Study On The Effect Of Free Ammonia (FA) On The Inhibition Of Nitrifying Bacteria Activity

Biological nitrogen nitrification mainly involves two types of independent flora(ammonia oxidation bacteria AOB and NOB nitrite oxidizing bacteria), take advantage of the differences in physiological characteristics of two types of bacteria that can effectively control the nitrification nitrosation stage, so as to realize the efficient and economy remove.of water nitrogen remove. Among all facters, the free ammonia(FA) and aeration time(t) are important factors to achieve partial nitrification and stable operation. A large number of studies have shown that FA for AOB and NOB exist inhibition, but relatively AOB, NOB more sensitive to inhibition of FA; The aeration time on nitrification effect and the influence of nitrification efficiency at the same time, also has an important influence on nitrification types. In order to study the impact of the FA and aeration time on biological nitrogen removal process of nitrification bacteria activity, we adopt the test in SBR process, respectively from the FA together three different aeration modes, the inhibition kinetics of FA for AOB, three aspects of the reversibility of the FA are activated to restrain activity of nitrifying bacteria examined the activity of nitrifying bacteria change and the transition of the nitration reaction system type.In order to investigate for the long-term effects of FA on the nitrification performance, different aeration methods(real-time control, advance 30 min stop aeration, delayed 30 min stop aeration) three parallel SBR reactor was used with respectively in different concentration gradient of the FA(FA=0.5, 5, 10 mg/L), based on nitrogen removal, the reaction rate changes, changes in the type of nitrification, NOB activity inhibition, etc., to study the effect of FA together different aeration way on the performance of the SBR nitrifying., mainly obtained the following conclusions:(1) Under the set feed concentration gradient of the FA, RAhead, RExact and RExceed system all can happen good biochemical effect. Effluent COD values of less than 50 mg/L, the effluent concentration of NH+ 4-N had a lot to do with aeration time, RAhead, RExact and RExceed system of effluent concentration of NH+ 4-N average were 21.4, 0.9 and 0.8 mg/L.(2) Using DO and p H in five characteristic points on the curve can effectively grasp and accurate grasp the nitration end of nitration in the RExact systems, avoid premature stop the happening of aeration and the aeration, simultaneously RExact system real-time control is also an important time RAhead and long running RExceed system basis.(3) FA has a significant impact to nitrification type of change in the RExact, RAhead and RExceed system. When the concentration of FA to 10 mg/L, the nitrification type of three systems were changes. But as a result of the differencet long-term effects of aeration time, after the realization of shortcut nitrification and shortcut nitrification screw stability, RAhead, RExact and RExceed system respectively in 56, 62 and 72 cycles to realize shortcut nitrification, the shortcut nitrification the best stability is RExact system after implementation, the worst is RExceed system. FA is the most critical factor in the realization of shortcut nitrification, early stop aeration synergy FA quicker to realize shortcut nitrification, aeration is a disadvantage factor to achieve nitrification.(4) FA has a significant impact to nitrifying bacteria activity in the RAhead, RExact and RExceed system. As FA concentration has increased, activity of AOB increased gradually, and NOB activity increased firstly(FA was 0.5, 5.0 mg/L) after reduced, and ultimately be completely inhibited(FA is 10.0 mg/L), NOB inhibited activity is the root cause of the realization of shortcut nitrification.(5) With the ascension of FA concentration, SV, SVI of sludge were gradually reduced in the RAhead, RExact and RExceed system, but the FA concentration is about 10 mg/L, three kinds of biochemical sludge settleability system comparatively large difference, including sludge settleability RExact system is best, worst RAhead system.In order to study the FA for three kinds of shortcut nitrification sludge(SAhead, SExact and SExceed) inhibitory activity of AOB influence, for the test to simulate a sewage water, improve FA concentration by periodic synergy limited aeration(4 h) method, based on the nitrogen removal and nitrification rate solution is mainly studied on the basis of the FA for AOB activity inhibition kinetics. Mainly obtained the following conclusion:(1) By the short-term effects of inhibiting FA, NH+ 4-N removal and NO-2-N quantity change obviously in the SAhead, SExact and SExceed sludge system. Three kinds of shortcut nitrification of NH+ 4-N removal sludge system are increased with increment of FA concentration. ARE showed a clear section change rule. NO-2-N quantity with concentration of FA increase firstly after down slowly, SAhead, SExact and SExceed sludge discharge system of NO-2-N maximum were 110.2, 82.9 and 72.8 mg/L.(2) The whole FA concentration,SAOR and SNi PR change present a bigger difference in the SAhead, SExact and SExceed system. SNi PR change is more suitable for characterization of AOB inhibition degree of influence by the FA. in the high concentration of FA shortcut nitrification system, On the high concentration of FA,can appeared FA escape. FA escape rate in different phases of FA concentration had different linear correlation. When FA=711mg/L, FA escape amount up to 65.9 mg/(L·h).(3) Luong model and Han-Levanspiel model are not suitable for describing FA inhibitory activity of AOB in sewage sludge in the SAhead, SExact and SExceed, Edwards(2) model is not suitable for SAhead and SExceed sludge. Compared to other three models, rmax of Haldane model differ with the actual value is bigger, but Ks is close to the real value.In order to investigate the reversibility of FA inhibitory activity of NOB, with the test method of water distribution, the higher concentration of FA(4.5mg/L) on the basis of real-time control under the condition of half a short-range(Ni AR is about 50%), based on NH+ 4-N removal characteristics, nitrogen transformation and the change of Ni AR, focuses on the different concentrations of FA coupling aeration time(real time control, aeration) the influence of the structure and activity of denitrifying bacteria flora. Mainly from the following conclusion:(1) By increasing concentration of NH+ 4-N in order to enhance the water FA, can quickly realize shortcut nitrification. High concentrations of FA(3.5 mg/L) collaborative real-time control can realize stable shortcut nitrification;(2) High FA(3.4 mg/L) after aeration condition, the NO-2-N in the role of NOB to NO-3-N transformation, causing Ni AR decline gradually. But at the end of the nitration, the system can still maintain high Ni AR. High concentrations of FA after aeration condition, the shortcut nitrification has been spared substantial damage. FA inhibition is to maintain a high aeration shortcut nitrification under the condition of not destroyed most of the key factors; And the aeration is leading to high concentrations of FA Ni AR down the direct cause of the system.(3) After removing the FA inhibition, under the condition of real-time control system can still maintain the original shortcut nitrification, show the FA to the irreversible inhibition activity of NOB; Remove after the FA inhibition, aeration condition has some damage on the stability of shortcut nitrification, its damage degree difference is obvious, but a different system NOB activity is reversible depends on the degree of original shortcut nitrification system stability. High FA high real-time control under the condition of shortcut nitrification and FA had compared aeration condition shortcut nitrification, the former NOB activity more completely, Ni AR higher, lift the FA after aeration condition, the inhibition of the former short-range stability is significantly higher than the latter.(4) After the FA disinhibition, different operating temperature(room temperature: 22.5±1.0℃, low temperature:15.1±3.0℃) conditions, the activity of NOB reversible showed significant difference. Temperature conditions to maintain the stability of shortcut nitrification under low concentrations of FA system plays an important role, and under the condition of normal temperature low concentrations of FA shortcut nitrification was damaged more easily.