There is no direct sunlight for outdoor swimming, and half of the swimming pool is blocked by the house. Will you get a tan?

With the development of social economy and the improvement of people's living standards, swimming is becoming more and more popular. In recent years, epidemic accidents of infectious diseases caused by poor water quality in swimming pools have occurred from time to time. More generally, the pathogens in swimming pool water make some diseases have a high incidence among swimmers. Therefore, the monitoring of swimming pool water quality should be strengthened. Based on the existing data and our practice, this paper discusses some problems of residual chlorine control in swimming pool water. 1, requirements for residual chlorine control According to the data, the control standards of swimming pool water quality in various countries are mainly bacteria and residual chlorine. Because the analysis and detection of bacterial indicators are relatively troublesome, more equipment and instruments are needed, and the technical requirements are high, which brings inconvenience to the management of swimming pools. The determination of residual chlorine is relatively convenient and can be quickly determined on site, so the control of residual chlorine is taken as the main project of swimming pool management. The so-called residual chlorine refers to the residual free chlorine in the water after the chlorine-containing disinfectant is applied to the swimming pool. It shows that the amount of pesticides used in the swimming pool is sufficient, and there is still surplus. This can ensure the disinfection effect of water body. In the swimming pool water quality index, the state stipulates that the residual chlorine content is 0.4~0.6mg/L(0.4~0.6ppm). However, in the national indicators, there is no time to reach this standard 24 hours a day or during the opening of the swimming pool. In fact, the change of residual chlorine in swimming pools is very rapid. In summer, the decline rate of bleach is 0.25mg/L.h, and TCCA is 0.1mg/l.h.. This means that in order to keep the residual chlorine at 0.4~0.6mg/L within 24 hours, it is necessary to supplement disinfectants for 24 hours continuously to reach this standard. So what we are discussing here is actually how to correctly understand and effectively implement the provisions on residual chlorine in China's national standards. It not only ensures the qualified water quality, but also saves drugs. We think we should consider this problem from the following aspects: First, the setting of the upper and lower limits of residual chlorine in national standards. We understand that the upper limit of 0.6mg/L depends on the sensory acceptance of swimmers. Generally speaking, skin and muscle tissue are below 3 1.5mg/L, and judging from the tolerance of human body to the concentration of residual chlorine in contact liquid (regardless of pH value here), no injury * reaction will occur. The tolerance of mucosa is below 12.5mg/L/L, but it is acceptable, which does not mean that it is not uncomfortable. In fact, when the concentration reaches 0.5mg/L, some people can smell it, but it is harmless. As for the lower limit, the US Health Bureau and FINA stipulate that it is 0.2 mg/L. According to the national conditions of China, the personnel are complicated and some people have poor hygiene habits. In order to better ensure the health of swimmers, the lower limit is 0.4 mg/L. Therefore, we think it is necessary to control the residual chlorine in the pool water between 0.4 and 0.6 mg/L during the opening hours of the swimming pool. Secondly, the pathogens in swimming pool water include spore bacteria, viruses, spirochetes, rickettsia, fungi, amoeba cysts, etc., which are easy to kill. One way to kill these pathogens is to increase the concentration of disinfectant; Another method is to extend the disinfection time. The type of disinfectant is also important. Some disinfectants have poor disinfection effect at low concentration. Since the opening hours of the swimming pool are limited, we can consider enhancing the disinfection effect during closed hours, specifically, applying disinfectant during closed hours to increase the residual chlorine in the pool water, so that the disinfectant can be used for a long time and achieve better disinfection purposes. To sum up, we think that residual chlorine can be controlled in this way to ensure that it meets the national standards during opening hours and maintain disinfection capacity as much as possible during non-opening hours. 2. Changes of residual chlorine in swimming pool After various chlorine-containing disinfectants are put into swimming pool water, they will change chemically and generate Hclo. Because Hclo is unstable *, it will gradually lose its bactericidal ability, and its detectable feature is the reduction of residual chlorine. According to the literature and our observation, among the many factors leading to the decrease of residual chlorine, the most important ones are as follows: 2. 1 Environment The outdoor swimming pool is exposed and is most affected by the environment, especially the direct sunlight. The most important thing in sunlight is ultraviolet rays, which have strong penetrating power. When the clouds cover the sun, the sunlight seems to be much weaker to the naked eye, but because the ultraviolet transmission is still very large, the disinfectant in the pool water is decomposed by light. The stronger the sunlight, the faster the decomposition speed; Air, rain and dust are all mixed with a large number of microorganisms and impurities, and their consumption of residual chlorine can not be ignored. It is for this reason that the water in some swimming pools will change after it rains. Why don't the water in some swimming pools change after it rains? The reason is that air pollution varies from place to place, and the amount of residual chlorine in swimming pool water is different when it rains. In other words, the residual chlorine in the disinfectant in the swimming pool is enough to resist the invasion of foreign microorganisms, so that the water quality can be kept good, otherwise it will change and sometimes get out of hand. Microorganisms live in pool water, and their regeneration speed develops mathematically in an environment with suitable temperature and pH