城市生活垃圾厌氧消化的关键生态因子强化研究

【作者】 张记市；

【导师】 孙可伟；

【作者基本信息】 昆明理工大学 ， 环境工程， 2007， 博士

【摘要】 厌氧消化城市生活垃圾（MSW）是集环保、能源和资源回收于一体的新的生物处理技术，其中如Dranco、Valorga、Kompogas和Biocel等工艺已经成功实现了工程化运行。然而，在厌氧消化过程中仍存在产气速率、产气量低，发酵周期长，有机物降解效率不高等问题。主要原因有：一是缺乏高效微生物；二是缺乏高效反应器；三是MSW的复杂性和可变异性；四是厌氧工艺过程稳定性差。本文在国内外已有的研究基础上，系统地研究了MSW可变异性与生物降解性、接种物筛选、好氧微生物强化厌氧消化城市有机生活垃圾（OFMSW）、OFMSW与剩余污泥的联合消化、有机负荷（OLR）波动对厌氧过程稳定性影响、温度因子对厌氧消化性能的影响与强化等内容。论文主要研究内容与结论有：MSW是厌氧消化的关键非生物因子，能显著影响厌氧消化的效率。论文在研究MSW可变异性的基础上，比较了城市生活垃圾（MSW）、机械分选城市有机生活垃圾（MS-OFMSW）、人工分选城市有机生活垃圾（HS-OFMSW）和源分城市有机生活垃圾（SS-OFMSW）的物理组成及有机质成分；并分析了它们在不同温度（35℃／55℃）下的厌氧生物降解率分别为47.8％／49.1％、66.7％／68.0％、80.5％／81.5％和86.1％／86.9％，可生物降解物质分数（BF）分别为51.4％、63.7％、72.1％和74.0％。因而它们的产沼气潜力（BMP）存在显著差异，MSW、MS-OFMSW、HS-OFMSW和SS-OFMSW的中温（35℃）BMP分别为215.9mLCH₄／gVS、302.5mLCH₄／gVS、368.8mLCH₄／gVS和391.9mLCH₄／gVS，高温（55℃）BMP分别为221.8mLCH₄／gVS、308.4mLCH₄／gVS、373.7mLCH₄／gVS和395.4mLCH₄／gVS。OFMSW厌氧消化的生物因子强化结果表明，初始接种物的最大比产甲烷活性（SMA）明显不同，以中温厌氧消化污泥的为最高（224mLCH₄／gVSS·d），其次为来自常温运行的UASB反应器污泥和化粪池底泥，SMA分别为196mLCH₄／gVSS·d和184.8mLCH₄／gVSS·d。经过两次中温培养、富集后，SMA显著提高，能加快OFMSW厌氧过程的启动和提高OFMSW的厌氧降解率；SMA与OFMSW厌氧降解率呈一定的正相关性，即SMA越大，OFMSW厌氧降解率越大。接种物-OFMSW比率（ISR）会显著影响OFMSW的厌氧消化性能。在相同质量的接种物下，ISR=1是厌氧消化的最适宜值，过大或过小都会影响有机物产气量和反应器利用率。ISR=1时发酵过程稳定性较高，产气速率和产气量较大，同时，有机物降解率和反应器利用率都得到合理的提高。此外，还利用好氧微生物（作为生物因子）对OFMSW高温厌氧消化进行了强化研究。好氧微生物能提高OFMSW的可生物降解性，增加后续厌氧过程的稳定性，提高产气量和消化效率。其中以好氧生物处理12h的OFMSW厌氧过程稳定性最好、产气量最大（29927.98mL），提高了25.8％。好氧Oh、6h、12h、24h、48h和72h的OFMSW厌氧消化速率常数分别为0.1517d^-1、0.1453d^-1、0.1428d^-1、0.1396d^-1、0.1748d^-1和0.1819d^-1。为改善消化底物的营养结构和C／N，提高厌氧消化性能，进行了OFMSW-剩余污泥联合消化实验研究。OFMSW-剩余污泥的BMP测试结果表明，理论甲烷产量（TMP）随着OFMSW组分的增加而降低（560CH₄mL／gVS～521 CH₄mL／gVS），而BMP随之增大（223CH₄mL／gVS～414CH₄mL／gVS）。OFMSW-剩余污泥的半连续联合消化结果说明，产气速率随着OFMSW组分的增加而增大，其中以90：10（OFMSW／剩余污泥，VS基）进料（HRT=15d和OLR=4.8gVS／L·d）时的产气速率最大（2456mL／L·d）。OLR的波动或突变对厌氧过程的稳定性有着显著的影响，主要表现在对产气速率、pH值、CH₄含量和VFA浓度的变化上。OLR对各参数影响的强弱顺序为：VFA浓度＞产气速率＞甲烷含量＞pH值。因而可以通过对上述参数的监测来判断厌氧过程的稳定性，其中以pH监测法最为便捷实用。在厌氧消化过程的生物因子与非生物因子强化实验中，还研究了半连续和间歇厌氧反应动力学模型，包括有机物产气动力学、降解动力学和大肠杆菌死亡动力学。由产气量和反应器的出口浓度模拟或计算，得出了有关动力学参数。35℃时半连续消化（CSTR）反应速率常数为0.119d^-1，大肠杆菌死亡速率常数为0.69d^-1（以消化污泥符合美国A级污泥排放标准为例）。25℃、35℃、55℃的间歇反应速率常数分别为0.013d^-1、0.047d^-1、0.1254d^-1；OFMSW厌氧反应的活化能为58.93kJ／mol；大肠杆菌死亡速率常数分别为0.001d^-1、0.0256d^-1和16.11d^-1（以消化污泥符合城镇垃圾农用控制标准GB8172-87要求为例）。温度对OFMSW厌氧消化的影响与强化结果表明，55℃为最适宜反应温度。55℃时OFMSW平均产气率为180.80mL／gTS，平均甲烷含量为70.0％，消化时间为20d左右；发酵残留物的比产甲烷活性（SMA）为477mLCH₄／gVSS·d，其中大肠杆菌浓度和蛔虫卵的死亡率分别为10^-3MPN／g和100％，符合GB8172-87控制标准的卫生要求。更多还原

