【作者】 查坤；

【导师】 刘丹；

【作者基本信息】 西南交通大学 ， 市政工程， 2009， 博士

【摘要】 准好氧填埋技术因具有填埋结构简单、垃圾降解速度快等优势而成为目前垃圾处理处置领域的一个研究热点。但是目前国内的研究仍以基于室内试验的理论分析为主,为了探索准好氧填埋技术的工程适应性和对准好氧填埋技术的一些重要问题进行深入研究,开展了三个规模为10m×10m×5m的不同回灌方式和前期不同覆盖方式的垃圾循环式准好氧填埋单元的现场试验。探讨了准好氧填埋场渗滤液水质在不同时期的降解规律;氧气在准好氧填埋场的传质和消耗规律以及填埋气体的排放规律。同时对填埋场污染物运移的平衡流与优先流进行数值模拟,确定影响污染物运移的主要因素。本研究可为准好氧填埋技术的推广应用提供相关的技术参数和理论依据。通过对试验单元渗滤液水质的监测,结果表明:三个单元的COD在分别经过742、704、697天后,从最初的26172 mg/L、72435 mg/L和65324 mg/L降低到1566mg/L、1443mg/L和2013mg/L,去除率分别为94.0%、98.0%和96.9%。BOD₅分别从21012mg/L、42800mg/L和33900mg/L降低到130mg/L、120mg/L和140mg/L,去除率为99.4%、99.7%和99.6%。可以看出准好氧填埋对有机物的去除效果明显,但是由于受到渗滤液收集管直径较小的限制,渗滤液氨氮的降解受到一定的影响,降解效果不够理想。分别利用Excel和Lingo软件对渗滤液COD降解模型进行拟合和预测,结果显示采用Lingo拟合的结果与实测值比较接近,其预测值也更为准确。在考虑弥散、对流、吸附和降解作用下,首次利用FlexPDE软件对填埋场污染物的平衡流和优先流运移模型进行模拟。研究表明:在平衡流条件下,当扩散系数和渗流速度增大时,污染物的浓度降低趋势很明显。当扩散系数为0.5m²/d和0.05m²/d时,扩散系数较小方向上的运移可以忽略不计,渗流速度降低到0.02m/d后,对污染物运移的影响可以忽略不计。污染物衰减系数对污染物运移的影响较大,衰减系数越大,污染物浓度降低得越快,而当污染物衰减系数减小到0.0008/d后,污染物浓度变化受衰减系数的影响大大减小。通过优先流模拟发现,在流动区域,由于污染物随着流体快速运移,其浓度也发生较大的变化,而对于不流动区域,由于污染物浓度的变化只受到降解以及动力学传质的影响,所以其浓度变化缓慢;流动区域的含水率越大,不流动区域污染物浓度降低的越快;传质系数越大,不流动区域污染物浓度降低越快,相对而言流动区域的浓度有所增大。在优先流发生时,渗流速度和扩散系数明显增大,当扩散系数为5m²/d,渗流速度为2m/d时,到了第50天,流动区域污染物浓度的最大值与扩散系数为0.5m²/d,渗流速度为0.2m/d相比较,降低了96.7%。说明优先流对污染物运移的影响大。对准好氧填埋场氧气的传质和消耗规律进行试验研究,并利用Surfer软件对试验数据进行分析。结果表明:氧气在垃圾层的传递方式主要以扩散传递为主;通过覆盖层进入垃圾层中的氧气分布具有一定的层次效应,从上到下浓度依次减小。在渗滤液收集管氧气供给的影响下,导气管周围的氧气浓度有所增加。三个试验单元上、中、下层氧气的平均浓度分别为:13.8%、2.1%、0.6%;13.6%、2.3%、0.3%;13.8%、2.4%、0.4%。利用氧气浓度的大小将填埋场的不同垃圾降解区域进行划分,好氧、兼氧和厌氧区的氧气浓度分别为大于2.4%、大于0而小于等于2.4%和等于0。利用静态箱法对准好氧填埋场填埋气体排放通量进行研究。结果表明,距离导气管较近的区域,在垃圾好氧降解的条件下,CH₄的排放通量绝大部分接近于零,即处于完全被氧化的状态。随着离导气管距离的增加,CH₄排放量逐渐增大,但是受到填埋场垃圾层厚度等的影响,不同的区域的CH₄和CO₂排放量有所不同,填埋垃圾层较厚的区域,气体的产量增大,排放量也较大。在填埋边坡地带,CH₄排放量较低,CO₂排放量较大,在覆盖层较薄区域,大气渗透到垃圾层的深度增加,使垃圾好氧降解区域增大,CO₂排放量增大。整个试验中的CH₄排放量远远低于CO₂排放量,两者的通量比值除了第二单元在4月为47外,其余时段都在688以上,最大比值达到204940,说明在准好氧填埋条件下,CH₄排放量大大减小。更多还原