value. If the local water source is seriously polluted by phosphorus, its regeneration speed is even more amazing. The water in the swimming pool can change from clear to turbid in an hour or two, and it takes a lot of chemicals and a long time to treat the turbid water again. Therefore, management should be strengthened at ordinary times, especially the control of residual chlorine, so as to nip in the bud. In the swimming pool water, according to our observation for 20 consecutive days, in the open air of a standard swimming pool, the average decrease rate of residual chlorine is 0.26mg/L. 10min (the initial concentration of floating water is 0.6-0.8 mg/L), and the decrease rate is 0.1-0.6558 in rainy days and at dusk. From the above observation, it can be seen that the rate of residual chlorine reduction at night is one tenth of that during the day. Therefore, the use of disinfectants should be carried out at night, which has the advantages of small loss of disinfectants, high concentration of residual chlorine at night and sufficient contact time under the same usage amount, thus achieving better disinfection effect. 2.2 Influence of Swimmers Under similar weather and temperature conditions, we can clearly see the influence of this factor by comparing the reduction rate of residual chlorine in the pool water when swimming and not swimming. It is observed that under normal circumstances, the residual chlorine in the pool water can be reduced by 0.04mg/L per hour 100 people (here refers to the decline after the decline itself). According to our analysis, the reasons for the decrease of residual chlorine caused by swimmers are as follows: urination. We have done many experiments, and the residual chlorine in 33L swimming pool water can be reduced by 0. 1mg/L on average per 1ml urine. That is to say, as long as a quarter of 400 swimmers urinate once, it is enough to reduce the residual chlorine in a standard swimming pool by 0.04 mg/L. According to our survey of swimmers, a quarter of this figure does not come out of thin air. Sweat and other secretions and fungi carried by human epidermis can also reduce residual chlorine. According to our test, the average sweat of 1ml can reduce the residual chlorine in 10L swimming pool water by 0. 1mg/L ... Because of the agitation of the moving human body, the contact between the pool water and the air is increased, and the dust in the air contains a lot of microorganisms, which will also increase the decrease of residual chlorine. 3. Influence of Disinfectants on Residual Chlorine At present, disinfectants used in swimming pools in China include liquid chlorine, bleaching powder, bleaching water and strong chlorine essence (TCCA). Liquid chlorine is dangerous, and there are many accidents of leakage and poisoning in swimming pools, so it is rarely used in swimming pools. Bleaching powder is gradually eliminated because of its residue, blocking pipelines and affecting water quality. The chlorine content in bleaching water is extremely unstable, and its available chlorine will gradually decrease with the influence of environment, temperature, humidity, light and storage time. According to our analysis, the available chlorine content of bleached water packed in plastic barrels will drop by 50% after being stored in the open air for 15 days, and the drop is so great that it is difficult for users to master the chlorine addition amount. The available chlorine content of bleaching water is 10% when leaving the factory. Some dealers buy them from manufacturers and store them for a period of time, but users buy more and store them for a long time, so the loss of available chlorine is greater. In addition, after the bleach is put into the swimming pool, its decomposition speed is very fast. All the data measured in item 2.2 of this paper use bleach as disinfectant. According to our determination, if 2ppm bleach is added as required. On a sunny day, after adding for two hours, the residual chlorine in the water is almost zero. Bleaching water in alkaline water has poor bactericidal effect, only 1% of hypochlorous acid. Obviously, if hypochlorous acid can be stabilized so that it does not decompose into hypochlorous acid, it is equivalent to improving the sterilization effect by 99 times. TCCA is a new bactericide developed according to this idea. Because TCCA molecule has * * * yoke bond, it gradually decomposes and releases hypochlorous acid in water, leaving isocyanurate to stabilize available chlorine in water. It is non-toxic, so it has special effects that bleach does not have. TCCA has strong bactericidal power, stable drug, wide pH range, long duration of drug effect and quite stable storage. According to the measurement, the loss of available chlorine of TCCA is only 65,438 0% when it is stored for one year. Therefore, TCCA is basically used as a disinfectant in swimming pools in Europe, America and Japan. In recent years, a considerable number of swimming pools in China have changed to TCCA as disinfectant. The effect is obvious, and the water quality all meets the requirements of national standards. 4. Determination of residual chlorine In fact, the determination of residual chlorine is relatively simple and convenient, and general managers can master it as long as they know how to use it. In water quality monitoring and analysis, many projects are carried out by colorimetric analysis. The same is true for measuring residual chlorine. It generates colored substances through the chemical reaction between reagents and available chlorine, and compares the concentration according to the color depth of this substance. Colorimetry has the advantages of simple operation, rapid determination, wide test range and stable and reliable data. The detection of residual chlorine should be available in every swimming pool, otherwise the change of residual chlorine in swimming pool can't be grasped. * Without scientific basis, it is difficult to ensure the water quality of swimming pools. SXZ-3 pocket colorimeter can measure residual chlorine and pH value in swimming pool. The measurement range of residual chlorine is 0.05 ~ 2.5 ppmpH and 6.0~7.6. It is easy to carry, simple to make and use, and quick and sensitive in response. When testing, the specific liquid is put in a box, which is not limited and influenced by the testing environment and conditions.