3,5-dimethylpyridine

Biodegradation in water and sediment: simulation tests

Description of key information

Supporting studies indicate that the test substance, 3,5-lutidine, is expected to be biodegradable in water, groundwater and sediment under aerobic conditions in the environment, particularly in the presence of fixed carbon sources and pre-adapted inoculum or in the presence of an oxygen injection pump and treat system.

Additional information

In the supporting study by Ronen, et al. (1998), carbon mineralization of the test substance was 89.1% mineralization at the end of the 8-d bacterial incubation test.  The study concluded that subsurface bacteria isolated from alkylpyridine contaminated subsurface sediments were capable of degrading the test substance as well as other alkylpyridines. Therefore, bacterial inoculation of a polluted site was offered as a possible biotreatment method. Results showed that different bacterial isolate strains have a unique degradation capacity for alkylpyridines, therefore biotreatment of a polluted site should include a mixture of bacterial cultures.

In the supporting study by Hsu et al. (1993), the influent concentration of the test substance (9.15 mg/L 3,5 -lutidine) into the two-stage cyclic bioremediation reactor resulted in an effluent concentration of 0.197 mg/L (i.e., 98% removal). The overall removal efficiency of alkylpyridines, including the test substance, in the two-stage cyclic fixed film aerobic reactor was as high as 98% when operating at a loading of 4.32 g COD/L-day and a hydraulic retention time (HRT) of 3 hours with pre-adapted inoculum (mixed liquor from a university wastewater treatment plant and groundwater from the contaminated site).

In the supporting study by Bollag, et al. (1993), the mean biodegradation of 3,5-lutidine in a preliminary batch culture experiment of subsurface sediment incubated at 15°C under aerobic conditions was reported as 50% biodegradation at 30 days (i.e., a reduction from an initial concentration of 4.2 ug/mL to 2.1 ug/mL at day 30).  The results of an enrichment culture grown on a single compound at 28°C showed that the test substance was completely degraded after 10 days. The results of a chemostat study performed after 7 fresh medium transfers and with a maximal removal dilution rate of 0.067 day^-1, showed a removal efficiency of 68% for the test substance. Similar removal efficiencies were noted for the other alkylpyridines in the study, indicating that the chemostat culture developed was successful at removing alkylpyridines from the groundwater. After 4 weeks of supplying inoculated groundwater to the chemostat, the removal of 3,5 -lutidine was nearly 100% (i.e., 99.2% degradation). Whereas, the degradation of 3,5 -lutidine after 4 weeks of supplying non-inoculated groundwater to the chemostat was insignificant (i.e., 4% degradation). 

The various supporting studies, including Ronen et al. (1996) indicate that the test substance, 3,5-lutidine, is expected to be biodegradable in water, groundwater and sediment under aerobic conditions in the environment, particularly in the presence of fixed carbon sources and pre-adapted inoculum or in the presence of an oxygen injection pump and treat system.