牛粪好氧发酵挥发性物质排放特征及恶臭物质分析

不同原料好氧发酵产生的臭气物质组分和浓度存在差异。以牛粪和玉米秸秆为原料研究好氧发酵过程挥发性有机物（Volatile Organic Compound,VOCs）的产排特征及主要致臭物质,开展牛粪好氧发酵试验,采用气相色谱-质谱法分析测定发酵升温期、高温期、降温期及腐熟期等不同发酵阶段的VOCs组分和浓度,硼酸溶液吸收,盐酸滴定法测定NH3,便携式检测器（Tion NH3-H2S 300 G）测定H2S,3点比较式臭袋法测定不同发酵阶段臭气浓度。结果表明,牛粪好氧发酵过程中共检出31种VOCs,其中含硫化合物42种,醇类1种,酯类1种,酮类1种,卤代烃4种,苯系物9种,烷烃类8种,烯烃3种;在好氧发酵高温期臭气浓度最高为724（无量纲）,VOCs产生与排放主要在高温期。基于恶臭污染排放标准和恶臭物质气味活度值,并结合各物质检出率、GS-MS图谱及相关性分析,发现NH3、H2S、甲硫醚是牛粪好氧发酵过程的主要致臭物质;其次芳香族化合物对臭气浓度贡献也相对较大,应进行重点监测与控制。该研究可为牛粪好氧发酵过程臭气物质减控提供理论支撑。

Emission characteristics of volatile matter and identification of odor substances during aerobic fermentation of cattle manure

Abstract: In the aerobic fermentation process, a large amount of volatile organic compounds (VOCs) can be produced. They are harmful to human health, while cause environmental pollution, due mainly to the VOCs with the complex component can be important source of odor pollutants. The VOCs vary in a large difference, with various raw materials for aerobic fermentation. So far, there is no report on the emission characteristics of volatile substances that produced by aerobic fermentation of cattle manure. In this study, an aerobic fermentation test was carried out with a period of 30 days, in order to explore the production and emission characteristics of VOCs during aerobic fermentation process of cattle manure. An intermittent forced ventilation way was selected, where the ventilation volume was 10 L/min. The materials were mixed evenly, according to the fresh mass ratio of 18:6, and the mixture was put into the 60 L fermentation device. The C/N ratio of materials was 26:1, and the moisture content was about 62%. In addition, a gas chromatogram-mass spectrometry was used to analyze the components and concentrations of VOCs in different fermentation stages, such as mesophilic, thermophilic, cooling and maturity stage. Boric acid solution absorption and hydrochloric acid titration were used to determine the concentration of ammonia gas. A portable detector was selected to measure the hydrogen sulfide, whereas, three-point comparative odor bag method was used to determine the total odor concentration of different fermentation stages. The results showed that 31 kinds of VOCs were detected during the aerobic fermentation of cattle manure, including carbonyl sulfide, dimethyl sulfide, carbon disulfide, dimethyl disulfide, ethanol, ethyl acetate, acetone, tetrachloroethylene, chloroform, 1,2-dichloroethane, dichloromethane, benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene, m-ethyltoluene, p-ethyl toluene, 1,2,4-trimethylene, heptane, cyclohexane, hexane, 2-methylbutane, 2-Methylpentane, pentane, octane, methylcyclopentane, limonene, 2-methyl-1, 3-butadiene, a-pinene. The above 31 kinds of VOCs were divided into sulfur compounds, alcohol, ester, ketone, halogenated hydrocarbons, benzenes, alkanes, and alkenes, which were 4, 1, 1, 1, 4, 9, 8, and 3, respectively. In the high temperature period of aerobic fermentation, the emission of odor concentration was the maximum of 724, indicating the main period of generation and emission of VOCs. According to the emission standard of odor pollution and odor activity value (OAV), ammonia, hydrogen sulfide, and dimethyl sulfide were included and their OAV values were relatively high. In correlation analysis, the concentrations of ammonia and odor were showed highly significant positive correlation, while, hydrogen sulfide and dimethyl sulfide had no significant correlation with odor concentration, but the odor threshold of hydrogen sulfide and dimethyl sulfide was low, while, the OAV value was large. Sulfur compounds were normally important components of odor gas, suggested that ammonia, hydrogen sulfide, and dimethyl sulfide can be listed as the primary odorants in aerobic fermentation of cattle manure. In GS-MS spectrum and correlation analysis, the detection rates of aromatic compounds, such as ethylbenzene, m-xylene, p-xylene, and o-xylene, were about 100%, and positively correlated with odor concentration (P<0.05). Therefore, these compounds should be focused on monitoring and control. The finding can provide a sound theoretical support for the reduction and control of odorous substances in the aerobic fermentation of cattle manure.