Reduction of chromate by fixed films of sulfate-reducing bacteria using hydrogen as an electron source

Abstract

The ability of sulfate-reducing bacteria (SRB) to reduce chromate, Cr(VI), was evaluated using fixed-film growth systems and H2 as the electron source. A main objective of the experiment was to distinguish between direct enzymatic reduction and indirect reduction by hydrogen sulfide, in order to subsequently verify and control the synergy of these two mechanisms. In batch experiments with the sulfate-reducing consortium CH10 selected from a mining site, 50 mg l(-1) Cr(VI) was reduced in 15 min in the presence of 500 mg l(-1) hydrogen sulfide compared to 16 mg l(-1) reduced in 1 h without hydrogen sulfide. Fixed films of a CH10 population and Desulfomicrobium norvegicum were fed-batch grown in a column bioreactor. After development of the biofilm, hydrogen sulfide was removed and the column was fed continuously with a 13-mg l(-1) Cr(VI) solution. Specific Cr(VI) reduction rates on pozzolana were close to 90 mg Cr(VI) h(-1) per gram of protein. Exposure to Cr(VI) had a negative effect on the subsequent ability of CH10 to reduce sulfate, but the inhibited bacteria remained viable.

The treatment of textile wastewater including chromium(VI) and reactive dye by sulfate-reducing bacterial enrichment

“…In these previous experiments, it was shown that the chromium(VI) reduction capacity of the microbial biomass varied with the pH values of the culture medium, where the optimum pH values were found to be 7 in bacterial cultures (Schmieman et al, 1998;Ram et al, 1999;Nepple et al, 2000;Zouboulis et al, 2004). In the experiments with SRB, chromium(VI) reduction was also investigated at pH 7 (Tebo and Obratzsova, 1998;Smith and Gadd, 2000;Lloyd et al, 2001;Battaglia-Brunet et al, 2002). In the present study, the optimum value for chromium(VI) reduction at about 50 mg l À1 initial chromium(VI) concentration was found to be pH 8.…”

Relationship Between Sulphate Starvation and Chromate Reduction in a H2-fed Fixed-film Bioreactor

“…It has been subsequently shown (Battaglia-Brunet et al 2002;2004a,b;2006) that this bioprocess was effective for removing chromate from different matrices (synthetic solutions, actual ground waters and actual waste waters), by using different supports (mainly pozzolana, ceramics and PVC crossfiller material), under continuous feed conditions, between 10 and 35°C, for several months, and in scaled up bioreactors (volume capacity of 2, 20 and 200 l). During the process development steps, whose main purpose was the efficient chromate immobilisation as Cr(III), certain aspects were not sufficiently detailed and we try to describe more precisely the process through some complementary experiments and investigations.…”

Reduction of chromium (VI) compounds by sulfate-reducing bacteria

“…Одним із основних шляхів появи резистентних до хромату мікроорганізмів може бути відновлення Cr (VI) до Cr (III). Відновлювати шестивалентний хром можуть мікроорганізми, що належать до родів: Acinetobacter [19], Aerococcus [51], Aeromonas [51], Aspergillus [23], Bacillus [57], Corynebacterium [55], Deinococcus [20], Desulfomicrobium [8,9], Desulfovibrio [13,33], Enterobacter [21,43,56], Escherichia [14,46], Microbacterium [38], Micrococcus [51], Ochrobactrum [19], Pseudomonas [10,11,32], Rhodobacter [36], Shewanella [35], Staphylococcus [44], Streptomyces [18], Vibrio [28] і Zoogloea [50]. Ефективно відновлюють Cr (VI) змішані культури сульфатвідновлювальних бактерій [48].…”