Operational pH in packed-bed reactors for ferrous ion bio-oxidation

The flooded packed-bed bioreactor plays a major role in the field of applications of ferrous ion bio-oxidation. The pH is an important variable in the control of this type of reactor, upon which the functionality of biofilm depends.In the present work, five continuous flooded packed-bed reactors have been inoculated with mixed cultures (Acidithiobacillus ferrooxidans and Leptospirillum ferooxidans) and fed with 9 k medium in the pH range 0.82 to 1.90.It has been experimentally tested that the operation of these reactors is stable at the maximum productivity levels when the pH varies within the interval 1.00 to 2.30 inside the reactor.It has been observed that the negative effect on the productivity when the upper pH limit is exceeded is reversible. No such reversibility occurs when the pH goes below the lower limit.The results of our experiments indicate that the limitations in operational pH are linked to the chemistry of precipitation ferric compounds and not to biological phenomena.