STUDIES ON BATCH ACTIVATED SLUDGE WITH BIOSORPTION FOR INDUSTRIAL WASTEWATER

Abstract

The use of some microorganisms to remove heavy metals from contaminated industrial wastewater may represent an innovative purification process. The property of certain type of inactive, dead microbial biomass to bind and concentrate heavy metals from even very dilute aqueous solutions is called biosorption. This property of microorganisms has been explored intensively which proved to have a great edge over other conventional process. This passive bioaccumulation has distinct advantages over other methods. The process does not produce chemical sludge (i.e. non polluting), it could be highly selective, more efficient, easy to operate and hence cost effective for the treatment of large volumes wastewaters containing low pollutant concentrations. There are wide ranges of biosorbents presently being tested out. Not only dead cells act as biosorbents, even active cells act as good biosorbents. In the present work activated sludge from paper and pulp industry is selected as biosorbent. The biosorption of cadmium, copper and nickel ions both single and in combinations in a batch system were tested. The investigations were done as a function of pH, temperature, initial concentration, and sorbent dosage, in a single and multi metal ion concentration. The optimum pH for Ni, Cd, and Cu were found be 4.5, 6.0 and 3.0. The experiments showed that biosorption is an exothermic reaction with pseudo second order with its constant value lc, equals 0.1906 min-1. Equilibrium Langmuir and Freundlich curves were drawn for each of the metals copper, cadmium and nickel. Competitive sorption was also studied with different combinations of the copper, cadmium and nickel metals. Freundlich and Langmuir curves were plotted for different combinations of the metals. The order in which the metals were sorbed was found to be cadmium, nickel and copper. It was found that the presence of copper decreased the percent removal of cadmium and nickel showing that inhibition effect of copper is more than other metals.