Study On Nitrogen Removal Performance Of Shortcut Nitrification-denitrification In A/O Coupled With Sludge Hydrolysis

Anoxic/oxic(A/O) process was adopted to deal with low C/N ratio(C/N ratio was 2.63) municipal wastewater in complete and shortcut nitrification-denitrification under the conditions of normal temperature,without adjusting pH.Results showed that the average removal efficiencies of COD,NH₄⁺-N and TN reached to 63.76%,96.31%and 43.97% respectively,with effluent average concentration of 41.08 mg/L,1.25 mg/L and 23.95 mg/L in complete nitrification-denitrification.Biological nitrogen removal under shortcut nitrificationdenitrification in AdO process was achieved by controlling dissolved oxygen at 2.0 mg/L. Stable nitrite accumulation ratio reached to 67.45%and the average removel efficiencies of COD,NH₄⁺-N and TN reached to 62.57%,94%and 55.79%respectively,with effluent average concentration of 42.51mg/L,1.86 mg/L and 18.97 mg/L.The removel efficiencies of TN increased by 11.82%than complete nitrification-denitrification.In completely mixed reactor,without adjusting initial pH of the sludge,the hydrolysis temperature was controlled at 33℃.When sludge was hydrolyzed after 18 hours,the SCOD and TN concentration of hydrolysate reached to 1338.66 mg/L and 218.6 mg/L,with the hydrolysis efficiency of 15.76%.SCOD/TN reached its maximum 6.12 which was 3.08 times of the influent one.Results showed that sludge hydrolyzate used as a carbon source could accelerate the rate of denitrification greatly which reached up to the maximum denitrification rate of 16.8 mg NO₃^--N/(gVSS·h),4 times of denitrification rate of municipal wastewater.Shortcut nitrification-denitrification in A/O process was coupled with sludge anaerobic hydrolysis process.Sludge hydrolyzate was added as a part of the carbon source in anoxic stage of A/O process to improve the efficiency of denitrification.After the hydrolysis products were mixed with the raw sewage at the ratio of 1:10,the concentration of COD,NH₄⁺-N and TN increased by 128.96 mg/L,28.92 mg/L and 26.3 mg/L compared to raw sewage,with the influent C/N ratio raising from 2.63 to 3.49.The average removel efficiencies of COD,NH₄⁺-N and TN reached to 80.78%,95.54%and 78.77%respectively,with effluent average concentration of 46.73 mg/L,2.80 mg/L and 14.77 mg/L.The removel efficiencies of TN increased by 22.98%than non-coupling which could meet the first grade primary effluent standard in the National Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant(GB 18918-2002).