Study On The Promotion Of Microbial Reduction Of Cr(?) By Humic Subtance In Livestock Manure Compost

Composting has become an environmentally friendly and economically feasible and effective method for processing livestock and poultry manure.The livestock and poultry manure compost product can be used to repair and improve the soil and accelerate the migration and conversion of pollutants.The humus produced during the composting process contains abundant active functional groups,has strong redox ability,and can act as an electronic shuttle to promote the reduction of pollutants,thereby changing the form of pollutants in the environment and reducing their toxicity.In this study,chicken manure,pig manure and rice bran were used for mixed high-temperature aerobic composting.Compost samples were collected at different periods to analyze the changes in conventional physical and chemical indicators during the composting process.The compost humus was then extracted and purified into humic acid(HA)and fulvic acid(FA),electrochemical analysis and spectroscopic analysis of HA and FA.Carry out research on the performance of compost humus to promote the reduction of Cr(?)by microorganisms,and analyze the influence of the electron transfer ability and composition structure of compost humus on the reduction ability of Cr(?).The following main results have been achieved:Analyzing the physical and chemical indicators of chicken manure and pig manure compost,the basic physical and chemical properties of the two types of compost are very similar,and both can reach the harmless standard,but the time,speed and amplitude of the change are slightly different.The organic matter of chicken manure and pig manure compost was reduced from initial 79.24% and 63.84% to final 61.58%and 50.63% respectively.The organic matter was decomposed in large quantities under the action of microorganisms;the GI values of the two types of compost reached 90.91%and 109.35% respectively at the end.The GI values are all over 80%,and the compost product is basically non-toxic to seeds.The electron transfer capacity and composition structure of HA and FA of chicken manure and pig manure compost are analyzed.The electron transfer capacity(ETC)of HA and FA of the two kinds of composts are generally increasing,and the change trend of the component structure is also similar.The aromaticity of HA in the two composts is higher than that of FA,but the content of oxyalkyl and carboxyl functional groups in FA is greater than that of HA.As the composting process progresses,the simple carbohydrates,fats,protein-like substances and amino acids in the two compost materials are gradually converted into humus-like substances,and their molecular weight,degree of polymerization,aromaticity and degree of humification have been greatly improved.HA and FA can act as electron shuttles,mediate the transfer of conductors between MR-1 and the final electron acceptor,and effectively promote the reduction of Cr(?).HA and FA contain redox functional groups such as hydroxyl,carboxyl and quinone groups,which have the ability to reduce and transform Cr(?).Their content will also affect the reduction of Cr(?),and HA and FA in the compost maturity period can be more effective promote the reduction of Cr(?)by microorganisms.