Relationship between COD and water ecosystem
Definition of COD
COD, or chemical oxygen demand, is the amount of oxidant consumed when a certain strong oxidant is used to treat wastewater under certain conditions. It is an indicator of the amount of reducing substances (especially organic matter) in water, measured in milligrams per liter, reflecting the degree of material pollution in the water. The higher the value, the more serious the degree of organic pollution in the water body.
Impact of COD on water ecosystem
Impact on aquatic organisms
Direct toxic effects: Organic pollutants such as organochlorine pesticides such as DDT may be adsorbed and accumulated by the bottom soil if not treated in time after entering the water body. Its toxicity will cause the death of a large number of aquatic organisms, destroy the ecological balance of the water body, and may even directly destroy the entire river ecosystem. Moreover, toxins will slowly accumulate in aquatic organisms such as fish and shrimp, affecting their growth, reproduction and other physiological processes.
Hazards transmitted through the food chain: After humans eat aquatic organisms that accumulate toxins in their bodies, the toxins will enter the human body and accumulate for many years, which may eventually lead to unpredictable serious consequences such as cancer, deformities, and gene mutations, thereby indirectly affecting the interactive relationship between the water ecosystem and humans.
Impact on dissolved oxygen in water
Consume a lot of oxygen: The self-purification of water requires the degradation of organic matter in the water, and the degradation of these organic matter will inevitably consume a lot of oxygen. When the reoxygenation capacity in the water cannot meet this demand, the dissolved oxygen (DO) in the water will drop directly to 0, turning the water into an anaerobic state.
Cause water body deterioration: In an anaerobic state, anaerobic microorganisms will multiply and decompose organic matter in large quantities, making the water body black and smelly and producing harmful gases such as hydrogen sulfide, further deteriorating the water ecological environment and affecting the survival of aquatic organisms.
Feedback of aquatic ecosystems on COD
Self-purification effect
The aquatic ecosystem itself has a certain self-purification ability, and the microorganisms in the water can decompose some organic matter and reduce the COD content. However, when the COD content in the water is too high and exceeds the self-purification capacity of the aquatic ecosystem, it will cause damage to the ecosystem.
Response of biological communities to COD
Different aquatic biological communities have different tolerances to COD. Some organisms with strong pollution tolerance may multiply in high COD water bodies, while sensitive organisms with high water quality requirements will decrease or disappear, thus changing the structure of biological communities and affecting the stability of water ecosystems.
Monitoring and controlling COD to protect water ecosystems
In order to effectively prevent the harm of excessive COD content in water to the ecological environment and human health, COD analyzers can be used to monitor the COD content in water bodies in real time. By timely discovering and taking corresponding measures to reduce the content of organic matter in water bodies, such as adopting appropriate sewage treatment methods, water resources and water ecological environment can be protected.