| This experiment studied the influence factors and the stability of shortcut nitrification-denitrification in the sequencing batch reactor.It studied the influence to shortcut nitrification-denitrification from temperature with controlling of DO and SRT;it studied the influence to shortcut nitrification-denitrification from DO and SRT at normal temperature; and it also studied the organic compounds and ammonia nitrogen removal rate, nitrite nitrogen accumulation rate and the stability of the system under the controlling of non-uniqueness factors.Controlling the condition of DO at 0.5±0.1mg/L, pH at 7.5±0.1,the MLSS 3800 mg/L,and the SRT at 14days under low temperature conditions.Firstly,at the temperature of 9 centigrade, keeping the system operating for 34 days, the nitrite nitrogen accumulation rate was always around 9% during the period and it was a failure for shortcut nitrification-denitrification.Secondly,at the temperature of 14 centigrade, system has formed shortcut nitrification-denitrification after 16 days,40days later, nitrite nitrogen accumulation rate has reached more than 91% and rate of nitrification was 1.344 mg/(g·h). Thirdly at the temperature of 19 centigrade,after 44days, nitrite accumulation rate remain more than 90%,but the nitrification rate was raised to 1.812mg/(g·h) which rose 34.82% compared with the condition of 14 centigrade.Thus it can be seen, the shortcut nitrification-denitrification has promoted by the increase of temperature under the condition of low DO and SRT. What's more, rising temperature can increase the nitration rate effectively under the steady operation of system.Controlling the condition of DO 0.5±0.1 mg/L,pH 7.8±0.1,MLSS4000 mg/L, shortcut nitrification-denitrification has succeed after 17days at the normal temperature,then 20days later, nitrite nitrogen accumulation rate has maintain the stability of more than 92%. On this basis, increasing DO consistence to (0.8±0.1)mg/L step-by-step,then more than 1.2mg/L, and keeping the system running for at least one month at every concentration gradient. The experiment result suggested, nitrite nitrogen accumulation rate was kept over 92% when controlling DO consistence at 0.5-1.0mg/L.When the consistence of DO was more than 1.2mg/L,the reaction became long-term nitrification-denitrification after 18 days. Under the premise of the removal rate of ammonia nitrogen reached 91%, the average oxidation rate of ammonia nitrogen increased 5.64%,and the increase rate of nitrite nitrogen increased 3.46% compared with the condition of DO consistence 0.5±0.1mg/L,and the nitration period reduced 40 min under the condition of DO consistence 0.8±0.1mg/LKept the condition identical with the condition of DO 0.8mg/L and studied the aeration volume comparative test which adjust the shortcut nitrification-denitrification's aeration volume at 60L/h, and the long-term nitrification-denitrification's aeration content at 76L/h. It was found that:the aeration volume of shortcut nitrification-denitrification saved 21.05% than that of long-term nitrification-denitrification,and the reaction time shortened 40min.Separated the sludge which average nitrosation rate is 84% averagely into three parts, then input them into three identical SBR reactor,and studied the influence from SRT which was set at 7d,11d and 15d to the shortcut nitrification-denitrification.It can be showed, when SRT was 7days the ammonia nitrogen removal rate decreased 27.7%, the nitrite accumulation content decreased 14.2mg/L after 90 days. When SRT was 11 days, nitrosation rate increased from 84.9% to 89.1%, the nitrate nitrogen accumulation quantity decreased to 3.1mg/L.When SRT was 15 days, nitrosation accumulation rate was decreased from 84.5% to 82.7%, and the nitrification rate was increased 2.34% compared with the SRT was 11 days. Experiments show that:the short SRT would reduce denitrification effectiveness; when the SRT was between the minimum time period of two nitrification bacteria, the stability of shortcut nitrification-denitrification system could be improved, but compared with which the SRT was 15 days, the nitrification rate was significantly lower.So by controlling non-uniqueness factors and seeking appropriate SRT is the key to making the system of shortcut nitrification-denitrification operated stably and efficiently.Studied the stability of system by controlling non-uniqueness conditions through comparative test .The first reactor: ammonia concentration was 4.61mg/L and DO concentration was 1-2mg/L, the system became the long-term nitrification-denitrification after 70 days, so concluded that the shortcut nitrification-denitrification was not stable by only controlling the ammonia concentration.The second reactor: ammonia concentration was 4.61mg/L, DO concentration was 1-2mg/L,pH was 8.4±0.1,and SRT was 15 days, founded the nitrite accumulation rate was reached 92%,and the system was stable.The conclusion was that by controlling higher DO concentration ,higher pH and proper SRT could keep the system stable, and the system had a high nitrite accumulation rate and stable denitrification effect for 130 days.The experiment broke out of the restraint in OLAND theory that DO concentration should be controlled under 1.0mg/L(even 0.5mg/L), raised organic compounds removal rate and widened the DO extent which can accomplish shortcut nitrification-denitrification, it also indicated that higher pH and proper SRT were benefit to improving the level of accomplishing shortcut nitrification-denitrification and stability of system. |
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