Effect of sulfate and iron on physico-chemical characteristics of anaerobic granular sludge
Hullebusch, E.D. van; Gieteling, J. ; Daele, W. van; Defrancq, J. ; Lens, P.N.L. - \ 2007
Biochemical Engineering Journal 33 (2007)2. - ISSN 1369-703X - p. 168 - 177.
extracellular polymeric substances - waste-water - viscosity evolution - reducing bacteria - blanket reactors - egsb reactors - uasb - precipitation - sulfide - localization
This research investigated the effect of the substrate composition (no substrate, glucose, glucose + sulfate or glucose + sulfate + iron) on the physico-chemical characteristics of two different anaerobic granular sludges as a function of time. The sludges were fed batch wise (pH 7, 30 °C) at an organic loading rate of 1.2 g COD l¿1 d¿1 (0.04 g COD g VSS¿1 day¿1) for 30 days. The presence of sulfate (COD/sulfate ratio = 1) in the feed of glucose fed anaerobic sludges did not change the physico-chemical characteristics throughout the incubation. In contrast, the presence of iron in the feed (in addition to glucose and sulfate, COD/iron ratio = 1) reduced the protein and carbohydrate content in the SMP and EPS with about 50% after 30 days incubation compared to the other feeding conditions. The sludge grown on glucose + sulfate + iron contained much more iron (+300¿500%) and sulfur (+200¿350%) than the other incubated sludges both after 14 and 30 days. The higher mineral content (lower VSS content) and the decrease of the EPS content contributed to the disintegration of iron fed granules, as shown by their lower size particles. However, the iron fed sludge displayed a higher granule strength than the other incubated sludges. Although an appreciable variation in the granule strength was noticed between the sludges investigated, it was not possible to relate these differences to their inorganic composition, the chemical composition of the extracted polymers or to the physical characteristics investigated
Cobalt sorption onto anaerobic granular sludge: Isotherm and spatial localization analysis
Hullebusch, E.D. van; Gieteling, J. ; Zhang, M. ; Zandvoort, M.H. ; Daele, W. van; Defrancq, J. ; Lens, P.N.L. - \ 2006
Journal of Biotechnology 121 (2006)2. - ISSN 0168-1656 - p. 227 - 240.
extracellular polymeric substances - sequential extraction procedure - soluble microbial products - heavy-metals - methanol degradation - activated-sludge - uasb reactors - nickel - sulfide - eps
This study investigated the effect of different feeding regimes on the cobalt sorption capacity of anaerobic granular sludge from a full-scale bioreactor treating paper mill wastewater. Adsorption experiments were done with non-fed granules in monometal (only Co) and competitive conditions (Co and Ni in equimolar concentrations). In order to modify the extracellular polymeric substances and sulfides content of the granules, the sludge was fed for 30 days with glucose (pH 7, 30 °C, organic loading rate = 1.2 g glucose l¿1 day¿1) in the presence (COD/SO42¿ = 1) or absence of sulfate. The partitioning of the sorbed cobalt between the exchangeable, carbonates, organic matter/sulfides and residual fractions was determined using a sequential extraction procedure (modified Tessier). Experimental equilibrium sorption data for cobalt were analysed by the Langmuir, Freundlich and Redlich¿Peterson isotherm equations. The total Langmuir maximal sorption capacity of the sludge fed with glucose and sulfate loaded with cobalt alone displayed a significantly higher maximal cobalt sorption (Qmax = 18.76 mg g¿1 TSS) than the sludge fed with glucose alone (Qmax = 13.21 mg g¿1 TSS), essentially due to an increased sorption capacity of the exchangeable (30¿107%) and organic/sulfides fractions (70¿30%). Environmental scanning electron microscopy coupled with an energy dispersive X-ray analysis of granular cross-sections showed that mainly iron minerals (i.e. iron sulfides) were involved in the cobalt accumulation. Moreover, the sorbed cobalt was mainly located at the edge of the granules. The sorption characteristics of the exchangeable and carbonates fractions fitted well to the Redlich¿Peterson model (intermediate multi-layer sorption behaviour), whereas the sorption characteristics of the organic matter/sulfides and residual fractions fitted well to the Langmuir model (monolayer sorption behaviour). The organic matter/sulfides fraction displayed the highest affinity for cobalt for the three sludge types investigated