【作者】 李媛媛；

【导师】 韦朝海；

【作者基本信息】 华南理工大学 ， 环境工程， 2010， 硕士

【摘要】 焦化废水通常含有高浓度氨氮,浓度范围在600-800 mg·L-1左右。在焦化废水脱氮处理研究及应用中,由A/O工艺发展起来的生物组合工艺较受青睐。但由于焦化废水成分复杂,含有大量有毒物质如挥发酚、氰化物、多种芳香族有机物、杂环及多环芳烃有机物等,对生物脱氮处理存在抑制作用,因此采用目前比较流行的生物脱氮组合工艺处理后氨氮浓度仍然难以实现稳定达标排放。针对通常焦化废水生物处理硝化过程不能有效进行的问题,本研究以课题组自行研制的新型A/O1/H/O2生物流化床组合工艺为对象,系统分析了该工艺的运行过程及处理效果,考察硝化过程的实现条件、影响因素及受到抑制的生物学机理,探索能够有效降解有机物同时稳定实现焦化废水硝化处理的高效新工艺。通过对从调试到稳定运行阶段的监测数据及对不同工艺单元运行的过程进行分析,探索A/O1/H/O2生物流化床组合工艺的处理效果：二级好氧流化床是硝化过程发生的主要工艺段,氨氮去除率可达到99.3%,硝化过程得以高效稳定的完成得益于二级好氧段前的工艺段；厌氧和缺氧段使得大部分难降解杂环有机物开环断链,削减毒性同时提高了废水的可生化性；一级好氧流化床去除大部分影响硝化过程的污染物,如COD、挥发酚、SCN-与CN-等,去除率分别高达76.8%,99.7%,96.9%和79.6%,为二级好氧段创造了良好的条件进行硝化反应,该工艺的生物系统出水氨氮浓度可持续低至3 mg·L-1以下,远低于污水综合排放一级标准。为了解硝化反应进行的最适条件及抑制影响因素构成机理,分别对硝化过程环境条件影响因素和焦化废水污染物抑制因素进行实验研究,确定适合硝化反应的最佳参数为：氨氮浓度≈150 mg·L-1,温度≈30℃,pH值≈8.5,DO=3-4 mg·L-1,C/N=4,该结果可为工程运行条件的优化控制提供指导依据。结合工程运行中出现的硝化抑制现象,实验证明焦化废水中的典型污染物如氨氮、苯酚、SCN-及含氮杂环化合物可产生硝化抑制效应,实验结果为,氨氮浓度在大于150 mg·L-1时会对硝化过程产生轻微的基质抑制；苯酚在低浓度情况下(30 mg·L-1)即可对硝化过程产生抑制；SCN-浓度为380 mg·L-1时氨氧化抑制率达78.1%,并出现亚硝氮积累；喹啉、吡啶、吲哚和吡咯四种典型含氮杂环化合物对硝化过程的半抑制浓度EC50分别为112.46 mg-L-1、59.51 mg·L-1、9.89 mg·L-1、13.46 mg·L-1。结果表明只有在低COD浓度及低有毒物质存在的条件下,硝化过程才能有效进行。氨氮转化为硝氮的生物硝化过程是生物脱氮的关键步骤,易受环境条件因素改变的影响,尤其容易受限于焦化废水中其他污染物的毒性抑制效应,这也是其他生物组合工艺难以实现高效、稳定去除氨氮的重要原因之一。因此,若要提高焦化废水的脱氮效率,并保持生物过程的持久稳定,必须在了解焦化废水污染物生物降解特性的基础上,采用合理的分段工艺,形成高效的除碳单元与脱氮单元,将有机物与氨氮分级降解,避免其他污染物对硝化过程的毒性抑制冲击,在最优运行条件的控制下,才能保证硝化过程得以高效稳定进行。更多还原

【Abstract】 Coking wastewater usually contains high concentration of ammonia (600-800 mg-L-1), in the field of coking wastewater nitrification research and application, biological combined processes developed from the A/O process are more appealing. However, coking wastewater is complicated, containing a large number of toxic substances such as phenol, cyanide, various aromatic organic compounds, heterocyclic and polycyclic aromatic hydrocarbons, which has negative effect on biological nitrogen removal process, so it is still difficult to reach the discharge standards by current popular biological combined processes. For the issue that nitrification in biological treatment of coking wastewater is usually hard to achieve effectively, a novel A/O1/H/O2 fluidized bed combined process was designed and developed by our research group. In this study, the operation process and treatment effect were systematically analysed; the optimal conditions, influencing factors and biological inhibition mechanism to nitrification were studied. The new A/O1/H/O2 technology employed in coking wastewater treatment can achieve stable and efficient nitrification as well as effective degradation of organic compounds at the same time.In order to study the treatment effect of A/O1/H/O2 biological fluidized bed combined process, the monitoring datas adopted from commission period to the stable operation and operation process of different units were analyzed. The results showed that the second aerobic fluidized bed is the main process where nitrification occurred and ammonia nitrogen removal rate reached 99.3%, nitrification process can be highly efficient and stable thanks to the completion of the process before the second aerobic segment; ring-opening reaction and degration of most of the refractory heterocyclic compounds happened in anaerobic and anoxic processes, reducing toxicity while improving biodegradability of wastewater; the first aerobic fluidized bed removes most of the pollutants which can affect the nitrification process, such as COD, phenol, SCN-and CN-, the remove rate were 76.8%,99.7%,96.9% and 79.6% respectly, and create suitable conditions for nitrification in the second aerobic stage. The ammonia effluent concentration of biological system is continuously lower than 3 mg·L-1, which was much lower than the integrated wastewater discharge standards.To find out the optimal conditions for nitrification and mechanism of nitrification inhibition, the impact of environmental conditions and pollutant inhibitory factors of coking wastewater on the nitrification process were studied by experiment. The optimal parameters for nitrification were obtained as follows:ammonia concentration≈150 mg·L-1, temperature≈30℃, pH value≈8.5, DO= 3-4 mg·L-1, C/N= 4; the results can provide the guidance for the operating conditions of the project. According to nitrification inhibition in the project operation, typical pollutants such as ammonia, phenol, SCN- and nitrogen containing heterocyclic compounds were proved to be nitrification inhibitors. Results showed that it has slight substrate inhibition when ammonia concentration greater than 150 mg·L-1; phenol in low concentration (30 mg·L-1) can inhibit nitrification; ammonia oxidation inhibition rate can reach 78.1% when SCN- concentration is 380 mg·L-1, and the nitrite accumulate; half inhibitory concentration of four kinds of typical nitrogen heterocyclic compounds like quinoline, pyridine, indole and pyrrole on nitrification process were 112.46 mg·L-1,59.51 mg·L-1,9.89 mg·L-1 and 13.46 mg·L-1 respectly. The results indicated that nitrification process can be effectively react only in low COD concentration and low-toxic pollutants existing conditions.Nitrification is a key step in biological nitrogen removal process, it is vulnerable to the impact of changes in environmental conditions, particularly prone to be inhibited by toxic pollutants in coking wastewater, which is the important reasons that it is difficult for other biological processes to remove ammonia efficiently and stablely.Therefore, to improve the efficiency and maintain lasting stability of nitrification in coking wastewater treatment, the biological degradation characteristic of pollutants in coking wastewater should be investigated. A reasonable combined process which formed by a highly efficient carbon remove unit and a nitrogen remove unit should be employed, it will prevent nitrification inhibition impact of other toxic pollutants, on the basis of optimal operating conditions, stable and efficient nitrification process can be ensured.更多还原