Phosphorus Retention Mechanisms of a Water Treatment Residual
| Autor: | D. M. Heil, James A. Ippolito, J. P. Chandler, Kenneth A. Barbarick, Edward F. Redente |
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| Rok vydání: | 2003 |
| Předmět: |
Environmental Engineering
chemistry.chemical_element Aluminium sulfate Management Monitoring Policy and Law Waste Disposal Fluid Calcium Carbonate Phosphates chemistry.chemical_compound Adsorption Water Supply Desorption Solubility Octacalcium phosphate Waste Management and Disposal Water Science and Technology Chemistry Phosphorus Hydrogen-Ion Concentration Pollution Inductively coupled plasma atomic emission spectroscopy Water treatment Aluminum Nuclear chemistry |
| Zdroj: | Journal of Environmental Quality. 32:1857-1864 |
| ISSN: | 0047-2425 |
| DOI: | 10.2134/jeq2003.1857 |
| Popis: | Water treatment residuals (WTRs) are a by-product of municipal drinking water treatment plants and can have the capacity to adsorb tremendous amounts of P. Understanding the WTR phosphorus adsorption process is important for discerning the mechanism and tenacity of P retention. We studied P adsorbing mechanism(s) of an aluminum-based [Al 2 (SO 4 ) 3 .14H 2 O] WTR from Englewood, CO. In a laboratory study, we shook mixtures of P-loaded WTR for 1 to 211 d followed by solution pH analysis, and solution Ca, Al, and P analysis via inductively coupled plasma atomic emission spectroscopy. After shaking periods, we also examined the solids fraction by X-ray diffraction (XRD) and electron microprobe analysis using wavelength dispersive spectroscopy (EMPA-WDS). The shaking results indicated an increase in pH from 7.2 to 8.2, an increase in desorbed Ca and Al concentrations, and a decrease in desorbed P concentration. The pH and desorbed Ca concentration increases suggested that CaCO 3 controlled Ca solubility. Increased desorbed Al concentration may have been due to Al(OH) - 4 formation. Decreased P content, in conjunction with the pH increase, was consistent with calcium phosphate formation or precipitation. The system appeared to be undersaturated with respect to dicalcium phosphate (DCP; CaHPO 4 ) and supersaturated with respect to octacalcium phosphate [OCP; Ca 4 H(PO 4 ) 3 . 2.5H 2 O]. The Ca and Al increases, as well as OCP formation, were supported by MINTEQA2 modeling. The XRD and EMPA-WDS results for all shaking times, however, suggested surface P chemisorption as an amorphous Al-P mineral phase. |
| Databáze: | OpenAIRE |
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