Ozone Applied to the Disinfection of Hospital Wastewater
Introduction of hospital sewage water
Hospital is generally divided into two categories. They are general hospital and infectious disease hospital. The types and concentrations of pollutants in hospital sewage are similar to that in urban sewage, but not exactly the same. In addition to the conventional pollutants, hospital wastewater also contains some special pollutants, such as drugs, disinfectants, diagnosis agent, detergent and so on.
Main sources of hospital wastewater are mainly effluents emitted by various wards, especially infectious ward, operation room and laundry room. In addition to containing a large number of pathogenic microorganisms, parasites such as Ascaris eggs and a variety of viruses such as hepatitis, tuberculosis and dysentery bacteria endures, it also contains large amounts of pollutants, which organic matter accounted for about 60% of the total amount of pollutants and insoluble matter accounted for the total amount of 40%. Due to a large amount of material, such as muscle tissue precipitation, the larger proportion of worms and eggs, a large number of bacteria, such as precipitation in the sludge. Due to a large amount of material, such as muscle tissue precipitation, the larger proportion of worms and eggs, a large number of bacteria, such as precipitation in the sludge.
In recent years, radioactive isotopes are widely used in medical treatment. Medical devices are cleansed with water, therefore, the sewage will contain radioactive isotope.
In addition, some hospitals also have a subsidiary pharmaceutical factory, which emit sewage water which contains acid and alkali and other harmful substances. Thus, the hospital sewage can be discharged into the river after disinfection and de-pollution.
Selection of Processing Technology
The choice of processing method and technological process are determined by the processing object including suspended, floating, organic matter, radioactive isotope, bacteria, virus, acid and alkali, etc. Among them, pathogen is the most harmful. It is explained in detail in the following analysis.
a. Suspended solids and floating objects
Generally, septic tank is installed at the outlet of the ward. After poured into the septic tank, the larger the proportion of pollutants in the pool begin to experience precipitation separation, digestion and fermentation. In the settlement process is also mixed with some viral pathogens, so the sludge should be treated accordingly. Septic tank effluent will still carry some floating and mechanical impurities into the pool disinfection, which will influence the germicidal efficacy of disinfectant, therefore, the sewage should get full precipitation and simple filtering before being disinfected.
b. Organic pollutants
Organic matter in hospital sewage is generally less than that in urban sewage and BOD5 is really more than 100 mg / L. Usually it can be digested through its self purification ability. However, if it is directly discharged into higher surface water body, scenic area and so on, the organic matter should be treated.
c. Radioactive isotope
The spontaneous disintegration of the nucleus causes the sewage to have radioactive pollution, which makes it impossible to change the strength and performance of the radioactive material in the waste water factitiously. So it is only used to reduce or avoid the harm by using the method of dilution or concentration. So we can only reduce or avoid the harm by using the method of dilution or concentration. For this kind of sewage, the treatment method can be determined according to the type and the half life of the radioactive material. For the short half-life of the elements, the storage method or dilution method can be adopted, while for the long half-life of radioactive material, the physical, chemical and biological method can be adopted. According to the survey, the radioactive isotope used in hospital in general is shorter, and the amount of sewage is less, so it is usually treated with storage.
Parasite eggs from feces, the proportion is greater than the fecal sewage (about 1.02-1.04), it can be separated from the sewage by sedimentation. The general use of Ascaris eggs as parasite death standard, namely when the Ascaris eggs died when they think other eggs have been killed. Ascaris eggs can live 1-5 years in the outside world, but in the fermentation environment, life period is greatly shortened. In the accumulation of feces, it can live 7 days in the summer, 21 days in winter. The sludge cleaning cutting cycle of septic tank is more than three months, parasite eggs can be precipitated in the pool and being killed in the fermentation environment.
Virus is a kind of object far smaller than bacteria. They do not have a complete cell structure, and must be in a certain living cells in order to survive and reproduce. About 80% of human infectious diseases are caused by viruses. Generally speaking, virus are resistant to cold heat labile (but hepatitis virus to hot, dry and frozen have a certain resistance, such as hepatitis a heat-resistant 56 DEG C, more than 1 hour; B heat resistant 60 DEG C, more than 4 hours). But all virus are sensitive to boiling temperature and strong oxidizing agents, so you can cast a certain concentration of chlorine to the inactivated.
f. Infectious bacteria
There are many kinds of germs, but its rules are similar, generally in the range of pH value 5-9.6 survival. When the pH value is beyond the scope of this pathogen is death. In clear water it can live for more than a month, but in the sewage it lives for a short time of life. This is because: A. fecal sewage containing its own decomposition of the formation of ammonia, can play a bactericidal effect; B. stool decomposition can also produce some of the bacteria to kill bacteria. In addition, most of the bacteria (except for tetanus) are good oxygen. Using this feature, such as the pool stamped seal, hand due to the decomposition of organic matter consumption of large amounts of oxygen, on the other hand for pool sealing oxygen supply difficulties, resulting in sewage dissolved oxygen decreased, resulting in aerobic bacteria in anoxic perish of itself. In addition, in the laboratory, laboratory and chromium, mercury and other heavy metals exist, can be removed by chemical methods.
g. Infectious bacteria
There are many kinds of germs, but its rules are similar, generally in the range of pH value 5-9.6 survival. When the pH value is beyond the scope of this pathogen is death. In clear water it can live for more than a month, but in the sewage in the sewage in a short time of life. This is because: A. fecal sewage containing its own decomposition of the formation of ammonia, can play a bactericidal effect; B. stool decomposition can also produce some of the bacteria to kill bacteria. In addition, most of the bacteria (except for tetanus) are good oxygen. Taking advantage of this feature, such as the pool stamped seal, hand due to the decomposition of organic matter consumption of large amounts of oxygen, on the other hand for pool sealing oxygen supply difficulties, resulting in decrease of sewage dissolved oxygen and perishment of aerobic bacteria. In addition, there exists hromium, mercury and other heavy metals in the laboratory which can be removed by chemical methods.
In summary, hospital sewage is an extremely complex system. Therefore, it is difficult to achieve satisfactory results with conventional treatment methods.
Introduction of technological process
The whole process can be divided into two stages:
A. Primary treatment
The main part of the disinfection and sterilization can be discharged into the urban sewage, and then enter the urban sewage treatment field, to carry out the depth treatment.
B. Secondary treatment
After secondary treatment, sewage water not only can be sterilized, and BOD, COD has a significant reduction to the national level of sewage discharge standards, can be directly discharged into the water.
Comparison of ozone disinfection method and other disinfection methods
1. Ozone disinfection overcomes the dangers of other modes of transportation, storage, and processing.
2. Contacting time of ozone disinfection is short. It can improve water quality and is an excellent disinfectant.
3. Ozone can kill virus and spores that cannot be killed by other disinfectants.
4. Ozone disinfection effect is not affected by the ammonia hydrogen content and pH value of wastewater.
5. Ozone can be produced by cheap air or oxygen.
6. Due to the development of electronic technology and ozone generation technology in recent year, today's ozone generator energy consumption is greatly reduced, and its volume is smaller and smaller, the stability of the operation is greatly improved. Coupled with low electricity cost and sufficient electricity, ozone begins to have an absolute advantage on sewage water treatment.
7. The price of ozone generator is almost the same as the price of chlorine, chlorine dioxide and sodium hypochlorite generator.