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ARS Home » Southeast Area » Fayetteville, Arkansas » Poultry Production and Product Safety Research » Research » Publications at this Location » Publication #402704
Research Project: Developing Best Management Practices for Poultry Litter to Improve Agronomic Value and Reduce Air, Soil and Water Pollution

Location: Poultry Production and Product Safety Research

Title: Treating biosolids with water treatment residuals to reduce phosphorus runoff

Author
item Moore Jr, Philip

Submitted to: SERA-IEG 17 Bulletin
Publication Type: Other
Publication Acceptance Date: 9/15/2024
Publication Date: 12/1/2024
Citation: Moore Jr, P.A. 2024. Treating biosolids with water treatment residuals to reduce phosphorus runoff. SERA-17 Website (https://sera17.wordpress.ncsu.edu/).

Interpretive Summary:

Technical Abstract: Water treatment residuals (WTRs) are added to biosolids to reduce phosphorus runoff. Biosolids, formerly known as sewage sludges, are waste products from wastewater treatment plants that have tremendous potential for agricultural use due to their high nutrient content. However, biosolids can have high concentrations of water soluble phosphorus which can cause non-point source phosphorus pollution. Research has shown that the amount of phosphorus runoff from biosolids is directly related to their soluble phosphorus content. Adding water treatment residuals to biosolids greatly reduces the soluble phosphorus levels, which results in much less phosphorus runoff and leaching. Water treatment residuals should be blended with biosolids at a rate equivalent to 10-30% by weight (WTR/biosolids). Biosolids are typically processed into what is referred to as “cake” at municipal wastewater treatment plants. The cake is the material remaining after water removal through centrifugation or belt pressing and usually contains around 80% moisture. Water treatment residuals are the waste products from drinking water treatment plants following the addition of metal salts, such as aluminum sulfate or ferric sulfate, to flocculate impurities, like organic matter and sediment, present in surface waters. After this flocculation process, the WTRs will be primarily composed of aluminum or iron hydroxides, which have a very high capacity for phosphorus adsorption. When WTRs are mixed with biosolids the soluble phosphorus levels in biosolids are reduced, resulting in less phosphorus runoff or leaching following land application. The blended mixture can be applied right after mixing or incubated for several weeks prior to application. The aluminum and iron oxides and hydroxides present in the WTRs adsorb soluble phosphorus and reduce its release during runoff events. The incubation period allows for greater interaction and adsorption to take place, increasing the effectiveness of the overall blend.