Study On The Construction Of Autotrophic Biological Filter And The Effect Of Manganese Removal

Biological removal of manganese in groundwater has been widely accepted and applied.Many studies have shown that the method is mainly to establish a biological filter layer with manganese oxidizing bacteria as the dominant bacteria,and use the microbial catalytic oxidation in the filter layer to remove manganese in groundwater.However,the content of organic matter in groundwater is usually very low,which often leads to the instability of manganese removal in the manganese filter layer with heterotrophic microorganisms as the predominant microflora.In this work,based on the characteristics of groundwater,a manganese removal filter with autotrophic microorganisms as the dominant group was constructed,and the start-up,operation effect and influencing factors of the filter were studied,the maturation process of it was also analyzed.The autotrophic manganese oxidizing bacteria were screened,acclimated and enriched by small-scale experiments.The activated sludge of nitrification stage in the aeration tank was chosen as the source of the autotrophic manganese oxidizing bacteria,and the autotrophic manganese oxidizing bacteria were screened and trained in the JFM medium.The optimal culture medium JFM4 for culturing autotrophic manganese oxidizing bacteria was obtained by adjusting the concentration of ammonium ferric citrate.And the manganese removal rate of the autotrophic manganese oxidizing bacteria enriched and cultivated in the medium is more than 90%.Three different colonies were obtained by plate culture.The preliminary identification results of the highly efficient autotrophic manganese oxidizing bacteria showed that the bacterium in the bacteria liquid contained three different strains: Alcaligenes,Dexesia and Pseudomonas,which were all Gram-negative bacterium,the result was got through 16 S r DNA sequencing and gram staining.Through the column experimental simulation of the actual biological manganese removal filter,the inoculation and start-up of the filter layer was studied.Quartz sand and glass beads were used as filter media in the experiment.The filter layer was inoculated with intermittent and inner loop.The inoculation circulating fluid were the backwashing bacteria liquid and the autotrophic manganese oxidizing bacterium solution which was enriched by JFM4 medium.The experimental results were found that in the case of the same inoculation conditions,inoculating above two different circulating fluid with the same filter layer Quartz sand,and inoculating one of the same two different circulating fluid with different filter layer Quartz sand or glass beads,the results of their manganese removal were basically consistent.Under the same raw water conditions,the effects of inorganic salt nutrition,nitrogen nutrition,p H and ORP on the start-up of filter were studied.The results showed that the adding of the 1% culture medium components(excluding ferric ammonium citrate and manganese sulfate)to the raw water can promote the maturation of the autotrophic biological manganese removal filter layer through supplying the inorganic salt nutrition.Nitrogen nutrition is a necessary factor for the success of the autotrophic biological manganese removal filter to start-up,for the result of adding 0.5mg / L of ammonia nitrogen(in nitrogen)was more effective than that of adding 0.5mg / L of nitrate nitrogen(in nitrogen)to the filter layer;When the p H value of the raw water between 7-7.2 and the ORP value of it needs more than 350 m V,the autotrophic biological manganese removal filter in order to start normally.The effect and influence of mature autotrophic biofilter were studied by using mature filter columns,and the maturation process of autotrophic biofilter was analyzed.Under the different raw water conditions,the effects of filtration rate,influent ammonia nitrogen concentration and influent manganese concentration on the operation of the autotrophic biological manganese removal filter were studied.The results showed that when the concentration of [Fe2+] was 0.15 mg / L,the DO was between 8-10 mg / L,the p H value was between 7-7.2,the water temperature was 15-28 ?,the backwashing strength was 6.5L /(s m2)The best filtration rate should be controlled below 12 m / h,the concentration of ammonia nitrogen should meet 0.5-1.5mg / L,the concentration of influent manganese is below 3.6mg / L.By observing the apparent change of the filter layer during the culture process and combining with the removal of Mn2+ in the filter layer,the formation process of biofilm in filter layer during maturation of filter layer was analyzed,The formation of biofilm can be roughly divided into the adaptation period and logarithmic growth phase,the biofilm was the main body of the filter layer to remove manganese ions.The SEM and IR spectra of mature quartz sand and glass beads showed that the surface of mature filter media contained a lot of manganese oxides and microbes,Which contains Leptothrix and Gallionella.The contents of the weight,moisture content,organic matter,inorganic matter the proportions of them on the surface of mature glass beads at different depths of filter layers were studied by means of combustion and some other physical methods.It was found that the moisture content of the load was higher than 60%,the content of inorganic matter was much higher than that of organic matter,and the water content of the filter surface was higher than that of the lower part of the filter,The ratio of organic matter on the upper part of the filter was less than that on the lower part of the filter in the load.