1 The nature of hospital wastewater due to the hospital has a special nature, about the discharge of sewage is mainly medical sewage and living sewage two. Medical sewage discharged from many departments, such as laboratory testing centers and isotope radiotherapy clinics, etc., because it contains a variety of radioactive substances must be treated to be discharged into the sewer, such as disinfectants, organic solvents, pathogens and so on. However, domestic sewage is patients and their families washing, living, cafeteria kitchen discharge, can be directly into the sewer. Hospital sewage has a complex composition and diverse source channels, with a wide range of pollution, acute and chronic and latent infectious, if discharged into the sewer before not effectively treated, it will lead to hazardous substances with the sewage spread around, which in turn, in the serious pollution of the environment at the same time will also jeopardize people's health.2 Hospital sewage treatment process design 2.1 Hospital sewage treatment process At present, the "hospital sewage treatment design specification" for the design of the hospital sewage treatment process. Sewage Treatment Design Code" for the design of hospital sewage treatment reference standards, while the hospital sewage has a more complex nature, radioactive wastewater discharged into the hospital drainage system must be processed by the decay pool. Because the hospital has a more dense population, in the selection of sewage treatment process needs to be advanced, affordability and stability for comprehensive consideration, which is high stability, less investment, less space, less operating costs for the first principle, to ensure that the sewage can be automated, the operation can be simplified.2.1.1 Discharged into the municipal pipeline with a first-class or first-class enhanced treatment discharged to the end of the second-level Sewage treatment plant in the municipal pipeline hospital sewage, so that the harmful gases, toxic and hazardous, flammable and explosive substances, pathogenic microorganisms, etc., can be effectively eliminated, because the hospital sewage will eventually be mixed with domestic sewage, so the general physical and chemical indexes set by the requirements do not need to be too harsh, such as COD, BOD and SS. Hospital sewage and residential sewage will be discharged into the municipal pipeline, compared to the hospital sewage, residential sewage water quality is much worse, COD, for example, hospital sewage pollution concentration between 90 ~ 250mg / L, residential sewage for 400 ~ 500mg / L. Compared to residential sewage, hospital sewage is small in quantity, but need to be treated separately and rigorously, and the two ultimately mixed in municipal pipelines, if you can not carry out sewage treatment, it will be very easy. If sewage treatment cannot be carried out, it is very easy to cause the waste of social resources.2.1.2 In the strict treatment does not save a lot of disinfectant in order to better save disinfectant, hospital wastewater is very necessary to carry out a high level of pre-treatment, in order to reduce the concentration of sewage pollution, and improve the disinfection effect. It has been found that raw sewage usually after one or two levels of treatment, the difference between the disinfectant input is less than 5mg / L. For the hospital sewage by the first level of treatment, in the second level of treatment by adjusting the amount of chlorine instead of the method, in the case of the same results, the operating costs per ton of water increased by 0.02 ~ 0.04 yuan. In addition, secondary treatment is not only costly, cumbersome and expensive to operate, but also induces various nuisance problems such as noise and odor. The project cost of primary and secondary treatment is 1:2 to 1:3, and the operation cost is 1:3. 2.1.3 Requirements of the World Health Organization According to the requirements of the World Health Organization, in the downstream municipal wastewater treatment plant, hospital wastewater can be discharged to the sewer as long as it is disinfected, that is, the downstream wastewater treatment plant is well operated, and more than 95% of the disease-causing microorganisms can be removed by the secondary treatment system; after being treated by effective anaerobic microorganisms, there are not enough parasitic eggs in the sludge. After effective anaerobic microbial treatment, there are less than 1 /L of parasite eggs in the sludge; Regarding the health and safety management system, the hospital is relatively strict, which can ensure that there will be no antibiotics, hazardous chemicals, pharmaceuticals, and radioactive wastewater in the municipal sewers; Patients' excreta are collected separately, and sufficient disinfectant is needed for disinfecting, to ensure that the treatment is done properly.2.2 Conventional Treatment ProcessesThe treatment process mainly consists of two stages, which is after general precipitation, disinfection, primary treatment can be directly after treatment, and then disinfection. After disinfection, the first level of treatment can be directly discharged, after the initial precipitation through the septic tank into the grille can remove debris, and then discharged into the adjustment pool, sedimentation