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船舶饮用水消毒试验研究及方案设计

船舶饮用水主要有二种:市政自来水和海水淡化水。船舶淡水舱内的水储存超过一定时间,水中的消毒剂衰减完,细菌重新繁殖,导致水质难以达到GB5749-2006《生活饮用水卫生标准》,因此必须对其进行持续消毒处理。本研究采用次氯酸钙、次氯酸钠、紫外线消毒等几种最常用方式对船舶淡水进行消毒,分析它们的适用性。使用次氯酸钙法进行消毒试验时,发现密闭环境下,其余氯自然衰减比较缓慢,当余氯初始浓度为0.64 mg/L时,保存半月后余氯含量仍在0.3 mg/L以上;对含有105CFU/100 mL大肠杆菌的贮水箱进行消毒,初始余氯为3.82 mg/L时,有良好的消毒效果;进行14 d的贮水箱循环消毒试验时,其副产物浓度远低于GB5749-2006要求,表明消毒处理的饮用水长期存储饮用是安全的。使用次氯酸钠进行消毒试验,结果表明其同样具有良好的消毒效果。采用紫外线消毒,发现其在一定流速内具有较好的杀菌效果,但没有持续消毒功能。根据试验研究结果,船舶上不同位置饮用水应采用不同的消毒方式,对船舶给水、反渗透淡化水及水舱淡水消毒推荐使用次氯酸钙(钠)法,对终端用水推荐使用紫外线消毒法。

There are two main types of ship drinking water: municipal tap water and desalination the water stores in the ship's water tank for some time, the disinfectant has decayed in the water and bacteria reproduction, resulting in water quality is difficult to meet Standards for drinking water quality (GB5749-2006).Therefore, it must be continuously this study, calcium hypochlorite, sodium hypochlorite, and ultraviolet disinfection were used to sterilize the ship fresh water, and their applicability was using calcium hypochlorite to sterilize water, it was found that the natural attenuation of residual chlorine was slow in a closed the initial concentration of residual chlorine was 0.68 mg/L, the residual chlorine content was still larger than 0.3 mg/L after half a experiment of sterilizing water containing 105CFU/100 mL Escherichia coli in the water storage tank and the disinfection showed a good effect when the initial residual chlorine content was 3.82 mg/L.The disinfection by-product (DBP)concentration was much lower than the limits in GB5749-2006 when doing the 14-day circulating disinfection test of water storage tank, which indicated that the drinking water treated by calcium hypochlorite was safe for long-term storage and results showed that the sodium hypochlorite also had a good disinfection testing ultraviolet disinfection, it was found that ultraviolet (UV)had better disinfection effect in a certain velocity, but without continuous disinfection to the result of the experiments, the different disinfection methods should be chosen based on the different spots of the drinking water on water feeding the ship, desalinated by reverse osmosis, and storage in the water tank should be disinfected by calcium (or sodium)hypochlorite, and the terminal water should be disinfected by ultraviolet ray.

1.前言

对船员的健康而言,船舶饮用水保障十分重要。船舶饮用水主要由岸基补给保障,水源为含有余氯的市政自来水,在短时间内水质有保证;此外,还有由船舶自备海水淡化装置提供的自保障。一般情况下,合格的海水淡化装置生产的淡化水经水质调节处理,能满足饮用要求[1]。伴随航行时间变长,水舱水中的消毒剂不断消耗,使水舱内的余氯含量下降,导致水中的微生物再度繁殖,如:致病菌的繁衍等[2]。供水水质问题一般由微生物,水中颗粒物质等致病菌、有机污染物引起的。肠道致病菌可引起很多致死的疾病例如霍乱、伤寒和其他腹泻类疾病[3][4]。对于由岸上补给的水源来说,由于存在一定的余氯,水质保鲜的时间稍长;对于海水淡化装置生产的淡水,其保鲜期则更短。当水舱内的水保存2天甚至更长的时间,由于细菌的大量繁殖,水质难以达到GB5749-2006《生活饮用水卫生标准》,必须对其进行消毒处理。一般情况下,水舱的储存容积可满足5~15天的供水要求,大大超过2天的供水容量。

福建检验检疫局曾对某口岸入出境船舶实施饮用水卫生监测44批次,现场调查发现,80%船舶至多每年清洗一次饮用水舱,20%船舶清洗时间超过一年,甚至只在修船时才清洗水舱,100%船舶在清洗时未进行有效消毒[5]。对目前舰船的调研,总体而言,舰船饮用水消毒措施处于落后状态。2005年以前建造的舰船,主要通过人工添加消毒剂方式进行消毒,由于未配备专门的添加装置,消毒剂的添加时机、数量没有严格规定,同时还存在消毒剂溶解不良现象,使得消毒效果无法保证,导致造成饮用水的污染。对某常规潜艇淡水供应卫生状况调查结果表明细菌学指标超标严重,细菌总数和大肠菌群均合格的只占45.7%,有69%未检出游离余氯。对水面舰艇水舱饮用水水质进行调查,结果发现某舰艇水舱饮用水的大肠菌群为63个/L。秦思昌等[6]对某舰艇的饮用水水质进行检测,发现细菌总数和大肠菌群分别为20个/ml和12个/L,均未达到GB5749-2006的要求,影响了舰员的身体健康。为满足舰船人员对饮水的需求,确保饮用水安全可靠,采取标准规范的净化消毒技术措施和方法对舰船饮用水进行必要的处理具有重要的现实意义[7]。