05/24/2021 | Aeration Wastewater Treatment | 8 MINUTE READ

Choosing Aeration in Wastewater Treatment Applications

aeration in wastewater

In order for wastewater to be reused for irrigation or to supply drinking water, it must first be treated at a wastewater treatment facility. Once the wastewater reaches this facility, there is a range of different treatments that can be used to get rid of the contaminants that are contained in the water. One of the more common treatment methods is aeration. The aeration process involves adding air into the wastewater, which promotes the consumption of pollutants by aerobic microorganisms.

Aeration is considered to be an essential component of many biological treatment systems. When the air has been effectively added to the wastewater, the dissolved oxygen levels in the water will naturally increase. The aerobic microorganisms in the water require dissolved oxygen to survive. If you want to maintain dissolved oxygen levels in the wastewater, aeration is essential.

Aeration will also mix the wastewater, which is necessary to keep solids in suspension. If you don’t keep the solids in suspension, they will accumulate and eventually form into sludge that can be more difficult to get rid of. While aeration systems are highly beneficial and provide you with a natural method for treating contaminated water, it’s important to understand that these systems have their downsides. For instance, it’s possible for pipes within the aeration system to become clogged, which increases the damage and mechanical stress to the aerator. You may also need to purify the used air, which can take time and money.

Aside from the few downsides, aeration systems work well with nearly all wastewater treatment applications. By effectively implementing an aeration system into your wastewater treatment facility, you can treat wastewater in a rapid and effective manner. This article offers a more detailed look at the aeration process and what happens when it’s used to treat wastewater.

How Wastewater Aeration Works

Before you start to use a wastewater aeration system, it’s important to understand how these systems work. There are two different system types that you can select from, which include subsurface aeration systems and surface aeration systems, both of which have their advantages. The option you select depends on the application and how much water needs to be treated.

Subsurface Aeration

There are two systems that can be used with wastewater aeration, the primary of which is subsurface aeration. This type of aeration system delivers oxygen to the microorganisms in the water by injecting a certain amount of air into the wastewater. Air pumps or blowers are used to compress the air before it’s sent through numerous airlines to diffusers. The diffusers are typically installed along the bottom of the lagoon or tank to achieve full coverage. Diffusers consist of small holes that are able to create air bubbles. The two types of bubble diffusers that can be found in subsurface aeration systems include fine bubble diffusers and coarse bubble diffusers.

Fine Bubble Diffusers

These diffusers are equipped with thousands of very small holes that are able to produce tiny bubbles. By creating small bubbles, it’s possible for the bubbles to reach the maximum surface area. You’ll also find that the bubbles rise to the top of the water at a very slow rate, which ensures that they have lengthy contact time. If oxygen transfer efficiency is a top concern of yours when selecting an aeration system, fine bubble diffusers may be your best option. Oxygen transfer efficiency refers to the total amount of air that the wastewater absorbs.

Coarse Bubble Diffusers

These diffusers typically have large holes that invariably produce large bubbles. Once these bubbles are produced, they will travel quickly to the surface. The main benefit of using a subsurface aeration system that’s equipped with a coarse bubble diffuser is that they are able to create more turbulence in the wastewater, which helps mix the wastewater. While these diffusers are great for mixing wastewater, they require at least double the amount of air that fine bubble diffusers do.

Surface Aeration

This form of wastewater aeration is commonly used in the creation of pond treatment systems and lagoon treatment systems. The different pieces of equipment that you can use for surface aeration include spray nozzles, small waterfalls, and jet fountains. All of these water features can either be fixed or positioned on a pontoon. When water is transported or sprayed with one of these features, agitation will occur that allows air to come into contact with the wastewater.

This aeration system is highly effective at mixing the wastewater and accommodating a high oxygen transfer rate. The main issue with this system is that only the area directly surrounding the aerator will benefit from it.

