硼泥对猪粪厌氧发酵重金属铬及其光谱特性的影响

Effects of boron mud on anaerobic fermentation of heavy metal chromium and its spectral characteristics in pig manure

随着含有重金属添加剂饲料的使用,规模化养殖场畜禽粪便中重金属含量增加。为减少重金属的危害,该文以猪粪为发酵原料,重金属Cr为研究对象,硼泥为钝化剂,在接种物量为30%、TS为10%、温度为35℃、pH值为7的条件下进行40 d厌氧发酵试验。研究添加2.5%、5.0%、7.5%3种比例的硼泥对猪粪厌氧发酵中重金属Cr的形态变化、有效态钝化效果及发酵前后沼渣光谱特征的影响,采用BCR连续提取法(European community bureau of reference sequential extraction)分析重金属Cr的形态变化,采用傅里叶红外光谱(Fourier transform infrared spectrometer, FTIR)对物料光谱特征的变化进行研究。结果表明:猪粪厌氧发酵过程中添加硼泥有利于重金属Cr从有效态转化为稳定态,当添加7.5%硼泥处理时有效态Cr转化为稳定态Cr的效果较好;猪粪在厌氧发酵过程中添加硼泥能提高重金属Cr的钝化效果,且随着硼泥添加量的增加,钝化效果越好;通过显著性分析,添加7.5%硼泥处理时钝化效果较好,达到63.79%,显著优于猪粪单独发酵和添加2.5%与5.0%硼泥的处理(P<0.05);FTIR显示厌氧发酵后,沼渣中酰胺化合物、碳水化合物、蛋白质、脂肪族化合物等有机物分解减少,芳香族等腐殖质增加,且添加7.5%硼泥时有机物腐殖化程度最好。因此猪粪在厌氧发酵过程中添加适量硼泥,可以降低沼渣中重金属Cr的生物有效性,促进有机物转化为腐殖质,研究结果可为减少猪粪中重金属的有效性和提高厌氧发酵质量提供参考。

In recent years, with the development of Chinese animal husbandry, some heavy metals have been added to animal feed to speed up the growth of livestock and poultry and prevent diseases. But most heavy metals can not be absorbed and digested, 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 deal with manure pollution. In this paper, using pig manure as the processing object, the heavy metals Cr as the research object, by adding different amounts of boron mud(boron content is 2.5%, 5%, 7.5% of dry matter content) The anaerobic fermentation period is 60 days, fermentation temperature is of 35℃, inoculum quantity is of 30% fermentation raw material, total solid is of 10% and p H value is of 7. The speciation analysis of heavy metal Cr are analyzed by BCR sequential extraction and the spectral characteristics of biogas residue before and after anaerobic fermentation are studied by Fourier transform infrared spectroscopy(FTIR), effects of different amount of boron on morphological changes, effective passivation effect 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) After the end of anaerobic fermentation, the effective content of heavy metal Cr in each treatment decreased. The effective state of heavy metal Cr decreased by 6.06 percentage points in pig manure alone, and the effective content of heavy metal Cr in pig manure added boron decreased by 11.33 percentage points, 13.40 percentage points and 14.98 percentage points, respectively. It is indicated that the anaerobic fermentation of pig manure and boron is beneficial to convert the heavy metal Cr from the effective state to the stable state. With the increase of the added amount of boron, the proportion of the effective Cr content to the total content of heavy metals is lower. The proportion of heavy metal Cr in the treatment of pig manure added with 7.5% boron is relatively large. 2) The passivation effect of the effective form of heavy metal Cr in pig manure alone was 24.17%, and the effective passivation effect of heavy metal Cr in pig manure was 44.32%, 55.38% and 63.79%, respectively. It is indicated that the anaerobic fermentation of pig manure added boron is beneficial to improve the passivation effect of heavy metal Cr. With the increase of boron addition, the passivation effect of heavy metal Cr is better. The significant analysis showed that the anaerobic fermentation of pig manure added boron had significant difference in the passivation of heavy metal Cr(P<0.05). The passivation effect of pig manure added with 7.5% boron was better than other treatment groups, and the difference was significant(P<0.05). 3) Fourier infrared spectroscopy showed that the materials of each treatment group had similar spectral characteristics before and after anaerobic fermentation. After anaerobic fermentation, the relative intensity of the absorption peaks of the biogas residue of each treatment group decreased at 3 408-3 450 and 2 850-2 922 cm-1, indicating that the organic matter such as amide compound, carbohydrate, protein, and aliphatic compound in the biogas residue were decomposed and reduced. The absorption peak intensity increased, indicating that the olefins, aromatic compounds and other substances in the biogas residue increased. The addition of boron during the anaerobic fermentation of pig manure is beneficial to the reduction of organic matter content, the increase of humus content, and the humification degree of organic matter is better when the amount of boron sludge is 7.5%. Adding an appropriate amount of heavy metal passivating agent to the anaerobic fermentation of pig manure can reduce the effectiveness of heavy metals in the biogas residue and the risk of heavy metal pollution.