Organic Loading Rate Calculation

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Organic Loading Rate (OLR) Calculator

Calculation Results

Organic Loading Rate (OLR): kg organic matter / (m³ · day)

Total Organic Load per Day: kg/day

function calculateOLR() { var flow = parseFloat(document.getElementById('flowRate').value); var concentration = parseFloat(document.getElementById('concentration').value); var volume = parseFloat(document.getElementById('reactorVolume').value); var resultArea = document.getElementById('olr-result-area'); if (isNaN(flow) || isNaN(concentration) || isNaN(volume) || flow <= 0 || concentration <= 0 || volume <= 0) { alert("Please enter valid positive numbers for all fields."); resultArea.style.display = "none"; return; } var totalDailyLoad = flow * concentration; var olr = totalDailyLoad / volume; document.getElementById('olrValue').innerText = olr.toFixed(3); document.getElementById('totalLoad').innerText = totalDailyLoad.toFixed(2); resultArea.style.display = "block"; }

Understanding Organic Loading Rate (OLR)

The Organic Loading Rate (OLR) is a fundamental parameter in environmental engineering, specifically in the design and operation of wastewater treatment plants and anaerobic digesters. It represents the quantity of organic matter (usually measured as Chemical Oxygen Demand – COD or Volatile Solids – VS) applied to the volume of the biological reactor per unit of time.

The OLR Formula

Calculating the OLR is straightforward once you have the primary operational data. The formula is expressed as:

OLR = (Q × S) / V
  • Q: Flow rate of the substrate (m³/day).
  • S: Concentration of organic matter in the feed (kg/m³).
  • V: Working volume of the reactor (m³).

Why is OLR Important?

In biological systems like anaerobic digestion, the microorganisms require a steady supply of "food" (organic matter). However, there is a delicate balance to maintain:

  • Underloading: If the OLR is too low, the microbial population may starve, leading to low biogas production and inefficient use of the reactor capacity.
  • Overloading: If the OLR is too high, the system may experience "souring." In anaerobic systems, acid-forming bacteria produce volatile fatty acids (VFAs) faster than methane-forming bacteria can consume them, leading to a pH drop and potential system failure.

Practical Example

Imagine an industrial biogas plant processing food waste. The facility receives 20 m³ of liquid waste per day. Laboratory analysis shows that the waste has a Volatile Solids (VS) concentration of 45 kg/m³. The anaerobic digester has an active volume of 600 m³.

Step 1: Calculate Total Daily Load
20 m³/day × 45 kg/m³ = 900 kg VS/day

Step 2: Calculate OLR
900 kg VS/day ÷ 600 m³ = 1.5 kg VS / (m³ · day)

Standard Operating Ranges

Reactor Type Typical OLR (kg COD/m³/d)
CSTR (Standard Digester) 1.0 – 5.0
UASB (High Rate) 5.0 – 15.0
EGSB / IC Reactor 15.0 – 30.0+

Note: These ranges vary significantly based on temperature (mesophilic vs. thermophilic), substrate biodegradability, and mixing efficiency.

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