tank and contact pool, and finally discharged after strict disinfection. Secondary treatment is mainly by biological means of treatment and discharge, and sometimes also use physical, chemical and biological joint way, the process is similar to primary treatment, by the grille can be effective removal of debris in the sewage, biological secondary treatment can be adjusted by the pool, to the secondary pool discharged into the pool will be passing through the contact pool and other equipment, and finally discharged into the sewer.2.2.1 Conventional buried type of non-powered wastewater treatment by the grille sinking Sand pool to facilitate the removal of large particles of floating matter and solids in the sewage; through the hydrolysis acidification pool and anaerobic biofilter, most of the organic pollutants can be effectively decomposed under the action of anaerobic microorganisms, so that most of the COD and BOD5 can be removed. then, after the sedimentation quantitative pool, the disinfection process can be better carried out by the ClO2 generator, and the effluent can be treated to meet the standards, and then sampling and wells outside. 2.2.2 Combined treatment process process description: First, the sewage into the sewage treatment station by the grille filter, through the regulating pool stabilization adjustment of water quality, complete the adjustment into the MBR reactor, most of the organic matter and suspended solids removal can ensure that the treatment system can retain all the active bacteria and microorganisms, to ensure that efficient operation of the sewage treatment system, and finally the use of high-efficiency chlorine dioxide on the treated wastewater for the disinfection process, the effluent is treated to meet the standards, and then sampling and wells outside the discharge. Chlorine dioxide contact disinfection of treated sewage, after reaching the standard can be discharged; Second, MBR (membrane - bioreactor) pool: the pool can dissolve more than 3.0mg / L, sludge concentration of 8,000 ~ 15,000mg / L, the advantages are mainly reflected in the customer to ensure that the effluent quality of water in line with the stability of the discharge standard, and can be in the treatment system to retain all of the effective micro-organisms and bacteria, the shortcomings The disadvantage is that the one-time investment is large, has a high cost, and the later also requires high cost of maintenance.3 Disinfectant selection in the hospital more commonly used disinfection methods are mainly two kinds, namely, the physical method and the chemical method, which can be divided into other methods according to the addition of different agents, that is, chlorination and ozone method, etc. Compared with the ozone method, liquid chlorine can be used to disinfect water. Compared to the ozone method, the liquid chlorine method of equipment failure rate is not high, and the cost is not high, however, chlorine is a toxic gas, and has a more complex equipment process, the possibility of corrosion is greater, and even induce leakage problems, in the application of a high risk factor, which liquid chlorine combined with a small number of organic matter in the sewage will lead to the production of carcinogenic halide, so it is usually banned in the city. Sodium hypochlorite is inexpensive to use and has a high degree of safety and reliability, but the disinfection effect is unsatisfactory and the residue is very easy to appear in the process of use. For wastewater disinfection, CIO2 has a broad-spectrum bactericidal capacity and is characterized by safety, efficiency and speed in use. Compared with chlorine, disinfectant effective chlorine is 2.63 times higher, with ozone and liquid chlorine does not have the killing, disinfection, and other harmful substances will not appear in the use of a higher safety factor; at the same time, the water can be trace organic pollutants have a destructive effect, the effect of sodium hypochlorite 5 times, the organic halide will not be present in the sewage; coupled with the ability to quickly carry out the reaction of the sewage, and the sewage will not appear in the process. Chlorine dioxide has a good sterilization effect, which can reduce the volume of the disinfection tank, at least 1/2, contributing to the reduction of floor space and space saving.4 Conclusion in the treatment of hospital sewage needs to be realized in the process of modern technology and advanced science and technology, the design process needs to be based on the construction and the actual operating costs, taking into account the effect of disinfectant use and the management of difficult coefficients, on this basis, the scientific design of sewage treatment process. On this basis, the scientific design of sewage treatment process, and scientifically formulate the relevant safety management system, in the operation of the equipment to strengthen the safety management, to ensure that it can be in strict accordance with the operating procedures, do a good job in the maintenance of equipment, in order to avoid unnecessary risks, the hospital wastewater must be strictly disinfection and sterilization treatment, to meet the standards to be discharged with the domestic sewage into the sewer.
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