RESUMO
High rate sulfate reduction under acidic conditions opens possibilities for new process flow sheets that allow the selective recovery of metals from mining and metallurgical waste and process water. However, knowledge about high-rate sulfate reduction under acidic conditions is limited. This paper investigates sulfate reduction in a membrane bioreactor at a controlled pH of 5. Sulfate and formate were dosed using a pH-auxostat system while formate was converted into hydrogen, which was used for sulfate reduction. Sulfide was removed from the gas phase to prevent sulfide inhibition. This study shows a high-rate sulfate-reducing bioreactor system for the first time at pH 5, with a volumetric activity of 188mmol SO(4)(2-)/I/d and a specific activity of 81mmol SO(4)(2-) volatile suspended. The microbial community at the end of the reactor run consisted of a diverse mixed population including sulfate-reducing bacteria.
Assuntos
Reatores Biológicos , Sulfatos/química , Bactérias Redutoras de Enxofre/isolamento & purificação , Biodegradação Ambiental , Biomassa , DNA Bacteriano/análise , DNA Bacteriano/genética , Formiatos/química , Formiatos/metabolismo , Concentração de Íons de Hidrogênio , Resíduos Industriais , Membranas Artificiais , Oxirredução , Proteobactérias/genética , Proteobactérias/isolamento & purificação , Proteobactérias/metabolismo , RNA Ribossômico 16S/análise , RNA Ribossômico 16S/genética , Sulfatos/metabolismo , Sulfetos/química , Sulfetos/metabolismo , Bactérias Redutoras de Enxofre/genética , Bactérias Redutoras de Enxofre/metabolismoRESUMO
Many industrial waste and process waters contain high concentrations of sulfate, which can be removed by sulfate-reducing bacteria (SRB). This paper reports on mesophilic (30 degrees C) sulfate reduction at pH 6 with formate as electron donor in a membrane bioreactor with a pH-auxostat dosing system. A mixed microbial community from full-scale industrial wastewater treatment bioreactors operated at pH 7 was used as inoculum. The pH-auxostat enabled the bacteria to convert sulfate at a volumetric activity of 302 mmol sulfate reduced per liter per day and a specific activity of 110 mmol sulfate reduced per gram volatile suspended solids per day. Biomass grew in 15 days from 0.2 to 4 g volatile suspended solids per liter. This study shows that it is possible to reduce sulfate at pH 6 with formate as electron donor at a high volumetric and specific activity with inocula from full-scale industrial wastewater treatment bioreactors operated at neutral pH. The combination of a membrane bioreactor and a pH-auxostat is a useful research tool to study processes with unknown growth rates at maximum activities.