蔬菜废弃物两相厌氧发酵工艺产沼气试验研究

发布时间：2018-05-15 05:20

本文选题：蔬菜废弃物 + 两相　；参考：《沈阳农业大学》2016年博士论文

【摘要】：我国由于人口和饮食习惯等特点,蔬菜产量居世界首位。但是蔬菜在运输,加工过程中以及民俗等原因,产生的固体废弃物数量较大。传统填埋等方式容易造成二次环境污染,而且不能产生经济效益。而依据蔬菜废弃物中含有较高的可降解有机物,故采用厌氧发酵技术进行处理不失为一种环保、廉价、并具备社会和经济效益的双赢选择。而且对农业废弃物起到了资源再利用的作用。但是厌氧发酵技术目前存在厌氧消化装置和运行工艺简单,系统运行效率低及稳定性差等问题。本文就蔬菜废弃物沼气应用中含水量高等特点,构建了一套两相厌氧发酵系统,并以北方区域主要蔬菜废弃物为发酵原料,开展了以单一底物和混合底物进料的产酸、产甲烷特性研究。采用了新兴的高通量测序方法--miseq技术,对混合蔬菜废弃物两相内相关发酵微生物的种类、功能及丰度进行了分析。最后,考察了甲烷相出水两种回流方式对两相厌氧发酵产气的影响。结合北方区域季节蔬菜供给特征,选取纤维类白菜(低固含量)和淀粉类马铃薯(高固含量)两种蔬菜废弃物分别为单一底物进料,中温条件(35℃)的情况下,对两相物料发酵机理进行了详细的考察。当白菜废弃物为单一底物发酵时,产酸相末端发酵产物主要为四种主要短链挥发酸一乙酸、丙酸、异丁酸和丁酸,总浓度随着酸化时间的延长而逐渐增加,并在第5d达到8058 mg·L-1。其中,乙酸于第4d达到峰值4289 mg·Lq,产量占总挥发性脂肪酸的53.2%。甲烷相最佳有机负荷率为2.9kgVs·m-3 · d-1,日沼气产量达到最大值169 L,此时最大沼气产率为0.57m3·(kgVS)-1,发酵过程中甲烷含量最高值为68%。当马铃薯废弃物为单一底物进行发酵时,酸化相中四种主要挥发酸为乙酸、丙酸、异丁酸和丁酸,总VFAs浓度于酸化第3d达到12625 mg·L-1,同时乙酸含量达到最大值为7364 mg·L-1,产量占总量的58.4%。马铃薯废弃物对比白菜酸化速度快速且挥发酸含量高,甲烷相有机负荷率在3.6kgVS · m-3 · d-1时,沼气产率最高达到0.62m3·(kgVS)-1,日沼气产量最大值为213 L,最高甲烷含量为72%,超过此负荷后,日沼气产量和甲烷含量逐渐下降。当白菜和马铃薯废弃物不同比例在中温(35℃)进行酸化时,随着马铃薯废弃物的提高,挥发酸产物也在增加。当白菜和马铃薯废弃物两者比例为7：3时,甲烷相达到最大负荷为3.3kgVS ·m3·d-1;当两者比例为3：7时,甲烷相达到最大负荷为3.9kgVS·m-3 · d-1。采用混合蔬菜废弃物为发酵底物时,酸化相选取干物质浓度TS为8%和TS为12%的发酵原料均获得了较好的产酸效果,总挥发酸在第3d分别达到峰值为3215mg/L和5697mg/L。酸化相中通过miseq技术进行分析,结果主要包括厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、拟杆菌门(Bacteroidete),四者占细菌门类的93.2%。按照属的分类主要为互营假单胞菌属(Syntrophomonas)和梭状芽孢杆菌属(Clostridium),分别占比为29.16%和23.41%,两者为厌氧发酵过程中常见的水解和产酸菌群。乳酸杆菌属(Lactobacillus),在产酸相中占比为19.23%。酸杆菌属(Acidobacterium)占到12.15%。甲烷相的启动效果达到了预期目标,快速稳定的实现了产气,最佳有机负荷为3.9～4.3 kgVS·m-3·d-1时,相应最大日沼气和甲烷产量分别为0.69m3/kgVS、0.48m3/kgVS。日容积产气率最高为2.9 m3·d-1·m-3。混合蔬菜废弃物的有机负荷率、产气率和甲烷含量对比单一蔬菜废弃物发酵时均有所提高。产甲烷相中优势甲烷菌主要为专性嗜酸厌氧菌—甲烷球菌属(Methanococcus)和非专一底物兼性厌氧菌—甲烷八叠球菌属(Methanosarcina),还有少量专性嗜氢厌氧菌—甲烷囊菌属(Methanoculleus)。非甲烷菌属中,变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)和厚壁菌门(Firmicutes)为主要的群落构成,三门细菌占比全部细菌的72.95%。为研究回流对两相厌氧发酵的影响,采用两种回流方式即相同负荷和不同负荷下回流分别至酸化相和甲烷相进行考察。当甲烷相保持相同负荷为2.0 kgVS/m3/d时,25%的回流比至产酸相对两相厌氧消化、产气影响效果最佳,相分离的作用得到有效的发挥。此时,产酸相的水解酸化率最高,甲烷相产气率为119.6L,甲烷含量范围在65%-72%之间；相同负荷下回流至甲烷相时,回流比为55%的产气影响效果最好。此时,甲烷相平均日沼气产量达到最大值为109 L,甲烷含量在60%-65%之间。甲烷相在不同负荷下,相同回流比为55%回流到产酸相,有机负荷为3.0kgVS/m3/d时,甲烷相获得最大产气量为186.4 L,回流缓解了酸化相负荷较高时对产酸菌的抑制作用,促进了酸化底物的水解酸化；而回流比为55%回流到甲烷相时,随着有机负荷的提高,回流可以促进甲烷相的产气,但是对甲烷含量影响不大。在甲烷相负荷率为3.0kgVS/m3/d时,回流后日沼气产量达到181.6 L。
[Abstract]:Due to the characteristics of population and dietary habits, the production of vegetable is the first in the world. But the number of solid waste produced by the vegetables in transportation, processing and folklore is larger. The traditional landfill is easy to cause two environmental pollution and can not produce economic benefits. Anaerobic fermentation technology is an environmentally friendly, inexpensive, and win-win choice for social and economic benefits. It also plays a role in the reuse of resources for agricultural waste. However, anaerobic digestion technology has a simple anaerobic digestion and operation process, low operating efficiency and poor stability. In this paper, a set of two phase anaerobic fermentation system is built on the