【Abstract】 Semi-aerobic landfill technology is a popular research field of waste disposal for the simple structure and faster degradation.But most researches are just in laboratory in present.To verify the applicability of semi-aerobic landfill and discuss many important thechnologies of it,three pilot-scale units(10m×10m×5m) are constructed at the Changan landfill site of Chengdu city,the leachate is recirculated in different ways,HDPE and clay are adopted as the cover in the beginning of the research,the degradation rule of leachate quality in different period,the transportation and consumption of the oxygen in the experimental units and the emission rule of landfill gas are discussed.Meanwhile,the influence factors of the contaminant transportation in balanced flow and preferential flow are discussed.Based on the research,technical parameters and theoretical basis are provided for the application of semi-aerobic landfill.The leachate quality of the experimental units are monitored,the results showed that,the leachate concentration of COD dropped from 26172 mg/L,72435 mg/L and 65324 mg/L originally to 1566mg/L,1443mg/L and 2013mg/L finally, and the removal rates are 94.0%,98.0%and 96.9%respectively.The concentration of BOD dropped from 21012mg/L,42800mg/L and 33900mg/L originally to 130mg/L,120mg/L and 140mg/L finally,the removal rates are 99.4%,99.7%and 99.6%respectively.Based on the results,it is obvious that the degradation of organic is effective in the semi-aerobic landfill experimental units.But the degradation of ammonia nitrogen is not good because of the small diameter of leachate collection pipe.The trend of COD is fitted by Excel and Lingo with a result that Lingo is more effective,so the results of predicted by Lingo are more reliable.Under the effect of dispersion,convection,adsorption and degradation,the balanced flow and preferential flow of the landfill contaminant are firstly modelled by FlexPDE.Under the balanced flow condition,with the increasing of the dispersion coefficient and the flow velocity,the contaminant concentration dropped obviously.When the dispersion coefficients are 0.5m~2/d and 0.05m~2/d,the contaminant transportation is negligible in the latter direction.When the flow velocity fell to 0.02m/d,its effect on contaminant transportation is negligible.The contaminant decaying coefficient influenced on the contaminant transportation effectively,when the decaying coefficient is greater,the contaminant dropped faster too,and when the contaminant decaying coefficient fell to 0.0008/d,the effect on contaminant transportation is negligible.From the model of preferential flow,due to the contaminant flow with the faster liquid in the mobile domain,the contaminant concentration changed faster.In the immobile domain,the contaminant concentration is effected by the degradation and first-order mass transfer,so it changed slowly.When the water content of the mobile domain is greater,the contaminant concentration in immobile domain dropped faster.And when the first-order mass transfer coefficient is greater,the contaminant concentration in the immobile domain dropped faster.Meanwhile,the contaminant concentration in the mobile domain increased accordingly.Under the condition of preferential flow,the flow velocity and dispersion coefficient is increasing obviously.When the dispersion coefficient is 5m~2/d,flow velocity is 2m/d,the maximum value of contaminant concentration in the immobile domain decreased 96.7%comparing with the dispersion coefficient is 0.5m~2/d and the flow velocity is 0.2m/d.So,the preferential flow effected the contaminant transportation obviously.The oxygen transportation and consumption in semi-aerobic landfill is tested by the experimental units,and the test data is analyzed by Surfer.Oxygen is transported in the waste mostly by dispersion.The oxygen is imported from the cover is stratifyed in the landfill,and from the upper layer to the under layer,the oxygen concentration is decreasing with the depth.But from the leachate collection pipe, oxygen could be taken in the landfill layer,so the oxygen concentration around the landfill gas collection pipe is increased.In the three experimental units,the average oxygen concentration of the upper layer,middle layer and under layer are 13.8%, 2.1%,0.6%,13.6%,2.3%,0.3%,13.8%,2.4%and 0.4%respectively.The area of waste degradation is partitioned by the oxygen concentration,in the aerobic,anoxic and anaerobic areas,the oxygen concentration is more than 2.4%,more than 0 and less than or equal to 2.4%and equal to 0 respectively.The semi-aerobic landfill gas flux is tested by static chamber method.The results showed that methane flux is closed to 0 mostly in the area around the landfill gas collection pipe,because methane is oxidized almost entirely.With the increasing distance to landfill gas collection pipe,methane flux is enhanced.Because of the difference depth of waste layer,methane and carbon dioxide flux are different.In the area with thicker layer,landfill gas yield is increased,and the flux is increased too.On the side of slopes,atmosphere is taken in deeper layer,so the aerobic area and carbon dioxide flux increased.At the same time,methane flux decreased.In the whole experiment period,methane flux is far smaller than carbon dioxide flux,the ratio of methane flux to carbon dioxide flux is almost more than 688,the maximal ratio is 204940,and the minimal ratio is 47,this is taken place in the second experimental unit in April.From the study,it is obvious that in semi-aerobic landfill,methane flux is very small.更多还原