Research On Mechanism Of Carbon And Nitrogen Transformation In Compost Habitat Drived By Advanced Persulfate Oxidation

Aerobic composting is an organic solid waste treatment method that uses microorganisms to realize resource reuse,but the degradation rate of lignocellulose is low in the traditional composting system.Persulfate is introduced to make up for the defects of traditional composting.To achieve better coordinated degradation of lignocellulose.In this study,using fresh dairy manure and bagasse pith as raw materials,a comparative experiment was conducted between the blank control group（CK group）and the experimental group with different levels of potassium persulfate（0.1%,0.5%,1%）.By comparing the temperature,moisture content,electrical conductivity,organic matter content,total potassium content and XRD analysis of the four groups,it indicated that 0.5%potassium persulfate（PS group）was the best addition ratio.In order to further explore the action mechanism of chemical additives in composting process,the basic physicochemical parameters,lignocellulose degradation rates,dissolved organic matter（DOM）content,humic substance（HS）formation and functional group changes in CK and PS groups were detected,and the effects of potassium persulfate on microbial community succession,carbohydrate active enzyme（CAZymes）composition and Kyoto Encyclopedia of Genes and Genomes（KEGG）function prediction during nitrogen transformation were investigated by metagenomics analysis.The results showed that autogenous heat of compost（>50°C）could activate persulfate to produce strong oxidizing sulfate radical（SO₄^-·）and increase the degradation rate of refractory substances.The degradation rates of cellulose,hemicellulose and lignin in PS group（61.47%,74.63%,73.1%）were higher than those in CK group（59.98%,71.47%,70.89%）,indicating that SO₄^-·attacking lignin structure for improving the accessibility of cellulase to promote the decomposition of lignocellulose.In addition,persulfate additives promoted the dynamic changes of DOM in composting and accelerated the formation of HS.The results of metagenomics analysis showed that the addition of persulfate changed the structure of microbial community in composting.The relative abundances of Actinobacteria and Proteobacteria in PS respectively increased by 17.64%and34.09%,while that in CK group increased by 12.09%and 29.96%.Glycoside hydrolases（GHs）and auxiliary activities（AAs）were relatively abundant in PS,which were the key functional enzyme to the degradation of lignocellulose.Furthermore,the influence of SO₄^-·on nitrogen biotransformation during composting was also discussed.The results showed that SO₄^-·guided the electron transfer during the biotransformation of NH₄⁺-N and NO₃^--N,destroyed the structure of extracellular polysaccharides（EPS）to promote the removal nitrogen process.Ammonia monooxygenase（AMO）and nitrate reductase（NR）showed interaction between microorganisms and substrates.Metagenomic analysis showed the difference of that nitrification and denitrification in microbial community composition and KEGG pathway.The correlation analysis between microbial community and environmental factors showed that Methanobrevibacter,Bacillus,Pseudomonas were closely related to nitrification and denitrification.This work is helpful to understand the effects of SO₄^-·on nitrogen cycling and retention during composting,as well as the possible nitrification and denitrification mechanisms.In summary,the introduction of potassium persulfate into compost system can regulate the degradation of lignocellulose and the formation of HS,which provided reference evidence for improving the growth and metabolism environment of microorganisms.Although it is not conducive to nitrogen retention,it provided a theoretical basis for SO₄^-·to participate in the process of nitrogen biotransformation.Moreover,a feasible resource utilization strategy of organic solid waste was proposed to improve the microhabitat,induce the succession of microbial community,thus accelerate the maturity and improve the quality of compost.