Biological Effectiveness Of 14 Mev Neutrons PDF Download

Sodium sulphonated naphthalene formaldehyde condensate (disal) is an organic superplasticizing agent used in small quantities (approximately 1 wt.%) in cement-based sealing materials (i.e., concrete and grout) in the canadian nuclear fuel waste disposal concept. the biodegradation of disal by bacteria naturally occurring in granitic groundwaters was studied. the experiments involved incubation of groundwater bacteria with disal alone, with nitrate, with phosphate and with a combination of phosphate and nitrate. results for aerobic incubation at 10 degrees celsium and 30 degrees celsius showed that the concentrations of disal remained unchanged and bacteria numbers did not differ significantly from controls without disal over the course of the experiment. anaerobic incubation of groundwater bacteria with disal and nitrate at 10 degrees celsius resulted in an order of magnitude more cells in the groundwater after 47 days than in a control containing nitrate and groundwater. this effect was not seen in the equivalent aerobic test. these results suggest that there is a potential for disal to support native groundwater microbes under certain conditions, although under the conditions of this experiment, (i.e., disal concentrations of 200 mg/l) significant amounts of disal were not degraded. identificaion of 16 randomly chosen strains of bacteria that could grow on a medium for hydrocarbon-degrading bacteria containing disal as the sole source of carbon showed that most belonged to the genus pseudomonas. the results obtained from this preliminary study are not conclusive and biodegradation of disal needs to be studied further, at lower disal concentrations, to give conclusive quantitative results.