characteristics of high water content in the application of vegetable waste biogas, and the characteristics of methane production with single substrate and mixed substrate feed are carried out with the main vegetable waste in the northern region as the fermentation material. A new high throughput sequencing method --miseq technology is used. The species, function and abundance of the related fermented microorganisms in the mixed vegetable waste were analyzed. Finally, the effects of two reflux modes on the biogas production of the two phase anaerobic fermentation were investigated. Two kinds of fibrous cabbage (low solid content) and starch potato (high solid content) were selected in combination with the seasonal vegetable supply characteristics in the northern region. Under the condition of medium temperature (35 degrees C), the fermentation mechanism of the two phase materials was investigated in detail. When the cabbage waste was fermented by a single substrate, the end fermented products of the acid producing phase were mainly four main short chain volatile acid mono acetic acid, propionic acid, isobutyric acid and butyric acid, with the total concentration with the acidification time. Increasing and increasing gradually, and reaching 8058 mg / L-1. in 5D, the peak value of acetic acid at 4D reached 4289 mg. Lq. The optimal organic load rate of 53.2%. methane phase of total volatile fatty acids was 2.9kgVs. M-3 D-1, and the maximum value of daily biogas production reached 169 L, and the maximum biogas yield was 0.57m3. High value of 68%. when potato waste is fermented by a single substrate, four main volatile acids in acidified phase are acetic acid, propionic acid, isobutyric acid and butyric acid. The total VFAs concentration is 12625 mg. L-1 at the acidification 3D, while the content of acetic acid reaches the maximum value of 7364 mg. L-1, and the total yield of 58.4%. potato wastes is faster than the acidification speed of Chinese cabbage. When the content of the volatile acid was high and the organic load rate of methane phase was 3.6kgVS. M-3. D-1, the biogas yield was up to 0.62m3. (kgVS) -1, the maximum value of daily biogas production was 213 L, and the maximum methane content was 72%. After the load, the biogas production and methane content gradually decreased. When the different proportion of cabbage and potato waste was in the middle temperature (35 degrees C). With the increase of potato waste, the product of volatile acid increased with the increase of potato waste. When the proportion of Chinese cabbage and potato waste is 7:3, the maximum load of methane phase is 3.3kgVS m3. D-1. When the ratio is 3:7, the maximum load of methane phase is 3.9kgVS. M-3. D-1. using mixed vegetable waste as fermentation substrate. The acidification phase selected the dry matter concentration TS 8% and TS 12% to obtain the better acid production effect. The total volatile acid reached the peak value of 3215mg/L and 5697mg/L. acidification phase respectively through the miseq technology analysis, the results mainly include the thick