The Study Of The Integration Of Anammox And Denitrification/Partial Nitrification Process

In the last decades, water pollution has become a main restricting factor for sustainable development and has a serious effect on the ecological balance and human health. The newly proposed ’water pollution control action plan’ in 2015 first proposes that enhancing the control of pollutant emission. The plan also points out that total nitrogen, total phosphorus, heavy metals and other pollutants which have prominent influences on the water quality of the environment should be included in the total emission control binding index system of basin and regional pollutants. Anammox process is a new biological nitrogen removal technology in recent years with the advantages such as the short process, the easy operability, the whole process without the generation of N2O, no external carbon and aeration and so on. But the anammox process has a limited TN removal and the theoretical maximum is only 88%, which means there is still a part of nitrogen in nitrate form can not be removed. Simultaneous anammox and denitrification (SAD) can achieve higher TN removal by simultaneously removing ammonia, organics and nitrate produced in the anammox process.In the reaction of anammox process, ammonia is the electron donor and nitrite is the electron acceptor, and waste water often contains only ammonia with tiny nitrite nitrogen contents, so the application of anammox process requires additional nitrate which increases the treatment costs. Anammox coupling partial nitration makes nitration reaction stay in the stage of nitrite. In other words, half of the ammonia is converted to nitrite, and then the anammox reaction occurs with the remaining ammonia and the generated nitrite nitrogen. The process reduces the nitrate production, the cost of aeration and the generated amount of N2O, and it does not require additional nitrite.In this paper, the submerged anaerobic membrane bioreactor (SAMBR) was adopted to start the simultaneous anammox and denitrification process (SAD). In order to reduce the membrane fouling, enhance nitrogen and COD removal efficiency, the activated carbon was added to one of the reactors as a biological carrier. At the same time, microbial could adsorb in the surface of activated carbon, which was beneficial to the growth of denitrifying bacteria in particular. A new-type sequencing batch biofilter granular reactor (SBBGR) was used to the study of simultaneous anammox and partial nitrification process (SNAP). The reactor set filler layer and aeration layer to distinguish aerobic and anaerobic areas effectively. Therefor, aerobic and anaerobic bacteria could grow in their own areas; it means that different microbial growing in different environment could coexist in one reactor. Sludge attached on the filler under the baffle could reduce biomass washout effectively. It could achieve the retention of sludge and faster start of SNAP process.The main research results are as follows:(1) The anammox bacteria are very sensitive to the organics at the start-stage because of the smaller amount and activity. The activity of the anammox bacteria can be completely inhibited when the concentration of COD is 100 mg/L, but this inhibition is reversible. When the concentration of COD reduced to 50 mg/L, the activity of anammox bacteria recovered.(2) After adding organics, the denitrifying bacteria can converse the nirtate which was producted from anammox process to nitrogen gas. On 108 d, three reactors are both completed anammox process start-up. The nitrate nitrogen production/amount of ammonia nitrogen removal has been maintained at 0.25-0.27 range in the contral, this ratio is about 0.2, sometimes even lower than 0.2 in the presence of organic matter.(3) The addition of organic matter to break the position of anammox bacteria as the dominant fungi. In the participation of organic matter under denitrifying bacteria number increased, and the presence of activated carbon, growing faster. The 120d qPCR results can be seen that the anammox gene copy number (4.39 x 109 copies/mL) in the reactor A is significantly higher than the other two reactors (3.19 x 109 copies/mL,3.28 x 109 copies/mL), the number of denitrifying bacteria as follow: reactor B>reactor C>reactor A. The Planctomycetes which anammox bacteria belongs to in the reactor A accounted for 40%, which is much higher than the other two reactors (22.5% and 11.6%, respectively).SBBGR can be divided into upper aeration layer and lower sludge filler layer. It distinguishes the aerobic and anaerobic areas effectively. The partition plays an important role on SNAP process and the reactor can be started up in a short period of time. The existence of filler anaerobic zone slows down the high concentration of dissolved oxygen on the toxicity of anaerobic ammonia oxidation bacteria in the aeration phase.(4) A running cycle in the SNAP process, the DO, pH and nitrogen transformation change is on a cyclical rule. And the AOB bacteria are dominated in the aerobic phase while anammox bacteria play an important role in the anaerobic phase.(5) The microorganisms are easy growing on filler and microbial abundance and diversity are higher than other places due to the smaller influence of hydrodynamic shear force on middle-layer mud. The OUTs number in middle-layer sludge is 500 more than other two layers, and the ACE, Chaol and Shannon index is both higher than the other two layers. In the middle-layer mud of filler, Planctomycetes which anammox bacteria are belong to are more than any other regions, while Chlorobium and Bacteroidetes are lower than other regions. Microorganisms live in different environment can coexistence in this reactor.