in each test to prevent nitrification. 500 ml test solutions were seeded with a filtered 10 ml volume of the non-adapted effluent from a biological sanitary waste treatment plant. Duplicate tests were run on a mixture of glucose and glutamic acid, as recommended in the APHA method, as a means of checking the activity of the inoculum. The COD test was conducted in accordance with the standard potassium dichromate method described in ASTM D 1252 -97 (reapproved 1974). The BOD5/COD ratio from these results is 0.11. As indicated in the REACH Endpoint Specific Guidance section R.7.9.5.1; where no other measured degradability data are available, BOD5 data can be used for classification purposes, but where the chemical structure is known, a calculated theoretical oxygen demand (ThOD) value should be used instead of the COD. According to Annex IV of OECD 301, the ThOD of this substance can be calculated to be 2.82 g O2/g, which gives a BOD5/ThOD ratio of 0.07. The value is < 0.5, at which level or above a substance can be considered to be readily degradable on the basis of a BOD5/ThOD ratio. The substance can therefore not be considered to be readily biodegradable under the conditions of this short study.