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 x 10(5) Pa, respectively. Complete regeneration was reached after three cycles under optimal experimental conditions when the biosorbent was saturated with synthetic ZnCl2 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. (C) 2003 Society of Chemical Industry.

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(-3)) 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(-1) (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(-3) on the biosorption capacity of the packed-bed was not significant. Biomass regeneration with 0.1 mol dm(-3) HCl gave a 90% recovery of the adsorbed Zn(II), (C) 1999 Society of Chemical Industry.

The zinc biosorption capacity of a Streptomyces rimosus biomass was studied in the batch mode. After a heat pretreatment, optimum conditions of biosorption were found to be: an average saturation contact time of 4 h, a biomass particle size between 140 and 250 mu m, the ambient temperature, a stirring speed of 250 rpm, and pH of 7.5. The equilibrium data could be fitted by a Langmuir isotherm equation. Under these optimal conditions, up to 30 mg(Zn)/g(biomass), was fixed. Moreover, additional chemical treatment of the biomass by NaOH (1 mol/L), increased the biosorption Capacity of about 80 mg(Zn)/g(biomass). (C) 1999 Elsevier Science Ltd. All rights reserved.

A new technique based on the combination of an activated alumina column and an electrochemical system for fluoride removal from water is reported in this study. In the first step, the optimization of the process was achieved under various experimental parameters (volumetric flow, temperature, pH, initial fluoride concentration and hardness) with a synthetic solution. The comparison of the performance of the current activated alumina process and the electrosorption system proved to be more efficienct than the latter in removing fluoride from water. Thus, the fluoride sorption capacity at the breakthrough point of the activated alumina column reached 3.8 mg F−/L. It was increased by about 60% by means of the electrochemical process than the results obtained in current mode. Moreover, it was found that the electrosorption system could be utilized to regenerate the saturated activated alumina. In the second step, the electrosorption process was utilized to treat Sahara drinking water naturally contaminated with fluoride (3 mg/L) under optimum conditions previously determined. The electrosorption process coupled with activated alumina column has been successfully applied for fluoride removal from drinking water.