Effects of pH, floc age and organic compounds on the removal of phosphate by pre-polymerized hydrous ferric oxides

Ascorbic acid-mediated reductive cleaning of iron-fouled membranes from submerged membrane bioreactors

“…For example, Mikutta et al [19] report that pure ferrihydrite has a specific surface area of 300 m 2 g À 1 and a total pore volume of 0.19 cm 3 g À 1 , significantly lower the surface area and pore volume estimates for the Fe-containing material on the membrane surface shown in Table 1. Interestingly, the surface area deduced here for the membrane-located Fe-containing material is similar to that estimated by Mao et al [21] for iron oxyhydroxides deposited "in situ" in the presence of phosphate.…”

Composition and structure of Fe(III)-precipitates formed by Fe(II) oxidation in water at near-neutral pH: Interdependent effects of phosphate, silicate and Ca

“…In the context of water treatment and nutrient and contaminant dynamics in environmental systems, the uptake of arsenic, phosphate, and other ions by Fe oxidation products is commonly modelled as an adsorption process on a single "hydrous ferric oxide phase" (Wilkie and Hering, 1996;Meng et al, 2002;Roberts et al, 2004;Li et al, 2012;Mao et al, 2012). Such models allow to quantify ion uptake by fresh Fe(III)-precipitates under specific chemical conditions, but do not account for the structural complexity of Fe oxidation products.…”

“…Phosphate uptake by Fe(III)-phases therefore has been extensively studied, for example with respect to phosphate dynamics in eutrophic aquatic systems (Buffle et al, 1989;Gunnars et al, 2002;Griffioen, 2006) or phosphate removal from wastewater (Hsu, 1973;Mao et al, 2012). At near-neutral pH, Fe(II) oxidation in the presence of phosphate leads to the precipitation of amorphous Fe(III)-phosphate in which phosphate limits Fe(III) polymerization to the stage of monomers and oligomers (Rose et al, 1996;Voegelin et al, 2010Voegelin et al, , 2013Châtellier et al, 2013).…”

Effect of ferric and ferrous iron addition on phosphorus removal and fouling in submerged membrane bioreactors

“…While the activated sludge process is normally capable of achieving effluent P concentrations of 2e4 mg/L, or 0.5e1 mg/L if an enhanced biological phosphorus removal process such as Bardenpho is used, many countries are targeting effluent P concentrations of 0.01e0.3 mg/L in order to prevent eutrophication (Piekema, 2004). These low effluent concentrations are typically achieved by addition of inorganic salts such as ferric chloride or aluminium sulphate which, on addition to aqueous solutions in the circumneutral pH range, readily form high surface area particulate oxyhydroxides which have a very high P scavenging ability (Sedlak, 1991;Waite, 2002;Kim et al, 2008;Caravelli et al, 2010;Mao et al, 2012). Membrane bioreactor (MBR) technology is widely viewed as being state of the art for municipal wastewater treatment due to the ability to achieve good contaminant removal whilst possessing small footprint and relatively low capital and operating costs (Judd and Judd, 2011).…”