An Activated Sludge Integration Process For Denitrifying Nitrate And Removing Carbon(DN-RC Process)

This paper developed a novel integration process for denitrifying nitrate and removing carbon removal(referred to DN-RC process),and its main features are as following:(1)High efficiency,with the low effluent COD and nitrate.When the loading rate of the system was 0.33 gNO3-N·L-1·d-1 with a COD/N at 3.5,the effluent NO3-N and COD were 0.35 mg·L-1 and 6.0 mg·L-1,respectively.(2)Less carbon source dosage.When the system loading rate was 0.33 gNO3-N-L-1·d-1,COD/N of 3.5 could realize COD and nitrate removal rate to 98.3%and 99.3%,respectively.(3)Long sludge retention time(SRT)and low sludge yield.When the system loading rate was 0.33 gNO3-N·L-1·d-1,the system’s SRT was 50.9 days and the sludge yield was 0.128 gVSS/gCOD.The mechanism of this process is proposed:(1)DN tank is efficient for denitrification.The nitrate removal rate of DN tank was 15.4 mgNO3-N·gVSS-1·h-1.(2)The RC tank could degrade the SMP which was produced from DN tank.When the loading rate of DN tank was 3 gNO3-N·L-1·d-1,the COD,polysaccharide and protein of DN effluent were 27.8 mg·L-1,1.44 mg·L-1,and 4.15 mg·L-1,respectively.Through the deep degradation of RC,the COD,polysaccharide and protein were reduced to 7 mg·L-1,0.80 mg·L-1,and 0.58 mg·L-1.(3)Stabilization of sludge,low effluent COD and NO3-N promoted the good performance of the secondary sedimentation tank,where no sludge flotation happened.(4)Biomass concentration is high and the SRT is long,which led to a stable system with a good effluent quality.This technology is characterized by simple,efficient,stable,economic and low energy consumption,etc.It is suitable for large-scale promotion and is of great significance for the reduction and reuse of nitrate wastewater.