The Upflow Anaerobic Sludge Blanket Reactor (UASBR) is an efficient wastewater treatment technology that is commonly used in dairy plants to control the levels of biochemical oxygen demand (BOD) and chemical oxygen demand (COD).
Now let us understand and discuss the design calculation of the UASBR technology and how it helps to control BOD and COD in dairy plants.
Design Calculation of UASBR Technology:
The UASBR technology is designed based on the following parameters:
Organic loading rate (OLR).
The OLR is the amount of organic matter that is introduced into the reactor per unit volume and time. It is calculated as follows:
OLR = Flow rate (m3/day) x influent COD (kg/m3) / reactor volume (m3)
Hydraulic retention time (HRT).
HRT is the time that wastewater spends in the reactor. It is calculated as follows:
HRT = Reactor volume (m3) / Flow rate (m3/day)
Sludge retention time (SRT).
SRT is the time that microorganisms spend in the reactor. It is calculated as follows:
SRT = Reactor volume (m3) / Sludge mass (kg)
Gas production rate (GPR).
GPR is the amount of biogas produced in the reactor per unit volume and time. It is calculated as follows:
GPR = Biogas volume (m3/day) / Reactor volume (m3)
Design Calculations of UASBR Technology for BOD and COD Control in Dairy Plants:
The following is a detailed calculation at each stage in the UASBR process for controlling BOD and COD in dairy plants.
Calculation of Wastewater Flow Rate:
The first step in designing a UASBR system is to calculate the wastewater flow rate. This can be done by multiplying the quantity of milk processed per day by the water to milk ratio. For example, if a dairy plant processes 10,000 liters of milk per day with a water to milk ratio of 3:1, the wastewater flow rate would be:
Wastewater Flow Rate = 10,000 x 3 = 30,000 liters/day
Calculation of BOD and COD Load:
Once the wastewater flow rate is determined, the next step is to calculate the BOD and COD load. This can be done by using the following formulas:
BOD Load = Wastewater Flow Rate x BOD Concentration
COD Load = Wastewater Flow Rate x COD Concentration
The BOD and COD concentrations can be obtained by analyzing the samples in a laboratory. For example, if the BOD concentration of the wastewater is 500 mg/L and the COD concentration is 1000 mg/L, the BOD and COD loads would be:
BOD Load = 30,000 x 500 = 15,000,000 mg/day
COD Load = 30,000 x 1000 = 30,000,000 mg/day
Calculation of UASBR Tank Size:
The UASBR tank size is calculated based on the BOD and COD loads and the hydraulic retention time (HRT). The HRT is the time required for the wastewater to pass through the UASBR tank. The UASBR tank size can be calculated using the following formula:
UASBR Tank Volume = BOD Load x HRT / (BOD Removal Efficiency x BOD Concentration in Effluent)
The BOD removal efficiency is the percentage of BOD removed during the treatment process. The BOD concentration in the effluent is the BOD level in the treated wastewater that is discharged from the UASBR tank. For example, if the HRT is 24 hours, the BOD removal efficiency is 80%, and the BOD concentration in the effluent is 50 mg/L, the UASBR tank size would be:
UASBR Tank Volume = 15,000,000 x 24 / (80 x 50) = 9,000 m3
Calculation of Sludge Retention Time (SRT):
The sludge retention time (SRT) is the time required for the microorganisms to degrade the organic matter in the wastewater. The SRT can be calculated using the following formula:
SRT = VSS in Reactor / VSS Destroyed per Day
VSS (volatile suspended solids) is the amount of organic matter in the sludge. The VSS destroyed per day is the amount of organic matter degraded by microorganisms per day. For example, if the VSS in the reactor is 10,000 mg/L and the VSS destroyed per day is 5000 mg/L, the SRT would be:
SRT = 10,000 / 5000 = 2 days
Operating Conditions:
The operating conditions, including the pH, temperature, and influent COD concentration, are crucial factors in the UASBR process.
The optimal pH range for UASBR is between 6.5 and 7.5, while the temperature should be maintained between 35°C and 37°C. The influent COD concentration should be monitored and controlled to avoid overloading the system.
How UASBR Technology Helps to Control BOD and COD in Dairy Plants?
Dairy plants generate large amounts of high-strength wastewater that require effective treatment to control BOD and COD levels.
UASBR technology is an efficient and cost-effective solution for treating dairy plant wastewater. The UASBR process works by converting organic matter in the wastewater into biogas and biomass through the anaerobic digestion process.
The UASBR technology can achieve high COD removal efficiencies of up to 90%. The BOD and COD reduction in UASBR technology occur through the following steps:
· Wastewater enters the reactor and flows upward through a blanket of anaerobic sludge.
· The organic matter in the wastewater is converted into biogas and biomass by anaerobic bacteria in the sludge blanket.
· The biogas produced is collected and used as a source of energy for the dairy plant.
· The biomass produced is recirculated back to the reactor to maintain the biological activity in the system.
The UASBR technology has several advantages over conventional aerobic treatment processes, including lower energy consumption, smaller reactor size, and lower sludge production. Additionally, UASBR technology can treat a wide range of wastewater types, including high-strength dairy plant wastewater.
Conclusion
UASBR technology is a proven and effective solution for treating high-strength wastewater in dairy plants. The UASBR design calculation involves determining the reactor volume, hydraulic retention time, and operating conditions. By utilizing the UASBR technology, dairy plants can efficiently control BOD and COD levels, reduce energy consumption, and produce biogas as a fuel.
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