How to Prevent Secondary Infection for Sewage Treatment Personnel

Due to the openness and sustainability of the epidemic, domestic sewage will carry a large number of COVID-19 into the sewage treatment plant. The personnel of the sewage treatment plant will be exposed to an environment with high concentrations of COVID-19 for a long time, so it is particularly important to prevent secondary infection!

Operation protection

• Basic protection. Employees who contact or inhale areas with relatively low exposure risk (such as control room, power distribution room, warehouse, etc.) should wear masks and work clothes.
• General protection. Employees who are exposed to relatively high risks of contact or inhalation but whose working space is relatively open (such as open inlet wells, distribution wells, aeration tanks, etc.) should wear masks, gloves, goggles, protective helmets, and work clothes.
• Key protection. Employees in enclosed and semi-enclosed working spaces (such as pipeline wells, indoor pump stations, sludge dewatering workshops, and operation inspection floors of underground sewage treatment plants) with relatively high exposure risk in contact or inhalation. Employees who may have direct contact with sewage or sludge (such as sampling personnel, gate residue cleaning personnel, machinery maintenance personnel, rescue workers, etc.). It is advisable to wear surgical masks, double gloves, goggles, protective helmets, and work clothes or protective clothing that meet the operation requirements.
• If the safety protection requirements of the above employees are inconsistent with the safety protection requirements of the work area, the relatively strict protection requirements shall be implemented.
• Based on the relationship between the current work type and pathogen exposure wind, the following classification is recommended for safe work process safety.

Traffic management

• The air circulation system in the working space for personnel from the areas such as the water reservoir, between the wedge wire filter, and the aeration sand pool, etc., are in good condition.
• The main processing unit is transparent, and when the conditions are met, it can be added to the deodorizing system to prevent the wind from blowing out.
• When the workspace is under pressure or deodorizing, the heating facility is controlled and the safety facility is operated. Within the available deodorizing facility processing capacity, the amount of air to be processed is increased.
• Relatively closed working space with undesigned compressed air or deodorizing equipment, required to move forward with forced air or forced air. There is an air outlet with increased UV radiation, odor, or chemical disinfection measures.
• Reduced number of workers entering the above-mentioned area, activities near the outlet during the work period, low inhalation exposure to wind.
• Daily disinfection of single workspace. Under certain conditions, additional anti-fog or ultraviolet disinfection measures may be taken, and ongoing disinfection work will be carried out on a regular basis.
• When using a deodorizing system for living organisms, use disinfectant-containing disinfectants to disinfect dust. The deodorant effect, controls disinfectant against the deodorant system microbial effect.
• During the period when workers enter the work area, stop disinfecting with dust or ultraviolet rays, avoiding injuries caused by workers.
• An antiseptic with an effective density of 500 mils/meat for disinfecting dust.
• Daily cleaning and disinfection of good residue and sand deposits.
• Use a non-leakage container to collect the residue and sand, then clean up, to avoid a long-term deposition.
• Periodically use a chlorine-containing disinfectant with an effective chlorine concentration of 1000-2000 mg/L to carry out spray disinfection on the grid slag and grit sticking points.
• Temporary spray disinfection measures can be added to the screening screw conveying equipment, and the chlorine-containing disinfectant with an effective chlorine concentration of 1000-2000 mg/L can be used for continuous spray disinfection of screenings.
• Closed facilities or deodorizing system air ducts can be installed around the grid slag and grit stacking points to avoid the spread of aerosols.
• Practitioners who enter the pretreatment unit to clean up grid slag and sand settling operations should take safety precautions throughout the process and meet the following requirements.
• Before cleaning, use a chlorine-containing disinfectant with an effective chlorine concentration of 1000-2000 mg/L to spray and disinfect the cleaning objects. After cleaning, use chlorine-containing disinfectant with an effective chlorine concentration of 1000-2000 mg/L to spray and disinfect the storage points, tools, and related equipment.
• The continuous operation time for cleaning grid slag and sand settling should not exceed 30 minutes each time. After finishing work, clean hands and face in time, change shoes, and use chlorine-containing disinfectant with an effective chlorine concentration of 500 mg/L to thoroughly disinfect the changed shoes.
• Check the pretreatment area and the sewage splash state around the equipment, and delineate the restricted access area for sewage splash. When conditions permit, measures such as adding protective covers can be taken to reduce the risk of sewage splashing.

