A model-based analysis of a three-phase continuously operated fluidized bed bioreactor is developed in order to determine the multi-objective optimal feeding policy of the immobilized biomass used for removing mercury ions from wastewater. The analysis is focus on finding the optimal feeding policy of alginate porous beads of known particle size containing immobilized biomass (Pseudomonas putida bacteria) to minimize the biomass consumption, while keeping a quasi-constant high conversion. The extended bioreactor model is accounting for the biomass growth, biodegradation, and its partial leakage and washout. Bioreactor dynamics prediction has been generated by using a simple Michaelis-Menten kinetic model adopted from literature. The resulted optimal feeding policy of the bioreactor points out the importance of the adoption of an extended and adequate process/reactor model able to solve engineering operation problems by quickly adjusting the feeding conditions according to the time-varying characteristics of the biomass culture and to the limited possibilities to control the process during the wastewater residence time in the bioreactor.Production of penicillin, [42] secreted recombinant proteins, [47] microbial growth, [56] acetic acid, [51] lactic acid from whey lactose, [52] citric acid, [53,57] polysaccharide pullulan by fungi Aureobasidium pullulans [58] and so on Asia-Pacific Journal of Chemical Engineering BIOREACTOR OPTIMIZATION FOR MERCURY UPTAKE FROM WASTEWATERS 723 Footnote: A Hg = 200.59 atom-g, mercury atomic mass; c XL, inlet,100 = inlet concentration of the immobilized biomass for the running time arc 0 ≤ t ≤ 100 min (ref. to the reactor liquid); c XL, inlet,200 = inlet concentration of the immobilized biomass for running time arc 100 ≤ t ≤ 200 min (ref. to the reactor liquid); c XL, inlet,300 = inlet concentration of the immobilized biomass for running time arc 200≤ t ≤ 300 min (ref. to the reactor liquid);G-L mass transfer on the liquid side: k L a L = 0.022 s À1 (experimental [19] ). L-S mass transfer on the liquid side: k s = Sh × D L /d p (for Hg 2þ L ; with Sh correlated with the operating conditions [37] ) a s = (6ε s )/d p (spherical particles); k s a s = 0.0114 s À1 (experimental [19] )Asia-Pacific Journal of Chemical Engineering BIOREACTOR OPTIMIZATION FOR MERCURY UPTAKE FROM WASTEWATERS 729