Mode of action of ferric and ferrous iron salts in activated sludge

Degradation of organic pollutants and characteristics of activated sludge in an anaerobic/anoxic/oxic reactor treating chemical industrial wastewater

“…This result can explain the decrease of MLVSS/MLSS ratio in this experiment. In addition, the SVI value decreased in the present experiment because of Fe(III) accumulation in activated sludge and the flocculation effect, which was also reported by Oikonomidis et al (2010). Changes in the properties of activated sludge flocs as shown by SEM: (a), (c), and (e) represent the activated sludge during the initial stage of operation (×200, ×500, and ×1000, respectively); (b), (d), and (f) represent the activated sludge during the stable stage of operation (×200, ×500, and ×1000, respectively).…”

“…Changes in the properties of activated sludge flocs as shown by SEM: (a), (c), and (e) represent the activated sludge during the initial stage of operation (×200, ×500, and ×1000, respectively); (b), (d), and (f) represent the activated sludge during the stable stage of operation (×200, ×500, and ×1000, respectively). Oikonomidis et al (2010) also reported that floc surface properties were modified and settleability was enhanced because of the effective flocculation of Fe. The positively charged Fe species could bridge the anionic chemical groups on the floc surface.…”

Nutrients removal and nitrous oxide emission during simultaneous nitrification, denitrification, and phosphorus removal process: effect of iron

“…During cycle 3, the time course of NH 4 + concentration was similar to the previous cycle, indicating that the addition of Fe(III) had no impact on ammonium removal. Although literature showed that activated sludge with 25 mg/L of ferric iron could enhance nitrification process and the removal of ammonium (Oikonomidis et al 2010), it was not observed in this study. The reason was that the nitrification in this study carried out thoroughly and ammonium was almost completely removed.…”

“…The results indicated that most of iron adding into the reactors combined with sludge and secreta of the microbes. Oikonomidis et al (2010) found that Fe could form ionic bonds with sludge flocs and floc surface properties would be enhanced, this being beneficial to the morphological characteristics and settleability with further implications for the operation of activated sludge. In addition, with the increase of Fe(III) load, more iron was washed away from the reactors.…”

Enhanced synergistic denitrification and chemical precipitation in a modified BAF process by using Fe2+

“…Hence, if dosing Fe salts in the proposed synergistic denitrification and chemical precipitation process, pH condition would be favorable for Fe 2+ rather than Fe 3+ to precipitate phosphorus. Despite Fe 2+ is considered potentially a suitable precipitant being used in the proposed process due to its relatively low cost and high phosphorus removal efficiency under the typical pH condition of denitrification, an uncertainty still lies in the possible smaller size of Fe 2+ dosed sludge flocs compared to Fe 3+ dosed ones (Oikonomidis et al, 2010), which might adversely affect liquid-solid separation performance in the settling tank. To date, report on applying Fe 2+ salt in the pre-denitrification stage of BAF process to achieve simultaneous chemical precipitation of TSS and phosphorus remains few.…”