Efeito da origem do inóculo, do doador de elétrons e da imobilização em biorreatores sulfetogênicos acidofílicos

Abstract

The disposal of sulfate-rich wastewaters is responsible for causing serious environmental problems. A promising alternative is the biological treatment using sulfate reducing bacteria (SRB), which is a specific type of bacteria responsible for reducing sulfate and generates alkalinity. Thus, the present study evaluated the efficiency of the biological removal of sulfate and the structure of the microbial communities in 8 anaerobic reactors operated in sequential batches treating synthetic sulfate rich wastewater with pH 4.0 using four different sources of inoculum, immobilized or not, operated in two phases, alternating the electron donor. The percentage of sulfate removal in the lactate phase ranged from 67±3% to 80±2% and in the ethanol phase between 37±11% and 67±3%. The removal of COD in the lactate phase ranged from 34±9% to 70±4% and in the ethanol phase from 31±2% to 65±5%. Except for the ETI2-I reactor, all reactors presented high alkalinity production (mainly in the lactate phase) and consequently reached effluent pH values above 5.50. Iron removal in all reactors was above 90%. The pyrosequencing analysis showed an increase in the relative abundance of SRB in the reactors during the operation, with the presence of the following genera: Desulfovibrio, Desulfobulbus, Desulfomicrobium and Syntrophobacteraceae. The analysis of diversity indexes showed that there was a decrease in microbial richness throughout the operation. The Desulfovibrium genus showed considerable percentages in all the reactors immobilized in the ethanol phase, while the Desulfobulbus genus was present in the lactate phase of all the reactors. This work showed through the operational parameters and microbial abundance that it is possible to achieve success in the acclimatization of a sludge with methanogenic profile for the removal of sulfate.