Dissolved oxygen (DO) is the amount of oxygen that is dissolved in water. It is essential for the survival of aquatic life, as well as for other processes such as wastewater treatment and odour control.
High temperatures reduce the solubility of oxygen in water (i.e., warm water holds less DO than cold water).
High nutrients can lead to excessive plant growth, resulting in DO declines due to respiration and decomposition.
Embedded sediments can prevent DO from permeating interstitial areas.
Oxygen is consumed as ammonia is oxidised (nitrification), and low oxygen levels increase ammonia levels by inhibiting nitrification.
DO levels are a key indicator of water quality, and low DO levels can lead to fish kills and other problems for aquatic life. Increasing DO levels can help to improve the health of aquatic ecosystems.
DO is essential for the biological treatment of wastewater. In wastewater treatment plants, microorganisms use DO to break down organic matter. Increasing DO levels can help to improve the efficiency of wastewater treatment and reduce the amount of pollutants that are discharged into the environment.
DO can also help to reduce odours from wastewater and other sources. This is because odours are often caused by the decomposition of organic matter, which consumes DO. By increasing DO levels, the decomposition process can be slowed down, which can help to reduce odours.
Aeration is the process of adding air to water. This can be done by using mechanical devices such as air pumps or by allowing water to cascade over waterfalls or other obstacles. Aeration is the most common way to increase DO in water treatment plants.
Diffusion is the process of oxygen molecules moving from an area of high concentration to an area of low concentration. DO can be increased by increasing the surface area of the water that is exposed to the air. This can be done by using fountains, sprayers, or by creating artificial wetlands.
Some bacteria and algae can produce oxygen as a byproduct of photosynthesis. This process can be used to increase DO levels in wastewater treatment plants and other bodies of water.
The amount of DO in water is measured in milligrams per liter (mg/L). The ideal DO level for aquatic life varies depending on the type of organism, but it is generally considered to be between 5 and 10 mg/L.
Low DO levels can also be a sign of water pollution. When organic matter decomposes in water, it consumes DO. This can lead to low DO levels, which can in turn lead to fish kills and other problems for aquatic life.
By monitoring DO levels and taking steps to increase DO when necessary, we can help to protect aquatic life and improve water quality.
The EPA (Environmental Protection Agency, USA) has set standards for DO levels in water due to its critical importance.
Mining tailings dams can contain high levels of organic matter, which can lead to low DO levels in the water downstream of the dam. This can have a negative impact on aquatic life and water quality.
Sewage treatment plants produce wastewater that contains high levels of organic matter. This organic matter can consume DO in the receiving waterbody, which can lead to low DO levels and fish kills.
Odour control is an important consideration in water treatment plants and other industrial settings where there is a risk of odour emissions. DO can help to reduce odours by slowing down the decomposition of organic matter.
The nitrogen cycle is a biogeochemical process that converts nitrogen from one form to another. DO plays an important role in the nitrogen cycle by providing oxygen for the oxidation of ammonia and other nitrogenous compounds.
Visit https://www.epa.gov/caddis-vol2/dissolved-oxygen for more specific information on the role of DO.
An anaerobic pond is a type of wastewater treatment system that uses anaerobic bacteria to break down organic matter in the absence of oxygen. Anaerobic ponds are typically used for the treatment of high-strength wastewater, such as that from food processing plants or slaughterhouses.
