Performance and kinetics of membrane and hybrid moving bed biofilm‐membrane bioreactors treating salinity wastewater

Abstract

A pilot‐plant membrane bioreactor (MBR) and two pilot‐plant hybrid moving bed biofilm reactor–membrane bioreactors (MBBR–MBRs), divided into three aerobic and one anoxic chambers, were started up for the treatment of salinity‐amended urban wastewater. The MBBR–MBR systems worked with and without carriers in the anoxic zone (MBBR–MBRanox and MBBR–MBRn/anox, respectively). The systems were operated from start‐up to stabilization, showing high removal of organic matter—a maximum of 90% chemical oxygen demand and 98% biochemical oxygen demand on the fifth day for MBBR–MBRn/anox in the stabilization phase—but low nitrogen elimination—30% maximum for MBBR–MBRn/anox in the stabilization phase. Biofilm attached to carriers reached less than 50 mg L−1 in the hybrid system. MBR showed faster kinetics than the two MBBR–MBR systems during start‐up, but the opposite occurred during stabilization. Maximum specific growth rates for heterotrophic and autotrophic biomass were 0.0500 and 0.0059 h−1 for MBBR–MBRn/anox in the stabilization phase. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3329–3342, 2017

Effect of variable salinity wastewater on performance and kinetics of membrane‐based bioreactors

“…Even though it has been observed that attached biofilms in MBBR‐MBR systems can adapt to salinity, the introduction of saline influent on a steady‐state system operating for the treatment of regular‐salinity urban wastewater showed a decrease of attached biofilm in concentrations of 1000 mg L ‐1 . Accordingly, the inability of the microbial communities in the salinity‐amended urban wastewater led to difficulties for the formation of attached biofilm to hybrid MBBR‐MBR systems started‐up using constant salinity or variable‐salinity urban wastewater has been reported previously …”

“…For a scenario of influent variable salinity with 6.5 mS cm −1 as maximum, the heterotrophic r su (4.57–24.60 mgO 2 L −1 h −1 ) was lower than that of 4.5 mS cm −1 (9.03–47.17 mgO 2 L −1 h −1 ) but similar to that of 8.5 mS cm −1 (7.23–26.01 mgO 2 L −1 h −1 ), while the autotrophic r su (0.59–14.26 mgN L −1 h −1 ) was higher for the 4.5 mS cm −1 case (2.87–52.10 mgN L −1 h −1 ) and similar between the 6.5 and 8.5 mS cm −1 (2.88–18.49 mgN L −1 h −1 ) scenarios . These results suggested that maximum influent salinity actively affects the r su of both heterotrophic and autotrophic biomass, which become inhibited when maximum salinity reaches a certain threshold.…”

“…ammonium, nitrite and nitrate. This was done following an established protocol . Briefly, the water samples were filtered with a 0.45 µm pore diameter filter right after collection from the bioreactors, then immediately measured using a Metrohm ion chromatograph (Herisau, Switzerland).…”

“…Salt constitutes a stress factor that could destabilize the microbial communities, reduce their metabolic activities and modify their biomass kinetics within the biological processes of removal of carbonaceous and nitrogenous compounds in WWTPs . Especially, nitrification process is particularly sensitive to inhibition by salt .…”

“…[5][6][7] Salt constitutes a stress factor that could destabilize the microbial communities, 8 reduce their metabolic activities and modify their biomass kinetics within the biological processes of removal of carbonaceous and nitrogenous compounds in WWTPs. 9,10 Especially, nitrification process is particularly sensitive to inhibition by salt. 11,12 Although substantial research of the effect of influent salinity over bioreactors has been done, these researches have always been constrained to influents with constant salinity conditions.…”