Design an STP plant for a 200-bed hospital in India as per CPCB
In order to manage and treat the wastewater produced while abiding by the Central Pollution Control Board (CPCB) standards, it is imperative to design a sewage treatment plant (STP) for a 200-bed hospital in India. We will go over the steps and calculations needed in designing such a facility in this comprehensive guide.
Step 1: Understanding CPCB Norms:
Understanding the CPCB standards and guidelines is essential before beginning the design process. These laws outline the maximum allowed concentrations of a number of characteristics in treated sewage, including Total Suspended Solids (TSS), Chemical Oxygen Demand (COD), and Biochemical Oxygen Demand (BOD). Refer to the most recent CPCB guidelines to guarantee compliance as these standards are subject to change.
Step 2: Estimating Sewage Generation:
Based on the number of beds and the amount of water used for hospital operations, you must estimate the daily sewage generation in order to design an efficient STP. You can perform the following calculations for a hospital with 200 beds:
· Average Water Consumption per bed (as per CPCB guidelines): Approximately 200-250 liters per bed per day, considering a healthcare facility.
· Daily Sewage Generation = Number of Beds × Average Water Consumption per Bed.
Daily Sewage Generation = 200 beds × 250 liters/bed/day = 50,000 liters/day.
Step 3: Treatment Process Selection:
Selecting the best sewage treatment method is essential. The decision will be made in light of the effluent quality criteria, budget, and available space. Hospital sewage treatment options frequently used include:
Activated Sludge Process (ASP): A biological treatment method that effectively removes BOD and TSS and is appropriate for hospital wastewater that is high in organic matter.
Membrane Bioreactors (MBRs): MBRs ensure high-quality effluent by combining biological treatment and membrane filtration. They are appropriate for institutions that have strict requirements for effluent quality.
Chemical Coagulation-Flocculation: Chemical treatment may occasionally be necessary to get rid of particular contaminants or improve how well biological treatment procedures work.
Step 4: Preliminary Design Parameters:
An Activated Sludge Process (ASP) is a good option for a 200-bed hospital. Here are some initial design specifications:
Daily production of sewage is 50,000 litres.
BOD Load (according to CPCB standards): This changes depending on the particular hospital medical procedures. To find out the BOD limitations applicable to healthcare facilities, consult the CPCB guidelines.
Hydraulic Retention Time (HRT): The HRT is determined by the treatment method that is chosen and the standards for acceptable effluent quality.
Sludge Production: The properties of the wastewater and the effectiveness of the treatment process determine how much sludge is formed during the process.
Membrane Bioreactors (MBRs): MBRs ensure high-quality effluent by combining biological treatment and membrane filtration. They are appropriate for institutions that have strict requirements for effluent quality.
Chemical Coagulation-Flocculation: Chemical treatment may occasionally be necessary to get rid of particular contaminants or improve how well biological treatment procedures work.
Step 5: Detailed Design of the Activated Sludge Process (ASP):
The following elements are commonly included in the activated sludge process:
Aeration Tank: This is where the biological treatment takes place. The hydraulic retention time (HRT) and average daily flow rate should be used to calculate the tank capacity. The aeration tank volume for a 24-hour HRT would be 2,083.33 litres, or around 2.083 cubic metres, or 50,000 litres per day divided by 24 hours. The real tank should be a little bit bigger to allow for sludge buildup.
Clarifier: Wastewater needs to settle after being treated in the aeration tank to get rid of suspended solids. The clarifier needs to have the right size to allow for effective solids settling. Key design factors include the clarifier's surface area and the settling velocity of solids.
Return Sludge: To keep the microbial population alive, some of the clarifier's activated sludge needs to be transferred back to the aeration tank. Typically, the influent flow rate is 20% to 30% higher than the return sludge flow rate. It would be between 10,000 and 15,000 litres per day in this situation.
Disinfection: To ensure pathogen elimination, treated effluent should go through a disinfection procedure after the clarifier. Chlorination or ultraviolet (UV) disinfection are frequent techniques.
Handling Sludge: The sludge generated throughout the process needs to be controlled. According to municipal restrictions, it can be dewatered and disposed of.
Step 6: Compliance with CPCB Norms and Effluent Quality:
The system must be regularly monitored and maintained to ensure compliance with CPCB standards. The BOD, COD, TSS, and faecal coliform thresholds should all be met by the effluent from the ASP.
Step 7: Power and Electrical Requirements
Electricity will be needed by the ASP for aeration and other components. The size and efficiency of the system will determine the power requirements. For continuous operation, be sure to have a dependable power source and backup systems.
Step 8: Environmental and Safety Considerations:
To safeguard hospital employees and patients, safety precautions should be put in place. Environmental issues like odour management and noise reduction should also be taken into consideration. These worries might be reduced with the help of adequate landscaping and fencing.
Step 9: Funding and Budgeting
Costs are involved in designing, constructing, and maintaining a STP. Government funds, hospital administration, or a mix of sources may provide funding. Create a thorough budget that includes construction capital costs as well as continuing operational and maintenance costs.
Step 10: Use and Maintenance
An STP must be regularly maintained and operated in order to work properly. The system should be monitored and maintained by qualified employees. Best practises must be followed when performing routine inspections, equipment servicing, and sludge removal.
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