Preparation Of Magnetic Bio-carrier And Its Application In AMBBR Process

As the core element of the MBBR process,the suspended biological carrier plays a decisive role in the effect of wastewater treatment.At present,single materials such as polyethylene,polypropylene and polyurethane are generally used to prepare carriers in the market.However,their poor biocompatibility and hydrophilicity lead to a long start-up cycle and poor effect of the microbial film.Therefore,a suspended biological carrier with good performance has been developed.The research hotspots.Magnetic properties have a wide range of applications in various fields.In recent years,more and more scholars have carried out key research on magnetic properties and the response of microorganisms.Magnetism has the effect of separating and inhibiting microorganisms,but under the action of micro-magnetic field,it can promote the metabolism of microorganisms and change the way of movement of microorganisms under the action of micro-magnetic force.In this study,in order to improve the problem of poor biocompatibility and long filming cycle of suspended biological carrier,the preparation of suspended biological carrier was combined with the above-mentioned biological magnetic effect,and 60-mesh neodymium iron boron magnetic powder was added to polyethylene substrate.The carrier provides weak magnetic properties,and hydroxyapatite powder is added to improve the hydrophilicity of the carrier.The magnetic carrier is magnetized after the preparation of the magnetic carrier is completed by the blending technology.The physical characterization and testing of the magnetic carrier are detected by scanning electron microscopy,energy spectrum detection,static contact angle,mechanical strength,magnetic properties and so on.From the SEM image under low magnification,it can be seen that the surface structure of the ordinary carrier and the magnetic carrier are relatively flat,indicating that the mixing of neodymium iron boron magnetic powder and hydroxyapatite powder in polyethylene is more uniform,while the magnetic carrier in the SEM image The surface structure is relatively rough,with obvious concave and convex corrugated structure,which increases the roughness of the carrier and facilitates the attachment and growth of microorganisms.The energy spectrum test further confirmed that the neodymium iron boron magnetic powder and hydroxyapatite powder were successfully and uniformly added to the polyethylene substrate.The static contact angle of the magnetic carrier is 17.9°-19.3°smaller than that of the ordinary carrier,indicating that the hydrophilicity of the magnetic carrier is significantly higher than that of the ordinary carrier.The mechanical strength of the magnetic carrier meets the requirements of the suspended biological carrier,and it is weakly magnetic,which not only ensures the exertion of the magnetic performance but also avoids the phenomenon of self-aggregation.The test of artificial water distribution to simulate domestic sewage is used to compare the filming effect of magnetic carrier and ordinary carrier,that is,efficiency.Brown plaques appeared on the surface of both carriers on the 7th day after the filming started.The color of the common carrier was darker,and the amount of biofilm of the common carrier was more than that of the magnetic carrier.On the 14th day,the surface of the carrier was covered with a light brown film.The amount of carrier microbial film increased significantly and accompanied by large fluctuations.By the 23rd day,the reactor membrane was started up.A thick layer of brown microorganisms could be seen on the surfaces of the two carriers.The magnetic carrier was thicker than the ordinary carrier.The amount of ordinary carrier biofilm reached the maximum value of 0.075g/piece on the26th day,and the amount of magnetic carrier biofilm reached the maximum value of0.085g/piece on the 20th day.It shows that the magnetic carrier has better start-up effect and short cycle.Compare the microbial diversity and community structure on the surface of the magnetic carrier and the common carrier respectively.The microbial diversity indexes of chao1,ACE and Shannon on the magnetic carrier are all higher than those on the common carrier,the Simpson index is lower than that of the common carrier,and the microbial diversity of the magnetic carrier is more than that of the common carrier.The phylum Nitrospirota and Acidobacteriota bacteria on the magnetic carrier are twice as large as those on the ordinary carrier,which can enhance the system's ability to remove NH₃-N,showing a good denitrification effect.Nitrospira,Dokdonella,and Nannocystis on the genus level magnetic carrier are about twice as much as those on the ordinary carrier,which promotes nitrification and denitrification.It shows that the microbial community is affected by the micro-magnetic field generated by the magnetic carrier,which promotes its grow on the carrier.In order to achieve the best treatment effect of the magnetic biological carrier,three operating parameters of the influent p H,DO and C/N were selected for the optimal operating conditions of the system optimization.Firstly,through single-factor experiments,both CODcr removal rate and NH₃-N removal rate were used to explore the impact of different influencing factors on wastewater treatment effects,thereby determining that the p H value is 7?8,the DO concentration is 6?8mg/L,and the C/N is 12?18.Within the above range is used for the optimal operating conditions of the response surface analysis.The optimal operating conditions of the system for the operation of the magnetic carrier in the AMBBR(Alternating Moving Bed Biofilm Reactor)system are obtained by response surface method:when the influent p H is 7.683,the DO is 6.306,and C/N is16.151,its fitting The effect is better.The AMBBR system runs repeatedly within the range close to the above-mentioned optimal operating conditions,and the average removal rate of CODcr and NH₃-N in the effluent reaches 89.48%and 81.43%.Magnetic carriers have good prospects for use,and the results of this study can provide a reference for the use of magnetic carriers.