wall bacteria gate (Firmicutes), the deformable bacteria gate (Proteobacteria), the acid bacilli gate (Acidobacteria). Bacteroidete, Bacteroidete, and the classification of 93.2%. in the category of bacteria are mainly Syntrophomonas and Clostridium (Clostridium), which are 29.16% and 23.41% respectively. Both are the common hydrolysate and acid producing bacteria in the anaerobic fermentation process. The Lactobacillus (Lactobacillus) and the acid producing phase are in the acid producing phase. The starting effect of the occupied ratio of 19.23%. acid bacilli (Acidobacterium) to 12.15%. methane phase reached the expected target, and the gas production was achieved rapidly and steadily. When the optimum organic load was 3.9 to 4.3 kgVS. M-3. D-1, the maximum daily biogas and methane production were 0.69m3/kgVS respectively, and the highest gas yield of 0.48m3/kgVS. daily volume was 2.9 m3. D-1. M-3. mixture. The organic load rate, gas production rate and methane content of vegetable waste were improved compared with single vegetable waste fermentation. The dominant methanogenic bacteria in methane producing phase were mainly specific eosinophilic anaerobes (Methanococcus) and non specific substrate facultative anaerobes - Methanococcus (Methanosarcina), and a small amount of specificity. Eosinophilic anaerobes - methanomonas sp. (Methanoculleus), non methanogens, deformable bacteria gate (Proteobacteria), acid bacilli (Acidobacteria) and thick walled bacteria (Firmicutes) constitute the main community. Three bacteria accounted for the 72.95%. of all bacteria to study the effect of reflux on two phase anaerobic fermentation, and two reflux methods were the same as negative. When the same load is 2 kgVS/m3/d, when the methane phase keeps the same load, 25% of the reflux ratio is relatively anaerobic digestion, the effect of gas production is the best, the effect of phase separation is effective. At this time, the hydrolysis acidification rate of acid producing phase is the highest and the methane production rate is 119. .6L, the methane content range is between 65%-72%; when the same load is reflued to the methane phase, the effect of the reflux ratio is 55%, and the methane phase average daily biogas production reaches 109 L, the methane content is between 60%-65%. The methane phase is under the different load, the same reflux ratio is 55% to the acid producing phase, and the organic load is 3.0kg At VS/m3/d, the maximum methane production was 186.4 L, and the reflux alleviated the inhibition of acid producing bacteria when the acidification phase was higher, and promoted the hydrolysis acidification of acidification substrate. While the reflux ratio was 55% to methane phase, the reflux could promote methane production with the increase of organic load, but it had little effect on the methane content. When the methane loading rate is 3.0kgVS/m3/d, the daily biogas yield reaches 181.6 L. after reflux.

【学位授予单位】：沈阳农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S216.4

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