BACKGROUND: This work develops a simplified mathematical model to predict the performance of a bioelectrochemical system (BES), first working as a microbial fuel cell (MFC) and then as a microbial electrolysis cell (MEC), for the recovery of dissolved metals (Fe, Cu, Sn, and Ni) from simulated industrial wastewater. Experimental data from a previous work were used as starting points for mathematical modelling. Wastewater was used as the catholyte and contained Cu 2+ and Fe 3+ (500 mg L −1 ) as well as Sn 2+ and Ni 2+ (50 mg L −1 ), while the anolyte was composed of sodium acetate. Two mixed microbial populations were considered in the anode compartment (electrogenic and non-electrogenic biomass). Dissolved metal ions were the electron acceptors in the electrogenic mechanism: Cu 2+ and Fe 3+ under MFC mode and then Fe 2+ , Ni 2+ , and Sn 2+ under MEC mode.
RESULTSThe model predicted the organic substrate and microbial biomass (anode chamber) and Fe 3+ and Cu 2+ (cathode chamber) concentrations during MFC operation. Monod kinetic and stoichiometric parameters were calibrated, and it was observed that most of the organic substrate underwent a non-electrogenic mechanism. The generation of electric current until electron acceptors were removed was also predicted. Concentration profiles and first-rate constant values for the decreased Sn 2+ , Ni 2+ , and Fe 2+ concentrations during the subsequent MEC operation were also obtained. The model was then used for simulations under different experimental conditions. CONCLUSION: This work offers a single grey-box model proposal that is easy to implement, and it can be used as a practical tool for testing the removal of dissolved metals in BESs.
The present work studies the removal of nutrients (nitrate and phosphate) from a synthetic wastewater simulating a secondary treatment effluent using the microalgae Chlorella vulgaris in autotrophic photobioreactors, together with an analysis of the critical points affecting the scaling-up process from laboratory to pilot scale. Laboratory experiments were done in open agitated 1-L photobioreactors under batch operation mode, while pilot-scale experiments were done using a 150-L closed tubular photobioreactor under continuous operation mode. In both scales, nitrate was the limiting substrate and the effect of its concentration on microalgae performance was studied. From laboratory experiments, an average microalgae productivity of 85 mg L day and approximate maximum N-NO and P-PO removal rates of 8 mg N g day, and 2.6 mg P g day were found. Regarding pilot scale, the average microalgae productivity slightly decreased (76 mg L day) while the approximate maximum N-NO and P-PO removal rates slightly were increased (11.7 mg N g day and 3.04 mg P g day) with respect to the laboratory-scale results. The pilot-scale operation worked under lower levels of turbulence and higher dissolved oxygen concentration and light intensity than laboratory experiments; those parameters were difficult to control and they can be identified as the critical points in the differences found on both nutrient removal and microalgae production.
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