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The removal efficiency of lead [Pb(II)], zinc [Zn(II)], nickel [Ni(II)] and chromium [Cr(VI)] from aqueous solutions by adsorption on non‐conventional materials (rice husk and sawdust) in its natural form and on their chemically modified form is presented. It is found that adsorption potential varies as a function of contact time, concentration, particle size, pH and flow rate. Of all the low cost adsorbents used in this study, sawdust is found to possess greater adsorption efficiency for all metals than rice husk under identical experimental conditions. Chemically activated sawdust could remove 95 percent of Pb(II), 93 percent of Zn(II), 80 percent of Ni(II) and 75 percent of Cr(VI) from the metal bearing industrial effluents.

During the past ten years, anaerobic process has become a popular technology for treating concentrated effluents. Research and development programmes led by both engineers and microbiologists have resulted in a better understanding of the microbiology of anaerobic reactions and reactor design for anaerobic processes. Considerable progress has been achieved in the development of high rate anaerobic reactors with several configurations for treating concentrated industrial effluents. In this review, attention is paid to highlighting the conceptual and full scale developments of anaerobic fluidized bed reactors, in respect of process performance, design concepts, start‐up of the reactor, stability of the system with respect to various operating parameters, reactor configurations, comparison with competing reactor designs for concentrated industrial effluents and kinetics and modelling of reactor systems.