Tertiary denitrification is an effective method for nitrogen removal from wastewater. A pilot-scale biofilter packed with suspended carriers was operated for tertiary denitrification with ethanol as the organic carbon...Tertiary denitrification is an effective method for nitrogen removal from wastewater. A pilot-scale biofilter packed with suspended carriers was operated for tertiary denitrification with ethanol as the organic carbon source. Long-term performance, biokinetics of denitrification and biofilm growth were evaluated under filtration velocities of 6, 10 and 14 m/hr. The pilot-scale biofilter removed nitrate from the secondary effluent effectively, and the nitrate nitrogen（NO_3-N） removal percentage was 82%, 78% and 55% at the filtration velocities of 6, 10 and 14 m/hr, respectively. At the filtration velocities of 6 and 10 m/hr, the nitrate removal loading rate increased with increasing influent nitrate loading rates, while at the filtration velocity of 14 m/hr, the removal loading rate and the influent loading rate were uncorrelated.During denitrification, the ratio of consumed chemical oxygen demand to removed NO_3-N was 3.99-4.52 mg/mg. Under the filtration velocities of 6, 10 and 14 m/hr, the maximum denitrification rate was 3.12, 4.86 and 4.42 g N/（m^2·day）, the half-saturation constant was 2.61, 1.05 and 1.17 mg/L, and the half-order coefficient was 0.22, 0.32 and 0.24（mg/L）1/2/min,respectively. The biofilm biomass increased with increasing filtration velocity and was 2845,5124 and 7324 mg VSS/m^2 at filtration velocities of 6, 10 and 14 m/hr, respectively. The highest biofilm density was 44 mg/cm^3 at the filtration velocity of 14 m/hr. Due to the low influent loading rate, biofilm biomass and thickness were lowest at the filtration velocity of 6 m/hr.展开更多
To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone（O3）, hydrogen peroxide（H2O2） and chlorine dioxide（Cl O2）were examined to peel off the film fro...To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone（O3）, hydrogen peroxide（H2O2） and chlorine dioxide（Cl O2）were examined to peel off the film from the quartz sand surface in four pilot-scale columns.An optimized oxidant dosage and oxidation time were determined by batch tests.Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33（H2O2）and to 53.67 hr（ClO2） after the oxidation treatments, and the increase of backwashing interval after treatment by O3 was much less than for the other two treatments.Interestingly, the treatment efficiency of filters was not affected by O3 or H2O2 oxidation;but after oxidation by ClO2, the treatment efficiency was deteriorated, especially the ammonia removal（from 96.96% to 24.95%）. The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy.Compared with the oxidation by O3 and H2O2, the structures on the surface of filter sands were seriously damaged after oxidation by ClO2. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO2. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H2O2 is a suitable agent for film peeling.展开更多
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment of China (No. 2012ZX07302002)
文摘Tertiary denitrification is an effective method for nitrogen removal from wastewater. A pilot-scale biofilter packed with suspended carriers was operated for tertiary denitrification with ethanol as the organic carbon source. Long-term performance, biokinetics of denitrification and biofilm growth were evaluated under filtration velocities of 6, 10 and 14 m/hr. The pilot-scale biofilter removed nitrate from the secondary effluent effectively, and the nitrate nitrogen（NO_3-N） removal percentage was 82%, 78% and 55% at the filtration velocities of 6, 10 and 14 m/hr, respectively. At the filtration velocities of 6 and 10 m/hr, the nitrate removal loading rate increased with increasing influent nitrate loading rates, while at the filtration velocity of 14 m/hr, the removal loading rate and the influent loading rate were uncorrelated.During denitrification, the ratio of consumed chemical oxygen demand to removed NO_3-N was 3.99-4.52 mg/mg. Under the filtration velocities of 6, 10 and 14 m/hr, the maximum denitrification rate was 3.12, 4.86 and 4.42 g N/（m^2·day）, the half-saturation constant was 2.61, 1.05 and 1.17 mg/L, and the half-order coefficient was 0.22, 0.32 and 0.24（mg/L）1/2/min,respectively. The biofilm biomass increased with increasing filtration velocity and was 2845,5124 and 7324 mg VSS/m^2 at filtration velocities of 6, 10 and 14 m/hr, respectively. The highest biofilm density was 44 mg/cm^3 at the filtration velocity of 14 m/hr. Due to the low influent loading rate, biofilm biomass and thickness were lowest at the filtration velocity of 6 m/hr.
基金supported by the National Natural Science Foundation of China (Nos.51278409, 51308438)the Natural Science Foundation of Shaanxi Province (No.2014JZ015)the Research Program of China State Construction Engineering Corporation Ltd.(No.CSCEC-2014-Z-32)
文摘To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone（O3）, hydrogen peroxide（H2O2） and chlorine dioxide（Cl O2）were examined to peel off the film from the quartz sand surface in four pilot-scale columns.An optimized oxidant dosage and oxidation time were determined by batch tests.Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33（H2O2）and to 53.67 hr（ClO2） after the oxidation treatments, and the increase of backwashing interval after treatment by O3 was much less than for the other two treatments.Interestingly, the treatment efficiency of filters was not affected by O3 or H2O2 oxidation;but after oxidation by ClO2, the treatment efficiency was deteriorated, especially the ammonia removal（from 96.96% to 24.95%）. The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy.Compared with the oxidation by O3 and H2O2, the structures on the surface of filter sands were seriously damaged after oxidation by ClO2. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO2. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H2O2 is a suitable agent for film peeling.
