BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) are two crucial parameters in effluent treatment, helping to assess the efficiency of treatment processes and ensure that treated effluent complies with environmental regulations.
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Monitoring BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) is essential when treating effluents and managing water quality, so it’s very important to understand a little about each of these two parameters.
BOD
BOD (Biochemical Oxygen Demand or Biological Oxygen Demand) is a measure of the amount of oxygen required for the biological decomposition of the organic matter present in the effluent. Knowing the Biochemical Oxygen Demand (BOD) of the effluent is essential for several important reasons. Here are some reasons why it is essential to know the effluent’s BOD:
- BOD (Biochemical Oxygen Demand or Biological Oxygen Demand) outside the parameters for disposal is a common problem in the industrial effluent of some segments.
- A high BOD indicates a high organic load, which can decrease dissolved oxygen levels in the receiving water. This can have a negative impact on aquatic life, resulting in the death of fish and other organisms.
- It is often used to evaluate the biodegradable organic load in effluents and to size and optimize biological treatment processes such as activated sludge and anaerobic reactors.
- In many cases, treated effluent can be reused for non-potable purposes, such as irrigation or industrial cooling. Knowing the BOD is crucial to ensuring that the treated effluent is within acceptable standards for reuse.
- BOD is measured in mg/L O2.
COD
COD (Chemical Oxygen Demand) is a parameter used to measure the amount of oxidizable organic and inorganic matter present in a sample of water and industrial effluents. Unlike BOD (Biochemical Oxygen Demand), which measures the amount of oxygen consumed by microorganisms during the biological decomposition of organic matter, COD involves chemical oxidation reactions that result in the measurement of the total amount of oxidizable compounds. It is expressed in milligrams of oxygen per liter (mg/L) or parts per million (ppm) of oxygen.
Why should monitoring BOD and COD be considered essential?
These two parameters provide essential information for evaluating the efficiency of treatment processes, ensuring compliance with environmental regulations and protecting water resources. Here are some reasons why it is important to monitor BOD and COD:
- Evaluation of the effluent organic matter removal efficiency of the treatment system;
- Compliance with the limits regulated by environmental legislation;
- Process optimization and effective decision-making for improvements in the treatment process;
- Protecting water resources.
How to measure organic matter in effluents?
The organic matter present in effluents requires primary attention, as it is the main cause of water pollution problems.
Indirect methods are often used to quantify organic matter, such as measuring oxygen consumption (BOD and COD). COD is often used in conjunction with BOD to assess the organic load in effluents and to monitor the efficiency of treatment processes.
After measuring the BOD and COD, divide the COD/BOD and evaluate the results and efficiency of your treatment to make decisions:
- < 2.5 – Easily biodegradable effluent
- 2.5 to 5.0 – Medium biodegradability and there is a need to evaluate the system and the treatment route implemented in order to study and assess the suitability of pre-treatment to reduce this ratio.
- > 5.0 – Effluent is difficult to biodegrade, with low treatment efficiency with the biological process alone, in which case there is a need for a study to evaluate the best treatment route and combination of technologies.
BOD legislation
CONAMA resolution 430/2011 establishes that the discharge must meet a minimum removal efficiency of 60%. In other words, the WWTP needs to have a removal efficiency of 60% in order to dispose of the effluent within the legislation.
We also have state legislation such as: Art. 18 state decree 8468 CETESB SP which establishes that the BOD parameter must be a maximum of 60mg/l or the system must be 80% efficient.
How can I increase the organic matter removal efficiency of my wastewater treatment plant?
– Carry out a full assessment of the system’s maximum organic load removal capacity and treatability route;
– If the system is not meeting the required efficiency, retrofit or revamp the system;
– Implement tertiary treatment
– Combine technologies or implement new technologies such as: MBR
How can Grupo EP help you?
Grupo EP provides personalized service in which it diagnoses problems in water treatment, effluent and reuse systems, providing complete solutions such as:
– Technical studies and evaluations;
– Characterization and treatability tests;
– Environmental analysis of the parameters of CONAMA 430/2011 and other state legislation;
– Implementation of WTP, ETE, MBR;
– Revamp and Retrofit;
– Supply of chemical products.
Contact us via the online quote and find out more about our water treatment system monitoring and evaluation services here: Wastewater Treatment Plants (WWTP)