Using Ferric chloride (FeCl3) as trace-element to enhance methane production of anaerobic co-digestion

Mohammad-Amin Oliaee¹ Alireza Khaleghzadeh Ahangar² Mohsen Taghavijeloudar³

1) Master of Environment Engineering, Faculty of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
2) Master of Environment Engineering, Faculty of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
3) PhD of Environment Engineering, Department of Civil and Environmental Engineering, Seoul National University, 151‑744 Seoul, South Korea

Publication : 6th International Conference on Applied Researches in Science & Engineering - Germany(6carse.com)
Abstract :
Ferric chloride (FeCl3) is widely used in sewage treatment process and influences anaerobic digestion process by remaining in waste-activated sludge (WAS). However, the effects and mechanisms of FeCl3 (FC) involved in the WAS anaerobic digestion system have yet to be thoroughly elucidated. In this research the utilization of FC as trace-element to enhance methane production of anaerobic co-digestion was evaluated. Furthermore, the different effects and underlying mechanism of FC addition on each key stage of WAS and food waste (FW) anaerobic co-digestion were investigated. It was found that FC enhanced methane production up to 50.74%, with the maximum obtained at the dosage of 300 mg-FC/L. FC promoted the WAS solubilization, hydrolysis, and acidification probably via dissimilatory Iron reduction process, since FC could serve as electron acceptors to accelerate the decomposition and degradation of WAS and FW complex organics, and accept the Intermediate electrons to stimulate the bioconversion of acetic acid from amino acids and monosaccharides. However, FC inhibited methane production at high dosage concentrations, which was attributed to Iron s toxicity and accumulation of volatile fatty acids and decrease in pH. Enzymatic analysis revealed that FC addition increased amylase activity which is an important hydrolytic enzyme and also decrease lag phase. Overall, this study contributes to a better understanding of the mechanisms of FC integrated into WAS and FW anaerobic co-digestion, and laid the foundation to optimize the routes for energy/carbon recovery.
Keywords : Anaerobic co-digestion Methane production Trace Element FeCl3