Control of hydrogen sulphide in full-scale anaerobic digesters using iron (III) chloride: performance, origin and effects

Abstract

The study presents the results of sulphide control using iron (III) chloride in full-scale anaerobic digesters (ADs) at a largescale municipal wastewater treatment plant (WWTP). Iron (III) (‘ferric’) chloride was applied at a range of 24–105 mg FeCl 3/L with and without alkali solution using different strategies. Introduction points were implemented at the feeding line and the sludge thickener unit. Response of the ADs in terms of biogas H 2S reduction over time, solid loading rates (SLR), feed sludge flow rate and pH level were investigated. Reduction of H 2S in the biogas reached 4 035 μg/L in directly-dosed AD versus a 1 345 μg/L drop in non-dosed ADs, as a result of internal recirculation among the digesters, where actual values were possibly higher as volatile solid (VS) degradation increased in all ADs during the dosing period. No noticeable effect on biogas production and pH was observed.

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