**13. Application of the biosorption process at pilot scale**

Many researchers have attempted pilot-scale studies to make the technology of biosorption available at the industrial scale. A small pilot plant with a three-zone contact settling was developed in a single vessel using anaerobically digested sludge as the biosorbent for the removal of Cu (II) ions. The efficient metal removal (similar to the batch experiments) of 90 mg/g of the biosorbent was observed [201]. Flotation is a separation process that can effectively separate the metal-loaded biosorbent suspended in the aqueous solution. The technique of biosorptive flotation was applied for the removal of nickel, copper, and zinc ions from the aqueous solutions using grape stalks as the sorbent. Two feed solutions containing different metal concentrations were prepared. The dilute metal solution was applied followed by the concentrated metal solution in the counter-current mode in order to improve the performance of the biosorbent. The experiments were conducted in 10 L columns and satisfactory metal removal was observed (Cu—95%; Zn—98%; Ni—70%; Ca—82%). The biosorbent after regeneration by using an aqueous mixture of sodium sulfate and sodium citrate can be used for the second cycle [202]. A two-step operation for biosorption and sedimentation was operated in a 200 L pilot plant for the removal of pollutants using biomass of *Cunninghamella elegans* and the obtained results proved that the biosorption process is effective in treating wastewaters efficiently [203].
