1. What is Oxygen Equivalent given Organic Matter at Start of BOD?

Definition: This calculator determines the remaining oxygen equivalent (oxidizable organic matter) in sewage after a given time period during BOD (Biochemical Oxygen Demand) testing.

Purpose: It helps environmental engineers and wastewater treatment professionals assess the organic pollution load in water over time.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Lt \) — Oxygen equivalent at time t (kg/m³)
• \( Ls \) — Organic matter at start (kg/m³)
• \( K_D \) — Deoxygenation constant (1/day)
• \( t \) — Time in days

Explanation: The formula models the exponential decay of organic matter as microorganisms consume it over time.

3. Importance of Oxygen Equivalent Calculation

Details: Accurate calculation helps in designing wastewater treatment systems, assessing pollution levels, and ensuring regulatory compliance.

4. Using the Calculator

Tips: Enter the initial organic matter concentration, deoxygenation constant (default 0.00000266 1/day), and time in days. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for deoxygenation constant?
A: For domestic sewage, K_D typically ranges from 0.000001 to 0.000005 1/day at 20°C.

Q2: How does temperature affect the calculation?
A: Higher temperatures increase K_D. The constant is often adjusted using the Arrhenius equation for different temperatures.

Q3: What's a typical value for initial organic matter?
A: Raw sewage typically has 100-300 mg/L (0.1-0.3 kg/m³) of organic matter.

Q4: How is this related to BOD?
A: BOD is the difference between initial oxygen equivalent (Ls) and remaining oxygen equivalent (Lt).

Q5: Why use base-10 exponent instead of natural exponent?
A: The base-10 form is traditional in BOD calculations and makes field measurements easier to interpret.