The Study Of Ammonia Removal In Wastewater Treatment Based On Immobilized Microorganism

As a traditional two-stage biological treatment technology,activated sludge process has been widely used in wastewater treatment.But the traditional application of this biotechnology has a series of disadvantages and problems,such as suspended sludge has poor settling performance which will lead to the sludge loss,and after treatment,suspended flocs is not easy to separate from the wastewater,these disadvantages limit the efficiency and performance of sewage treatment.In order to accommodate the development of wastewater treatment,the traditional activated sludge process has been improved by immobilization technology.The immobilized microorganism technology always get the free microbial cells fixed in specific materials by physical or chemical method or aggregated to granules by themselves,which means that the wastewater and the sludge can be easily separated from each other,and the immobilized microorganism can keep the activity and can be repeatedly used in a certain period.As an economical and feasible biological treatment method,the technology has shown great potential in the future.In order to study the application of immobilization technology in the treatment of ammonia wastewater,according to the principle and method of immobilization,among all those immobilization methods,the physical and chemical immobilization methods were studied in this experiment.As for the physical method,a physical crosslinking method was studied based on the enhancement of aerobic granular sludge by adding magnetic nanoparticles(MNPs).As for the chemical method,the embedding method was studied based on the immobilization of partial nitrification(PN)sludge and anaerobic ammonia oxidation(ANAMMOX)sludge.The main conclusions are as follows:(1)The addition of MNPs can significantly promote the formation of activated sludge granulation,and the particle size is obviously larger than that of the blank group since 9d.At the beginning of experiment,the biomass of reactors are in the same level 3.5?3.8 g/L,and at the end of the experiment,the MISS of experiment group is 4.9 g/L which is 1 g/L higher compared with the initial investment,the MLSS of blank group decreases to 2.37g/L,which means that the MNPs plays an important role to avoid the loss of the sludge.And the SVI of experiment group was approximately 40 mL/g which is less than the initial level,the sludge settle ability can significantly enhanced by MNPs.Through the analysis of q-PCR,ammonia oxidizing bacteria(AOB)amount of blank group is 7.45×108 copies/mL while that of experiment group is 1.84×109 copies/mL which is almost two times of the blank group;the nitrifying bacteria(NOB)amount of experiment groups are higher than the blank group.And the effect of MNPs on aerobic granular sludge is mainly through the influence of the surface characteristics of microorganisms,and the MNPs can effectively enhance the electric potential and hydrophobic property of the microbial surface,which can promote the agglomeration of microorganism particles.In the process of aggregation,the MNPs can effectively change the polarity of the Lewis acid-base force especially ?B(blank group and experiment group are 49.26 and 4.86 mJ/m2,respectively),and the adsorption free energy ?Gadh(mJ/m2)can be affected(blank group and control group were 36.73,-36.81 mJ/m2).(2)The immobilized gel beads have obvious smooth surface and spherical structure,the diameter is about 4-5mm.The inside of gel beads presents a network structure,which can ensure the transmission of substrate and oxygen.Meanwhile,the network structure can effectively prevent the loss of sludge.Although the immobilized cross-linking reagent has a slight toxicity,the target strains shows no obvious lethal phenomenon,and the cells still keep the metabolic activity in the immobilized reagent.The immobilized sludge has a good ability to adapt to the load of ammonia nitrogen,the immobilized PN can get the ratio of nitrite and nitrate equal to 1:1 in a short time,and can effectively reduce the nitrite accumulation in autotrophic nitrogen removal process.The immobilization can ensure the existence of the target bacteria in a large number,but it has certain requirements for the amount of immobilized sludge.(3)The immobilization technology can make sure the exist of the target bacteria,in the phylum level,the Proteobacteria which includes nitrite bacteria and the Planctomycetes which includes ANAMMOX bacteria have high proportion of whole bacteria.And in level of class,the ?-proteobacteria and Planctomycetacia are dominant bacterial strains,and the relative abundance are 18.94%and 1.71%,respectively.