The application of aluminum salts (alum) effectively removes phosphorus from water and controls its release from sediment. This process, known as phosphorus inactivation, can reverse the harmful effects of excessive nutrient loading in bodies of water like ponds and lakes.
Here's a more detailed look at how it works:
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Aluminum Salts (Alum): Alum, typically aluminum sulfate (Al2(SO4)3), is the primary agent used to "kill" or, more accurately, remove phosphorus. When alum is added to water, it reacts to form aluminum hydroxide (Al(OH)3), a solid precipitate.
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Phosphorus Binding: The aluminum hydroxide precipitate has a strong affinity for phosphorus. It binds with dissolved phosphate ions (PO43-), effectively removing them from the water column.
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Sediment Control: The aluminum-phosphorus compound settles to the bottom sediment, forming a layer that prevents the release of phosphorus from the sediment back into the water. This process is particularly important because sediment can act as a reservoir for phosphorus, continually feeding the water column with nutrients and perpetuating issues like algal blooms.
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Reversal of Eutrophication: By reducing the available phosphorus, a key nutrient for algae growth, alum treatment can help to reverse the effects of eutrophication (nutrient enrichment) in lakes and ponds. This leads to clearer water, reduced algal blooms, and improved overall water quality.
In summary, aluminum salts (alum) are used to bind with phosphorus and remove it from the water, preventing it from fueling algal blooms and reversing the effects of nutrient pollution.
