Chemical Oxygen Demand (COD) refers to the amount of oxidizing agents consumed by reducing substances that are easily oxidized by strong oxidizing agents (generally potassium dichromate) in the water body, resulting in the amount of oxygen (measured in mg/L). It is a comprehensive index to characterize reducing substances in water. Except for special water samples, the reducing substances are mainly organic compounds, and the elements of organic compounds such as carbon, nitrogen, sulfur and phosphorus are often in lower oxidation valence states. The following water quality online monitoring instrument manufacturers to understand the relevant knowledge of COD in water with you.
What Effect Does COD Have on the Water Body?
Once the organic pollutants with increased COD content enter the rivers and lakes, if they cannot be treated in time, many organic matter may be adsorbed by the soil under the water, and for many years, these organic matter will cause harm to various organisms in the water, and will last for a long time. This poison has two aspects: 1. It will cause a large number of aquatic organisms to die, the ecological balance in the water will be destroyed, and even the entire river ecosystem will be destroyed. 2. Toxins accumulate slowly in the body of fish and shrimp, and once the human body eats poisoned aquatic organisms, toxins will then enter the human body, causing cancer/deformity/gene mutation and other serious consequences.
What is the Reason for the Increase of COD Content in Water?
The reducing pollutants in the water are mainly organic pollutants, the source of these organic pollutants may be domestic water or industrial water, industrial water such as chemical plants/pharmaceutical factories/printing and dyeing plants, and pesticides/organic fertilizers may be the reason for the increase in cod content in the water body.
Why Monitor COD Content in Water?
In the natural cycle, reducing substances in water, especially organic compounds, consume dissolved oxygen in the process of biooxidation and degradation, resulting in water oxygen defects. The defects of dissolved oxygen will destroy the ecological balance of the environment and the biological community, cause the deterioration of water quality, and even cause the depletion of dissolved oxygen, the breeding of anaerobic bacteria, and cause the water to turn black and stinky. This requires monitoring of organic matter in the water.
What Equipment is Used to Monitor COD Content in Water?
The COD 8000–COD online analyzer produced by Hangzhou Moody is to determine the COD content in water by potassium dichromate digestion at high temperature and colorimetry. Cr (VI) in the mixed solution formed by water sample, potassium dichromate, silver sulfate (as a catalyst to oxidize the straight chain aliphatic compounds more fully) and concentrated sulfuric acid is reduced to Cr (III) under high temperature and high pressure environment, so that the color of the mixture solution changes. The degree of change of the color of the solution corresponds to the solubility of COD (chemical oxygen demand) of the measured water sample. The instrument can directly determine the COD value of the water sample by photoelectric colorimetry. In addition, chloride ions in water samples are the main interfering substances. The COD online analyzer can eliminate the interference of chlorine by adding chloride ions in water samples.
