Biochemical Oxygen Demand (BOD). What is it?
Pulp and paper mill effluent contains organic materials such as dissolved wood components and paper additives, which can be consumed by microorganisms. This process requires oxygen. The amount of oxygen used by microorganisms as they consume, or biodegrade organic matter is the biochemical oxygen demand (
BOD).
Why does it matter?
When materials high in
biodegradable organic matter, and thus high in BOD, are added to a lake, river, or ocean, the microorganisms that naturally live there will want to consume the organic matter as food. In consuming it, they use up dissolved oxygen, which is present in the water, leaving less dissolved oxygen for fish and other organisms. As a result, the oxygen level may not be suitable to support a healthy fish community.
How is it measured?
The BOD test involves adding microorganisms to a sample of the water or
effluent, and measuring the amount of oxygen used up by the microorganisms as they biodegrade the organic matter in the sample. The amount of oxygen used by the microorganisms over a fixed time period is the BOD. If there is a significant amount of biodegradable organic material present in a sample, the microorganisms will be very active and will use a lot of oxygen. This will result in a high BOD measurement. If there is only a small amount of organic material present, the microorganisms will use less oxygen, resulting in a lower BOD measurement.
How do we control it?
BOD from the Resolute Forest Products mill is controlled in the mill or by treatment. In-plant measures include effluent recycling, spill control, or evaporation and combustion of the organic matter. Effluent treatment systems in which microorganisms are used to consume the biodegradable material before it enters the lake, river, or ocean are also used.