RESUMO
Increased tightening of air regulations is leading more electric utilities to install flue gas desulfurization (FGD) systems. These systems produce brine containing high concentrations of nitrate, nitrite, and selenate which must be removed before discharge. The H2-based membrane biofilm reactor (MBfR) was shown to consistently remove nitrate, nitrite, and selenate at high efficiencies. The maximum selenate removal flux reached 362 mgSe m(-2)d(-1) and was higher than that observed in earlier research, which shows continual improvement of the biofilm for selenate reduction. A low pH of 6.8 inhibited precipitation when treating actual FGD brine, yet did not inhibit removal. SO4(2-) was not removed and therefore did not compete with nitrate, nitrite, and selenate reduction for the available H2.
Assuntos
Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Membranas Artificiais , Nitratos/isolamento & purificação , Compostos de Selênio/isolamento & purificação , Dióxido de Enxofre/isolamento & purificação , Purificação da Água/métodos , Biodegradação Ambiental , Desenho de Equipamento , Concentração de Íons de Hidrogênio , Modelos Teóricos , Oxirredução , Ácido Selênico , Purificação da Água/instrumentaçãoRESUMO
The H(2)-based membrane biofilm reactor (MBfR) was shown to consistently remove nitrate, nitrite, and selenate at high efficiencies from flue-gas desulfurization brine. Selenate was removed to <50 ppb which is the National Pollutant Discharge Elimination System (NPDES) criteria for the brine to be released into the environment. When selenate was removed to <50 ppb, nitrate and nitrite were still present in the mg/L range which suggests that selenate is able to be secondarily reduced to low levels when nitrate and nitrite serve as the main electron acceptors for bacterial growth. SO(4)(2-) was not removed and therefore did not compete with nitrate and selenate reduction for the available H(2).