【作者】 夏芳芳；

【导师】 吴祖成； 何若；

【作者基本信息】 浙江大学 ， 环境工程， 2014， 博士

【摘要】 垃圾填埋处理过程产生的还原态硫化物是导致填埋场恶臭污染的主要原因,其中的H2S在还原态硫化物中占主导地位,是该类物质浓度和流量的敏感指标,因此,H2S减排对填埋场恶臭污染控制具有重要意义。填埋场覆盖土层是“填埋气(Landfill Gas, LFG)-大气”体系的环境界面,当LFG通过覆盖土层进入大气时,其所含的H2S会在覆盖土层的物化和生物作用下被去除。生物覆盖土是一种类似腐殖质的物质,在CH4氧化和减排方面具有优良性能,但目前关于其在H2S净化性能方面的研究鲜有报道。鉴于此,本论文以生物处理后的垃圾为材料,制备了垃圾生物覆盖土(Waste Biocover Soil, WBS),考察其对H2S的去除和影响因子,并构建了模拟土柱和垃圾填埋场反应器,探究了WBS作为新型的填埋场覆盖材料对LFG中H2S的净化作用和机理,获得如下主要研究结果：(1)考察和检测了垃圾填埋场现场大气中H2S的浓度和排放量,获得了实际运行中的不同年龄填埋场的H2S排放规律。在填埋场中,H2S的排放量和大气中H2S的浓度范围分别是141-9854μgm-2d-1和4.4～261μg m-3。填埋场覆盖土呈现出较强的硫氧化能力和硫酸盐还原能力,且两者分别与其中的硫氧化细菌(Sulfur Oxidizing Bacteria, SOB)和硫酸盐还原菌(Sulfate Reducing Bacteria, SRB)的数量有一定相关性。填埋场覆盖土中主要的SOB有Halothiobacillus、Rhodothalassium、Paracocccus、Allochromatium和Thiobacillus;主要的SRB有Desulfovibrio、Syntrophobacter、Desulfomonile和Desulfobacca。在覆盖土的pH、含水率、有机质及含硫化合物含量等理化指标中,pH值是影响其中SOB和SRB群落结构分布与丰度的最主要因素。(2)制备了WBS,对比于填埋场覆盖土(Landfill Cover Soil,LCS)、桑园土和砂土,WBS对H2S具有较高的吸附脱除性能。WBS组成影响实验研究表明,粒径是影响WBS吸附脱除性能的主要因素,其次是含水率和pH。WBS脱除H2S的最佳条件为：原始pH值(7.9)、含水率40%和粒径≤4mm。在温度为4-45℃和O2浓度为0%-21%(v/v)时,WBS对H2S吸附脱除量随着温度和02浓度的增加呈先升高后降低的趋势,在35℃和O2浓度为10%(v/v)时分别达到最大吸附脱除量,分别为55.6±5.0mgkgd.w.-1和59.6±1.3mg kg d.w.-1。当H2S顶空浓度为0.1%-10%(v/v)时,WBS对其吸附可在2-3h内达饱和,且随着H2S浓度的增大,吸附饱和时间延长。(3)探究了WBS的矿物质组成,主要有石英、莫来石(硅酸铝)、钠长石、白云母、白云石、方解石等。WBS中水分和硅酸铝对其吸附脱除H2S有较大贡献,分别可占36.9%和24.9%,其后,依次是石英砂(1.6%)>钠长石(1.5%)>白云母(1.1%)>方解石(0.7%)>腐殖质(0.4%)>白云石(0.3%)。在低温及中温条件下(≤30℃),WBS对H2S的硫有较好的吸附保持能力；当温度达到45℃时,WBS上层含水率的急剧降低使其吸附的H2S在120h内完全释放或转化,但下层仍有88.6%的吸附硫残余量。此外,酸性降水(pH=3.5～6.0)可短期内(12～36h)使WBS的吸附硫几乎全部释放或转化,但酸的种类(H2SO4和HNO3)和pH对吸附硫的释放或转化无显著影响。(4)探索了WBS土柱对模拟LFG中H2S的净化特性,结果表明,暴露于含H2S的LFG后,WBS和LCS的硫氧化能力、硫酸盐还原能力和硫化物含量都出现了增长。相较于LCS, WBS具有较高的硫氧化和硫酸盐还原能力。在土柱运行结束时(第35d),WBS下层的硫氧化潜力达到最大值(82.5±7.9μmol g d.w.-1d-1),为LCS的4.3～5.4倍；此时,WBS上、中、下层土样的CH4氧化活性分别是LCS对应层土样的3.1、3.5、6.6倍。与LCS相比,WBS对H2S和CH4具有更强的净化性能,是一种可有效减少LFG中污染物排放的填埋场覆盖材料。(5)分析了WBS和LCS土柱层中微生物群落结构,结果表明,WBS和LCS中主要的优势微生物是Proteobacteria、Firmicutes和Bacteroidete。暴露于含H2S的LFG后,WBS中的微生物多样性指数出现了下降,而LCS中却有所升高。在WBS和LCS中参与硫代谢的微生物主要是Proteobacteria和Firmicutes门微生物,包括Ochrobactrum、 Paracoccus、Comamonas、Pseudomonas、Enterobacteriaceae、Acinetobacter,以及Firmicutes门的Bacillus (Bacilli)和Clostridium (Clostridia)。(6)研究了在填埋场稳定化过程中WBS作为新型覆盖材料对H2S的净化效果。在模拟垃圾填埋场反应器中LFG的产生量和气体组分随垃圾填埋时间的增长呈动态变化。由于填埋垃圾异质性高,不同反应器产生的LFG中H2S浓度相差较大,其随时间的变化波动也较大。在整个实验运行过程中WBS和LCS对H2S的去除率均保持在90%以上。含H2S的LFG持续通入,有效地刺激了WBS中好氧异养细菌、放线菌、真菌以及SOB和SRB的生长,而LCS土样中微生物数量增长较少,在LCS下层中放线菌、真菌和SRB甚至出现了下降。这表明,WBS中的微生物对H2S的毒害不仅有更高的耐受性,而且可以在其中生长繁衍并将H2S转化和脱除。WBS和LCS中硫化物含量和pH分析表明,LCS对H2S的去除主要是吸附作用,而WBS不仅能吸附H2S,而且具有较高的生物硫代谢活性,促进了其中H2S的转化和脱除。更多还原

【Abstract】 Reduced sulfur compounds (RSCs), generated during the landfilling of municipal solid waste, are the main sources of odor in landfills. H2S is an important RSC and is the most sensitive indicator for the concentrations and fluxes of RSCs. So the reduction of H2S emission is of great significance to odor control in landfills. Landfill cover soil is the environmental interface of landfill gas (LFG) and the atmosphere. A part of H2S can be removed by physico-chemical and biological reactions in landfill cover soils while LFG is escaping