【作者】 宋丽；

【导师】 李秀金；

【作者基本信息】 北京化工大学 ， 环境科学与工程， 2010， 硕士

【摘要】 蔬菜废物具有产生量大、含水率高、挥发性固体含量高、易于生物降解、无毒和产生较为集中等特点,对其进行合理处置具有重要意义。而厌氧消化作为一种环境友好、经济可行的高效生物处理技术,为实现果蔬废物的减量化、资源化和无害化提供了有效途径。本研究以北京化工大学学生食堂择菜过程中产生的蔬菜废物作为研究对象,结合国家科技部863重点项目生物质垃圾厌氧消化关键技术研究(2008AA062401),针对蔬菜废物成分复杂、非均质、非连续和半流动等特性,采用两级强化水解分路厌氧消化的技术路线,分别研究了中温条件下,基质微生物比(F／M)对蔬菜残渣酸化的影响和蔬菜汁的厌氧消化产气性能。在负荷为4gVS·L-1、6gVS·L-1和8 gVS·L-1情况下,分别考察了F/M(VS/VS)=0.5、1.0、1.5、2.0、2.5、3.0和无接种7种情况对于蔬菜残渣的影响,发现当F／M≤1.0时,反应体系以产甲烷为主,有机酸积累情况不明显；当F／M>1.0时,反应器内发生不同程度的挥发性脂肪酸积累,使反应器内产气量降低,反应器内反应以水解酸化为主。未接种的情况下,虽然在实验过程中发酵液的pH均最低,但是其挥发性脂肪酸酸浓度均较低。实验证明F／M对蔬菜残渣厌氧消化产物的影响较为显著。通过控制反应体系进料时的F／M可以影响厌氧消化反应体系的进程。在负荷为80gVS·L-1情况下,考察了F/M(VS/VS)=3.0、6.0、9.0和无接种4种情况对于蔬菜厌氧消化过程的影响,发现F／M在3.0-9.0之间变化对蔬菜残渣水解酸化反应影响不大,经过接种的体系的有机酸产量分别为13457、11624和11480 mg·L-1,均高于未接种的体系。在对蔬菜残渣进行厌氧酸化实验研究之外,又进行了蔬菜汁的序批式厌氧消化实验,以验证其产气性能并确定最佳工艺参数。通过150d蔬菜汁厌氧消化实验得出蔬菜汁厌氧消化产气性能良好,其最佳有机负荷为8.0 gVS.L-1·d-1,单位负荷产气率高达860 mL·gVS-1,甲烷含量为65%左右,出水COD低于2800 mg·L-1, COD去除率持续维持在95%左右,有机氮去除率维持在85%以上,达到了很好的处理效果。负荷更高的情况下导致物料不能够被完全消耗,单位负荷产气率、COD去除率下降等现象；反应器内氨氮浓度处在1348 mg·L-1到2383 mg·L-1之间,没有抑制现象发生。同时,实验发现,在进料有机负荷相同的情况下,物料成分以及水力停留时间的差异对产气量的影响不大,故可采用基于VS的单位负荷产气率作为表征厌氧消化产气性能的指标。本论文深入研究了蔬菜废物经过固液分离后菜渣和菜汁的强化酸化工艺参数和产甲烷工艺参数,为蔬菜废物的两级强化水解厌氧消化处理技术路线提供了实验依据。更多还原

【Abstract】 As the world’s largest agricultual country, China is encouraging the famers to build more centralized vegetable processing facilities to prepare semi-finished or "cleaned" products for city residents. In year 2009, there were approxiamately 100 million tons of vegetable waste produced in this process. With the characteristics of high moisture content and degradability, vegetable waste gives a lot of pressure to the waste disposal unit. However, this large amount of waste has the potential to be used as the feedstock of industrial anaerobic digestion because the volatile solids content is relatively high. Moreover, the digestate also could be used as soil amendment because of the low toxicity. Anaerobic digestion is a kind of environment-friendly, economic-viable and highly effective biological treatment technology. It has proved an effective way to carry out reduction, recycling and harmles sness of fruit and vegetable waste.Funded by the China National "863" Project "the key technology of the anaerobic digestion of biomass (case number:2008AA062401)", the study discussed in this thesis conducted lab scale batch and sequence-batch anaerobic digestion on vegetable wastes and investigated the optimal paramenters for digestion. The feedstock was collected from the dinning house in Beijing University of Chemical Technology and grinded to get the solid fraction (residue) and liquid fraction (juice) separately. As the vegetable waste was heterogeneous, a new method, called two-step strengthened hydrolysis anaerobic digestion, was developed to enhance the degradation of the solid fraction in vegetable. Under mesophilic condition(35℃), batch and sequence-batch anaerobic digestion were carried out to determine the effect of food-microorganism (F/M) ratio on hydrolysis and acidification of vegetable residue and the performance of anaerobic digestion of vegetable juice, respectively. The organic loading rates used in the batch digestion were 4gVS·L-1、6 gVS·L-1 and 8 gVS·L-1, respectively. Six kinds of F/M ratios were 0.5,1.0,1.5,2.0,2.5 and 3.0, respectively. Also, a blank trial was carried out without inoculums to test the self-degradation or the original microorganisms in the feedstock. As the result, methanogenesis was the main reaction in the system when F/M≤1.0. A significant step of hydrolysis reaction was not observed in the digestion system; when F/M> 1.0, various degrees of hydrolysis reaction were observed in the different digestion systems, for example the gas production reduced and effluent pH decreased. Although the effluent pH of blank trial was the lowest, the concentration of the volatile fatty acid was not as high as that of the other trials. The above results proved that the effect of F/M on the acidification of vegetable residues were significant. The process of anaerobic digestion could be affected by controlling the F/M of the system. At the organic loading rate of 80 gVS·L-1, four F/M ratios as of 3.0、6.0、9.0 and blank were investigated to find out the effect of inoculum on hydrolysis and acidification of vegetable residue at high organic loading rate. The results showed that when F/M was in the range of 3.0-9.0, the effect of F/M on hydrolysis and acidification of vegetable residue was not significant. The concentration of volatile fatty acid of these three conditions with inoculum were 13457、11624 and 11480 mg·L-1, respectively, higher than the condition without inoculum.Besides the study of the effect of F/M on hydrolysis and acidification, sequence-batch digestion experiments were carried out to determine the performance of anaerobic digestion of vegetable juice and the optimal process parameters. Anaerobic digestion of vegetable juice through an 150 days experiment showed that anaerobic digestion of vegetable juice has good performance, The optimal organic load rate was 8.0 gVS·L-1·d-1, the biogas yield was as high as 860 mL·gVS-1, the methane content was around 65%, the COD concentration of the effluent were lower than 2800 mg·L-1, COD removal efficency remained at about 95%, organic nitrogen removal efficency kept more than 85%. A higher organic loading rate of 8.5 gVS·L-1·d-1 lead to an overload. The substance was not adequently degraded and the biogas yield and COD removal efficiency decreased respectively. The concentration of ammonia in reactor was in the range of 1348-2383 mg·L-1. No inhibition was observed. The difference between the biogas yield of various vegetable juice samples and HRTs at the same OLR was small. As a conclusion, the VS of the feedstock could be used as a performance indicator of the biogas potential of certain materials.This study was carried out to determining the optimal process parameters of strengthened hydrolysis and anaerobic digestion of vegetable residues and juices. It has provided an experimental basis for an enhanced two-phase anaerobic digestion of vegetable waste.更多还原