Calculate Theoretical Oxygen Demand

ThOD Equation:

\[ ThOD = \frac{(2C + 0.5(H - 3N) + 3S + 2.5P - X - O) \times 32}{MW} \]

Number of Carbons (C):

Number of Hydrogens (H):

Number of Nitrogens (N):

Number of Sulfurs (S):

Number of Phosphorus (P):

Number of Halogens (X):

Number of Oxygens (O):

Molecular Weight (MW):

g/mol

Theoretical Oxygen Demand (ThOD):

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1. What is Theoretical Oxygen Demand?

The Theoretical Oxygen Demand (ThOD) represents the total amount of oxygen required to completely oxidize an organic compound to CO₂, H₂O, and other inorganic end products. It's a fundamental concept in environmental chemistry and wastewater treatment.

2. How Does the Calculator Work?

The calculator uses the ThOD equation:

\[ ThOD = \frac{(2C + 0.5(H - 3N) + 3S + 2.5P - X - O) \times 32}{MW} \]

Where:

\( C \) — Number of carbon atoms
\( H \) — Number of hydrogen atoms
\( N \) — Number of nitrogen atoms
\( S \) — Number of sulfur atoms
\( P \) — Number of phosphorus atoms
\( X \) — Number of halogen atoms
\( O \) — Number of oxygen atoms
\( MW \) — Molecular weight (g/mol)

Explanation: The equation accounts for the oxygen required to oxidize each element in the compound, with different coefficients for different elements.

3. Importance of ThOD Calculation

Details: ThOD is important for understanding the environmental impact of organic compounds, designing wastewater treatment systems, and comparing with measured BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand).

4. Using the Calculator

Tips: Enter the molecular formula by specifying the count of each atom type and the molecular weight. All counts must be non-negative integers, and molecular weight must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between ThOD, BOD, and COD?
A: ThOD is theoretical, BOD measures oxygen consumed by microorganisms, and COD measures oxygen consumed by chemical oxidation. ThOD is typically higher than BOD and COD.

Q2: Why is the coefficient different for each element?
A: Different elements require different amounts of oxygen for complete oxidation (e.g., carbon becomes CO₂, hydrogen becomes H₂O, nitrogen becomes NO₃⁻).

Q3: How accurate is ThOD compared to actual measurements?
A: ThOD represents the theoretical maximum. Actual BOD is typically lower due to incomplete biodegradation, and COD may be higher if it oxidizes compounds not included in ThOD.

Q4: What if my compound contains other elements?
A: This calculator handles C, H, N, S, P, X, O. For other elements, you'll need to modify the equation to account for their oxidation.

Q5: What units does ThOD use?
A: The result is in mg of oxygen per mg of compound (mg/mg), which can be converted to mg/L by multiplying by the compound's concentration.