Continuous-flow biological denitrification with zeolite as support for bacterial growth

Zeolite particles with bacterial culture (Bio-NPC) were used for nitrate removal from surface water (SW) and effects of Bio-NPC, and the methanol amount and the pH value of SW were investigated in the batch reactor and the process was then monitored in the continuous-flow stirred reactor. The application of Bio-NPC particles (10%w/w) in the batch reactor was efficient for the removal of 100mgNO(3)-N/L from the SW, and the addition of methanol was optimal at CH3OH/N ratio of 2.5:1. The process was stable in the pH range of 5.85-8.03, but the highest denitrification rate was obtained at the pH value of 7.13. In the continuous-flow stirred reactor, nitrate removal was investigated at different hydraulic retention times (HRTs) (37.04, 23.26, 10.53, 2.33 and 1.32h) and the efficient nitrate removal was achieved even at HRT of 1.32h with nitrate and organic removal higher than 99 and 79%, respectively. The volumetric denitrification rates during the first eightdays of continuous flow were in the range of 39.2-51.28mgNO(3)-N/Lh and then it fluctuated within the range of 63.47-79.90mgNO(3)-N/Lh. The use of Bio-NPC was demonstrated as an efficient method for complete nitrate removal from the surface water.