【作者】 翟黎明；

【导师】 尹军； 黄汝常；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2011， 博士

【摘要】 淡水危机是人类社会共同面临的环境问题,随着人口的不断增长和城市化水平的逐步提高,未来淡水资源的形势更加严峻。在沿海城市海水直接利用成为缓解淡水供需矛盾的重要途径之一,但是海水利用所产生的高盐污水在处理后携带的化学污染物质和病原微生物引起的健康风险问题也随之产生。因此,以控制城市污水处理厂的高盐二级出水和混凝出水中病原微生物的数量及消毒副产物生成量为目的的研究已成为目前的研究热点之一。污水氯化消毒技术是最普遍的消毒方式,具有杀菌效果好、处理成本低、使用方便、易管理等优点,对于提高城市污水的生物安全性具有重要意义。为促进沿海城市海水利用的研究发展与实践应用,本课题以实际高盐二级出水和混凝出水为处理对象,通过现场模拟管路实验及小试实验,全面系统研究了高盐污水氯化消毒的效能,考察了高盐二级出水、混凝出水中大肠菌的灭活规律与物化指标的关系,首次探讨了二级生物处理系统中污泥龄的变化对消毒副产物生成的影响,并研究了温度、投氯量、氨氮、溴离子浓度等对消毒副产物的影响,分析了氯化对管道腐蚀加剧的限度及对管内壁生物膜生长脱落的影响。高盐混凝出水需氯量的日变化/月变化较大,没有呈现明显的变化规律。白天波动量高达8.0 mg/L,早上的需氯量最高;夜间需氯量略低,月平均需氯量变化趋势与白天基本一致。高盐混凝出水需氯量的日变化系数、时变化系数、总变化系数分别为K_d=1.477,K_h=1.094,K_z=1.616。高盐混凝出水中的大肠菌对自由性余氯的抵抗力较弱而对一氯氨等结合性余氯的耐受性较强,出水中大肠菌(E. coli)的数目主要受控于水中TRC(total residual chlorine)的量,接触反应时间非主要调控参数,只要长于6-8 min。高盐二级出水温度对投氯量的影响较小,但温度升高将导致消毒副产物生成的总量增加。氨氮含量对投氯量的影响十分显著,建议在污水厂的实际氯化工序中紧密监测出水中氨氮的含量。氯和氨氮浓度的共同增加将提高氯-氨反应的反应物浓度而使副产物的生成量相对减少。二级生物处理系统的污泥龄对消毒副产物的生成有较大影响,采用较长污泥龄的二级生物处理出水会生成较多的消毒副产物,说明出水中的有机物与氯有较高的反应活性,具有较高的比有机物的CBPs生成能力,即CBPs/DOC(chlorination by-products/dissolved organic carbon)值较高。高盐污水中的溴离子使生成的CBPs向含溴的副产物方向移动,CHBr3和DBAA在副产物总量中所占比例较大,比有机物的溴代消毒副产物的生成量与污水的SUVA(specific UV absorption )值之间不存在正相关关系。氯化过程对污水传输管系影响的模拟研究表明,在传输高盐二级出水时,溶解氧所引起的对铸铁管的腐蚀是氯的17.8倍。当溶解氧与氯同时出现时,即使溶解氧含量接近饱和,也并未产生协同腐蚀作用。加氯消毒对铸铁管的腐蚀主要受控于溶解氧而不是水中余氯的含量。腐蚀速率随氧化剂含量的增加而提高,但随余氯提高的速率要比随溶解氧提高的速率小得多。管道内壁附着的生物膜的生长与出水中有机物的含量存在动态平衡的关系。对于BOD(biochemical oxygen demand)含量仅为10 mg/L的高盐二级出水,其相应的生物膜厚度约为200μm,对于高盐混凝出水,生物膜厚度可达300-500μm,即使水中余氯增加到5.0 mg/L甚至更高,并未影响生物膜的生长和脱落,出水中悬浮物的含量也并未显著增加。通过本文的研究,对高盐出水中E. coli的灭活规律和消毒副产物生成特性有了更深入的认识,并探明了管道内投氯消毒对传输管系的影响限度,所得结论为今后深入进行理论探讨奠定了基础,为其它沿海城市开展相关的工程应用提供了重要的理论依据和技术支持。更多还原

