Nickel sorption by acclimatized activated sludge culture

The sorption of Ni^2+ by acclimatized activated sludge treating Ni^2+ bearing wastewater was investigated using a once-through completely mixed tank reactor. The culture developed from sewage was acclimatized to 85.2 (mu)mole/L Ni^2+ influent concentration by stepwise increases, at a low dilution rate 0.11/h. Acclimation was found to enhance the sorptive capacity of the activated sludge. In fact, at all of the intermediate concentrations, percentage Ni^2+ adsorbed by the biomass and also the sorptive capacity of the activated sludge drastically increased with an increase in the influent Ni^2+ concentration. All influent Ni^2 + concentrations were found to significantly stimulate the observed biomass yield of the culture over that observed in the base line. Experimental findings obtained at two other dilution rates; namely, 0.25/h and 0.45/h revealed that dilution rate is a significant operational parameter affecting the Ni^2+ sorption characteristics of acclimatized activated sludge microorganisms. Considerable complexation of nickel and organic and inorganic ligands in the wastewater appeared to be responsible for a relatively lower Ni^2+ sorption capacity.