Laboratory scale column studies on transport and biotransformation of Cr(VI) through porous media in presence of CRB, SRB and IRB

Combined abiotic and biotic in-situ reduction of hexavalent chromium in groundwater using nZVI and whey: A remedial pilot test

“…A very similar situation was found in monitoring wells PV-214 and PV-217, where facultative or strictly anaerobic bacteria were detected, including sulfate-, iron-or nitrate-reducing bacteria represented by the genera Geobacter, Sulfuritalea and families Desulfobacteraceae, Desulfobulbaceae, Comamonadaceae, Oxalobacteraceae, Holophagaceae, Rhodocyclaceae, Nitrospinaceae, Catabacteriaceae [39,40,41]. The detected genera and families indicate that the Cr(VI) reducing process could be mediated by iron-reducing and sulfate-reducing bacteria that are known to react up to 100 times faster than chromium-reducing bacteria from other laboratory studies [10]. This conclusion is also supported by the elevated concentration of soluble Fe (see Figure 4), the Pourbaix stability diagrams (see Figure 5) during the biotic phase that remained even after the decrease in bacterial biomass (see Figure 7) and depletion of TOC during the two last sampling campaigns (see Supplementary Information Figure S2).…”

“…FeS) as a result of anaerobic oxidation of an organic substrate by iron-reducing bacteria where Fe(III) acts as an alternative electron acceptor. Cr(VI) as chromate (CrO 4 2-) or bichromate (Cr 2 O 7 2-) then reacts with biogenic Fe(II) to form insoluble Cr x Fe 1-x (OH) 3 (s) or Cr(OH) 3 (s) [9,10]. Similarly, hydrogen sulphide (H 2 S) produced from microbially mediated reduction of sulfates by sulfate-reducing bacteria is able to reduce Cr(VI) to Cr(III) [11,12,9].…”

Molasses as an efficient low-cost carbon source for biological Cr(VI) removal

“…However, most of these carbon sources cannot be used at industrial scale because of their high cost. Recently the use of molasses, a by-product of the sugar industry which is an economical and readily available carbon and energy source, has gained more ground [23,25,30,38,39], especially in attached growth reactors [30,38]. These studies (Table 1) examined the efficiency of molasses over other carbon sources without indicating the effect of their concentration on Cr(VI) reduction.…”

Membrane bioreactor for the treatment of voc laden pharmaceutical wastewater: Effect of biological treatment systems on membrane performance

“…Extra cellular polymeric substance in the bioreactor was extracted using the procedure described by Somasundaram et al [13] and was evaluated in terms of carbohydrate and protein.…”