DAF or dissolved air flotation systems are used in a wide range of industries to remove suspended solids and contaminants from water and other liquids. Their most significant applications are in the treatment of wastewater to remove effluents and in the treatment of drinking water. Another important use for DAF water treatment equipment is to prevent and remove algae blooms, which are potentially toxic and hazardous, from the water supply.
What is Dissolved Air Flotation (DAF)?
Dissolved Air Flotation systems are used to treat wastewater by removing suspended materials. It works to remove solids as well as oil from water. Air is dissolved into the water or liquid to be treated under pressure, and released at atmospheric pressure in a floatation tank. The air bubbles that form when the air is released attach themselves to the matter to be removed and float it to the surface of the water. The suspended materials can then be skimmed off from the top.
DAF wastewater systems can be used to remove industrial effluents from polluting industries like oil, paper mills, petrochemicals, etc. In the oil industry, the air bubbles are replaced by nitrogen to prevent the risk of explosions. DAF water treatment equipment can remove three kinds of pollutants – suspended solids, biochemicals, and oils and greases. By the time wastewater is released into the natural environment after primary and secondary treatments, some 85% to 95% of all pollutants have been removed.
What are algae blooms and why are they harmful?
DAF water treatment equipment is also used to treat drinking water on a municipal scale. In fact, it can also be used to remove potentially harmful algae blooms from drinking water. Algae blooms thrive on the phosphorous and nitrogen found in water. When there are excess amounts of phosphorous and nitrogen in water, due to runoff pollution from agricultural and residential fertilizer use, algae blooms grow into huge colonies that cut off the oxygen supply to the water below.
This creates anoxic dead zones, where nothing can live. Dead fish and plants in the water can make the entire supply toxic. Algae blooms can be found in all kinds of water bodies, from ponds and streams to rivers and ocean waters adjoining estuaries. They are becoming an increasing problem in the summer with rising summer temperatures and vast quantities of nitrogen and phosphorus from commercial agriculture and residential lawn care finding their way into these water bodies.
How can DAF water treatment equipment remove algae blooms from water?
Some recent toxic algae blooms in Lake Erie and Florida have underlined the scale of the problem. The best way to prevent algae blooms is to cut off the supply at the source, namely the excess agricultural and residential use of fertilizer and the runoff into water bodies. This may seem straightforward, but for both social and political reasons, it can be difficult to implement. That makes it necessary to focus on the second stage, which is the removal of existing algae blooms and phosphorous from the water.
Dissolved air flotation equipment can be used to remove floating algae blooms and also to reduce the concentration of the phosphorous that sustains them. The water supply first undergoes coagulation and flocculation processes before being sent to the DAF equipment. The air bubbles then move all floating solid materials to the surface, where they can be removed. The cleaned water can be removed from the bottom of the tank.
DAF water treatment systems are widely used to treat both wastewater and the drinking water supply. They are also being used to remove algae blooms as well as the pollutants like phosphorous they live on, to clean the water supply before distribution.