Drinking water quality testing

- Dec 11, 2019-

1.Drinking water quality inspection and routine analysis

In order to facilitate the research in this paper, a water plant with a large water supply capacity and water supply coverage in a certain city was selected as the research. According to the layout of the water plant's water supply network, three more typical detection points were selected for water quality analysis. In view of the many indicators of drinking water quality detection, several representative indicators were selected for this study, namely pH, water turbidity, aluminum, residual chlorine, total bacteria, TOC, etc.

1.1 Key indicators and detection

water meter 1.1.1 pH

It can reflect the acid-base equilibrium state reached by various soluble compounds contained in the solution. Related research results show that temperature has a greater impact on the acid-base equilibrium. Experiments have shown that when the temperature in pure water rises by 25 ° C After that, its pH value will drop by about 0.45. Many indicators in the water will affect the pH value. When the pH is less than 7, the sulfur-contaminated water will emit an unpleasant smell of eggs, and the formation of nitrogen trichloride will produce a strong irritating taste. At the same time, the pH value of the water will increase, the taste of the water will become bitter, and the color will increase accordingly. In addition, the pH value will also affect the coagulation, precipitation and filtration of water, which will cause the impurity content in the water to exceed the standard. At present, it has not been proven whether there is a direct relationship between pH in water and human health, but it has been verified that pH in water will affect other water quality indicators, thereby indirectly affecting human health. Therefore, the current pH value of water in China's current sanitary regulations for drinking water clearly stipulates that the pH value should be in the range of 6.5-8.5. In this study, an electronic pH tester was used to test the pH of each measurement point.

1.1.2 Water turbidity

The turbidity of water is mainly formed by the particulate matter and some microorganisms, and the size of the particulate matter related to turbidity is generally between 1nm-1mm. The turbidity of drinking water is a key parameter for the effluent quality of the water plant. The turbidity must be detected in all links of the water treatment, especially the effluent link, which requires the use of online turbidity measuring instruments. When the turbidity of the water body is greater than 10 NTU, the turbidity is higher, and when the turbidity is less than 5 NTU, the turbidity is lower, which can be accepted by people. Relevant survey statistics show that the turbidity of effluent after domestic centralized water treatment is basically less than 5NTU, and most can reach about 1NTU. Internationally, the turbidity of water is listed as a microbial indicator. Bacteria and viruses will be exposed in water with low turbidity. While reducing the turbidity of the water body, it can make various bacteria in the water, trivalent iron and tetravalent manganese Significantly reduced. The turbidity of the water body is high, and the microorganisms in it cannot be effectively disinfected. These microorganisms will promote the breeding of bacteria in the pipe network over time, and this water will cause harm to human health. In this study, the intelligent turbidity meter independently developed by a domestic company was used to detect the turbidity of water.

1.1.3 Aluminum

As a relatively large element in the earth's crust, aluminum is widely distributed in nature. Humans mainly consume aluminum through drinking water. Relevant research results show that the average aluminum content in fresh water is about 0.24 mg / L and about 0.001 mg / L in seawater. Because water plants use aluminum salts as coagulants in the process of water supply treatment, which leads to an increase in the aluminum content in drinking water. When aluminum is enriched in the body beyond a certain level, it will cause biological diseases such as Excessive levels of aluminum in the mother's body can inhibit the development of the fetus, and cause damage to the ultrastructure of the cells, thereby causing defects in the newborn baby in some aspects. In addition, when there is a large amount of aluminum in the human body, it will affect the activity of some enzymes and easily cause diseases such as bone atrophy. China has clearly stipulated the aluminum content in drinking water, that is, the aluminum content per liter of drinking water must not exceed 0.2 mg. There are many detection methods for aluminum ions in water. After comprehensive comparison, this study uses the aluminum reagent colorimetric method to detect the aluminum content of water in each measurement point.

1.1.4 Organics

There are two major types of organic pollutants in water, one is NOM and the other is SOC. The former includes humus, microbial secretions, etc., and the latter includes "three-inducing" organic pollutants. In view of the complexity of the types of organic pollutants in water, it is necessary to measure the amount of organic matter through total evaluation indicators. The more commonly used indicators are TOC, DOC, and COD. In this study, TOC and two indicators were selected to measure and analyze the organic matter content in the tap water of the water plant. To ensure the accuracy of the test results, an organic carbon analyzer and a UV-visible spectrophotometer produced by a foreign company were used to measure TOC in water.

1.1.5 free chlorine

That is, after using chlorine as a disinfectant, the remaining chlorine content in the water. In order to kill bacteria in drinking water and ensure the safety of water quality, water plants need to disinfect the water. Chlorination disinfection has become the first choice for water disinfection in major water plants due to its advantages such as low cost, good effect and simple and convenient use. In this study, titration was used to determine the residual chlorine in water.

1.1.6 Microorganisms

In the water quality standard, microorganisms are the key indicators and the primary indicators to measure the safety of water quality. This is because microorganisms are more harmful and can cause a large number of drinkers to be infected at the same time. The new standard stipulates that the total number of bacteria is ≤80CFU / ml, and no coliform bacteria can be detected in every 100ml of water sample. In this study, the membrane method was used to detect microorganisms in water.