1. What is Organic Matter at Start of BOD?

Definition: This calculator determines the initial organic matter present in sewage at the start of the Biochemical Oxygen Demand (BOD) reaction.

Purpose: It helps environmental engineers and wastewater treatment professionals analyze sewage composition and oxygen demand.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( L \) — Organic matter at start (kg/m³)
• \( L_t \) — Oxygen equivalent (kg/m³)
• \( K_D \) — Deoxygenation constant (1/sec)
• \( t \) — Time in days (converted to seconds)

Explanation: The formula calculates the initial organic matter based on the oxygen equivalent measured after a certain time period and the deoxygenation rate constant.

3. Importance of Organic Matter Calculation

Details: Knowing the initial organic matter helps in designing wastewater treatment systems and predicting oxygen demand in water bodies.

4. Using the Calculator

Tips: Enter the oxygen equivalent (Lt), deoxygenation constant (default 2.66×10⁻⁶ 1/sec), and time in days. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the oxygen equivalent (Lt)?
A: It represents the oxidizable organic matter present in sewage, typically measured through BOD tests.

Q2: What's a typical deoxygenation constant?
A: For domestic sewage at 20°C, it's typically around 0.23/day (2.66×10⁻⁶ 1/sec), but varies with temperature and waste type.

Q3: Why convert time to seconds?
A: Since the deoxygenation constant uses seconds, we convert days to seconds (1 day = 86400 sec) for unit consistency.

Q4: How accurate is this calculation?
A: It provides a theoretical estimate. Actual values may vary due to factors like temperature and microbial activity.

Q5: What if I get extremely high values?
A: Check your inputs, especially the deoxygenation constant. Values over 0.5 kg/m³ may indicate measurement errors.