What does Aeration Do To Wastewater?

how aeration affects wastewaterAeration is commonly used as a kind of secondary treatment method to rid wastewater of contaminants. In many situations, this process will be a part of the activated sludge process, which can be used to oxidize biological matter and assist with the eradication of wastewater contaminants. When aeration is used as an activated sludge process, it will occur by pumping air directly into the lagoon or tank. When aeration is performed correctly, microbes or microorganisms will naturally grow in the water.

The microbes that develop will feed on any organic pollutants that can be found in the water. From here, they form into masses of fine particles that settle out into a separate lagoon or settling tank. Once these particles accumulate towards the bottom of the lagoon or tank, they will form activated sludge. Along with being used as an activated sludge process, aeration can also be used for storage purposes in lagoons and tanks.

When used for storage purposes, it’s essential to maintain the living organisms that are currently present in the tank or lagoon. If the microorganisms start to die, the wastewater could become septic, which would produce a strong and unpleasant odor. As mentioned previously, there are two main jobs that aeration performs when added to wastewater, which include adding air to the wastewater and mixing the wastewater.

Step 1: Adding Air to Wastewater

When you obtain an aeration system, it will automatically add air to the surrounding wastewater. In order for microorganisms to survive and consume any contaminants in the water, they must have constant access to dissolved oxygen. By adding air to the wastewater, you’re directly increasing dissolved oxygen levels. An aeration system will allow you to maintain the correct dissolved oxygen levels, which will keep contaminants at bay.

Step 2: Mixing The Wastewater

Another benefit of using the aeration process is that it can mix the wastewater and make sure that every area of the water receives at least some oxygen. If the water isn’t properly mixed, it’s possible that the microorganisms in certain areas will die off as a result of not having access to the amount of dissolved oxygen that they require. Keep in mind that properly mixing the water will also help you keep sludge at bay.

Why Aeration is Important for Wastewater

importance of aerationAeration is important for wastewater for a number of reasons. For one, aeration is able to keep costs down compared to other treatment methods. In most situations, using a natural treatment will be more affordable than a chemical treatment or similar solution. Unlike the chemicals that are commonly used to treat wastewater, air doesn’t need to be bought for you to use an aeration system.

Along with saving you an ample sum of money, aeration is also considered to be an Eco-friendly process. Since aeration is a part of the activated sludge process when treating wastewater, you shouldn’t need to use chemicals at any stage of the treatment process. While not using chemicals helps you save money, it also ensures that you don’t do too much damage to the environment while treating wastewater. Every type of chemical is damaging to the environment, which is why it’s highly recommended that you opt for a natural treatment like aeration.

If you use aeration correctly, dissolved oxygen will spread evenly throughout the water, which should allow you to break down all of the organic matter that’s present in the water. Keep in mind that wastewater is sent back to the environment once it’s been treated, which is why it’s important that you use the most effective treatment methods available to you.

To understand how important it is to remove all contaminants from the wastewater, any organic materials that remain will eventually start to decay. Over time, the decayed matter will consume the dissolved oxygen in the water, which will result in the water becoming increasingly contaminated. When you’re attempting to purchase the right aeration system for wastewater treatment, the factors that you should consider include:

  • Plant location and climate
  • How much you want to reduce maintenance
  • Total wastewater volume
  • Your capital cost, maintenance cost, and energy cost goals
  • The tank or lagoon size
  • Wastewater oxygen requirements
  • System efficiency requirements

With these factors in mind, you should be confident in the decision you make.

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Posted by Dominic O'Donnell on May 24, 2021

Sensorex is a global leader in the design and manufacture of quality sensors for water quality and process applications. The company offers more than 2000 sensor packages for pH, ORP, conductivity, dissolved oxygen, free chlorine, chlorine dioxide, UV transmittance and other specialty measurements, as well as a full line of sensor accessories and transmitters. Its expert technical support engineers solve analytical sensor challenges with custom designs and off the shelf products.

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