Cultivation Of A Novel Manganese-Oxidizing Aerobic Granular Sludge For Removal Of Arsenic From Wastewater

Aerobic granular sludge?AGS?is a powerful biotechnology that can remove various pollutants from wastewater.It has good settling ability,higher biomass and impact resistance.It is a further innovation of the traditional activated sludge process and is an ideal biological treatment technology.The surface carries a large amount of negative charge.Under the action of electrostatic attraction,the heavy metal cations in the wastewater can be removed by adsorption,but does not include arsenic?As?.This study developed a new type of manganese-oxidizing aerobic granular sludge?Mn-AGS?for the removal of arsenic from organic wastewater.The results are as follows:?1?The Mn-AGS with manganese oxidation function were successfully cultivated.Mn-AGS had certain removal efficiency for As,Sb,Cr,.The oxidation of Mn-AGS was not enough to oxidize low-toxic Cr?III?to Cr?VI?,but highly toxic As?III?and Sb?III?can be efficiently oxidized to low-toxic As?V?and Sb?V?,so there was a possibility of simultaneously removing As,Sb and Cr.?2?Mn-AGS had better arsenic removal effect than AGS.Eight sequencing batch reactors?SBRs?were operated in duplicate to investigate the feasibility of As removal by Mn-AGS.In Mn-AGS,As?III?was efficiently oxidized into As?V??74.6%-82.6%?.?3?Adding a small amount of Fe?II?to the Mn-AGS reactor can greatly improve the As?III?removal rate.It might be primarily caused by Fenton reactions,because this improvement was removed when H₂O₂,self-generated in Mn-AGS,was scavenged by exogenous catalase?CAT?.This study provided a novel extension of the traditional AGS technology to treat As in organic wastewater with a satisfactory efficiency.?4?Multiple-pathway arsenic oxidation in Mn-AGS.Batch experiments revealed As?III?was oxidized by multiple pathways in Mn-AGS,including microbial metabolism?⁴6%?,bio-MnOx?³1%?,and Fenton reactions?²3%?.?5?The existence form of arsenic in Mn-AGS.The immobilized As in granule was characterized by sequencing extraction,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?,scanning electron microscopy-energy dispersive spectroscopy?SEM-EDS?,and Raman spectroscopy.A range of characterizations showed that the immobilized As in Mn-AGS sludge was mostly in As?V?and bound to amorphous ferrihydrite and bio-MnOx?56.2%-65.0%?,while metal arsenates,such as ferric arsenate,were not detected.?6?Simultaneous removal of As and Cu.In the experiment of removing As and Cu from the leachate of bottom ash by Mn-AGS for 91 days,the simultaneous removal of As and Cu can be achieved,with efficiencies of 79.4%and 89.8%,respectively.It can be found that the effect of Mn-AGS on Cu removal was more stable after two consecutive failure experiments.?7?The presence of As and Cu in Mn-AGS was analyzed by SEM,XRD and Tessier continuous extraction methods.It can be found that As and Cu in Mn-AGS mainly exist in the form of carbonate-bound state,and it can also be indicated that the metallic As and Cu in Mn-AGS can be recovered by acidizing.