Influence of water treatment residuals on phosphorus solubility and leaching.
Laboratory and greenhouse studies compared the ability of water treatment residuals (WTRs) to alter P solubility and leaching in Immokalee sandy soil (sandy, siliceous, hyperthermic Arenic Alaquod) amended with biosolids and triple superphosphate (TSP). Aluminum sulfate (Al-WTR) and ferric sulfate (Fe-WTR) coagulation residuals, a lime softening residual (Ca-WTR) produced during hardness removal, and pure hematite were examined. In equilibration studies, the ability to reduce soluble P followed the order Al-WTR > Ca-WTR = Fe-WTR >> hematite. Differences in the P-fixing capacity of the sesquioxide-dominated materials (Al-WTR, Fe-WTR, hematite) were attributed to their varying reactive Fe- and Al-hydrous oxide contents as measured by oxalate extraction. Leachate P was monitored from greenhouse columns where bahiagrass (Paspalum notatum Flugge) was grown on Immokalee soil amended with biosolids or TSP at an equivalent rate of 224 kg P ha(-1) and WTRs at 2.5% (56 Mg ha(-1)). In the absence of WTRs, 21% of TSP and 11% of Largo cake biosolids total phosphorus (PT) leached over 4 mo. With co-applied WTRs, losses from TSP columns were reduced to 3.5% (Fe-WTR), 2.5% (Ca-WTR), and <1% (Al-WTR) of applied P. For the Largo biosolids treatments all WTRs retarded downward P flux such that leachate P was not statistically different than for control (soil only) columns. The phosphorus saturation index (PSI = [Pox]/ [Al(ox) + Fe(ox)], where Pox, Al, and Fe(ox) are oxalate-extractable P, Al, and Fe, respectively) based on a simple oxalate extraction of the WTR and biosolids is potentially useful for determining WTR application rates for controlled reduction of P in drainage when biosolids are applied to low P-sorbing soils.
Elliott
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HA
Agric and Biol Eng Dep, Pennsylvania State Univ, University Park 16802, USA. hae1@psu.edu
O'Connor
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GA
Lu
P
P
Brinton
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S
D000534:Alum Compounds / Q000737:chemistry; D003247:Conservation of Natural Resources; D005290:Ferric Compounds / Q000737:chemistry; D005308:Fertilizers; D008372:Manure; D010758:Phosphorus / Q000737:chemistry*; D012822:Silicon Dioxide; D012987:Soil; D012995:Solubility; D014865:Waste Disposal, Fluid / Q000379:methods*
D000534:Alum Compounds; D005290:Ferric Compounds; D005308:Fertilizers; D008372:Manure; D012987:Soil; C000499:ferric oxide; D010758:Phosphorus; C041524:aluminum sulfate; C024823:ferric sulfate; D012822:Silicon Dioxide