A comparative study of hybrid membrane photobioreactor and membrane photobioreactor for simultaneous biological removal of atrazine and CNP from wastewater: A performance analysis and modeling

In this study, an innovative hybrid microalgal-bactrial membrane photobioreactor (HMPBR) and a microalgal-bactrial membrane photobioreactor (MPBR), was evaluated to biologically remove atrazine and CNP simultaneously from the secondary effluent and experimental models were employed to investigate the biokinetics of substrates applied in the systems. Three numerical independent variables (initial atrazine (0.01-0.09 mg/L) and chemical oxygen demand (COD) (30-90 mg/L) concentration, and hydraulic retention time (HRT) (4-12 h)) were optimized with experimental design. The results showed that the addition of kenaf fibers as biofilm carriers in HMPBR significantly improved Atrazine, COD, TN and TP removal efficiency from 84.36%, 91.59% and 85.51% in MPBR to 95.39%, 99.64% and 98.02% in HMPBR. The best atrazine removal efficiency in HMPBR and MPBR at HRT of 12 h and atrazine initial (0.01 mg/L) and COD influent concentrations (30 mg/L). To fit the experimental data and predict the bioreactors' performance, the Stover-Kincannon model, as the most reliable methods (R-2 > 0.97) was used. The total biomass accumulated in the HMPBR and MPBR were respectively above 6 and 4 g/L. The salinity (NaCl) increase in influent flow above 10 g/L seriously inhibited biodegradation process of atrazine, while HMPBR easily tolerated less than 10 g/L concentrations. As a result the HMPBR showed better performance than the MPBR in all operational condition.