Enhancement Of Humus Formation In Residue Compost By Fenton-Like And EM Microbial Agent

With the wide application of insects in the treatment of kitchen waste,a large amount of residue will be produced every year.If not properly disposed,it will cause environmental pollution.As an environmentally friendly treatment method,composting has an important environmental significance to solve the problem of residue.In order to solve the problem of difficult reaction and poor quality in the composting process of residue,the combination of Fenton-like reagent and EM（Efficient microorganism,EM）microbial agent was used in this study,which effectively shortened the composting time and improved the content and quality of humus.At the same time,this study compared the effects of Fenton-like reagent and EM microbial agent used alone and combined,and found that combined application could change the production sequence of Humic Substances（HS）to a greater extent and improve the efficiency of composting.X-ray diffraction,Fourier infrared spectroscopy and high-throughput sequencing were used to reveal the crystal structure,functional groups and microbial community changes during the humification process of residue compost.Finally,the compost product with the best rot evaluation was applied to cabbage planting.The main research results are as follows:（1）In the fertilizer process,Fenton-like reagent and EM microbial agent combined treatment（MF）,EM microbial agent treatment（M）and Fenton-like reagent treatment（F）were heated faster than blank treatment（CK）,and the peaks of MF and M were higher,61.4℃and59.4℃,respectively.All treatments could kill pathogens and parasites.The initial pH of the compost is 7.52-7.65（the optimum pH is 6.50-8.00）,there is a brief downward trend midway,and the pH at the end of the compost is 8.05-8.27（the standard reference value is 6.00-9.00）.The turning point of the MF and F groups is different from that of the other two groups.The pH turning point of group F appeared later than that of other groups.The Eh value of all treatment groups decreased,and the reductivity of compost substances gradually increased.MF was the first to reach the lowest value of-46.70 m V,followed by M group,with the lowest value of-45.17 m V.（2）The organic matter degradation rates of M,MF,F and CK were 11.55%,8.72%,8.49%and 6.15%,respectively.Total nitrogen（TN）increased slightly with compost reduction.On the 28th day of composting,the C/N of MF,M and F decreased to 13.13,14.03 and 16.63,respectively,and all entered the rot stage in advance.MF had the most obvious effect on accelerating the composting process.After composting,the humic substances（HS）content of MF,M and F increased by 26.44,21.83 and 12.26 g/kg,respectively,and fulic acid（FA）decreased by 13.38,8.69 and 10.27 g/kg,respectively.The humic acid（HA）increased by 39.82,30.52 and 22.53 g/kg,respectively.In contrast,the HS of CK group decreased by 7.20 g/kg after 42 days of composting,which did not reach the process of assembling small molecule FA into HA.After composting,the humification polymerization indexes of MF,M,F and CK were1.61±0.08,1.39±0.05,1.28±0.01 and 0.89±0.01,respectively.The results showed that the humification effect of MF was the best,followed by M and F.（3）All the four composting methods can change the complete rigid structure of residue surface,and F and MF are more destructive.X-ray diffraction peak and Fourier infrared spectra showed that Fenton-like reagents had better degradation effect on cellulose.In addition,the absorption peaks of F,MF and M groups at 2925 cm^-1 and 2855 cm^-1 were significantly weakened,while the absorption peaks at 1640 cm^-1 were preserved or even enhanced.It can be seen that both Fenton-like reagents and EM microbial agent promote the degradation of macromolecular compounds and synthesize HA.In contrast,EM microbial agent have a better effect on the formation of highly aromatic HS than Fenton-like reagents,and Fenton-like reagents have a stronger ability to degrade refractory fibers.（4）The Alpha diversity index of MF,F and M decreased in the early stage,but the microbial diversity was higher than CK in the middle and late stage.All the three exogenous additives had effects on the abundance and richness of bacteria in the reactor,and the bacterial communities were significantly different among the groups（p<0.001）,the M and MF groups were the most,and the difference tended to be stable in the maturation stage.At the gate level,Fenton-like reagents adjusted the relative abundance of Bacteroidetes,Proteobacteria and Firmicutes,which decreased the abundance of Bacteroidetes and Proteobacteria in F and MF in the early compost period.The relative abundance of Firmicutes increased during the whole composting process,which was closely related to the oxidation tolerance of firmicutes.The species abundance of MF was the highest in the middle and late compost.The combined addition of EM microbial agent and Fenton-like reagents could improve microbial diversity and assist microbial colonization.At the genus level,the abundance of bacteria in different stages varied greatly.The stable bacteria mainly from Gracilibacillus and Brevibacterium predominate in M,F and MF,and contribute to the degradation of lignocellulose.In the middle and late stages of the compost,the number of Alcanivorax in MF and M decreased by 6.45%and 3.22%,respectively,compared with CK,which was conducive to the formation of HS.The abundance of Altibacter in MF was less than that in the other three groups,indicating that the humus formed by MF group was not easy to be decomposed by bacteria.（5）In the F and MF groups,Firmicutes had a strong correlation with FA and HA with HS.The addition of Fenton-like reagents changed the metabolism of the flora,resulting in a large amount of small molecules of FA in the early stage,and then formed HA.A similar effect was achieved in group M with EM microbial agent alone.In addition,random forest and Spearman correlation analysis were used to identify microorganisms that could distinguish F,M,MF from CK,and most of these bacteria genera were related to FA generation.Marinobacter and Alcaligenes were positively correlated with HA（p<0.05）;Seven genera including Virgibacillus,Alcanivorax and Lentibacillus were negatively correlated with HA（p<0.05）.（6）The length and fresh weight of the edible part of Chinese cabbage were increased by1.49 and 2.64 times respectively at 2%MF compost,and the best effect was obtained at 2%MF compost.In addition,different proportions of compost had positive effects on chlorophyll a,chlorophyll b and carotenoid content of Chinese cabbage,but had no obvious effect on soluble sugar content.In practical application,the quality of cabbage is better when the amount of compost is 2-5%.