【Abstract】 The integrative anaerobic digestion is a new bioremediation technique with advantages in environment protection, energy and resource recovery treating municipal solid waste （MSW）, among that Dranco, Valorga, Kompogas and Biocel processes have been industrialized. However, there are several disadvantages such as low gas production rate and gas production, long digestion time and inefficient organic compounds-decomposing in anaerobic process because of lack of effective microorganism and anaerobic reactor, complex-variability of organic fraction of municipal solid waste （OFMSW） and instability of anaerobic process. On basis of domestic and abroad references, there have been some systematic researches of key factors enhancement of anaerobic digestion for treating MSW including comminution and separation of MSW, variability and biodegradability of MSW, filtration and enrichment culture of inoculum, aerobic microorganism pretreatment of OFMSW enhancing anaerobic process, codigestion of OFMSW with waste sludge, influence of organic loading rate （OLR） and temperature on anaerobic process in this dissertation.MSW play an important role in anaerobic process, which is the key abiological factor having influence on anaerobic performance. On basis of the variability of MSW, the comminuting and sorting experiments were carried out for MSW in Kunming University of Science and Technology.The analyses were taken about the physical compositions and organic chemical components of MSW respectively by machine-sorted, hand-sorted, and source-sorted method which called MS-OFMSW, HS-OFMSW and SS-OFMSW. Based on the data from the experiments it was about 47.8%/49.1%,66.7%/68.0%,80.5%/81.5% and 86.1%/86.9% at 35℃/55℃respectively for biodegradability percentage while their biodegradable fractions （BF） based lignin content was 51.4%,63.7%,72.1% and 74.0% respectively. The biochemical methane potential （BMP） of MS-OFMSW, HS-OFMSW and SS-OFMSW were 215.9mLCH₄/g VS, 302.5mLCH₄/gVS, 368.8mLCH₄/gVS and 391.9mLCH₄/gVS in the mesophilic condition,221.8mLCH₄/gVS,308.4mLCH₄/gVS,373.7mLCH₄/gVSand 395.4mLCH₄/g VS in the thermophilic condition respectively.The results of biological factors enhancement under the mesophilic anaerobic digestion of OFMSW showed that each inoculum possessed particular characteristics because of their different source, among that the initial specific methanogenic activity （SMA） were the most important. The mesophilic anaerobic sludge （MAS） presented the highest SMA value. UASB sludge （UAS） and septic tank bottom sludge （STBS） were much of SMA value which were 196mLCH₄/gVSS·d and 184.8mLCH₄ /gVSS·d respectively. These inoculums after incubation and enrichment shorted the lag time of anaerobic process and improved the biodegradability of organic waste. The relationship between OFMSW and anaerobic degradability was positive, namely the more the SMA was, the more the anaerobic degradability was.The inoculum-substrate ratio （ISR） had influence on the mesophilic anaerobic performance of OFMSW evidently. When ISR being one was the best condition under the same mass （based volatile solid） which kept anaerobic process high stability; meanwhile the biodegradability, gas production rate （GPR） and accumulative gas production were higher than that of others. The biodegradability of organic waste and utilization of reactor capacity improved reasonably.Aerobic microorganism was regarded as