Studies On A Heterotrophic Nitrification-Aerobic Denitrification Bacteria

A heterotrophic nitrification-aerobic denitrification strain was isolated fromthe reactors for wastewater denitrification which has been working stably for half ayear in our laboratory. The observation with light microscope and transmissionelectron microscope showed it with a diameter between 700-800nm, gram-, belongingto coccus; by the physiological and biochemical identification and molecularidentification based on 16S rDNA homogeneitical analysis it was firstly identified asPseudomonas putida, named as Pseudomonas putida sp. DN 1.2.Denitrification capability of DN1.2 was studied here. We found that DN1.2 could notonly remove ammonium in autotrophic condition, it could also remove COD andammonium simultaneously.Either of these Denitdfication processes had nitrite andnitrate accumulation. Growing DN1.2 on Beef extract medium, it reached its logphase at 3-10h, and got its state phase after 10h growth. The most optical density canbe up to 1.12.Furthermore, we studied ammonium removal capability of DN1.2 in heterotrophiccondition.the results indicated that its ability to use organic carbon sources wasarranged in the order as: acetate＞glucose＞citrate＞glycerol;in the organicdenitrification medium containing 100mg/l ammonium and glucose as carbonsource,the most suitable initiating COD concentration for the strain to removeammonium was 3000mg/l,after 24h cultivation,it can remove 78.39%COD and 86.2%ammonium. The most suitable initiating pH value was 7.0-7.5,and the most suitableincubation temperature was 30-34℃, when the initiating COD concentration was2000mg/l and the ammonium concentration was 60 mg/l, DN1.2 can removed 93%COD and 100% ammonium after 24h cultivation.When the initiating CODconcentration was 2000 mg/l, the strain still could remove ammonium in the situationthat the initiating ammonium concentration was 1000mg/l. The affection to the abilityof using COD and ammonium was little as long as the initiating ammoniumconcentration was lower than 500mg/l.Nitrogen balance experiments for DN1.2 in the heterotrophic circumstance indicatedthat 38.5% of the removal ammonium was transformed into intracellular N, and58.8% of which was transformed into denitrification product, which was finallyremoved from the water completely.We also studied the aerobic denitrification of DN1.2, the results indicated that it canuse nitrite and nitrate respectively in the aerobic condition, and under the sameconditions, the removal efficiencies of nitrite is higher than that of nitrate. When bothof these two nitrogen sources were added simultaneously at the almost sameconcentration, neither of them had the priority to be used.We explored initially the application of mixed culture of DN-bacteria for domesticwastewater treatment,and found that the mixed culture of DN-bacteria could removeboth of COD and ammonium,and the improvement of the ratio of carbon to nitrogencould achieve better effect of denitrification.