【Daily Question】10.30 True or False: COD is biological oxygen demand ( )

Wrong. It is Chemical Oxygen Demand COD: Chemical Oxygen Demand refers to the measurement, using chemical methods, of the amount of reducing substances in water. Biological Oxygen Demand should be BOD

COD is Biological Oxygen Demand (correct)

Chemical Oxygen Demand (COD) is the amount of reducible substances in a water sample that need to be oxidized, as measured by chemical methods

Wrong, COD stands for Chemical Oxygen Demand

Is COD biological oxygen demand? () Wrong. Chemical oxygen demand (COD)? Under certain conditions, the amount of oxidizing agent consumed when treating a water sample with a strong oxidizer is referred to as chemical oxygen demand, abbreviated as COD. Its unit is milligrams of oxygen per liter (O2, mg/l). The chemical oxygen demand determined using potassium dichromate (K2Cr2O7) as an oxidant is expressed as CODcr. Chemical oxygen demand can reflect the degree of pollution of water bodies by reducing substances. Reducing substances in water include organic matter, sulfite salts, ferrous salts, sulfides, etc. Potassium dichromate can oxidize organic substances in water quite completely; for example, its oxidation rate for low-carbon straight-chain compounds is 80–90%, so CODcr can represent the content of organic substances in water quite accurately. Furthermore, the determination of CODcr takes a short time and is not restricted by water quality; therefore, it is now used as an indicator for monitoring industrial wastewater pollution. The disadvantage of CODcr is that it cannot, like BOD5, indicate the amount of organic matter oxidized by microorganisms and thus directly reflect hygiene conditions. For wastewater with a relatively constant composition, a certain correlation can be maintained between its BOD5 value and CODcr. Therefore, the BOD5/CODcr ratio is commonly used as an indicator to determine whether wastewater is suitable for biological treatment (i.e., its biodegradability); the higher this value, the greater the biodegradability of the wastewater. One form of pollution in the water sphere is the introduction of organic substances, fertilizers, detergents, and similar materials into the water. In this type of organic pollution, they are broken down by oxygen-consuming bacteria in water, which reduces the oxygen level in the water; therefore, we refer to such organic substances as oxygen-consuming pollutants. Due to the highly complex composition of organic pollutants, the oxygen consumption in water is commonly used as an indicator of the degree of water pollution, with the unit being mg·L-1. It is further divided into Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). Generally, for the same water sample, CODcr > BOD20 > BOD5, and the difference between CODcr and BOD5 values can roughly indicate the amount of organic matter that cannot be degraded by microorganisms.

This post was last edited by Shuangli Chemical on 2015-10-30 at 14:15. It should be: Error – COD stands for Biological Oxygen Demand. ( X) Because biological oxygen demand is BOD, while COD is chemical oxygen demand.

COD is Biological Oxygen Demand (X)

Error. ------It should be chemical oxygen demand. Under certain conditions, it refers to the amount of strong oxidizing agent consumed when treating a water sample.

COD stands for Biological Oxygen Demand (X). Chemical Oxygen Demand, or COD, is the amount of reducing substances in a water sample that need to be oxidized, as measured using chemical methods. The oxygen equivalent of substances (usually organic compounds) that can be oxidized by strong oxidants in wastewater, effluents from wastewater treatment plants, and contaminated water. In the study of river pollution and the properties of industrial wastewater, as well as in the operation and management of wastewater treatment plants, it is an important organic pollution parameter that can be measured relatively quickly; it is often denoted by the symbol COD.

COD is biochemical oxygen demand (incorrect). Answer: COD is chemical oxygen demand