Biochemical Oxygen Demand (BOD) และ Chemical Oxygen Demand (COD): ตัวชี้วัดคุณภาพน้ำที่สำคัญ

Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD): Essential Indicators of Water Quality

Before diving into details regarding online BOD/COD measurement for industrial applications, it is important to understand the significance of these two key parameters for water quality monitoring and wastewater management. Let’s explore what BOD and COD are, as well as their roles in wastewater treatment processes.

The Importance of BOD and COD in Water Quality Monitoring

     BOD refers to the amount of dissolved oxygen required by aerobic biological organisms to break down organic material in water. When organic matter or effluents are discharged into water bodies, microorganisms consume oxygen for decomposition. If the BOD level is too high, it can deplete the dissolved oxygen, resulting in harm to aquatic life.
     COD, on the other hand, measures the total quantity of oxygen required to chemically oxidize both biodegradable and nonbiodegradable organic substances in water. It is especially useful in detecting industrial pollutants that may not be captured by
BOD alone.

What is BOD

     BOD, or Biochemical Oxygen Demand, is the amount of oxygen needed for the biological decomposition of organic substances by microorganisms in water. It serves as an important indicator in environmental monitoring, particularly in assessing the pollution level of surface water, rivers, lakes, and wastewater. If BOD levels are high, it implies the presence of a large amount of biodegradable organic matter, which can lead to oxygen depletion and negatively impact aquatic life. 

BOD Measurement Method
     The BOD test is conducted by placing a water sample into an airtight bottle and incubating it in the dark at a temperature of 20°C for 5 days (BOD5). After the incubation period, the amount of oxygen consumed is calculated and expressed in mg/L or ppm.
Impact of High BOD

• Indicates high organic pollution: Elevated BOD levels reflect high concentrations of decomposable organic matter in
  the water.
• Affects aquatic life: High BOD can reduce dissolved oxygen levels, threatening fish and other organisms.
• Requires larger treatment systems: Wastewater with high BOD requires greater oxygen input and more advanced treatment processes to meet environmental standards.
  

What is COD
     COD, or Chemical Oxygen Demand, measures the amount of oxygen needed to chemically oxidize organic compounds in water. It is widely used for assessing the quality of wastewater, especially in industrial discharges and non-biodegradable pollutants.
COD includes both biologically oxidizable and non-biodegradable organics, making it more comprehensive than BOD in certain applications. For instance, potassium dichromate (K₂Cr₂O₇) is commonly used as the oxidizing agent in COD tests.

COD Measurement Method
     The COD test is conducted by oxidizing the sample using strong oxidizing agents such as potassium dichromate in the presence of sulfuric acid (H₂SO₄). The sample is then heated at approximately 150°C for 2–3 hours. The amount of oxidant consumed is used to determine COD, expressed in mg/L or ppm.

•  Indicates high chemical pollution: Elevated COD levels signal the presence of oxidizable compounds, whether biodegradable or not.
• May imply toxic substances: A high COD value might indicate industrial discharges that are toxic or persistent.
• Influences treatment design: Knowing the COD value helps in designing proper wastewater treatment systems to ensure compliance with environmental standards.

Conclusion
     Both BOD and COD are crucial parameters for evaluating water quality and monitoring wastewater discharges. BOD focuses on biodegradable organics, while COD covers a broader range including chemicals that may not break down biologically. Industries discharging wastewater should consider both values to assess the true impact on the environment.


     ASE offers BOD and COD analyzers that help facilities measure these indicators with accuracy and reliability, aligning with environmental regulations and ensuring optimal wastewater treatment. For inquiries or further technical consultation, please
Contact us for further information or technical consultation:
• Email: sales@ase-thai.com
• LINE: @ase-thai
• Tel: 083-298-9222