biological factor to pre-treat OFMSW, which improved the biodegradability of OFMSW.Therefore the anaerobic process stability, gas production and digestion efficiency improvement presented in the anaerobic process, especially in the OFMSW pretreated for 12 hours by aerobic microorganism, which gas production increased 25.8% being the most gas production （29927.98mL） of all others. The reaction rate constants of anaerobic digestion of OFMSW pretreated for Oh, 6h, 12h, 24h, 48h and 72h by aerobic microorganism were 0.1517d^-1, 0.1453d^-1, 0.1428d^-1, 0.1396d^-1, 0.1748d^-1 and 0.1819d^-1 respectively.The experiments of OFMSW and waste sludge codigestion were carried out in order to improve the nutrition ingredients and C/N of OFMSW and their anaerobic performance. The results of batch codigestion of OFMSW and waste sludge showed that theoretical methane production （TMP） decreased with OFMSW content increase from 560CH₄mL/gVS to 521CH₄mL/gVS; while BMP increased with OFMSW content increase from 223CH₄mL/gVS to 414CH₄mL/gVS. The results of semicontinuous codigestion of OFMSW and waste sludge showed that gas production rate（GPR） increased with OFMSW content increase. The appropriate proportion of OFMSW and waste sludge was 90/10（based VS content）,which GPR was the highest under the conditions that HRT and OLR was 15d and 4.8gVS/L·d respectively. The GPR was 2456mL/L·d.OLR fluctuation or sudden variation had influence on stability of anaerobic process distinctly by the fluctuation of some important parameters. The influence degree of OLR fluctuation on some important parameters as follows:VFA concentration > GPR > methane content > pH. Therefore, the anaerobic process stability was estimated by inspecting these parameters above-mentioned, among that pH assay was the most convenient and effective.During the biological and abiological factors enhancing anaerobic digestion dynamics model of semi-continuous and batch anaerobic process have been studied including gas production, degradability and fecal coliform destruction. The parameters concerned obtained according to these data and dynamics model. The reaction rate constant of semicontinuous anaerobic process was 0.119d^-1; while the rate constant of fecal coliform destruction according to the class A criterion of sludge （USA） was 0.69d^-1 under the mesophilic （35℃） condition. However, the reaction rate constants of batch anaerobic process were 0.013d^-1,0.047d^-1 and 0.1254d^-1;meanwhile the rate constant of fecal coliform inactivation of the criterion in GB8172-87 were 0.001d^-1,0.0256d^-1 and 16.11d^-1 under the psychrophilic （25℃）, mesophilic （35℃）, and thermophilic （55℃） conditions respectively. The activation energy of anaerobic reaction of OFMSW was 58.93kJ/mol.Laboratory-scale experiments were carried out to assess the influence of temperature enhancement on anaerobic treatment of OFMSW. The results showed that it was 55℃for the optimum temperature. The parameters were obtained such as 180.80mL/gTS for average biogas production, 70.0% for average methane concentration in biogas, about 20d for digestion time, 477mLCH4/gVSS·d for the residue SMA, 10^-3MPN/g for fecal coliform and 100% for destruction rate of roundworm eggs under thermophilic condition, which exceeded the psychrophilic and mesophilic conditions. The inactivation of pathogens in the residue under thermophilic condition was in accordance with the citerion in GB8172-87.更多还原