Removal Performance of Organic Matter of MBR and Hybrid MBBR-MBR Systems During Start-up and Stabilization Phases Treating Variable Salinity Urban Wastewater

A MBR and two hybrid MBBR-MBR with different configurations were used for the treatment of variable salinity wastewater. The systems were started-up and operated until stabilization conditions while being fed with salinity-amended urban wastewater. The salinity-amended urban wastewater was generated by the mixture of urban wastewater and salinity-amended tap water to obtain a feeding with salinity in the range of 1-6.5 mS cm(-1). The three bioreactors were subjected to cyclical salinity variations with a cycle consisting of 6 h at 6.5 mS cm(-1) salinity and 6 h at regular wastewater salinity. The system was evaluated for its performance in organic matter removal by COD and BOD5 measurements. Also, the kinetics of its heterotrophic biomass was characterized by the means of respirometric tests. The results showed a very good removal of COD and BOD5, with the MBBR-MBRanox showing the highest performances. The heterotrophic kinetics were higher at lower total solids concentrations with the MBR system having the fastest kinetics during the start-up. These results will be of use for the future application of MBR and hybrid MBBR-MBR systems to the treatment of variable salinity wastewater.