Unlike chemicals wastewater treatment plants, which uses chemical to stabilize contaminants, wastewater aeration is a natural method of eliminating organic pollutants in the water, by using microorganisms already present in the wastewater to decompose contaminants.
Wastewater aeration is essentially the process of aerobic biodegradation of pollutants in the wastewater when air is added directly to it. It is a vital part of wastewater treatment and is highly effective besides being environmentally friendly and commercially viable.
When is aeration used?
Aeration occurs in the Secondary Treatment Process stage of industrial and municipal wastewater treatment. It is an activated sludge process when air is pumped into the wastewater to enable microbial growth in the water. The microbes feed on the organic matter in the wastewater, forming flocks that easily settle out in a separate settling tank. This is the activated sludge which is recirculated back into the aeration basin to increase the rate of biodegradation.
How does wastewater aeration work?
An efficient aeration system has two main activities:
- It supplies oxygen to the wastewater, which enables microorganisms to decompose pollutants in the water. Enough dissolved oxygen (DO) is needed for bacteria to survive and thrive. Without adequate oxygen, the microorganisms cannot get rid of incoming organic pollutants in a reasonable amount of time. A well-design aeration system will ensure that adequate DO is maintained.
- The aeration system will ensure that the oxygen is properly mixed into the wastewater. Proper mixing is necessary to avoid the buildup of sludge as it keeps solids in suspension. Mixing also ensures that there are no pockets of anaerobic (without oxygen) zones in the wastewater, which can affect the degradation process.
Types of aeration systems
Different aeration systems operate differently from each other and come with their own unique set of benefits. There are two main types of aeration systems:
Sub-Surface Aeration
A sub-surface aeration system provides oxygen to the system by injecting compressed air through airlines to diffusers installed at the bottom of the tank or the lagoon. The diffusers are installed in a pattern for uniform coverage of the water. Diffusers come in two basic types: Fine bubbles and coarse bubbles.
Fine Bubble Diffusers
Fine bubbles diffusers introduce air into the water through thousands of tiny holes producing fine bubbles. These smaller bubbles provide maximum surface area for contact with the wastewater. They also rise slowly to the surface, ensuring contact for a longer time. Fine bubble diffusers offer the best ‘oxygen transfer efficiency’ because of the above factors.
Coarse Bubble Diffusers
Coarse bubble diffusers have larger holes to disperse bubbles. The larger bubbles travel faster to the surface but create more turbulence and mixing. However, these diffusers require more oxygen to operate than fine bubble diffusers.
Coarse bubble diffusers are most suited for systems that require more mixing, such as conventional aeration, highly loaded systems, sludge storage, aerobic digesters, and channels.
Surface Aeration
Surface aeration systems are the best choice for shallow water applications or when large amounts of oxygen are needed immediately. These systems are used in lagoons or pond treatment systems.
Surface aeration uses low waterfalls, jet fountains and spray nozzles to deliver air to the wastewater. The agitation created when air is added creates the maximum amount of mixing with a larger surface area for oxygen exchange. The drawback of this system is that it only effects that wastewater in the area where the aerator is located.
How to pick the right type of aeration system for you
When trying to choose the right aeration system for your requirements, consider the following factors to help you determine the best choice:
- Costs, including maintenance, energy, and capital costs
- Wastewater volume
- Oxygen requirement for the wastewater
- Tank size
- Efficiency requirements
- Climate, location, and environment
- Maintenance required
At Hynds, we offer aerated wastewater systems for both residential and commercial purposes. If you are interested in any of our products, or want to learn more, contact Hynds today.
