Oxygen (O)

Basic Information

Physical and Chemical Properties

• At normal temperature and pressure, oxygen is a colorless and odorless gas
• Oxygen is slightly soluble in water. At 20°C and 1 atm pressure, its solubility is about 7-8 mg/L
• 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 has no direct impact on human health, but drinking water with very low DO may contain harmful contaminants. Normal DO levels in drinking water range from 5-8 mg/L.

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.

Regulatory Guidelines and Standards

The recommended minimum DO limit for drinking water is 5 mg/L based on WHO guidelines. Water quality standards used by the water treatment industry, such as AWWA and IBWA, also set similar standards for DO.

For natural waters, Indonesia's water quality standards categorize water conditions based on DO levels:

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.

Future Trends and Research

Emerging research is focused on optimizing aeration technologies, such as microbubble and nanobubble aerators that can improve gas transfer efficiency. Cutting-edge technologies such as biohydrogenation reactors are also being explored for the simultaneous removal of oxygen and organic contaminants from wastewater.

Remote sensing and the Internet of Things (IoT) open up opportunities for real-time monitoring of DO and water quality. Wireless sensors and advanced data analytics will enable better decision-making in water resources management.

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
• Fish can survive in water with DO levels as low as 2 mg/L, but require at least 5-6 mg/L for optimal growth
• Dissolved oxygen concentration in water is affected by temperature, altitude, salinity and atmospheric pressure