【作者】 王树涛；

【导师】 马军；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2007， 博士

【摘要】 水环境污染和水资源短缺加速了污水深度处理与回用的研究。城市污水二级处理出水水质稳定、水量大,是良好的第二水源。生活污水经过二级生化处理后,一般悬浮物颗粒微小、浓度低,溶解性污染物大多为难生物降解有机物。即使如此,由于生物法（如生物膜法）仍然是目前最经济的污水处理方式,这使得人们仍不放弃将生物法作为组合工艺（如与化学法组合）的一部分来对其进行深度处理以实现再生回用。针对现行深度处理工艺存在的去除效率低、占地面积大等问题,在对生活污水二级出水的水质特性进行系统分析的基础上,提出了臭氧预氧化/曝气生物滤池（ozonation/biological aereated filter, O3/BAF）联合工艺,并考察了该联合工艺的长期运行效果、工艺参数和影响因素,并对臭氧预氧化有机物的反应动力学、后续BAF净化有机物的机理、生物膜特性等进行了探讨与分析。二级出水的水质特性分析结果表明,溶解态COD占78.17-86.54%;悬浮物中有机组分占总物质含量的75.54-89.93%;二级出水中大约80%的颗粒分布在2-6.84μm之间。二级出水中分子量（MW）小于1k Dalton的有机物占56.3-62.8%。二级出水的可生化性较差,BDOC仅占DOC的15.5-26%。溶解性有机物和悬浮物（SS）中有机物的GC/MS分析结果表明,具有环状结构的化合物分别占各自总化合物的58%和35%。从结构上看,大多为难降解有机物。上述分析表明,溶解性有机污染物是生活污水二级出水深度处理的主要目标,但由于其可生化性差,采用化学预氧化提高后续BAF的处理效率十分必要。研究了臭氧氧化二级出水的特性。在臭氧投量为10 mg/L、接触时间为4 min情况下,单独臭氧氧化对二级出水的COD、TOC、UV254和色度的去除率分别为25.7%和16.5%、69.3和79.2%;臭氧预氧化使二级出水的可生化性显著提高:使MW<1k Dalton的有机物的比例由52%提高到72.6%、使BDOC从1.08 mg/L提高到2.6 mg/L。建立了臭氧预氧化/曝气生物滤池（O3/BAF）联合工艺。实验发现,臭氧预氧化能够提高二级出水的可生化性,促进后续BAF的生物膜生长,提高生物活性,进而强化BAF的除污染效能。臭氧预氧化与曝气生物滤池具有协同作用,O3/BAF对有机物总量的去除率比单独O3和BAF去除率之和高7-10%;O3/BAF对TOC、UV254、色度的去除效率分别为20-27%、65-75%和87-93%;此外,O3/BAF出水中MW<1k Dalton的有机物比例明显降低。BAF对水力负荷、pH等条件具有较好的适应性。O₃/BAF对NH₃-N和TN的去除率分别为87-92%和13-17%,TN的去除率主要来源于厌氧氨氧化。实验还发现,温度、NH₃-N负荷和pH是影响NH₃-N去除的重要因素。在一定温度范围内,温度升高,NH₃-N去除率升高;NH₃-N负荷增加去除率降低。亚硝化作用最佳pH范围为7.3-7.9,硝化作用的最佳pH范围为6.75-7.5。氮平衡分析表明,供氧受限时,NH₃-N被好氧氨氧化菌氧化成NO₂-N,然后在生物膜的厌氧区由厌氧氨氧化菌再将NH₃-N和NO₂-N氧化为N₂,同时产生少量NO₃-N。上述过程是氮流失的主导原因。气-水联合反冲洗能够有效地去除滤层中的悬浮物和多余的非活性生物膜。适当控制反冲洗强度和时间,反冲洗对有机物去除、硝化作用仅有轻微影响,反冲洗结束后BAF净化效能能较快地恢复到正常水平。臭氧氧化水中有机物的动力学分析认为,臭氧与有机物的氧化反应在0-1.6、1.6-16、16-30 min范围内均呈一级动力学反应,各阶段反应速率常数分别为0.0241、0.00296和0.000732 （L·mg-1·min-1）。在实验和理论分析的基础上,总结提出了曝气生物滤池降解有机物是生物氧化、过滤截留、生物絮凝和食物链分级捕食综合作用的结果。观察发现,进水端生物膜较厚,颜色较深,填料的空隙较小;随着滤层高度增加,生物膜逐渐变薄,颜色逐渐变浅。整个系统中活跃着大量的杆菌、丝状菌、钟虫、藻类、球菌等。进水端、中间段和出水端生物膜表面形态结构、种群组成等各有特点,异养菌和硝化菌分布与有机物去除和硝化作用规律一致。建立了基于有机物浓度和反应器高度两参数的有机物生物降解动力学模型,并根据实验数据进行了线性回归分析,计算得出了模型总体运行常数和填料特性常数,并验证了模型的实用性,该模型可为实际工程提供一定的设计参考。研究结果表明,臭氧预氧化/曝气生物滤池联合工艺对生活污水二级出水具有良好的净化效能,工艺出水的COD、NH₃-N低于20 mg/L、2 mg/L,是很有应用前景的污水深度处理工艺。更多还原

