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Uses of Dewatered Alum Sludge

Wastewater treatment requires the removal of harmful contaminants from sewage and runoff from farms. Chemical precipitation presents an economical alternative to physical and biological processes. However, the treatment of wastewater with aluminum sulfate creates excessive amounts of alum sludge. Uses for this byproduct include the production of fertilizer and the creation of wetlands for purification of farm waste.

  1. Removal of Phosphates

    • Aluminum sulfate is used as a coagulant for the purification of drinking water. The dewatered alum sludge that remains can be reused for further isolation and removal of phosphates from discharged water from treatment facilities. According to an article in the August 2010 issue of the "Journal of Environmental Science and Health," dewatered alum sludge can remove 13 milligrams of phosphorus for each gram of the material. The authors concluded that the full capacity of alum sludge is not being used and further studies on its adsorption capacity need to performed.

    Fertilizer Production

    • Algal blooms compromise water quality due to excessive levels of nitrogen and phosphorus deposited in aqueous ecosystems from water treatment facilities. A study published in the November 2009 issue of "Recent Patents on Food, Nutrition and Agriculture" investigated the use of dewatered alum sludge for removal of the elements from wastewater to control algal blooms. The researchers found that alum sludge efficiently removes nitrogen and phosphorus and the resultant product can be used as a raw material for fertilizer production.

    Construction of Wetlands

    • The use of dewatered alum sludge has been proposed to construct a wetland system for enhancing wastewater treatment. An article appearing in the July 2009 issue of the "Journal of Environmental Science and Health" documented the performance of a wetland system for the removal of organic material from wastewater. The study found that up to 90 percent of organic materials can be removed from wastewater using "cakes" produced from dewatered alum sludge.

    Treatment of Farm Waste

    • Animal farm waste is rich in phosphorus and nitrogen, which must be removed before being released into the environment. A study published in the January 2009 issue of "Bioresource Technology" explored the applicability of dewatered alum sludge to treat farm waste in a reed bed. The researchers found that this system was able to remove up to 85 percent of phosphorus and nitrogen in farm waste and offered a long-term solution to this ongoing problem.

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