Bonding Form Analysis of Metals and Sulfur Fractionation in Methanol‐Grown Anaerobic Granular Sludge

Abstract

This study investigates the metal and sulfur bonding form distribution in mesophilic (30 °C, pH 7) methanol‐grown anaerobic granular sludge from upflow anaerobic sludge bed reactors operating at an organic loading rate of 3.8 g CH3OH‐COD/L d. This was achieved by applying a modified Tessier sequential extraction scheme to investigate the metal bonding forms and a sequential extraction scheme for sulfur and simultaneously extracted metals to granular sludge samples of the reactors after 0, 22, 35 and 43 days of operation. Metals were also determined in the sulfur extracts. Co and Ni predominated in their oxidizable bonding forms, which increased together with the pseudo‐total content during reactor operation. An omission of Co and Ni from the influent led to only a minor decline of the pseudo‐total content in the sludge, mainly from the acid‐soluble fraction. The ratio of simultaneously extracted metals (Co, Fe, Mn, Ni) to acid‐volatile sulfides was lower than 1, indicating that the sludge contained sufficient sulfide to bind the metals as metal monosulfides. The bioavailability of metals in the methanol‐grown anaerobic granular sludge investigated is therefore mainly controlled by sulfide formation/dissolution.

Screening of trace metal supplementation for black water anaerobic digestion

“…The sludge was collected from the bottom of the UASB reactor and contained total solids (TS) of 56. . The distribution of metals in the sludge was analyzed according to a modified Tessier method [17,18] (Table 1). …”

Biogas Production from Thin Stillage on an Industrial Scale—Experience and Optimisation

“…Irrespective of source, sulphur causes problems during anaerobic digestion as it is converted to hydrogen sulphide (H 2 S), either during the degradation of amino acids or through the activity of SRB [11]. In addition to the malodorous and corrosive properties of H 2 S gas, it is also toxic to microorganisms and can cause precipitation of trace elements required for microbial growth and activity [11,20,33]. Furthermore, the H 2 S formed have to be removed to meet Swedish legal requirements on vehicle fuel and to reduce negative effects on anaerobic digestion.…”

“…The high protein content in thin stillage also results in the release of organic sulphur as sulphides, which have various negative effects on the industrial biogas production process. These include corrosion, precipitation of trace elements, inhibition of microorganisms and consumption of organic material [mainly alcohols, volatile fatty acids (VFA) and hydrogen] that would otherwise be used for methane production [11,[18][19][20].…”

Sulfur K-edge XANES and acid volatile sulfide analyses of changes in chemical speciation of S and Fe during sequential extraction of trace metals in anoxic sludge from biogas reactors

“…Processes regulating the chemical speciation and bioavailability of trace metals are complex involving dynamic interaction of microorganisms with organic and inorganic compounds [11,12]. Laboratory and practical evidences have demonstrated that speciation and bioavailability of trace metals essential for the anaerobic digestion process are highly influenced by the chemistry of sulfur (S) [11][12][13][14][15]. The precipitation of metal sulfide phases and/or adsorption of trace metals to iron sulfide particles are considered to be the most important processes contributing to trace metal dynamics in biogas reactors.…”

“…Sulfur K-edge XANES is a suitable method for identification and quantification of various S compounds, their oxidation states and binding forms in a sample [20,21], which allow us to follow the fate of S species during sequential extraction. Acid volatile sulfide analysis is a classical approach for measurement of the sulfide fraction reactive towards metals in anoxic samples, based on volatilization of reduced S bonded in mineral fractions, mainly FeS [12,22,23]. The method has in principal similar disadvantages as sequential extraction regarding the uncertainty in selectivity of the applied reagent for volatilization of reduced S compounds and simultaneously extracted metals [22].…”