【作者】 王伟；

【导师】 韩洪军；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2011， 博士

【摘要】 我国煤制气的发展是由“富煤、少油、缺气”的能源特点决定的。在向清洁新能源和可再生能源过渡的未来几十年中,新一代煤制气产业将扮演特殊重要的角色。但是,由于煤制气废水含有高浓度的酚类化合物、难降解有机物和有毒污染物,国内外煤制气废水的治理技术普遍存在出水效果不理想、系统稳定性差和处理成本高等问题。目前,该废水处理问题已成为制约煤制气产业发展的瓶颈。随着厌氧技术的不断发展,研究者对厌氧工艺在煤制气废水处理领域中所发挥的作用有了前所未有的重视。针对煤制气废水的水质特点,本课题系统和深入的研究了厌氧工艺处理煤制气废水中酚类化合物的效能,考察了传统厌氧工艺(升流式厌氧污泥床工艺(Upflow anaerobic sludge blanket,UASB)、高温厌氧工艺、两相厌氧工艺和两级厌氧工艺)和厌氧强化工艺(甲醇共基质和粉末活性炭)对酚类化合物的去除效能以及废水好氧生化性能的改善情况;在工程应用中考察了甲醇共基质和两级厌氧分点进水方式对厌氧处理煤制气废水中酚类化合物效能的影响;研究了共基质条件下厌氧降解酚类化合物的效能和规律,并对厌氧降解酚类化合物的影响因素进行了探讨。通过色质联用技术(Gas chromatography-mass spectrometry,GC-MS)分析得出,煤制气废水中酚类化合物主要是由苯酚、烷基苯酚和苯二酚等组成,约占废水化学需氧量(Chemical oxygen demand,COD)总量的30%～50%;同时,煤制气废水含有多环芳烃、杂环化合物、长链脂肪烃、氨氮和氰等污染物。研究表明传统厌氧工艺有助于改善废水的好氧生化性能,但对酚类化合物的去除效能较低,其中UASB工艺对总酚的去除率仅为30%～40%,高温厌氧工艺对总酚的去除率可达55%～60%,两级厌氧分点进水工艺和两相厌氧工艺对酚类化合物的去除率达到60%和40%左右。稀释进水总酚浓度或延长水力停留时间(Hydraulic retention time,HRT)对厌氧工艺处理酚类化合物的效能并没有显著的改善效果。研究比较了甲醇共基质和粉末活性炭厌氧强化工艺处理煤制气废水中酚类化合物的效能,结果表明投加粉末活性炭(1g/L)和甲醇共基质(500mgCOD/L)分别将酚类化合物的去除率提高至73%和75%左右;厌氧强化工艺不仅能够大幅度提高煤制气废水中酚类化合物的去除效能,而且能够显著改善煤制气废水的好氧生化性能。比较不同厌氧工艺对废水好氧生化性能的改善效果上:甲醇共基质厌氧工艺>粉末活性炭厌氧工艺>两级厌氧分点进水工艺>高温厌氧工艺>两相厌氧工艺>UASB工艺。厌氧工艺采用甲醇共基质协同处理煤制气废水可以降低废水的生物毒性,改善厌氧细菌的代谢活性,能够在本质上提高厌氧工艺处理酚类化合物的效能。在工程应用研究中,厌氧工艺处理煤制气废水中酚类化合物的效能较低,COD和总酚的去除率分别低于20%和26%。稀释进水或者延长HRT也难以显著提高厌氧工艺处理酚类化合物的效果。当煤制气废水中投加甲醇浓度200～500mgCOD/L,COD和总酚的去除率可达40.7%和35.2%,厌氧工艺处理酚类化合物的效能以及产甲烷情况均有明显的改善。但是,水质冲击对厌氧工艺处理酚类化合物的效能影响较大,而且恢复周期也较长。以苯酚、(间-、对-)甲酚、邻甲酚、二甲酚和邻-、间-、对苯二酚合成的酚类化合物废水为考察对象,研究表明采用乙酸、甲醇和苯酚共基质对厌氧降解酚类化合物的效能均有不同程度的改善。当进水酚类化合物浓度分别为408mg/L,612mg/L和816mg/L左右时,与无共基质处理效能相比,甲醇共基质(500mgCOD/L)条件下酚类化合物的去除率分别提高了13.8%,14.4%和15.6%;乙酸共基质(500mgCOD/L)条件下酚类化合物的去除率分别提高了11%,12.4%和10.3%。甲醇和乙酸共基质能够明显提高厌氧降解酚类化合物中甲基苯酚的效率。适量浓度的苯酚基质也有助于提高酚类化合物的去除效率,但是高浓度的苯酚基质将会抑制厌氧细菌的活性。试验研究表明,酚类化合物的厌氧降解性能难易程度依次为:二甲酚,邻甲酚,间甲酚,对苯二酚,邻苯二酚,对甲酚,间苯二酚,苯酚。甲基苯酚的厌氧降解性能要远低于苯二酚及苯酚,五日平均降解速率仅为1.3～4.5mg/d(不包括对甲酚)。酚类化合物的厌氧降解性能与其化学结构有着密切联系,其中羧化阶段和苯甲酰化阶段是其降解的关键步骤。在厌氧降解酚类化合物的抑制试验中,高浓度的酚类化合物造成的抑制属于暂时性抑制;氰化物和长链脂肪烃造成的抑制属于干扰性抑制。在氰化物(5mg/L)和长链脂肪烃(50mg/L)的抑制条件下,共基质的存在能够降低抑制效应,协同提高厌氧降解酚类化合物的效能。更多还原

【Abstract】 In China, the development of coal gasification was decided by the energy characteristics of rich in coal, less oil and gas shortage. In the next few decades, the energy transition will make a new generation of coal gasification industries play a special role in the new clean and renewable energy market. However, coal gasification wastewater was typically high concentrations of phenols, refractory organics and toxic pollutants. The treatment technologies of coal gasification wastewater from abroad and domestic usually had several problems, such as unsatisfactory effluents, poor stability and high handling costs. Now, the wastewater treatment has become the restricting bottleneck for the development of coal gasification industries. With the continuous development of anaerobic technology, the researchers had an unprecedented attention to the role of anaerobic biotechnology in the field of coal gasification wastewater treatment. For the characteristics of coal gasification wastewater, the subject aimed to system and in-depth study anaerobic treatment efficiency of phenolic compounds in coal