wastewater operator calculating a problem using a calculator

Specific Oxygen Uptake Rate (SOUR) Calculator

SOUR Calculator

SOUR Calculator

Here’s an article on how to use a Specific Oxygen Uptake Rate (SOUR) Calculator, including a brief explanation of the formula:


How to Use the Specific Oxygen Uptake Rate (SOUR) Calculator

Lab tech running a SOUR

If you work in wastewater treatment, one critical parameter you may need to evaluate is the Specific Oxygen Uptake Rate (SOUR). SOUR helps to assess the activity level of microorganisms in activated sludge, making it a vital metric for monitoring the health of a wastewater treatment system. With a simple SOUR calculator, you can easily calculate this important value in just a few steps. Here’s how to do it.

Understanding the SOUR Formula

Before using the calculator, it’s essential to understand the formula used to determine SOUR. The Specific Oxygen Uptake Rate (SOUR) is calculated as:

SOUR=MLVS/SOUR​

  • SOUR: Specific Oxygen Uptake Rate (mg O₂/g MLVSS/hr)
  • OUR: Oxygen Uptake Rate (mg O₂/L/hr)
  • MLVSS: Mixed Liquor Volatile Suspended Solids (g/L)

The SOUR formula divides the oxygen consumption rate by the concentration of active biomass, giving you an indicator of how efficiently the microorganisms in your system are using oxygen.

Step-by-Step Guide to Using the SOUR Calculator

Follow these easy steps to use the calculator:

  1. Input the Oxygen Uptake Rate (OUR):
  • This value is typically measured in mg O₂/L/hr and represents how much oxygen is being consumed by the microorganisms in the system. Ensure this value is accurate and measured over a specific time period.
  1. Enter the Mixed Liquor Volatile Suspended Solids (MLVSS):
  • This value is expressed in g/L and refers to the concentration of active microorganisms (biomass) in the sludge. The more biomass you have, the higher the MLVSS.
  1. Click “Calculate”:
  • The calculator will then divide the OUR by the MLVSS to give you the Specific Oxygen Uptake Rate (SOUR), typically expressed in mg O₂/g MLVSS/hr.

Example Calculation

Let’s say you’ve measured the following values:

  • Oxygen Uptake Rate (OUR): 50 mg O₂/L/hr
  • Mixed Liquor Volatile Suspended Solids (MLVSS): 2.5 g/L

Using the formula:

SOUR=2.550​=20mg O₂/g MLVSS/hr

This result means that the microorganisms are consuming 20 mg of oxygen per gram of volatile suspended solids every hour.

Why SOUR Matters

Calculating SOUR helps wastewater treatment operators gauge the health and activity of the biomass in their system. A high SOUR value indicates highly active microorganisms, which may suggest good treatment efficiency. Conversely, a low SOUR could indicate that the biomass is under stress or less active, signaling potential process issues.

By using the SOUR calculator, you can quickly and accurately monitor the performance of your system, allowing you to make informed adjustments to ensure optimal wastewater treatment.


This article should help users understand the significance of SOUR and how to use a calculator to determine it effectively.

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