Functionality of denitrification with minerals composition, process conditions and microbial community

Nitrate removal from water has been receiving much attention in water treatment. The presence of minerals is very important for biological denitrification. In this study, minerals concentration for efficient denitrification was optimized and the optimal minerals composition was 0.5 g/L sodium citrate·2H 2 O, 0.01 g/L magnesium and 0.01 g/L iron. Maximum 32.10 mg NO 3 − -N/L/h removal rate was found using 0.88 g/L initial acetate concentration. PO 4 3− -to-NO 3 − -N ratio should be maintained higher than 0.30 for efficient denitrification. Magnesium did not have any significant effect on mixed culture denitrification, but in case of iron low concentration was favorable. 16S rRNA analysis had shown that Pseudomonas and Halomonas species were predominate in this mixed culture system. The fraction of microbial composition did not change significantly with minerals concentration except phosphate. At high phosphate concentration, Halomonas and at low phosphate concentration Pseudomonas were predominant. Both Pseudomonas and Halomonas species had shown similar denitrifying capacity. The optimal temperature range for denitrification was 34 °C to 42 °C. Low temperature limits the growth of Pseudomonas species but not Halomonas species. Low pH leads to nitrite accumulation, whereas maximum denitrification rate was found at pH 9.0. This mixed culture denitrification exhibited similar denitrification capacity over a wide range of dissolved oxygen (DO) concentration.