Leaching and accumulation of trace elements in sulfate reducing granular sludge under concomitant thermophilic and low pH conditions

G. Gonzalez-Gil, S.I.C. Lopes, P.E. Saikaly, P.N.L. Lens
Bioresource Technology, 126, 238-246, (2012)

Leaching and accumulation of trace elements in sulfate reducing granular sludge under concomitant thermophilic and low pH conditions

Keywords

Trace metals, Acidogenesis, Sulfate reduction, Anaerobic granule, Thermophilic

Abstract

​The leaching and/or accumulation of trace elements in sulfate reducing granular sludge systems was investigated. Two thermophilic up-flow anaerobic sludge bed (UASB) reactors operated at pH 5 were fed with sucrose (4 g COD lreactor−1 d−1) and sulfate at different COD/SO42− ratios. During the start-up of such acidogenic systems, an initial leaching of trace elements from the inoculum sludge occurred regardless of trace elements supplementation in the reactor influent. The granular sludge maintained the physical structure despite high Fe leaching. After start-up and nonetheless the acidic conditions, Co, Ni, Cu, Zn, Mo and Se were retained or accumulated by the sludge when added. Particularly, Ni and Co accumulated in the carbonates and exchangeable fractions ensuring potential bioavailability. Otherwise, the initial stock in the inoculum sludge sufficed to operate the process for nearly 1 year without supplementation of trace elements and no significant sludge wash-out occurred.

Code

DOI: 10.1016/j.biortech.2012.09.044

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