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DIV. TEEMARK CORPORATION 1132 Air Park Drive AITKIN MN, 56431 PHONE: 218 - 927 - 2200 FAX; 218 - 927 - 2333 TOLL FREE: 800 - 428 - 9900 |
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DIV. TEEMARK CORPORATION 1132 Air Park Drive AITKIN MN, 56431 PHONE: 218 - 927 - 2200 FAX; 218 - 927 - 2333 TOLL FREE: 800 - 428 - 9900 |
What is Alum and How Does it Control Phosphorus? |
 ALUM (aluminum sulfate) is a nontoxic material commonly used in water treatment plants to clarify drinking water. In lakes alum is used to control the amount of the nutrient phosphorus in the water. |
| Phosphorus enters the water either externally, from run-off or ground water, or internally, from the nutrient rich sediments on the bottom of the lake. Phosphorus is released from the sediments under anoxic conditions that occur when the lake stratifies and oxygen is depleted from the lower layer. |
| Even when external sources of phosphorus have been curtailed by best management practices, the internal recycling of phosphorus can be a significant water quality problem. Alum is used primarily to control this internal loading of phosphorus from the sediments of the lake bottom. |
| On contact with water, alum forms a fluffy aluminum hydroxide precipitate called floc. Aluminum hydroxide (the principle ingredient in common antacids such as Maalox) reacts with phosphorus to form an aluminum phosphate compound. This compound is insoluble in water under naturally occurring conditions so the phosphorus in it is permanently unavailable. |
| As the floc slowly settles, some phosphorus is removed from the water. The floc also tends to collect suspended particles in the water and carry them down to the bottom, leaving the lake noticeably clearer. |
| On the bottom of the lake the floc forms a layer that acts as a phosphorus barrier by combining with phosphorus as it is released from the sediments. The floc is harmless to water creatures and aquatic plants. (Sorry, alum does not control rooted aquatic weeds.) |
| A sediment alum treatment can last up to ten years, depending on how much alum is applied, and lake conditions such as sedimentation rate and external phosphorus loading. Best results are obtained when steps are first taken to control the external sources of phosphorus .
Some of these steps are simple, like encouraging the use of phosphorus free fertilizers and detergents or discouraging large flocks of waterfowl. More costly measures may be necessary such as installing a sewer system, building sedimentation impoundments, and diverting agricultural and urban run-off.
Alum can also be used to treat water from a nutrient rich inlet before it enters the lake. Any of these best management practices that are in place before the alum treatment will improve its effectiveness and extend its life. |
 Aluminum Dose Calculation |
LAKE AND STREAM RESTORATION