The Performance Of Corn Husk Hydrolysate As Carbon Source For Aerobic Denitrifiers

In the biological nitrogen removal wastewater treatment,the cost of carbon source takes up more than half of the equipment and management costs.Denitrification is the reduction of nitrate to nitrite and subsequently to nitrogen gas,requiring sufficient external organic carbon source to act as electron donors.The agroforestrial wastes have huge potential of being carbon sources because of their economy and widespread sources.Compared with the traditional anoxic denitrification,aerobic denitrification has advantages of higher denitrification rate,stronger adaptability to environment and easier operation without the inhibition of oxygen.In order to reduce the cost in biological denitrification,corn husk was studied first as the alternative carbon source for aerobic denitrification.The pretreatment conditions of corn husk were studied in order to make the organic carbon more available for aerobic denitrifier,overcoming the weaknesses of solid carbon sources.The optimized pretreatment conditions were as follows,the particle size from 10 to 40 mesh,the NaOH dose of 0.01 mol/L,the loading rate of 60 g/L,the temperature of 40°C,the pretreatment time of 24 h.Thermophilic Chelatococcus.daeguensis TAD1 could utilize corn husk hydrosate to grow fast and denitrify efficiently.When pH was 8.5,the denitrification efficiency was 94.26%,the maximum production of N₂ O was 0.053% of denitrified NO₃^--N.When intial NO₃^--N was from 100.35 to 302.13 mg/L,the maximum denitrification rate was 24.55 mg/?L h?,the peak production of N₂ O was 0.265%.When NO₂^--N was from 30.80 to 100.20 mg/L,higher initial NO₂^--N stimulated the growth of TAD1 and reduction of NO₂^--N with low levels of N₂ O emssion.But when NO₂^--N was 149.75 mg/L,the activity of TAD1 was inhibited.A novel aerobic denitrifier B2 with high nitrogen removal performance was isolated from corn husk hydrolysate and identified by physiological and biochemical studies combined with molecular biology method as Bacillus licheniformis.When corn husk hydrolysate was employed as carbon source,the optimal conditions for growth and denitrification of B2 were as follows,shaking speed of 160 rpm?dissolved oxygen was 7.25 mg/L?,pH of 7⁹ and temperature of 40 °C.B2 possessed denitrification efficiency higher than 96.50% in 15 h from 35 to 50°C,carrying out effective aerobic denitrification under mesophilic and thermophilic conditions.When intial NO₃^--N was 298.85 mg/L,the peak denitrification rate was 27.61 mg/?L h?.When NO₂^--N was 248.85 mg/ L,the peak denitrification rate was 24.89 mg/?L h?.Higher nitrogen load stimulated the growth of B2.Thus,B2 could take advantage of corn husk hydrolysate as carbon source to remove heavy concentrations of NO₃^--N and NO₂^--N.