COD Water Analysis
Chemical Oxygen Demand
What is Chemical Oxygen Demand (COD)?
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Chemical Oxygen Demand (COD) is defined as the amount of oxygen equivalents consumed in the chemical oxidation of organic matter by strong oxidant (e.g., potassium dichromate). The COD value indicates the amount of oxygen which is needed for the oxidation of all organic substances in water in mg/l or g/m3. Chemical oxygen demand (COD) is an indirect measurement of the amount of organic matter in a sample. With testing COD, you can measure virtually all organic compounds that can be digested by a digestion reagent.
COD water analysis is critical in wastewater for determining the amount of waste (contamination) in the water. Waste that’s high in organic matter requires treatment to reduce the amount of organic waste before discharging into receiving waters. Why does this matter? If wastewater treatment facilities do not reduce organic content of the wastewater before it reaches natural waters, microbes in the receiving water will consume the organic matter. As a result, microbes will consume the oxygen in the receiving water to breakdown the organic waste. This oxygen depletion is called eutrophication and can lead to the death of animal life.
Chemical oxygen demand tests are typically performed on wastewater. The pollution level is calculated by measuring the amount of organic matter in the water. Water with too much organic material can have a negative effect on the environment in which the wastewater is discharged. The COD (Chemical Oxygen Demand) is closely related to the laboratory standard method named Dichromate-Method. With this method the chemical oxygen demand is determined during chromic acid digestion of organic loads in wastewater. Based on this method the COD became a commonly used sum parameter in wastewater analysis. It is used for planning of wastewater treatment plants, for controlling the cleaning efficiency and for the calculation of wastewater taxes.
WHAT IS chemical oxygen demand?
what is the CORRELATION BETWEEN TOC & COD?
Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) are both parameters used in water analysis to assess the organic content and pollution level of water. While there is a correlation between TOC and COD, it is important to understand their differences and the relationship between them.
TOC measures the total amount of carbon in a water sample, including both organic and inorganic carbon compounds. It quantifies the concentration of carbon present in the sample, regardless of its oxidizability. TOC analysis involves the measurement of the carbon content directly, typically using high-temperature combustion or wet chemical oxidation methods.
COD, on the other hand, measures the amount of oxygen required to chemically oxidize both organic and inorganic compounds in a water sample. It provides an estimation of the oxidizable organic content of the sample. COD analysis involves the use of a strong oxidizing agent to oxidize the organic compounds in the sample, and the consumed oxidizing agent is then measured to determine the COD value.
While both TOC and COD provide information about the organic content of water, they differ in terms of their measurement principles and the scope of compounds they quantify. TOC measures the total carbon content, including both organic and inorganic carbon, while COD specifically focuses on the oxidizable organic content.
In many cases, there is a positive correlation between TOC and COD. This means that as the TOC concentration increases, the COD value also tends to increase. This correlation occurs because the majority of organic compounds contribute to both the TOC and COD values. However, it is important to note that the correlation may not be perfect due to the presence of inorganic carbon compounds, non-oxidizable organic compounds, and variations in the composition of organic pollutants.
WHY SHOULD YOU MONITOR COD IN WATER?
THERMAL OXIDATION (HIGH TEMPERATURE METHOD)
The thermal oxidation method, also known as the high-temperature method, is a technique used in water analysis to determine various parameters, such as total organic carbon (TOC) or total carbon (TC). It involves the oxidation of organic and inorganic carbon compounds present in a water sample at high temperatures.
In this method, a water sample is introduced into a combustion furnace or reactor, where it is heated to temperatures typically ranging from 850°C to 1,200°C in the presence of an oxidizing agent, such as oxygen or ozone. The high temperatures and oxidizing conditions cause the carbon compounds in the sample to oxidize completely, converting them into carbon dioxide (CO2).
Our LAR high temperature thermal oxidation method offers several advantages in water analysis:
- Versatility: It can be used for the determination of various carbon-related parameters, including total organic carbon (TOC), total inorganic carbon (TIC), and total carbon (TC).
- Wide Measurement Range: The high-temperature method can measure carbon concentrations over a wide range, from low levels (parts per billion) to high levels (percentage levels).
- Sample Matrix Compatibility: The thermal oxidation method is applicable to a broad range of water sample matrices, including drinking water, wastewater, surface water, and industrial process water.
- Complete Carbon Oxidation: The high temperatures used in the combustion process ensure the complete oxidation of carbon compounds, providing accurate and reliable measurements.
ELECTROCHEMICAL MEASUREMENT PRINCIPLE