gasification wastewater. The treatment efficiencies and improvement of aerobic biodegradability were investigated in the conventional anaerobic processes of upflow anaerobic sludge blanket (UASB), thermophilic anaerobic process, two-phase anaerobic process, two-stage anaerobic process and the enhanced anaerobic processes of methanol addition of co-substrate and powdered activated carbon, respectively. In the engineering application, the effects of methanol addition and two-stage anaerobic process with step-feed on the treatment efficiencies of phenolic compounds were studied. Anaerobic degradation efficiencies and properties of phenolic compounds were investigated and anaerobic degradation metabolism of phenolic compounds was discussed preliminarily.By the analysis of gas chromatography and mass spectrometry (GC-MS), the phenolic compounds in the coal gasification wastewater were mainly composed of phenol, alkyl phenols and binary phenols, etc., accounting for about 30-50% of the total chemical oxygen demand (COD) of the wastewater; while the wastewater also contained more aromatic hydrocarbons, heterocyclic, long chain aliphatic hydrocarbons, ammonia and cyanide and other pollutants. Studies showed that the treatment efficiency of phenolic compounds was very low in the conventional anaerobic process, and the removal efficiency of total phenols were only about 30-40% in the UASB process, 55-60% in the thermophilic anaerobic process, around 60% in the two-stage anaerobic process and around 40% in the two-phase anaerobic process. Dilution of influent phenolic concentration or extended hydraulic retention time (HRT) had no significant promoting effect on anaerobic treatment efficiency of phenolic compounds.The treatment efficiencies of phenolic compounds in coal gasification wastewater were compared with the enhanced anaerobic processes of methanol co-substrate and powdered activated carbon. The results showed that the addition of powdered activated carbon (1g/L) and methanol co-substrate (500mgCOD/L), enhanced the removal efficiencies of phenolic compounds to 73% and 75%, respectively. The enhanced anaerobic processes could not only greatly improve treatment efficiency of phenolic compounds, but also significantly improved aerobic biodegradability of coal gasification wastewater. In a comprehensive comparison of these anaerobic processes in the improvement of aerobic biodegradability, the order was: methanol co-substrate anaerobic process > powdered activated carbon anaerobic process > two-stage anaerobic process with step-feed > thermophilic anaerobic process > two-phase anaerobic process > UASB process. Co-metabolism of coal gasification wastewater with methanol substrate could reduce the biological toxicity of the wastewater, and improve the metabolic activity of anaerobic bacteria for enhancing the removal efficiency of phenolic compounds in essence.In the engineering application, anaerobic treatment of phenolic compounds in coal gasification wastewater was difficult and ineffective. The removal efficiencies of COD and total phenols were less than 20% and 26%. Dilution or extension of hydraulic retention time was difficult