Study On The Effect Of Straw On The Passivation Of Heavy Metal In Anaerobic Fermentation Of Pig Manure

In recent years,with the development of domestic animal husbandry and the application of the method of mixed feed farming,some heavy metals have been added to animal feed to speed up the growth of livestock and poultry and prevent diseases.Most heavy metals can not be absorbed and discharged,resulting in increasingly serious pollution problems of heavy metals in livestock and poultry manure,which seriously affects the resource utilization of livestock and poultry manure.Anaerobic fermentation is an effective approach to treatment.In this paper,using pig manure as the processing object,the heavy metals Cu,Zn as the research object,by adding 2 kinds of different proportion of straw(corn straw,rice straw),according to the amount of corn straw and pig manure as 1:1.3,1:2,1:5;rice straw and pig manure as 1:0.8,1:1.5,1:3.At the temperature of 35 DEG,inoculum amount 30%,TS10%,pH 7 under the condition of anaerobic fermentation test.Using BCR sequential extraction method of speciation analysis of heavy metals,effects of different kinds and different amount of straw on biogas production,production of pig manure anaerobic fermentation methane content,heavy metal content,morphological changes and spectral characteristics before and after anaerobic fermentation residue.The aim of this study is to provide a scientific basis for the treatment of heavy metals in livestock and poultry manure.Through the above experimental research,the following main conclusions are drawn:(1)Adding straw during the anaerobic fermentation of pig manure will lead to delayed gas production and prolong the fermentation period,and increase total gas production and pool volume gas production rate.In adding corn straws,the cumulative gas production is the highest quality of corn straw and pig manure ratio of 1:1.3(C/N30)in the treatment group,the total gas production 14454mL,tank volume gas production rate can reach 0.34 m~3/(d?m~3).Rice straw and pig manure straw group,the mass ratio of 1:0.8(C/N30)in the treatment group the highest cumulative biogas production,total biogas pool 13791mL,volumetric gas production rate of 0.32 m~3/(d?m~3)than the same condition,treatment group add corn straw cumulative biogas yield higher.(2)Adding straw can reduce the content of heavy metals in the raw material fermentation,anaerobic fermentation biogas residue increased after heavy metal content,reduce the contents of heavy metals,increase the total content of heavy metals in biogas slurry.Add corn straw treatment group,treatment group of heavy metals Cu,Zn content increment for straw and pig manure ratio of 1:5(C/N20)treatment group were increased by 33.28%and 30.78%,rice straw and pig manure straw treatments,the mass ratio of 1:1.5(C/N25)treatment group Cu,Zn heavy metal content increment respectively,increased by 36.25%and 38.56%,the same C/N ratio,the increment of heavy metal content of rice straw treated more.(3)Before anaerobic fermentation,the heavy metal Cu in each treatment group was mainly reducible(37.40%to 51.76%),and the heavy metal Zn mainly existed in exchangeable state(40.91%~71.90%).After the anaerobic fermentation,the heavy metal Cu was mainly in oxidizable state(35.62%to 40.02%),and the heavy metal Zn still existed mainly in exchangeable state(37.40%to 57.31%),but the exchangeable proportion was reduced.After anaerobic fermentation,the proportion of heavy metals Cu and Zn decreased.In the treatment group adding corn straw,the proportion of the ratio of the heavy metal Cu and Zn in the 1:5(C/N20)treatment was the largest,which decreased by 21.04%and 12.94%,and the ratio of the mass ratio of the straw and pig manure in the rice straw treatment group was the proportion of the heavy metal Cu and Zn in the 1:1.5(C/N25)treatment group.The maximum degree is 24.09%and 8.21%respectively.Under the same C/N ratio,the proportion of heavy metal Cu in the rice straw treatment group decreased significantly in the same C/N ratio condition.Under the same C/N ratio,the proportion of heavy metal Zn in the corn straw treatment group decreased significantly in the same C/N ratio condition.(4)The passivation effect of heavy metals Cu in each treatment group was 26.39%to36.62%,and the passivation effect of heavy metal Zn was 1.44%to 16.09.Adding straw can improve the passivation effect of heavy metals Cu and Zn in pig manure.When the weight ratio of straw and pig manure was 1:5(C/N20),the effective passivation effect of heavy metal Cu and Zn was best,which could reach 35.57%and 16.09%.In the rice straw treatment group,when the mass ratio of straw and pig manure was 1:1.5(C/N25),the passivation effect of heavy metal Cu and Zn was best,which could reach 34.37%.8.94%,under the same C/N ratio,the effective effect of heavy metals Cu and Zn in corn straw treatment group is better.(5)Fourier transform infrared spectroscopy showed that before the anaerobic fermentation,the addition of straw had little influence on the infrared spectrum of pig manure,and the group had similar spectral characteristics.After anaerobic fermentation,the treatment groups were at 3408 to 3422cm-1 and 2850~2922cm-1,due to amides,carbohydrates,proteins,aliphatic compounds and methylene groups in carbohydrates.The decomposition of group compounds decreased,which resulted in the decrease of absorption peak intensity.At 1642~1653cm-1,the peak intensity of the absorption peak was increased due to the increase of aromatic,olefins and amides groups(humus).