| The rapid development of economy and society has led to a large number of direct discharge of sewage and a large number of black and smelly water bodies.Its effective treatment has become an important work of ecological civilization construction in China.It is found that traditional treatment methods have many defects due to the complexity of black and smelly water.Microbial agent method has been gradually recognized for its strong adaptability,rapid reproduction and effective removal of pollutants.In particular,the technology of combining iron and carbon carriers with microorganisms has attracted widespread attention.In this paper,the iron-carbon carrier combined with Bacillus subtilis was selected to purify the bottom mud and overlying water of the black odorous river,which was tested and further studied,providing technical support and theoretical basis for the in situ treatment of the bottom mud and overlying water of the black odorous river by micro-electrolysis of iron-carbon carrier coupled with Bacillus subtilis.Firstly,we used the control variable method to carry out a single factor test to study the treatment effects of iron and carbon carrier amount,aeration rate and Bacillus subtilis amount on black sediment and overburden water.Then,the most appropriate amount of different combinations of methods were compared to analyze the purification effect of black sediment and overlying water and the changes of sediment microbial community.Finally,the synergistic purification mechanism of iron-carbon packing carrier without adding concentration,aeration and Bacillus subtilis alone as well as coupling method was explored,and the following conclusions were obtained:（1）Single factor addition test results:When the dosage of iron and carbon filler was 20 g/kg,aeration was 25 m L/min,and Bacillus subtilis was 15 mg/L,Overlying water chemical oxygen demand（COD）,ammonia nitrogen（NH4+-N）,total nitrogen（TN）and total phosphorus（TP）are significantly decreased,dissolved oxygen and reoxygen-reduction Potential are significantly increased,the transparency of river water is greatly improved,and black odor is basically eliminated.Organic pollution and nitrogen and phosphorus in the sediment were also obviously removed.（2）The results of different combinations of iron-carbon+Bacillus subtilis,iron-carbon+aeration,Bacillus subtilis and iron-carbon+aeration+Bacillus subtilis showed that:The effects of iron-carbon composite Bacillus subtilis and aeration on the treatment of black sediment and the purification of overlying water are obviously better than those of other combinations.After 21d of continuous operation,the COD,NH4+-N,TN and TP of overlying water decreased to 21.38 mg/L,0.91 mg/L,7.58mg/L and 0.35mg/L,respectively.The removal rates were 70.88%,95.91%,3.67%and 80.66%,respectively.After 21 days,the total organic matter（DTOC）,total nitrogen（DTN）and total phosphorus（DTP）decreased to 30.36 mg/g,2.63 mg/g and3.33 mg/kg,respectively.Removal and conversion were 55.27%,55.35%and 63.73%,respectively.（3）The Shannon index of microorganisms in the coupled treatment group was4.649,which was lower than that in the blank control group and the other combined treatment groups,and the Simpson index was 0.0208,which was higher than that in the other combinations and the blank control group,indicating that the coupled method would not have adverse effects or microbial safety risks on the original black sediment microbial community.In the water samples of the coupled system,Proteobacteria was the most dominant phyla,while Chloroflexi,Bacteroidetes and Firmicutes were numerically dominant phyla.Proteobacteria is a microorganism commonly used in the treatment of complex organic macromolecular compounds in wastewater.Chloroflexi is a typical bacterium of complex organic matter in anaerobic wastewater treatment system.Bacteroidetes and Terrumicrobia have the functions of nitrogen fixation,methane oxidation and polysaccharide degradation.Firmicutes is a kind of denitrification resistant bacteria which can remove specific organic pollutants.Acidobacteria are the dominant bacteria in sediment.Actinobacteria play an important role in nitrogen cycling in nature,as well as organic matter decomposition and phosphorus mineralization.Compared with the blank control group,the abundance of the above functional flora（phyla）was significantly increased in the four experimental groups.Iron carbon particles,bacillus subtilis and aeration method collaborative purification mechanism include:1)the iron carbon micro electrolysis reaction,ferrous iron ions and reduction of hydrogen[H],and provides the denitrifying electron donor,oxidation reduction to remove carbon,organic matter and generation of iron,ferrous ion and phosphate ions,formation of iron phosphate phosphorus removal in wastewater;2)Activated carbon adsorbed pollutants efficiently,and iron-carbon particles provided a good carrier for microbial degradation of Bacillus subtilis.3)Aeration significantly improved the dissolved oxygen level in water,accelerated aerobic and microelectrolysis reactions,and promoted the transformation of anaerobic and anoxic microorganisms into aerobic in bottom mud,creating a virtuous cycle system. |
