Wastewater produced during recycling of spent lithium primary battery was biologically treated with Acidithiobacillus ferrooxidans to decrease the pH and metal concentration. Since the wastewater contains high concentrations of Cr, Ni, and Li, the effects of these metals on the bacterial activity in a 9 K medium were also investigated. Samples of the medium with different metal concentrations were treated, and the oxidation ratio of Fe(2+) ions was measured to examine the activity of bacteria. In the treatment of simulated wastewater, the presence of Cr and Ni ions with concentrations of 8000 g m(-3) and 13,000 g m(-3), respectively, did not inhibit the bacterial activity, whereas the oxidation ratio of Fe(2+) ions was observed to be low in the medium when Li ion was present with a concentration at 5000 g m(-3). This observation suggested that at this concentration, Li ion suppressed the bacterial activity. In the case of treatment of real wastewater containing Cr, Ni, and Li, the oxidation ratio of Fe(2+) to Fe(3+) was observed to be low while the Fe concentration and pH decreased to 21,633 g m(-3) and 1.8, respectively. Thus, the wastewater produced during the recycling of spent lithium primary batteries can be effectively treated biologically for re-circulating in the recycling process. (C) 2009 Elsevier Ltd. All rights reserved.