Phosphorus removal from wastewaters: Experimental and theoretical support for alternative mechanisms

Otimização de processos físico-químicos na remoção de fósforo de esgotos sanitários por processos de precipitação química com cloreto férrico

“…Isto implica que, qualquer que seja o mecanismo de remoção de fósforo na fase líquida, deverá estar presente em meio aquoso hidróxido férrico precipitado e a sua formação tenderá a ser de fundamental importância a fi m de que as frações de fósforo particulado, orgânico solúvel e polisfosfatos de alto peso molecular possam ser removidos por mecanismos de coprecipitação e adsorção na fase sólida formada (Galarneau et al, 1997).…”

Removal capacity of water plant alum sludge for phosphorus in aqueous solutions

“…The amorphous form of Al (21,100 mg/kg) was a dominant phase of the sequentially extracted Al (exchangeable, organic, and amorphous forms) in the air-dried alum sludge and a significant amount of organically complexed Al (6,620 mg/kg) was contained. The extracted amorphous Al was probably short ranged Al(OH) 3 (Galarneau and Gehr, 1997), and was expected to be the major adsorbent for P. The sludge had kaolinite, mica, and quartz as major mineral components. Among the major minerals in alum sludge, kaolinite has been known as one of the effective P adsorbents in soils and sediments (Bennoah and Acquaye, 1987).…”

“…The P removal capacity of alum sludge increased with decreasing initial solution pH during the column test ( Figure 6). For the pH 3 solution, P concentration of the effluent was below the P discharge limit of wastewater, 1 mg/L (Galarneau and Gehr, 1997), until 750 pore volumes of P solution passed through the alum sludge column, and 250 pore volumes for pH 4 solution and 200 pore volumes for pH 5 solution, respectively. The pH of the effluent sharply increased to 12 with a increasing volume of filtered solution for the pH 12 solution and the effluent pH decreased to 3 for the pH 3 solution (Figure 7).…”

“…Low cost materials including blast furnace slag (Johansson and Gustafsson, 2000), red mud (Baker et al, 1998), alum sludge (Galarneau and Gehr, 1997), natural soil (Stuanes, 1984), fly ash (Ugurlu and Salman, 1998), and limestone (Higgins et al, 1976;Kuo and Lotse, 1972) were tested as P removal agents in the wastewater treatment process. These materials efficiently removed P from wastewater, and major components in the materials for P removal were identified to be Al hydroxide, Fe oxide, calcium oxide, and calcium carbonate.…”

Effectiveness of a drinking-water treatment sludge in removing different phosphorus species from aqueous solution

“…OH -ions compete strongly with phosphates for available sites when the suspension is within the alkaline ranges [26]. Past studies [8,24,27] have proven that aluminium solubility is highly dependant on pH. Yang et al [26] reported that the surface charge of Al-based DWTS sludge showed a variation from +75.8 mV to -33.7 mV that corresponds to a pH change from 4.3 to 9.0.…”