Solid phosphorus phase in aluminum- and iron-treated biosolids.
Stabilization of phosphorus (P) in sewage sludge (biosolids) to reduce water-soluble P concentrations is essential for minimizing P loss from amended soils and maximizing the capacity of the soil to safely serve as an outlet for this waste material. The chemical form at which P is retained in biosolids stabilized by Al(2)(SO(4))(3) x 18H(2)O (alum) or FeSO(4) x 7H(2)O (FeSul) was investigated by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray elemental spectrometry (EDXS) and by X-ray diffraction (XRD). Both treatments resulted in the formation of a Ca-P phase, probably brushite. Phosphorus was further retained in the alum-treated biosolids by precipitation of an Al-P phase with an Al/P molar ratio of about 1:1, while in the FeSul-treated biosolids, P was retained by both precipitation with Fe/P molar ratios of 1:1 or 1.5:1, and by adsorption onto newly formed Fe hydroxides exhibiting an Fe/P molar ratio of up to 11:1. All of these mechanisms efficiently reduced P solubility and are crucial in biosolids environmentally safe agronomic beneficial use for this waste product; however, each P phase formed may react differently in the amended soil, depending on soil properties. Thus, the proper P stabilization method would depend on the target soil.
Huang
Xiao-Lan
XL
Department of Soil and Water Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76-100, Israel.
Chen
Yona
Y
Shenker
Moshe
M
D000534:Alum Compounds / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods
D000534:Alum Compounds; D005296:Ferrous Compounds; D012722:Sewage; D010758:Phosphorus; C041524:aluminum sulfate; C020748:ferrous sulfate; D013455:Sulfur; D000535:Aluminum; D007501:Iron; D002118:Calcium