Biogas upgrading to methane and removal of volatile organic compounds in a system of zero-valent iron and anaerobic granular sludge

Combination of Alkaline and Heat Pretreatments with Zero-Valent Iron Application in Cassava Pulp and Wastewater for Methane Generation: Development from Batch to Continuous Systems

“…This reactor was used to obtain the optimum conditions to later be applied in the continuous system. The batch experiments were conducted at room temperature (27)(28)(29)(30)(31)(32)(33)(34)(35) Meanwhile, after obtaining the most suitable conditions, the comparison between the control and formulated pretreatment was conducted in the continuous stirred tank reactor (CSTR), guaranteeing the complete mixing with no sediment with a total volume of 12 L and a working volume of 10 L. The food/microbe (F/M) ratio, which implies the amount of incoming food per amount of microorganism in the system, was adjusted to be 0.5 at the beginning of the experiments. Food value was based on the organic matter load from the pulp and wastewater (COD), while the microbe ratio was based on the MLVSS concentration in the pulp and cassava [34].…”

“…Daily and cumulative biogas composition were documented each day. The continuous experiment was carried out for 60 days at room temperature (27)(28)(29)(30)(31)(32)(33)(34)(35) • C) to ensure the sustainability of methane production, and the experiment ended when there was no significant methane produced from the system (<1% of generated biogas).…”

“…H 2 S is also toxic to the archaea methanogens that produced CH 4 [28]. Interestingly, ZVI was proven to reduce H 2 S, increasing CH 4 percentage by removing the inhibition factor [30]. In consequence, Zou et al [31] also reported that ZVI has successfully captured the majority of the CO 2 fraction in biogas by forming Fe 3 C. The captured CO 2 can be utilized optimally to generate CH 4 as it is not directly released into the gas phase of the reactor.…”