【作者】 王领全；

【导师】 季民； 李成江；

【作者基本信息】 天津大学 ， 环境工程， 2004， 硕士

【摘要】 本文主要是根据大生活用海水示范工程的实际需要,研究了大生活用海水水质控制技术。选用次氯酸钠和二氧化氯作为消毒剂,研究了其投量与BOD5、细菌总数、大肠菌群数去除率之间的关系。结果为:二氧化氯对海水中大肠菌群的去除率较次氯酸钠高,3.0 mg/L的次氯酸钠对海水中大肠菌群的去除率为97.89%,而相同浓度的二氧化氯对海水中大肠菌群的去除率则高达99.94%。对海水中细菌总数及BOD5的去除率也是二氧化氯较次氯酸钠高,5.0 mg/L的二氧化氯对海水中细菌总数、BOD5的去除率分别为99.96%、74.5%,出水中残余细菌数及BOD5分别为470个/L、0.79 mg/L;而相同浓度的次氯酸钠对细菌总数及BOD5的去除率分别为99.92%、72.9%,出水中残余细菌数、BOD5分别为1000个/L、0.84mg/L。当取水水质较好时,只需采用加消毒剂工艺就能杀灭海水中的生物,而保证管网末端余氯浓度≥0.2 mg/L,就可抑制藻类等的生长繁殖,并可保证管道中有足够的溶解氧。如果取水海域的海水水质较差,那么要进行曝气,以增加海水中的溶解氧含量。通过对海水供水系统中溶解氧的现场实测发现,在管道运行中,海水中的溶解氧会逐渐降低,尤其是从取水泵后到厂区使用前这一段,由于管道较长,使得封闭时间也相应较长,外界充氧能力大大降低,海水中的生物消耗氧的速度相对升高,导致海水中的溶解氧浓度明显降低。通过调研和查阅文献发现:沿海污损生物的分布受季节、温度、盐度和水流畅通程度的影响;电解海水制取次氯酸钠是最经济有效的防海洋生物附着措施,大生活用海水也应采用此法防止生物附着;为了有效防止海生物附着,海水中的有效余氯浓度不应低于0.5mg/L。对于连续加氯方式,初始投加量应控制在1.5～2.0mg/L,并确保海水的余氯浓度为0.5～1.0mg/L;对于间歇投加方式,应密切监视余氯,当其不足时应及时投加,每次加入量为2～4mg/L,加氯时间为20min。更多还原

【Abstract】 According to the actual demand of seawater demonstration project, technology ofseawater quality control for domestic use was studied. Relationships betweendisinfectant dosage and the removal of BOD5, total count of bacteria and density ofcoliform were investigated by using sodium hypochlorite and chlorine dioxide as thedisinfectant. The research result is as follow: The higher removal efficiency oncoliform in the seawater can be achieved by using chlorine dioxide as disinfectantthan sodium hypochlorite under the same dosage and reaction time, the removalefficiency of coliform can be achieved about 97.89% by using sodium hypochloritewith dosage of 3.0mg/L, and it can be achieved about 99.94% by chlorine dioxideunder the same dosage. The removal efficiency of total number of bacteria in theseawater is higher by using chlorine dioxide as disinfectant than sodium hypochlorite,the removal efficiency of total count of bacteria in the seawater can be achieved about99.96% by chlorine dioxide using with dosage of 5.0mg/L, and the residual count ofbacteria is 470CFU/L. It can be achieved about 99.92% by sodium hypochlorite underthe same dosage, the residual count of bacteria is 1000CFU/L. The higher BOD5removal efficiency in the seawater can be achieved by using chlorine dioxide asoxidant than sodium hypochlorite under the same dosage and reaction time, the BOD5removal efficiency can be achieved about 94.5% by using chlorine dioxide withdosage of 3.0mg/L, and the residual BOD5 is 0.79mg/L. It can be achieved about92.9% by sodium hypochlorite under the same dosage, and the residual BOD5 is0.84mg/L. Chlorine dioxide is better than sodium hypochlorite in both organicpollutants and microbe removal. If the seawater quality in intake area is good,disinfection technology is needed only to remove microbe in the seawater, and shouldguarantee residual chlorine in the end of pipe network to be more than 0.2 mg/L torestrain the growth of alga, and enough dissolved oxygen in the pipe could beguaranteed, so anaerobic environment will not be developed in the pipeline. Seawatershould be aerated during pre-treatment process to increase dissolved oxygenconcentration when for domestic use if the water quality in intake sea area is not sogood.Onsite monitoring of the seawater supply system finds that DO concentration inthe seawater will reduce gradually during the pipe transportation, especially from thewater intake pump station to the treatment plant, because the length of pipe andtransportation time are relative long, the ability of oxygen refilling is greatlydecreased and oxygen consumption speed of the microbe in the seawater is relativehigh, which would cause a evident reduction of DO concentration in the seawater.Through investigation and research, comprehensive analysis was made on thecommon used anti-biological fouling technologies, conclusion can be made as follows:The distribution of inshore fouling organisms is affected by factors such as season,temperature, salinity, and water current smoothness etc. In seawater utilization project,the sodium hypochlorite production by seawater electrolysis is the most economicaland effective method for preventing biological fouling caused by sea organisms. Theelectrolysis method should be also used for anti-biological fouling of domestic usedseawater. In order to control biological fouling effectively, the residual chlorine levelin seawater should not be less than 0.5 mg/L. For continuous chlorine dosing, theinitial dosage should be controlled at 1.5 ～2.0 mg/L, and residual chlorineconcentration should be 0.5～1.0 mg/L. For intermittent dosing, the residual chlorinelevel should be monitored carefully, dosing should be carried out when there is notenough residual chlorine, with dosage of 2～4 mg/L and dosing time of 20 min.更多还原