COD (Chemical Oxygen Demand) Digestion Unit is sometimes referred to as a COD digestion apparatus or thermo reactor, and it represents a specialized heating block designed specifically for preparing environmental samples from water or wastewater.

The basic function of the device is to digest the organic contaminants within a water sample through heating them along with powerful oxidizers.

Why COD Digestion is Necessary

Chemical Oxygen Demand is a key factor when considering the quality of the water. The more organic material there is, the more polluted the water becomes, and the dissolved oxygen is depleted.

Since the organic compounds do not break down immediately, artificial digestion of the water sample is necessary. The COD digestion unit heats the sample up to 150 degrees Celsius using sulfuric acid and potassium dichromate, which take two hours for oxidation. At this extreme condition, the organic materials become oxidized fully. The digesting process is followed by determination of the COD with a colorimeter or spectrophotometer.

Key Components of a COD Digestion Unit

• Heating Block: Usually constructed from high-quality aluminum, which is then coated with a substance that makes it resistant to chemicals. High-quality aluminum guarantees that heat is distributed evenly throughout the entire heating block.
• Sample Vials: Heavy-walled glass vials (the standard size for this type is 16 mm) with screw tops that provide resistance against internal pressure.
• PID Digital Controller: Temperature regulating microprocessor systems maintaining the block within tight tolerance levels.
• Safety Shield: The safety shield refers to the strong transparent protective shield covering the test tubes. It protects the lab technicians as the tubes are exposed to heat and chemicals; hence, in the event that a test tube shatters, the technicians will not be harmed.

Core Specifications to Look For

When selecting COD analyzer units for your environmental, industrial, or quality control testing laboratory, be sure to consider the following technical specifications:

1. Capacity (Number of Places)

The capacity refers to the number of samples that can be digested at once and may vary as follows:

• 12 - 15 places: Best suited for smaller industrial facilities or lower throughput laboratories.
• 24 - 30+ places: Specifically designed for larger commercial environmental testing centers with high daily sample volume.

2. Pre-set Timers and Auto Shut-Off Functionality

Overheating, if prolonged, may result in a bursting of the vials containing chemical indicator solutions. You should consider purchasing equipment with pre-set timers and shut-off functionality, which automatically switches off after two hours of usage and sounds an alarm.