OECD SIDS 3. ENVIRONMENTAL FATE AND PATHWAYS
ID: 79-50-5 DATE: 18.01.2006
Theoretical CO2 production The Theoretical CO2 production (ThCO2) of dl-Lactone was calculated to be 2.03 mg CO2/mg. The concentration of dl-Lactone was 43.3 mg in 2 litres test medium. Hence, the theoretical CO2 production following complete degradation was 87.9 mg per 2 litres for the duplicate bottles A
and B, the abiotic control and The positive control contained 1.07 mg CO2/mg) resulting in a following complete degradation
the adsorption control. 81.0 mg sodium acetate (ThCO2= theoretical CO2 production of 86.7 mg per 2 litres. The
toxicity control contained 81.0 mg sodium acetate and 43.3 mg dl-Lactone in 2 litres of test medium. Hence, the theoretical CO2 production following complete degradation of dl-Lactone plus sodium acetate was 174.6 mg per 2 litres.
Biodegradation (based on CO2 determinations) The relative degradation values calculated from the measurements performed during the test period revealed 82 and 76% degradation of dl-Lactone, for the duplicate bottles tested. Furthermore, more than 60% degradation of dl-Lactone was reached within a 10-day window. In the toxicity control more than 25% degradation occurred within 14 days (56%, based on ThCO2). Thus, dl-Lactone was not inhibitory to microbial activity. The relative degradation values calculated from the measurements performed during the test period revealed no significant degradation of dl-Lactone in the abiotic control and the adsorption control.
DOC determinations No significant DOC removal was observed in the abiotic control and the adsorption control (both containing sterilizing agent). The degradation values calculated from the DOC measurements in the abiotic control and in the adsorption control, revealed no degradation of dl-Lactone (both containing sterilizing agent). In the additional adsorption control (dl-Lactone 100 mg/l, inoculum 1000 mg/l ss, no sterilising agent), 18% DOC removal was observed after 3 hours. This was the result of adsorption of dl- Lactone by the activated sludge. Since the DOC oncentration of day 1 was approximately the same as after 3 hours, no more adsorption of dl-Lactone by the activated sludge was observed. The degradation values calculated from the DOC measurements in the additional adsorption control (dl-Lactone 100 mg/l, inoculum 1000 mg/l ss, no sterilising agent) revealed more than 60% biodegradation (79%) within 14 days. This was in agreement with the biodegradation pattern obtained after CO2 determinations. Monitoring of temperature and pH The temperature recorded in a vessel with water in the same room varied between 21.1 and 22.9°C. The pH values in all vessels at time 0 and 29 days were all within the range of 7.5 to 7.8. dl-Lactone from DSM (until 2003 Roche) Dalry, sample no. 06085776, purity 99.6%, dated 24-Sep-2004. dl-Lactone was readily biodegradable under the conditions of the modified Sturm test presently performed. Furthermore, no significant elimination of dl-Lactone (22 mg/l), by abiotic degradation or adsorption by the activated sludge (30 mg/l ss), was observed.