to the atmosphere. Biocover soils are similar to humus soil and had been extensively studied as an alternative landfill cover materials. Biocover soils had a good performance in CH4oxidation and reduction. However, studies on its effects on H2S removal are rarely found. Thus, we chose waste biocover soil (WBS), collected from a waste treating bioreactor, as raw materials, and studied its characterization on H2S adsorption removal, as well as the influencing factors. Moreover, we designed and established the soil coloumns and simulated landfill bioreactors to study the efficiency of H2S elimination by WBS as a novel alternative landfill cover soil. The major results are as follows:(1) The concentrations of H2S in the air of landfills and its emission rates were detected. The concentrations of H2S in the ambient air and its emissions from landfills were in ranges of35-261μg m-3and1361-9854μg m-2d-1, respectively. The landfill cover soils showed high activity of sulfide oxidation and sulfate reduction, which had good correlations with the populations of sulfur-oxidizing bacteria (SOB) and sulfate-reducing bacteria (SRB), respectively. In the investigated landfill cover soils (LCS), the main SOB species were Halothiobacillus, Rhodothalassium, Paracocccus, Allochromatium and Thiobacillus, and main SRB species were Desulfovibrio, Syntrophobacter, Desulfomonile and Desulfobacca. Among the factors including pH, moisture content and the contents of organic materials and sulfur compounds, pH was the most important factor in influencing the microbial community structures and abundance in the landfill cover soils.(2) We selected biologically treated waste to prepare the WBS. Compared to LCS, mulberry soil and sand soil, WBS had the higher adsorption removal capacity of H2S. Particle size was the main factor affecting the adsorption capacity of WBS, followed by moisture content and pH. The effects of different environmental conditions on the adsorption capacity of WBS for H2S were studied and results showed that with the increase of temperatures (4-45℃) and O2concentrations (0%-21%(v/v)), the H2S adsorption removal capacity of WBS firstly increased and then decreased. When the temperature and O2concentration were35℃and10%(v/v), the H2S adsorption removal capacity of WBS reached the maximum value of55.6±5.0mg kg d.w.-1and59.6±1.3mg kg d.w.-1, respectively. Adsorption equilibrium for H2S on WBS was achieved within2-3h at the H2S concentrations of0.1%-10%(v/v). The time for adsorption equilibrium of H2S on WBS became longer with the increasing concentrations of H2S.(3) The main mineral components of WBS were studied, which included Mullite (Aluminum Silicate), Quartz, Albite, Muscovite, Dolomite and Calcite. Water and Aluminum Silicate contribute most to H2S adsorption removal of WBS, accounting for36.9%and24.9%, respectively, followed by Humus> Quartz> Muscovite> Dolomite> Calcite> Albite. At the temperatures below30℃, little amount of sulfur was loss from WBS after it was saturated adsorption for H2S. However, the adsorbed sulfide was almost totally released or converted in the top layer of WBS after it was put at45℃for120h for the significant drop of its moisture content, while88.6%of residual sulfide was in the bottom layer of WBS. Acid solutions precipitation of22.3-66.9mm could leach the sulfide from WBS within12-36h, but acid types (HNO3and H2SO4) and the pH values had no significant influence on the contents of residual sulfide (i.e. the release and transformation of adsorbed sulfide).