RESUMO
The H(2)-based membrane biofilm reactor was used to remove nitrate from synthetic ion-exchange brine at NaCl concentrations from â¼3 to 30 g/L. NaCl concentrations below 20 g/L did not affect the nitrate removal flux as long as potassium was available to generate osmotic tolerance for high sodium, the H(2) pressure was adequate, and membrane fouling was eliminated. Operating pHs of 7-8 and periodic citric acid washes controlled membrane fouling and enabled reactor operation for 650 days. At 30 psig H(2) and high nitrate loading rates of 15 to 80 g/m(2) d, nitrate removal fluxes ranged from 2.5 to â¼6 g/m(2) d, which are the highest fluxes observed when treating 30 g/L IX brine. However, percent removals were low, and the H(2) pressure probably limited the removal flux.
Assuntos
Reatores Biológicos , Nitratos/metabolismo , Cloreto de Sódio/farmacologia , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Fenômenos Fisiológicos Bacterianos/efeitos dos fármacos , Biofilmes , Desnitrificação , Hidrogênio , Concentração de Íons de Hidrogênio , Resíduos Industriais , Troca Iônica , Membranas Artificiais , Polietileno , Poliuretanos , Potássio/química , SaisRESUMO
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).
