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The ability of Streptomyces rimosus biomass to bind zinc ions in batch mode was shown recently. The aim of this study was to determine the zinc uptake capacity by Streptomyces rimosus biomass in continuous mode. Bacterial biomass was able to bind more Zn(II) after pretreatment with sodium hydroxide (1 mol dm À3 ) than without treatment. The maximum adsorption capacity and the adsorption capacity at the saturation point calculated by means of both the exchange zone model and the Thomas model were practically identical of about 2.9 mg Zn(II) g À1 biomass . This result was lower than the batch adsorption capacity of Streptomyces rimosus, indicating that the packed-bed is not the most appropriate process to exploit the bacterial biomass adsorption capacity. The effect of zinc concentration in the range of 10 to 200 mg Zn(II) dm À3 on the biosorption capacity of the packed-bed was not signi®cant. Biomass regeneration with 0.1 mol dm À3 HCl gave a 90% recovery of the adsorbed Zn(II).

The performance of biofiltration of zinc utilising pretreated Streptomyces rimosus was studied. Streptomyces rimosus biomass is able to bind zinc ions in batch mode. The biomass granules may be regenerated easily by using a biomass pretreatment which confers rigidity to biosolids, without decreasing the zinc uptake capacity, thus allowing collection of the biomass by filtration. Accordingly, biomass was pretreated with an anionic enzymatic tension active product (Extran AP41) and regeneration with a cleaning product (HCl) was successfully realised. It was shown that the optimum concentration of biomass and pressure range are found to be between 50 and 120 g dm −3 and 0.5 and 1 × 10 5 Pa, respectively. Complete regeneration was reached after three cycles under optimal experimental conditions when the biosorbent was saturated with synthetic ZnCl 2 solution. The filterability of biosolids was demonstrated. A combination of a batch reactor and a filtration process made it possible to increase the performance of the complete treatment process. The biosorption capacity of the biomass to bind Zn ions was slightly increased (from X = 14 mg g −1 in batch mode to X = 16.1 mg g −1 in a process combining batch reactor and pressure filtration) and the experimental contact time was considerably reduced. Integration of the filtration process produced a dewatering cake which considerably facilitated the regeneration operation.