(4) The removal efficiency of WBS as an alternative landfill cover was studied. Results showed that, under the continuous inflow of simulated LFG (CH4:CO2=1:1, H2S concentration of1%(v/v)), the potential sulfur oxidation rate and sulfate reduction rate as well as the contents of sulfur compounds were all increased in WBS and LCS. Compared to LCS, the potential sulfur oxidation rate and sulfate reduction rate were higher in WBS. On35d, the potential sulfur oxidation rate of the bottom layer of WBS reached the maximum value (82.5±7.9μmol g d.w.-1d-1), which was4.3-5.4times of that of LCS, while the the potential CH4oxidation rate in the top, middle and bottom layers of WBS were, respectively,3.1,3.5,6.6times of that of LCS. Compared with LCS, the performance in H2S elimination and CH4oxidation was better in WBS, demonstrating that WBS would be an excellent alternative cover material for landfills.(5) The microbial community structures in WBS and LCS were analyzed. The main microorganisms in WBS and LCS were Proteobacteria, Firmicutes and Bacteroidetes. After exposure to LFG with H2S, the diversity indexes decreased in WBS, while they increased in LCS. The main microorganisms participating in the sulfur metabolism were Proteobacteria and Firmicutes, ncluding Ochrobactrum, Paracoccus, Comamonas, Pseudomonas (Gammaproteobacteria), Enterobacteriaceae, Acinetobacter, as well as Bacillus (Bacilli) and Clostridium (Clostridia) of Firmicutes. (6) Simulated landfills were designed and established, and the removal of H2S by WBS as an alternative landfill cover soil were studied. The LFG production rate of the and the LFG compositions varied a lot during the stabilization process of landfills. Owing to the great heterogeneity of the wasted landfilled, the H2S concentration in LFG from the landfills differ much from each other, and changed greatly over time. During the whole experiment, the removal efficiencies of H2S of the two soils were both above90%.The input of LFG with H2S stimulated significantly the growth of aerobic heterotrophic bacteria, actinomyces, fungi, SOB and SRB in WBS. However, the increase of the microbial populations in LCS was lower than that in WBS. In the bottom layer of LCS, the populations of actinomyces, fungi and SRB even decreased. These results indicated that the microorganisms in WBS had higher tolerance to the toxicity of LFG and could covert and remove H2S during their growth. The variation of sulfur compounds contents and pH values in WBS and LCS indicated that LCS eliminated H2S mainly by adsorption, while the higher biological sulfur metabolic activity of WBS additionally enhanced its ability in H2S conversion and removal.更多还原