For the disinfection effect of sodium hypochlorite generator, chlorine dioxide generator and finished product sodium hypochlorite after disinfection
The generation of disinfection by-products was studied, and the characteristic test of the finished sodium hypochlorite solution was carried out.
Safety management and operating costs of a disinfection method. The results showed that the disinfection and sterilization effects of the three disinfection methods were not significant.
However, the types of disinfection by-products produced by chlorine dioxide and sodium hypochlorite are different, and the disinfection by-products of sodium hypochlorite are different.
Most of them are trihalomethanes and haloacetic acids, and chlorine dioxide disinfection mainly produces chlorate and chlorite. Sodium hypochlorite
There was no significant difference in the level of disinfection byproducts between the sodium hypochlorite solution prepared by the bioreactor and the finished sodium hypochlorite solution. to make
The content of bromate in the sodium hypochlorite solution was significantly higher than that of the solution prepared by the sodium hypochlorite generator, and increased with the storage time.
With the increase of , the finished sodium hypochlorite solution has the phenomenon that the available chlorine decays and the chlorate content increases.
At present, the disinfection of tap water generally adopts liquid chlorine,
Disinfection methods such as chlorine oxide and sodium hypochlorite [1]. liquid chlorine disinfection
The cost is relatively low, and it is the most widely used in water plant disinfection, but
Liquid chlorine and chlorination rooms are a major source of danger in cities. With the country’s
The requirements for the management of dangerous goods are becoming more and more stringent, and some areas have
The article stipulates that the use of liquid chlorine for disinfection is not allowed. Chlorine dioxide is a broad-spectrum high-efficiency disinfectant.
In comparison, the killing effect on pathogenic microorganisms in water is good, and the effect
Fast [2]. Chlorine dioxide generators generally use hydrochloric acid and chlorine
Sodium is the raw material, both of which belong to the control of hazardous chemicals
range, especially hydrochloric acid, is highly corrosive in transportation and use,
There are safety hazards; and pungent in daily production configurations
odor, and the production operating environment is poor.
Sodium hypochlorite not only has a strong bactericidal effect, but also
And it has the characteristics of easy decomposition, no residue, less toxic to human body, etc.
It is an important development direction of drinking water disinfection in the future [3]. out
For hazardous chemicals management, safety, production operating environment
Considering that more and more water plants choose to use sodium hypochlorite to eliminate
poison. There are two ways to obtain sodium hypochlorite, one is to chlor-alkali
The factory buys the finished sodium hypochlorite solution, and the second is to use water, electricity,
Salt is electrolyzed to safely produce hypochlorite on-site in water plants
Sodium solution. Chlorine dioxide generator and sodium hypochlorite generator
Toxic effect comparison.
Table 1 Comparison of raw water characteristic indicators
| Item | June | July |
| Thermotolerant coliforms(pc/L) | 1600 | 540 |
| Arsenic(mg/L) | 0.0032 | 0.0053 |
| Iron(mg/L) | 1.00 | 0.67 |
| Copper(mg/L) | 0.0019 | 0.0022 |
| Fluoride(mg/L) | 0.51 | 0.61 |
| Nitrate(mg/L) | 0.99 | 1.08 |
| Chloride(mg/L) | 50 | 56 |
| Sulfate(mg/L) | 53 | 56 |
| Permanganate Index(mg/L) | 3.00 | 3.20 |
| Ammonia Nitrogen(mg/L) | 0.07 | 0.07 |
| Chenical Oxygen Demand(mg/L) | 12 | 9 |
| Total Phosphorus(mg/L) | 0.101 | 0.124 |
| Total Nitrogen(mg/L) | 1.48 | 1.38 |
| Petroleum(mg/L) | 0.03 | 0.029 |
| Dissolved Oxygen(mg/L) | 6.8 | 4.74 |
