The Experimental Study Of COD Removal From The Coke Plant Wastewater By Adding The Preponderant Bacilli In A~2/O~2 Process

Coke plant wastewater is a typical,containing high concentration ammoniacal nitrogen,and difficult biodegradational industry wastewater.The traditional method to deal with the coke plant wastewater is a means using by the active dreggy mud,which has less effect on the hard-degraded substance and ammoniacal nitrogen.According to characteristic of the coke plant wastewater, the paper studied the nitrogen removal mechanism and effect in detail by A²/O² process,during which also added the preponderant bacilli at the process of O² and made the systemic study of wiping off the high chroma COD,to treat the coke wastewater of the second coke plant which belongs to taiyuan coal gas company.The paper experimental results demonstrated:the average level rate of the inpouring coke plant wastewater could reach 5.5L/d by A²/O² process of adding the preponderant bacilli.The influent COD concentration could reach 817.4～1874.2mg/L and ammoniacal nitrogen could reach144.4～687.93mg/L.On the condition that the water could the level of PH 7.0～8.2 and the average rate of circumfluence was 3.27,the effluent COD and NH₃-N removal rate concentration could achieve 92.01%and 97.22%respectively.The temperature of influent wastewater in anaerobic pool was 24～36.5℃while that of the reactor was 25.8～33.5℃.The PH value of influent wastewater was 7.0～8.2 while the PH value of effluent wastewater was 6.7～8.7.The chroma of the influent wastewater of dissolving oxygen was 0.0～2.5mg/L while that of the wastewater in anaerobic pool was 0.1～0.3mg/L.The average HRT was anaerobic pool,the average rate of COD and ammoniacal nitrogen removal could achieve 10.2%and 9.95%respectively,when the total HRT of the whole system was 8.4 hours.The temperature of influent wastewater in anoxic pool was 25.8～33.5℃and the PH value was 6.7～8.69,the chroma of DO 0.1～0.3mg/L.The temperature of the circumfluence nitration liquid was 26.5～32.3℃,the PH value was 6.0～7.89,the chroma of DO 2.3～4.7mg/L,alkalinity was 252.3～577.03mg/L(measured by CaCO₃),the ratio of the circumfluence was 1.37～4.09.Under this condition,the temperature of the influent wastewater in anoxic pool was 26.9～32.1℃,the PH value was 6.40～8.14,alkalinity was 432.33～560.35mg/L,the settle time of the wastewater in anoxic pool was 6.05～8.01h,the chroma of DO was 0.3～1.0mg/L(the average was 0.7mg/L), the average removal ratio of COD 82.15%.After considering the diluting effect of the circumfluence,the average removal ratio of was still 42.15%.In the first aerobic pool(O₁),the removal ratio of COD was 91.5～499.3mg/L(the average was 207.8mg/L),that of ammoniacal nitrogen removal was 13.7～305.99mg/L(the average was 113.93mg/L)when the temperature of the wastewater was 26.9～32.1℃,the PH value was 6.4～8.14,the chorma of DO was 0.3～1.0mg/L,alkalinity was 432.3～560.35mg/L(measured by CaCO₃)Under the whole condition,the ratio of removal COD was 91.5～499.3mg/L(the average was 207.8mg/L),ammoniacal nitrogen removal was 13.7～305.99mg/L(the average was 113.93mg/L).Used the 16.0～21.18h of HRT(the average was 18.45h),the temperature was 24.7～29.1℃,the PH value was 5.8～7.97,the alkalinity was 319.5～500.12mg/L,the chroma of dealing DO was 2.3～6.1mg/L(the average was 4.6mg/L),COD was 50.9～447.3mg/L(the average 146.3mg/L),the average removal ratio of COD was 27.43%, ammoniacal nitrogen removal was 3.1～101.22mg/L(the average was 21.86mg/L),the average removal ratio was 75.26%.The key stage of the process controlling was aerobic reactor(O₂),in which put the predominance bacterium could control the last effluent COD and let it reduce quickly.The experimental result showed:the aerobic stage(O₂)of dealt with COD was 50.9～447.3mg/L(the average was 146.3mg/L),ammoniacal nitrogen was 3.1～101.22mg/L(the average was 21.86mg/L)when the temperature of the effluent wastewater was 24.7～29.1℃,the PH value was 5.8～7.97,the chroma of DO was 2.3～6.1mg/L,alkalinity was 319.5～500.12 mg/L(measured by CaCO₃).At the first aerobic reactor(O₁),the chroma of ffluent DO was 2.3～4.7mg/L(the average was 32mg/L),the COD was 23.4～208.8mg/L(the average was 104.6mg/L),the average removal ratio of COD was 22.56%,ammoniacal nitrogen was 0.9～87.23mg/L(the average was 23.98mg/L),the average removal ratio was 48.53%when the HRT was 13.7～18.13h(the average was 15.83h,the temperature was 26.5～32.3℃,the PH value was 6.0～7.89,alkalinity was 252.3～577.03 mg/L.It will make the chroma of effluent COD reach the secondary national standard(COD＜150mg/L)about "The standard of sewage comprehensive discharge"(GB8978-1996)to adopt the anaerobic-anoxic-aerobic-aerobic biological reactor(A²/O²),in which put predominance bacterium to deal with coke plant wastewater when the chroma of effluent of COD increases constantly. This technology is economic and technique feasible and has stable effect.