【Abstract】 Fresh water shortage crisis has been a vital environmental issue that the whole world faces. Alone with population growth and urbanization level increase, the situation of fresh water resource is extremely serious. The seawater direct use is one of the most important means to relax the contradiction between fresh water supply and demand. However, the health risk arises which derived from the consequent high salinity sewage effluent containing chemical pollutants and pathogenic microorganisms. So, the current study for the purpose of controlling pathogenic microorganism counts and disinfection by-products formation becomes research hotspot. The chlorination technique is the most widely used disinfection method, which has many advantages, such as good kill effectiveness, lower treatment cost, easy to use and operation. Chlorination disinfection has great significance for increasing the bio-safety of sewage effluent.To promote R & D and practical application of seawater utilization in coastal cities, based on field experiment, a pipe loop simulator study combined with lab batch test has been conducted to explore chlorination efficiency of wastewater with high salinity; to observe the exact pattern of E. coli inactivation correlated with the final TRC (total residual chlorine) in saline sewage effluent; to assess the biofilm growth and sloughing when the effluent is subjected to chlorination; to assess the corrosion extent in ductile iron pipe when it is used to transport chlorinated saline sewage effluent. In addition to studying the effect of temperature, chlorine dosage, ammonia and bromine concentration on CBPs formation (chlorination by-products), this is the first case to explore the relationship between sludge age and CBPs formation.Diurnal/monthly change of chlorine demand in high salinity CEPT (chemically enhanced primary treatment) effluent varied greatly, no obvious changing regularity was observed. The variation could reach 8.0 mg/L at daytime, the chlorine demand was high in the morning, which lowered down a lesser degree at night, and the change tendency of monthly average chlorine demand was almost the same as daytime. Daily/hour/total variation coefficient (K_d, K_h and K_z) of chlorine demand in high salinity CEPT effluent was 1.477,1.094 and 1.616, respectively. The resistance of E. coli in CEPT effluent was low to free chlorine and high to combined chlorine, say monochloramine. The remaining E. coli level was mainly dependent upon the prevailing residual chlorine level, the contact time was non-essential parameter as long as it’s over 6-8 mins.The temperature of high salinity secondary effluent had minor effect on chlorine dosage, the CBPs formation increased with increasing temperature. However, the ammonia-N level had major effect, which should be closely monitored in the real chlorination process in sewage treatment works. The more chlorine dosage and ammonia-N level, the more chloramine formed and the other products-CBPs formation relatively decreased. The sludge age in biological treatment had a major effect on CBPs formation. A longer sludge age had been found to yield a higher CBPs formation in the chlorinated saline secondary effluent. The effluent organic matters from the longer sludge age operation had a higher reactivity with chlorine, which resulted in a greater specific total CBPs/DOC (dissolved organic carbon) yield. The rich bromine ions in saline sewage shifted some CBPs to bromine-containing species, such as CHBr3 and DBAA, which represented a large fraction of the total CBPs. These was no positive relationship between Br-CBPs/DOC and SUVA (specific UV absorption) value.Simulation study of sewage conveyance system upon chlorination suggested that in carrying the saline secondary effluent, the ductile iron force main corrosion by DO (dissolved oxygen) was about 17.8 times higher than that by chlorine. When DO and chlorine residual were present together, even DO approached saturation, there appeared no synergistic corrosive action, the corrosion rate was mainly dictated by DO while chlorine played only a very insignificant role in affecting the corrosion. The corrosion rate increased when the oxidant increased, however the corresponding rate was much higher with DO increasing than chlorine. The level of biofilm growth in the pipe wall was always in a dynamic equilibrium with the organic strength of the carried flow. For conveying the saline secondary effluent with a BOD (biochemical oxygen demand) of about 10 mg/L, the biofilm thickness was approximately 200μm; for conveying the saline CEPT effluent, the biofilm thickness could reach 300-500μm. With chlorination of up to 5.0 mg/L even higher, the biofilm growth and sloughing were not adversely affected; there was no noticeable deterioration of the current effluent qualities with respect to suspended solids.This study developed a better understanding about E. coli kill profile, CBPs formation and proved up the impact degree of the chlorination on sewage conveyance system. The results obtained laid a foundation for further research, also provide technical support and theoretical basis in practical application for the other coastal cities.更多还原