The combination of microbial reduction and further microbial oxidation of iron was applied to the treatment of food-processing wastewater and recovery of ammonium. Fe2+ ions were formed by iron-reducing bacteria under anaerobic conditions. Ammonium was recovered by co-precipitation with negatively charged iron hydroxides produced during oxidation of Fe2+ by iron-oxidizing bacteria under microaerophilic conditions. The value-added by-product of this process can be used as a slowly released ammonium fertilizer.

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Bioreduction of Fe(III) and biooxidation of Fe(II) can be used in wastewater engineering as an innovative biotechnology BioIronTech, which is protected for commercial applications by US patent 7393452 and Singapore patent 106658 "Compositions and methods for the treatment of wastewater and other waste". The BioIronTech process comprises the following steps: 1) anoxic bacterial reduction of Fe(III), for example in iron ore powder; 2) surface renovation of iron ore particles due to the formation of dissolved Fe 2+ ions; 3) precipitation of insoluble ferrous salts of inorganic anions (phosphate) or organic anions (phenols and organic acids); 4) (bio)oxidation of ferrous compunds with the formation of negatively, positively, or neutrally charged ferric hydroxides, which are good adsorbents of many pollutants; 5) disposal or thermal regeration of ferric (hydr)oxide. Different organic substances can be used as electron donors in bioreduction of Fe(III). Ferrous ions and fresh ferrous or ferric hydroxides that are produced after iron bioreduction and (bio)oxidation adsorb and precipitate diferent negatively charged molecules, for example chlorinated compounds of sucralose production wastewater or other halogenated organics, as well as phenols, organic acids, phosphate, and sulphide. Reject water (return liquor) from the stage of sewage sludge dewatering on municipal wastewater treatment plants represents from 10 to 50% of phosphorus load when being recycled to the aeration tank. BioIronTech process can remove/recover more than 90% of phosphorous from this reject water thus replacing the conventional process of phosphate precipitation by ferric/ferrous salts, which are 20-100 times more expensive than iron ore, which is AIMS Environmental ScienceVolume 1, Issue 2, 53-66.used in BioIronTech process. BioIronTech process can remarkably improve the aerobic and anaerobic treatments of municipal and industrial wastewaters, especially anaerobic digestion of lipidand sulphate-containing food-processing wastewater. It can also remove the recalcitrant compounds from industrial wastewater, enhance sustainability and quality of water resources,restore eutrophicated lakes due to removal of phosphate, ammonium, and pesticides from water, and recover ammonium and phosphate from municipal and food-processing wastes.