Oxygen (O) in Water Treatment
Quick Answer
Oxygen (O) is a nonmetal with atomic number 8. PubChem lists its standard state as gas and its relative atomic mass as 15.999.
Dissolved oxygen controls biological treatment, corrosion and oxidation-reduction conditions. Aeration can add oxygen; deaeration or oxygen scavenging may be required for boilers and other corrosion-sensitive systems.
Interesting Facts
- Oxygen dissolved in water is measured separately from the oxygen bound inside H2O molecules.
- Oxygen transfer is limited by equilibrium and mass transfer; bubbling more air does not guarantee the target dissolved-oxygen concentration.
- Too little oxygen can limit aerobic biology, while too much can aggravate corrosion or gas problems in sensitive systems.
Water-treatment Design Implications
An element name alone is not enough to select treatment equipment. Confirm chemical form or speciation, total and dissolved concentration, pH, alkalinity, competing ions and the product-water target. Send the water-analysis results to Watermart to identify additional testing and shortlist processes before equipment is specified.
Summary Data Sources
Basic Information
| Atomic Number | 8 |
| Symbol | O |
| Atomic mass | 15.999 g/mol |
| Electron configuration | 1s2 2s2 2p4 |
| Block | p |
| Category | Non-metallic |
Physical and Chemical Properties
- At normal temperature and pressure, oxygen is a colorless and odorless gas
- Oxygen solubility depends on temperature, pressure, salinity and gas composition; correct for conditions when comparing data.
- Oxygen is highly reactive and easily reacts with many other elements to form oxides
- Oxygen supports combustion and is required for respiration
Presence in Water and Health Effects
Dissolved oxygen (DO) is a key parameter of water quality. Adequate DO concentrations are necessary to support aquatic life such as fish and beneficial microorganisms. Water with low DO may reflect pollution and pose a risk to ecosystem health. However, DO levels that are too high can cause corrosion in water piping systems.
Dissolved oxygen is not a direct measure of drinking-water safety. Low DO may indicate reducing conditions or biological activity, but it does not prove a particular contaminant is present; test the relevant parameters directly.
Water Treatment Applications and Removal Methods
Aeration is the primary process for increasing DO in water treatment. Some aeration techniques include:
- Tray aerators
- Spray aerators
- Diffused aerators
- Cascade aerators
Dissolved oxygen levels can also be increased with renewable technologies such as photocatalytic water treatment that utilizes sunlight.
Conversely, deoxygenation or oxygen removal is sometimes required in water treatment to prevent corrosion or reduce microbial growth. Techniques such as inert gas spraying, vacuum, membrane deaeration, or addition of reducing chemicals can be used.
Environmental Impacts and Sustainability Considerations
Organic load pollution in water bodies can deplete dissolved oxygen levels and cause hypoxic conditions that are harmful to aquatic life. Effective wastewater treatment to remove organic contaminants can help restore and maintain DO levels.
Energy-efficient and sustainable water treatment technologies should be selected to avoid increasing the carbon footprint. For example, aerators that use renewable power sources can minimize energy consumption while increasing DO.
Fun Facts
- Oxygen is the third most abundant element in the universe after hydrogen and helium
- Photosynthesis by plants produces almost all the oxygen in Earth’s atmosphere
- Aquatic oxygen needs vary by species, life stage, temperature and salinity; aquaculture targets must be system-specific.
- Dissolved oxygen concentration in water is affected by temperature, altitude, salinity and atmospheric pressure