to significantly improve the anaerobic treatment efficiency of phenolic compounds. When the methanol concentration of 200-500mgCOD/L was added in coal gasification wastewater, the removal efficiencies of COD and total phenols were around 40.7% and 35.2%, and the treatment efficiency of phenolic compounds and methane production had been significantly improved. However, the relatively stable wastewater quality was the prerequisite and important guarantee to achieve successful treatment of phenolic compounds in coal gasification wastewater in the anaerobic process.The phenolic wastewater composing of phenol, (m-, p-) cresols, o-cresol, xylenols, catechol, resorcinol and hydroquinone was treated with acetic acid, methanol and phenol as co-substrates, respectively. Results indicated the co-metabolism was helpful to improve anaerobic degradability of phenolic compounds. When the influent concentration of phenols were around 408mg/L, 612mg/L and 816mg/L, the removal efficiencies of phenolic compounds under the condition of methanol co-substrate (500mgCOD/L) were increased by 13.8%, 14.4% and 15.6% with compared to the results under the condition of without co-substrates; and under the condition of acetic acid co-substrate (500mgCOD/L) were increased by 11%, 12.4% and 10.3% with compared to the results under the condition of without co-substrates. Moderate concentration of phenol co-substrate also helped to improve the removal efficiency of phenolic compounds, but the high concentration of phenol co-substrate would inhibit the activity of anaerobic bacteria, resulting in removal efficiency of phenolic compounds dropped significantly. Co-substrates of methanol and acetic acid could significantly enhance the degradation efficiencies of methyl phenols, which played a key role in the improvement of anaerobic biodegradability of phenolic compounds.The experimental results showed that the difficulty of anaerobic degradability of phenolic compounds were as follows: xylenol, o-cresol, m-cresol, hydroquinone, catechol, p-cresol, resorcinol, phenol. Anaerobic degradability of methyl phenols was much lower than the phenol and binary phenols, and the five-day average degradation rates of methyl phenols were only 1.3-4.5mg/d (except p-cresol). Anaerobic degradation ways of phenolic compounds closely linked to its chemical structure, in which the carboxylation stage and benzene acylation stage were the key step in the degradation process. In the process of anaerobic degradation of phenolic compounds, the inhibition caused by high concentrations of phenolic compounds was a temporary inhibition, and the inhibition caused by cyanide and long-chain hydrocarbons belonged to interference inhibition. The inhibition of anaerobic degradation of phenolic compounds was not only affected by the type and concentration of inhibitors and other factors, but was also closely associated with the phenolic composition. Under the inhibiting environment of cyanide (5mg/L) and long chain fatty hydrocarbon (50mg/L), the presence of co-substrate could reduce the inhibitory effect and synergistically improve anaerobic degradation efficiency of phenolic compounds.更多还原