【Abstract】 Both the pollution of water environment and the shortage of water resources are driving the researches in applications of advanced treatment and in the reuse of wastewater. The secondary effluent of municipal wastewater can be used as a good potential water source due to its stable quality and large quantity. Generally, the secondary effluent of chembiological treatment has lower particle size and concentration of suspended solid （SS）. Evenhough, biological processes （i.g. biofilm processes） are often adoptted as a combined unit for advanced treatment of wastewater due to its economical characteristics. Based on the systematic analysis of the secondary effluent, the combined process of ozonation and biofiltration （O3/BAF） was established for the advanced treatment of secondary effluent aiming at water reuse. Except for the general index, some chemical and biological methods including the molecular weight distribution （MWD）, GC/MS, biodegradable analysis was employed to assess the quality fo the water in the research of operating characteristics of O3/BAF process and impact factors. Further more, the enhancement of the subsequent BAF by ozonation, the mechamisms of removal in BAF processes as well as some biofilm characteristic analysis were discussed.Commonly, the secondary effluent is characterized with the following index, such as BOD、COD、SS、NH3-N、TN and TP. However, they are too general to depict the characteristics of the secondary effluent with the upgrading of the standard of reused water and broadening of the water reuse field. Therefore, the significant characteristics need more research such as molecular weight distribution of organics, type of organics characterized by their functional groups, as well as the classes and structures of the organics in colloidal and suspended forms. Thus, the secondary effluent was fractionated into three parts: dissovled, colloidal and suspended and characterized individually. The analysis results indicated that the dissolved organics were dominating since the dissolved COD accounted for 78.2-86.5% in the secondary effluent. The secondary effluent is poorly biodegradable since the BDOC accounted for 15.5-27% of DOC. Furthermore, the organics with molecular weight <1k Dalton accounted for 56.3- 62.8%. The organic components dominantly accounted for 75.54-89.93% of the total mixture of suspended and colloidal pollutants. The paticle size distribution analysis showed that 80% of the particles ranged from 2 to 6.84μm. GC/MS analysis of the organics in dissolved form and in suspended solid indicated that 58% and 35% of them had cyclic structures, respectively. From this point, most of the organics were refractory. In summary, the secondary effluent is poorly biodegradable, which makes it necessary to adopt chemical oxidation as a pretreatment unit for improvement of the removal efficiency of the organic matter. The ozonation of the secondary effluent indicated that the removals of COD, TOC, UV254 and color were 25.7%, 16.5%, 69.3% and 79.2%, respectively, at the ozone dose of 10 mg/L and the contact time of 4 min. At the same time, the ozonation changed the percentage of organics with MW<1k Dalton from original 52% to final 72.6%. More important, the ozonation enhanced the biodegradability of secondary effluent by inproving BDOC from 1.08 mg/L to 2.6 mg/L, which accelerated the growth of biofilm and improved the biological activity of the biofilm. As a result, the removal function of the sequent BAF is thus efficiently enhanced.The long-term running data showed that the removal of organic matter by O3/BAF was higher that the sum of those by ozonation alone and BAF alone.At the same time, the removal of TOC, UV254 and color reached 20-27%, 65-75% and 85-95%, respectively. The percentage of organics with MW<1k Dalton decreased obviously.Furthermore, BAF was adaptable for the changes of hydraulic loading and pH for the organics removal. The removal of NH3-N and TN by O3/BAF is 87-92% and 13-17%, respectively. It is considered that the TN removal arised mainly from some anaerobic ammonia oxidation. Temperature, NH3-N loading and pH significiantly affected the NH3-N removal. The NH3-N removal increased with the increasing of temperature and decreased with the increasing of NH3-N loading. Besides, the optimal pH for Nitrification is from 7.27-7.89. The N element balance analysis indicated that NH₃-N was oxidized to NO₂-N by aerobic ammonia oxidizer firstly and then NO₂-N oxidized to dominant N₂ and a little of NO₃-N at the same time, by anaerobic ammonium oxidizing bacteria. The anaerobic ammonium oxidization was the main cause of nitrogen loss. The combined water-air backwashing could effectively remove the suspended pollutants and the unwanted non-active biofilm in BAF and backwashing only had a little negative impact on the removal of COD and nitrification by controlling proper condition such as backwashing intensity and backwash time. The removal function could be recoveried within shorter time after backwashing.The kinetic analysis of the reaction between ozone and organics indicated that the reactions were all one orders in 0-1.6, 1.6-16, 16-30 min and the kinetic constants were 0.0241, 0.00296, 0.000732 （L·mg-1·min-1）, respectivly. Based on the exprimental and thoredical analysis, it was summarized that the removal of organic matter was attributed to biological oxidation, filtration, biological flocculation and the consumption in the food chain in BAF. It was found that the biofilm in the forepart of BAF is much thicker through microscope and the color is deeper, the hole between media particles is smaller.The diversities of microbial polulation and special characteristics of community sucession of BAF were observed. There were a lot of communities bacillus, filamentous, vorticella, algae, coccus and so on. The configuration of the biofilm and the composition of micorbial populaiton differed from different height of meida layer. On the whole, the distribution of heterotrophic bacteria and nitrobacter is related to the organics degradation and nitrification characteristics.An experiential model was established, which is only based on the organics concentration and height of the media layer. The model constants were calculated based on the experimental data. At last, the model was validated and it can be used as a reference for actual engineering design and operating management.In conclusion, the concentration of COD and NH3-N is lower than 20mg/L and 2 mg/L, respectively. O3/BAF is an effective as well as promising combined process for advanced treatment of the secondary effluent for reuse purpose.更多还原