TA10 Microbial Remediation of Acid Mine Drainage Wastes
D135-136
8:00 AM - 12:00 PM, Tuesday
() Cobalt and nickel retention capacity of anaerobic granular sludge from methanol fed UASB reactors.
Lens, P1, van Hullebusch, E1, Zandvoort, M1, van der Veen, A1, 1 Wageningen University, The Netherlands
ABSTRACT- Mine waters and industrial effluents contain high sulphate and metal concentrations and pose significant disposal problems, which require an urgent solution to avoid serious environmental problems. Anaerobic bioreactor are a promising option for treatment of mine water because the biogenically produced sulphides can react with the dissolved metals to form metal sulphide precipitates, characterized by low solubility products. Metal accumulation in anaerobic biofilms will therefore depend on the nature of the metal and organic constituents, as well as the metal and the nature, the composition and pH of the influent. The first part of the presented work describes the retention of metals (cobalt and nickel) in the anaerobic granular sludge in non-fed conditions by batch equilibrium techniques. Anaerobic sludge granules consist of a matrix of inorganic precipitates, biomass and extra cellular polymeric substances (EPS). Metals can bind to each of these phases of the granular sludge. The sorption data are described by langmuir isotherms, which was shown to be the most accurate model for describing metal sorption. This model provides information about the metal retention capacity and binding strength of the sludge. However it does not provide information about the partitioning of metals in various chemical phases. In order to make this distinction the sorption isotherms were combined with sequential extraction procedures. In this study a modified Tessier sequential extraction scheme was used to make a distinction between the preferred phases for sorption. The second part of this work describes the metal (cobalt and nickel) retention dynamics in lab-scale up flow anaerobic sludge bed (UASB) bioreactors when fed with an influent containing methanol as the carbon source. The reactors were inoculated with anaerobic granular sludge, which was pre-loaded with cobalt. The metal sorption and retention dynamics in the granules were compared to the results batch sorption experiments by using the same sequential extraction scheme. Also the effect of the absence or presence of a sulphur source as well as the type of sulfur source (cysteine and sulfate) on the metal retention was studied.
Key words: heavy metals retention, bioreactor, sulfate reduction, granular sludge