Table 2 Comparison of two disinfection methods of chlorine dioxide and sodium hypochlorite generators
| Item | Chlorine Dioxode Generator | Sodium Hypochlorite generator | ||
| Factory water | I clean water | Ⅱ clean water | Factory water | |
| Total Coliform | ND | ND | ND | ND |
| Thermotolerant coliforms(pc/L) | ND | ND | ND | ND |
| Escherichia coli | ND | ND | ND | ND |
| Total bacterial count CFU/ML | ND | 4 | 2 | ND |
| Chloroform（mg/L） | <0.001 | 0.0027 | 0.0088 | 0.0061 |
| Dichloromonocromomethane(mg/L) | 0.0016 | 0.0055 | 0.014 | 0.0091 |
| Dichlorodibromomethane(mg/L) | 0.0032 | 0.0068 | 0.014 | 0.0092 |
| Tribromomethane(mg/L) | <0.0025 | <0.0025 | 0.0039 | 0.0043 |
| Total trihalomethanes | 0.09 | 0.22 | 0.56 | 0.37 |
| Trichloroacetic acid(mg/L) | <0.001 | 0.0033 | 0.0039 | 0.0043 |
| Dichloroacetic acid(mg/L) | <0.0004 | 0.0029 | 0.0042 | 0.0039 |
| Chlorite(mg/L) | 0.21 | <0.01 | <0.01 | <0.01 |
| Chlorate(mg/L) | 0.64 | 0.046 | 0.055 | 0.06 |
| Disinfectant residue(mg/L) | 0.13(chlorine dioxide) | 0.54(Free residual chlorine) | 0.80(Free residual chlorine) | 0.56(Free residual chlorine) |
Table 3 Small test experiment on the disinfection effect of sodium hypochlorite generator and finished sodium hypochlorite
| Item | Finished sodium hypochlorite | Sodium hypochlorite generator preparation solution | ||||
| Initial effective chlorine concentration(mg/L) | 1.25 | 1.88 | 2.5 | 1.25 | 1.88 | 2.5 |
| Total bacterial count(CFU/ML) | ND | ND | ND | ND | ND | ND |
| Chloroform（mg/L） | 0.0045 | 0.0068 | 0.006 | 0.0046 | 0.0073 | 0.0067 |
| Dichloromonocromomethane(mg/L) | 0.0053 | 0.0066 | 0.0064 | 0.0055 | 0.0076 | 0.0072 |
| Dichlorodibromomethane(mg/L) | 0.0053 | 0.0057 | 0.0052 | 0.0052 | 0.0062 | 0.0055 |
| Tribromomethane(mg/L) | <0.0025 | <0.0025 | <0.0025 | <0.0025 | <0.0025 | <0.0025 |
| Total trihalomethanes | 0.23 | 0.29 | 0.27 | 0.23 | 0.32 | 0.3 |
| Trichloroacetal | 0.003 | 0.0051 | 0.0056 | 0.0034 | 0.0041 | 0.0062 |
| Trichloroacetic acid(mg/L) | 0.0036 | 0.0052 | 0.0056 | 0.0036 | 0.0055 | 0.0061 |
| Dichloroacetic acid(mg/L) | 0.0021 | 0.0041 | 0.005 | 0.0026 | 0.0057 | 0.0069 |
| Chlorite(mg/L) | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 |
| Chlorate(mg/L) | 0.053 | 0.077 | 0.103 | 0.075 | 0.109 | 0.140 |
| Terminal residual chlorine(mg/L) | 0.51 | 0.89 | 1.27 | 0.57 | 0.95 | 1.40 |
Table 4 Comparison of operating costs of chlorine dioxide, finished sodium hypochlorite and on-site preparation of sodium hypochlorite
| Disinfection Method | Raw Material | Running cost(cny.kg available chlorine) |
| Chlorine Dioxide | Sodium chlorate, hydrochloric acid | 7 |
| Finished sodium hypochlorite | Purchased from chlor alkali plant | 8 |
| Site preparation of sodium hypochlorite | Salt | 3.7-5 |
There is no significant difference in disinfection and sterilization effect between sodium hypochlorite generator and chlorine dioxide generator, but the types of disinfection by-products are different. Sodium hypochlorite disinfection will generate trihalomethanes and haloacetic acid disinfection by-products, chlorine dioxide disinfection by-products are mainly
are chlorate and chlorite. There was no significant difference between the sodium hypochlorite solution prepared by the sodium hypochlorite generator and the finished sodium hypochlorite solution in the disinfection and sterilization effect and the level of disinfection by-products. The bromate content in the finished sodium hypochlorite solution is significantly higher than that of the sodium hypochlorite solution prepared by the sodium hypochlorite generator. And with the increase of storage time, the finished sodium hypochlorite solution exists
Phenomenon of available chlorine decay and chlorate content increase. 1% sodium hypochlorite prepared on-site in a sodium hypochlorite generator
The solution is a safe product, is non-toxic to the environment, has good safety, and significantly reduces operating costs, which is convenient for production operations.