COMBINED EFFECTS OF NI(II) AND CR(VI) ON ACTIVATED-SLUDGE

The combined effects of Ni(II) and Cr(VI) on activated sludge kinetics were studied in this paper. The metals were added to a synthetic medi um with a chemical oxygen demand (GOD) of 1300 mgl(-1) to give various combinations of Ni(II) and Cr(VI). Activated sludge performance, in t erms of COD removal, was not adversely affected in an acclimatized cul ture by the metal combinations, compared with the single metals. The c ombination effects of Ni!II) and Cr(VI)on biokinetic constants, i.e. t he maximum specific growth rate, mu(m), was found to be stimulatory in general. The same effect was observed on the half-saturation substrat e concentration, K-s. Effects were therefore classified as synergistic with respect to these constants. (C) 1998 Elsevier Science Ltd. All r ights reserved.