C/N ratio and carbon source effect on water denitrification by pure culture of Hyphomicrobium denitrifican

Pure culture of Hyphomicrobium denitrifican DSM 1869 was investigated for biological denitrification. The bacterium was cultured in an optimized mineral salt medium with acetic acid and methanol as carbon sources in 100-milliliter flasks. The initial concentrations of nitrate were 100, 250 and 400 mg NO3-N/l and carbon to nitrogen ratios were 1.2, 2.6 and 4.0. The results show that increasing carbon to nitrogen ratio from 1.2 to 2.6, consequences in higher nitrate conversions. The maximum specific denitrification rate (2.53 mg/l.h) was obtained for (NO3-N)0 concentration of 400 mg/l, carbon to nitrogen ratio of 2.6 and acetic acid as the sole carbon source. However, increasing carbon to nitrogen ratio from 2.6 to 4.0 resulted in the decrease of specific denitrification rate. Although removal of NO3-N was seen by using methanol as the sole carbon source, it was not very suitable for Hyphomicrobium denitrifican to decrease high NO3-N concentrations, and acetic acid was a better alternative. The results showed that Hyphomicrobium denitrifican DSM 1869 is a good alternative for activated sludge, which is widely used in water denitrification processes. Nitrite accumulation was seen in experiments with low carbon to nitrogen ratios and the ones that methanol was used as the sole carbon source

Keywords:

Heterotrophic biodenitrification , pure culture , carbon source , C/N ratio , groundwater