Phosphogypsum biotransformation in cultures of sulphate reducing bacteria in whey

Assemblages of anaerobic sulphidogenic microorganisms were isolated from soil polluted by oil-derived products and grown using the microcosms method. The cultures were grown in minimal and Postgate media with phosphogypsum (PG) as the sole electron acceptor and with lactate, casein or lactose as the sole carbon source. The most effective was the assemblage in Postgate medium with lactose as the sole carbon source. A reduction of 980 mg COD l−1 (reduction of about 40%) and 790 mg SO42− l−1 (reduction of 53% of phosphogypsum introduced to the medium) was noted in the culture. The lowest activity was observed for minimal medium with lactose as sole carbon source (reduction of 4.4% COD and 40% PG). The selected assemblage became an inoculum for a culture in Postgate, minimal and/or distilled water medium with PG (6 g l−1) and cheese whey (2.5 and 4.5 g l−1).A percentage reduction of COD and SO42− of PG was observed in all cultures. After growth, the residues were weighed and in all cases a distinct mass reduction of PG was observed in comparison to the 6 g l−1 introduced to the medium. Diffractometric studies of the residues confirmed the presence of calcite and apatite. The presence of these mineral phases in the residues allows their application as agricultural fertilisers.