Dissolved Air Flotation and Wastewater Clarification

Suspended Solids Found in Industrial Wastewater

Solid matter, including all sludge, fats, oils and greases, must be removed from industrial wastewater before the supply can be repurposed. Dissolved air flotation acts effectively to remove food and animal processing wastes, hydrocarbon emulsions and other contaminants. Water supplies with algae also require purification. It is possible to achieve a 97 percent removal rate using this method for wastewater clarification.

The Process of Wastewater Clarification

Using compression, the dissolved air flotation system creates whitewater in a dissolving pump or tube. Whitewater is a mixture of already purified wastewater and a high-powered concentration of air. This solution is then pumped into the tank and mixes with the still contaminated water supply. As the compressed air in the whitewater makes contact with the contaminants, microscopic air bubbles attach to the surface of all solid particles. The solids float to the surface of the tank. A skimming device is used to scrape off the sludge coating and deposit it waste in a separate system.

When heavier solids do not float to the surface after contact with whitewater and stay lodged at the bottom of the tank, they are automatically discharged through a draining valve. Purified water then flows out of the system for reuse via exit drains. Some of the water is recycled back into the system to create another spurt of whitewater. sodium diisobutyl dithiophosphate

Types of System Materials

Dissolved air flotation systems can be constructed of a variety of different materials, including concrete, polypropylene, carbon steel and stainless steel. Systems constructed of concrete require extensive planning and take the most time to build. They are permanent fixtures and non-movable, so concrete tanks are most commonly used for municipal purposes. The benefits of a concrete system are increased durability and a minimized chance of leaks.

Polypropylene systems are less expensive than concrete, but still provide a high level of sturdiness. However, polypropylene cannot hold up under extreme high temperatures, and in temperatures below freezing, the material will crack. These tanks are sensitive to UV exposure and may develop cracks over time if placed in direct sunlight. As a positive, the material is resistant to chemicals and is usually covered under a 10-year warranty.

Carbon steel tanks are coated with an epoxy covering. This prevents corrosion in most cases, but carbon steel is not ideal for systems purifying food waste. The acids have the potential to break down the epoxy and jumpstart oxidation and rusting.

While the more expensive of the system material options, stainless steel provides decade after decade of reliable use and resistance to wear and tear. Stainless steel’s performance is not compromised in extremely low or high temperatures, so the material is eligible for outdoor and indoor use. The only chemical that may instigate rusting in stainless steel is chloride.


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