Biological and advanced processing unit

• Combined with the water quality testing results of the influent and effluent water of sewage treatment plants, the impact of the large-scale use of chlorine-containing disinfectants in public places and households on sewage treatment plants during the epidemic period was analyzed. According to the residual chlorine value of the influent, a small amount of excess sludge can be returned to the water inlet of the sewage treatment plant at an appropriate time, and dechlorination agents or carbon sources can be added to reduce the impact of chlorine-containing disinfectants.
• Pay close attention to the operating status of biological and advanced treatment unit facilities, take anti-splash measures, and reduce the risk of contact or inhalation exposure of practitioners.
• Check the muddy water splashing status in areas such as various drop points, overflow weirs, mechanical aeration, blast aeration, mechanical stirring, etc., and delineate the areas where there is a risk of muddy water splashing.
• If mechanical surface aeration equipment such as rotating discs, rotating discs, and rotating brushes are used, it is advisable to add a cover or protective cover to prevent mud and water splashing on the equipment.
• Strengthen the operation guarantee of key equipment such as blowers, lift pumps, return pumps and sludge discharge pumps, and ensure the normal operation of key equipment through daily inspections, remote monitoring and periodic maintenance.
• Strengthen the ventilation and disinfection of closed and semi-closed areas of biological and advanced treatment units, and temporarily increase spray disinfection or ultraviolet disinfection measures in areas where employees regularly operate.
• Before employees enter, spray disinfection or ultraviolet disinfection can be carried out. When employees enter the work area, stop spray disinfection or ultraviolet disinfection to avoid harm to employees.
• If the ventilation of the biological and advanced treatment unit is connected to the biological deodorization unit, the spray disinfection point should be far away from the air inlet of the deodorization unit.
• For spray disinfection, it is advisable to use a chlorine-containing disinfectant with an effective chlorine concentration of 500 mg/L.

Sludge Handling and Storage Units

• Take measures such as demarcating risk areas and adding protective covers to reduce the risk of operators directly contacting or splashing with sludge during sludge treatment.
• It is advisable to temporarily increase spray disinfection or ultraviolet disinfection measures in sludge treatment, storage and loading and unloading workshops, and ensure that the ventilation system is running well to reduce the risk of contact or inhalation exposure of practitioners.
• If there is no subsequent anaerobic digestion or aerobic fermentation, chlorine disinfectants can be added appropriately before sludge dehydration, and attention should be paid to the impact of chlorine disinfectants on dehydration performance and disposal methods. When the sludge dehydration effect is directly affected, the amount of chlorine disinfectant should be reduced or the dosage should be stopped.
• For subsequent anaerobic digestion or aerobic fermentation, it is not advisable to add chlorine disinfectant to the sludge to avoid the impact of chlorine disinfectant on microorganisms in anaerobic digestion or aerobic fermentation process.
• Strengthen the safety protection of employees in belt dehydration or plate and frame dehydration workshops, and reduce the risk of contact or inhalation exposure of employees.
• The dewatered sludge should be cleared as it is produced, and it should not be stacked in the open air in the factory. If it is really necessary to stack in the open air, spray disinfection of the piled sludge and protective measures for employees should be done well. The outer surface of the sludge dump is disinfected at least once a day with a chlorine-containing disinfectant with an effective chlorine concentration of 1000-2000 mg/L. Sludge should be sprayed and disinfected before leaving the factory.
• Do a good job of cleaning and disinfecting sludge loading and unloading and transportation vehicles to avoid the sludge contaminated on the wheels and boxes during loading and unloading from being scattered during transportation. Sludge transport vehicles are washed with water before leaving the factory, and sprayed with chlorine-containing disinfectants with an effective chlorine concentration of 1000-2000 mg/L. When using open vehicles to transport sludge, measures should be taken to cover with thatch.