Pretreated Corn Husk Hydrolysate as the Carbon Source for Aerobic Denitrification with Low Levels of N2O Emission by Thermophilic Chelatococcus daeguensis TAD1

The major obstacle to biological denitrification is the cost of the carbon source used as electron donor. Therefore, it is desirable to identify inexpensive alternatives to enable efficient denitrification. Corn husk, a type of agroforestrial waste, has the potential to release organic materials. This study investigated the possibility of enhancing aerobic denitrification by thermophilic Chelatococcus daeguensis TAD1 when corn husk that had been pretreated with hydrolysate was employed as the carbon source. The results showed that the particle size of 10-40 mesh, the NaOH dose of 0.01 mol L-1, the loading dose of 60 g L-1, the temperature of 40 degrees C, and pretreatment time of 24 h were appropriate to release available carbon source for denitrification by TAD1. Additionally, an initial pH of 8.5 was optimal for denitrification with maximum N2O production as low as 0.053 % of denitrified NO3--N, which was the least at pH 6.0-9.0, taking advantage of corn husk hydrolysate (CHH). At an initial NO3--N of 253.36 mg L-1, the denitrification rate and removal efficiency reached 24.55 mg L-1 h(-1) and 96.91 %, respectively, without accumulation of nitrite and N2O utilizing CHH as a sole carbon source. To sum up, CHH was an economical and efficient carbon source for aerobic denitrification by TAD1 with low levels of N2O, capable of tolerating the fluctuation of pH and the high nitrate load.