Water Research Centre, School of Civil & Environmental Engineering, The University of New South Wales, Sydney 2052, Australia.
Water Research Centre, School of Civil & Environmental Engineering, The University of New South Wales, Sydney 2052, Australia; Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia; Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany.
Water Res. 2015 Jun 1;76:213-26. doi: 10.1016/j.watres.2015.02.020. Epub 2015 Mar 5.
Iron dosing of membrane bioreactors (MBRs) is widely used as a means of meeting effluent phosphorus targets but there is limited understanding of the nature of iron and phosphorus-containing solids that are formed within the bioreactor (an important issue in view of the increasing interest in recovering phosphorus from wastewaters). Of particular challenge is the complexity of the MBR system and the variety of reactions that can occur on addition of iron salts to a membrane bioreactor. In this study, the performances of bench scale MBRs with dosing of either ferrous or ferric salts were monitored for a period of four months. The distributions of Fe and P-species in the Fe-conditioned sludges were determined using X-ray absorption spectroscopy (XAS) at the Fe K-edge and the P K-edge. Regardless of whether iron was dosed to the anoxic or aerobic chambers and regardless of whether ferrous (Fe(II)) or ferric (Fe(III)) iron was dosed, iron present in the minerals in the conditioned sludges was consistently in the +III oxidation state. Fitting of the Fe K-edge EXAFS spectra revealed that an Fe(III)-phosphate species was the main Fe species present in all cases with the remaining fraction dominated by lepidocrocite (γ-FeOOH) in the Fe(II)-dosed case and ferrihydrite (am-FeOOH) in the Fe(III)-dosed case. Approximately half the phosphorus in the activated sludge samples was present as a distinct Fe-PO4 mineral (such as strengite or an amorphous ferric hydroxyl phosphate analogue of strengite) and half as phosphorus adsorbed to an iron oxyhydroxide mineral phase indicating that both co-precipitation and adsorption of phosphorus by iron contribute to removal of phosphorus from the MBR supernatant.
膜生物反应器（MBR）中广泛使用铁投加作为满足出水磷目标的方法，但对于在生物反应器内形成的含铁和含磷固体的性质了解有限（鉴于从废水中回收磷的兴趣日益增加，这是一个重要问题）。特别具有挑战性的是 MBR 系统的复杂性以及在向膜生物反应器添加铁盐时可能发生的各种反应。在这项研究中，监测了四个月时间内投加亚铁或高铁盐的台式 MBR 的性能。使用 X 射线吸收光谱法（XAS）在 Fe K 边和 P K 边测定了铁调理污泥中 Fe 和 P 物种的分布。无论铁是投加到缺氧室还是好氧室，也无论投加的是亚铁（Fe(II)）还是高铁（Fe(III)），调理污泥中矿物质中的铁始终处于+III 氧化态。Fe K 边 EXAFS 光谱的拟合表明，在所有情况下，主要的 Fe 物种都是 Fe(III)-磷酸盐，其余部分在 Fe(II)投加的情况下主要由纤铁矿（γ-FeOOH）组成，而在 Fe(III)投加的情况下主要由水铁矿（am-FeOOH）组成。活性污泥样品中约一半的磷以一种独特的 Fe-PO4 矿物存在（例如，蓝铁矿或蓝铁矿的无定形铁羟基磷酸盐类似物），另一半磷吸附在铁氢氧化物矿物相中，表明磷的共沉淀和吸附都有助于从 MBR 上清液中去除磷。
