| In the context of environmental pollution and energy shortages,the resource utilization of pig manure has attracted much attention.The use of pig manure for anaerobic fermentation and bio-energy production has important practical significance.This study is based on the principle of anaerobic fermentation,using pig manure as the fermentation raw material,through the addition of Fe,Co,and Ni elements,to explore the relative optimal dosage of Fe,Co,and Ni.The effect of three kinds of trace elements on pollutant removal,gas production process and stability in anaerobic fermentation process.At the same time,used high-throughput sequencing technology to concluded the microbial community changes and diversity in the anaerobic fermentation tank after puting trace elements,and reveal the influence of Fe,Co,and Ni on the microbial activity and community structure in the anaerobic fermentation process.The experimental research obtained the following results.（1）The relative optimal dosages of Fe,Co and Ni in the process of anaerobic fermentation of pig manure are:10mg Fe/L,1.5mg Co/L,0.8mg Ni/L,the optimal dosages of mixed Fe,Co and Ni is 9mg/L,1mg/L and 0.7mg/L.（2）The COD removal rates of the three elements,Fe,Co,Ni and blank experimental group reached 93%,90%,87%,89%and 74%,respectively.Biogas production was 65.49,32.28,41.23,58.89 and 34.86 m L·g-1·ts-1,respectively.The percentage of methane were 79.67%,71.89%,72.96%,75.69%and 64.71%,respectively.（3）At the end of the anaerobic reaction,the dominant form of Fe,Co and Ni was transformed from soluble state to carbonate state.Co mainly existed in the form of organic matter,while the soluble form of Ni was still the dominant form.The difference was that after the experimental fermentation of single Ni element,it mainly existed in the form of carbonate.The results indicated that the utilization rate of trace elements was reduced in the later stage of anaerobic reaction,and there was no interaction between elements to affect their morphology.（4）The addition of Fe,Co and Ni would increase the abundance of Firmicutes and make it the dominant bacterium,while inhibit the abundance of Bacteroidetes,and Fe would contribute to the increased metabolism of Proteobacteria.At the subordinate level,Fe,Co and Ni can promote the abundance of B.methaneae.Fe and Ni had a slight inhibitory effect on the proliferation metabolism of methaneocadiococcus,while the synergistic effect of Fe,Co and Ni could promote the proliferation and metabolism of methaneocadiococcus.The effluent of anaerobic fermentation of pig manure with Fe,Co and Ni elements was aerobic treated,and the COD removal rates of the effluent with Fe,Co and Ni elements added alone or mixed with Fe,Co and Ni elements were 72%,66%,69%and74%,respectively.The removal rates of ammonia nitrogen were 71%,62%,45%and73%,respectively.The total nitrogen removal rates were 66.46%,58%,39%and 69%,respectively.The total phosphorus removal rates were 36.48%,35%,34%and 38%,respectively.The effluent quality can reach GB18596-2001.The use of the addition of Fe,Co,and Ni elements not only improves the anaerobic methane gas production and substrate degradation rate of pig manure,enriches the diversity of microorganisms,but also promotes the anaerobic fermentation of the biogas slurry through aerobic treatment to meet the discharge standards.The scientific addition of trace elements is of great significance for improving the gas production efficiency of anaerobic fermentation of pig manure and increasing its substrate removal rate.This study has guiding significance for the practical application of biomass fermentation technology and the treatment and disposal of pig manure. |
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