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Intro to dissolved air flotation systems

2nd April 2020 Print

Dissolved air floatation is a process that removes grease and oil from industrial wastewaters. While DAF has been around since the late 1960s, very few professionals know about it. In fact, this water purification method didn't become widely used in the U.S. until the early 2000s.

What makes this process so unique? Well, with traditional sedimentation, the settled particles and solids are removed from the bottom of the clarification chamber. But with DAF, flocculated particles and solids are removed from the surface.

How DAF systems work

The process is pretty simple. First, an air compressor is used to generate air bubbles. Next, these microbubbles are released into the flocculated water. After this, the bubbles begin to bind the particles and solids together. As the sludge floats to the top and is periodically removed to a desludging trough, the clarified water settles at the bottom of the chamber for collection.

The pros

There are several benefits to this method. One of the biggest advantages is that it's great for removing lighter particles. With traditional sedimentation, it's hard to get rid of smaller things like algae because they don't really settle.

Another huge benefit is that you don't need heavy floc to ensure settling. This means that your flocculation time will be shorter. Your coagulant dosage will be lower as well.

Also, you won't have to thicken the sludge before you dewater. DAF sludge is made of up to 6 percent solids, so it's already quite thick.

The cons

This isn't to say that DAF doesn't have its challenges, especially when it comes to raw water. It's not the best solution if you're dealing with high-density solids. As the pumped recycle percentage increases, so does the amount of required energy -- which can be costly.

Technologies and Applications

Three of the most popular DAF technologies are AquaDAF, Clari-DAF, and Enflo-DAF. 

Aqua-DAF features the use of an orifice plate floor and a slant wall. This gives the tank the ability to function at an SLR of up to 20 gpm/ft2. It also improves flow distribution.

Clari-DAF features the use of various lateral draw-off pipes along the bottom of the cell. This gives the tank the ability to function at an SLR of up to 20 gpm/ft2. It also allows for uniform distribution.

Enflo-DAF features the use of tubes. This gives the tank the ability to function at an SLR of up to 20 gpm/ft2. It increases the separation zone and also improves hydraulic flow distribution.

What to Look For In DAF Technology

As you can see, there are a variety of technologies available. So it's essential that you do the proper research before investing in a DAF wastewater removal system. Let's take a moment to discuss a few things that you should be on the lookout for.

Cost Efficiency

Whether your company is in the oil and gas industry or pharmaceuticals, it's important that you look for a system that's cost-effective. DAF is known for being a great way to save money. 

However, you should consider the initial investment and how much energy the system requires. The more energy your system requires, the more you should expect to spend in the long run.

Low Maintenance

A big problem that a lot of businesses face is the amount of time that it takes to maintain their equipment. Most systems require you to do a weekly draining and cleaning of the unit, an inspection of your filters and strainers, and replacement of your purge plate packs. However, if you want to save time, it's a good idea to search for a system that cuts down on the daily procedures.

Easy to Operate

Perhaps the most essential aspect you should be on the lookout for is a system that's easy to operate. Ideally, the design should be intuitive and feature automation. This way, the only thing you'll be responsible for is simple check-ups to ensure that it's running smoothly.

Standard Parts

When a system features parts that are standard, they're easy to access. This makes maintenance easier if something, such as a hose, needs to be replaced. Simple things can make a huge difference.

The Takeaway

According to research, even some of the most polluted waters can be treated and reused. However, it's important that you choose the right filtration method. DAF is known for its unique approach to water clarification.

It's ideal for getting rid of lighter particles that would otherwise not settle to the bottom of the chamber. Its flocculation times are shorter. Also, it's sludge doesn't require thickening. Essentially, DAF is becoming one of the most popular methods for water clarification. No matter what industry you're in, DAF is an ideal choice.