Sludge and waste gas treatment technology of hospital sewage treatment system
1 Hospital sludge treatment
1.1 Classification and amount of sludge
1. Sludge is divided into septic tank sludge, primary sedimentation sludge, excess sludge, chemical (coagulation) sedimentation sludge, digestion sludge, etc. according to the process.
2. The amount of sludge generated in the hospital sewage treatment process is related to the suspended solids in the raw water and the treatment process. The amount of sludge generated by the hospital sewage treatment structure is shown in Table 1.
|Source of sludge||Total solids(g / person.d)||Water content(%)||Sludge volume(L / person.d)||Sludge volume(L / person.a)|
|Primary sink||54||92 ～ 95||0.68 ～ 1.08||249 ～ 395|
|Second sink||31||97 ～ 98.5||1.04 ～ 2.07||380 ～ 755|
|Coagulation precipitation||66 ~ 75||93 ～ 97||1.07 ～ 2.20||390 ～ 840|
Average amount of sludge
3. The sludge in the septic tank comes from the feces of the hospital medical staff and patients. The amount of sludge depends on the cleaning cycle of the septic tank and the daily amount of feces per person. The daily amount of feces per person is about 150g.
4. Septic tanks or treatment tanks that handle radioactive sewage are cleaned once every six months. Before cleaning, the radioactive standards should be monitored before they can be disposed.
1.2 Hospital sludge treatment process
The sludge treatment process is mainly sludge disinfection and sludge dewatering. The remaining sludge generated by the water treatment process is in the sludge disinfection tank, and lime or bleach powder is added as a disinfectant for disinfection. If the amount of sludge is small, the disinfected sludge can be discharged into a septic tank for storage; if the amount of sludge is large, the disinfected sludge needs to be dehydrated, packaged and shipped out, and incinerated as hazardous waste.
1.3 Sludge disinfection
1. The sludge is first disinfected in the disinfection tank or mud storage tank. The capacity of the disinfection tank or mud storage tank is not less than the 24h sludge output of the treatment system, but not less than 1m3. Stirring measures need to be taken in the mud storage tank to facilitate sludge chemical disinfection.
2. The hospital sewage treatment system with a daily wet sludge output of less than 2m3 can be discharged into the septic tank after disinfection. At this time, the volume of the septic tank should take into account the amount of sludge in this part. Daily sewage sludge treatment system with a wet sludge output greater than 2m3 can be dehydrated after disinfection.
3. The main purpose of sludge disinfection is to kill pathogenic bacteria and avoid secondary pollution, which can be achieved by chemical disinfection. Chemical disinfection often uses lime and bleach.
(1) The dosage of lime is about 15g per liter of sludge, so that the pH of the sludge can reach 11-12, keep it in contact for 30-60min after fully stirring, and store it for more than 7 days.
(2) The dosage of bleaching powder is about 10-15% of the amount of mud.
(3) Ultraviolet irradiation can be used for disinfection in areas where conditions permit.
1.4 Sludge dewatering
1. The purpose of sludge dewatering is to reduce the moisture content of sludge. Sealing and gas treatment must be considered in the dewatering process.
2. The centrifugal dehydrator should be used for sludge dewatering. The sludge conditioning before centrifugal separation generally uses organic or inorganic chemicals for chemical conditioning.
3. The dehydrated sludge should be sealed and transported.
1.5 Final disposal of sludge
Sludge is classified as hazardous waste according to the State Environmental Protection Administration. It belongs to the category of hazardous waste and must be disposed of in a centralized (incinerated) manner in accordance with medical waste disposal requirements.
2 Selection of exhaust gas treatment route
2.1 Process flow
1. In order to prevent the virus from evaporating from the surface of the hospital water treatment structure to the atmosphere and causing the secondary propagation of the virus, the water treatment tank is sealed with a cover plate, and the cover plate is reserved for the inlet and outlet ports to keep the free diffusion state. The gas is organized.
2. The tissue gas enters the pipeline and flows directionally to equipment that can intercept, filter, adsorb, irradiate, or kill viruses and bacteria. After effective treatment, it is discharged into the atmosphere.
3. Exhaust gas treatment can use ozone, peroxyacetic acid, chlorine disinfectant, ultraviolet light, high voltage electric field, filter adsorption and photocatalytic disinfection treatment to effectively inactivate airborne viruses.
2.2 Design points
1. According to the principle of local ventilation design, for the emission of harmful gases, priority is given to the closed cover.
2. For the grille and sludge removal, open cover can be adopted due to operation requirements.
3. The centrifugal fan is used, and the exhaust height is 15m.
4. The flow rate and pressure head of the ventilator need to be selected according to the requirements of different treatment methods. For the case of using oxidizing disinfectant, the ventilator and pipe materials should be considered for corrosion protection.
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