What is Biochemical Oxygen Demand (BOD)?

Biochemical Oxygen Demand (BOD) measures how much oxygen microorganisms need to break down the organic materials in water. It’s a key indicator of water quality because it reflects the level of organic pollution. High BOD levels signal that there’s a lot of decomposable organic material, which can deplete oxygen in aquatic environments, making them less habitable for fish and other organisms.

BOD Simplified

Think of BOD as a measure of how much “food” is available for the tiny creatures living in the water. Just as humans breathe oxygen while eating, these microorganisms consume oxygen while breaking down organic material. If there’s too much organic matter (high BOD), these microorganisms will use up more oxygen, leaving less for other aquatic life. This can lead to unhealthy water bodies, which is why wastewater treatment plants focus on reducing BOD before releasing treated water back into the environment.

What is the BOD5 Test?

The BOD5 test is a standard way to estimate the amount of oxygen-consuming organic material in wastewater. Over a five-day period at a controlled temperature (20°C), the test measures how much oxygen microorganisms consume. This gives operators a clear picture of how much organic matter is present and how much biological treatment is required to remove it. Understanding the BOD5 test is crucial for operators because it helps determine the effectiveness of the treatment process and ensures that the treated water meets environmental standards.