Uso de glicerol bruto da produção de biodiesel como fonte de carbono para desnitrificação

Abstract

This work investigated the use of crude glycerol from the biodiesel production as a carbon source for denitrification. Experiments were initially performed in a sequencing batch reactor to determine the minimum COD/N ratio required to obtain complete denitrification with the glycerol used. Six different COD/N ratios were tested, ranging from 6.5 to 8.5. For COD/N ratios equal to or greater than 7, complete denitrification was obtained, while for ratios less than 7, incomplete nitrate reduction and partial denitrification to nitrite were observed. From these data, subsequent denitrification tests were carried out in a continuously operated moving-bed biofilm reactor (MBBR) under the hydraulic retention time of 12 h. The results showed that even when applying a COD/N ratio of 7, theoretically sufficient for complete denitrification, the nitrate reduction percentage was low, suggesting a possible degradation of the glycerol before entering the reactor. In fact, additional experiments showed that this substrate was degraded at room temperature (26 ± 2 °C), a problem solved by keeping the feeding medium under refrigeration at 4°C. Complete denitrification in the continuous system was only possible at a COD/N ratio of 8, capable of compensating for the degradation of the carbon source during its feed to the reactor.