Home
Back
Ratio of BOD to Ultimate BOD Formula:
| From: | To: |
The Ratio of BOD to Ultimate BOD represents the proportion of oxygen consumed in the first 5 days compared to the total oxygen required for complete decomposition of organic matter. This ratio helps in understanding the biodegradation rate and efficiency of wastewater treatment processes.
The calculator uses the simple ratio formula:
Where:
Explanation: This ratio indicates what fraction of the total biodegradable organic matter is decomposed within the first 5 days of the BOD test.
Details: The BOD ratio is crucial for wastewater treatment plant design, efficiency assessment, and predicting the oxygen demand in receiving waters. It helps engineers determine the appropriate treatment time and aeration requirements.
Tips: Enter both BOD₅ and Ultimate BOD values in kg/m³. Ensure values are positive and measured accurately. The ratio typically ranges between 0.6-0.8 for most domestic wastewaters.
Q1: What is a typical BOD ratio value?
A: For domestic wastewater, the ratio typically ranges from 0.6 to 0.8, meaning 60-80% of the ultimate BOD is consumed in the first 5 days.
Q2: Why is the 5-day BOD test standard?
A: The 5-day period was established as a standard because it represents a reasonable time frame for measuring oxygen demand while most of the carbonaceous matter is decomposed.
Q3: How does temperature affect the BOD ratio?
A: Higher temperatures generally increase the decomposition rate, potentially increasing the 5-day BOD value and thus the ratio, while lower temperatures have the opposite effect.
Q4: What factors influence the BOD ratio?
A: The ratio depends on the nature of organic matter, microbial population, temperature, pH, and presence of toxic substances that might inhibit biological activity.
Q5: How is this ratio used in treatment plant design?
A: Engineers use this ratio to determine the required detention time in treatment units and to calculate the oxygen demand for aeration systems in biological treatment processes.