Impact of Nanoscale Magnetite and Zero Valent Iron on the Batch-Wise Anaerobic Co-Digestion of Food Waste and Waste-Activated Sludge

Abstract

As a potential approach for enhanced energy generation from anaerobic digestion, iron-based conductive nanoparticles have been proposed to enhance the methane production yield and rate. In this study, the impact of two different types of iron nanoparticles, namely the nano-zero-valent-iron particles (NZVIs) and magnetite (Fe3O4) nanoparticles (NPs) was investigated, using batch test under mesophilic conditions (35 °C). Magnetite NPs have been applied in doses of 25, 50 and 80 mg/L, corresponding to 13.1, 26.2 and 41.9 mg magnetite NPs/gTS of substrate, respectively. The results reveal that supplementing anaerobic batches with magnetite NPs at a dose of 25 mg/L induces an insignificant effect on hydrolysis and methane production. However, incubation with 50 and 80 mg/L magnetite NPs have instigated comparable positive impact with hydrolysis percentages reaching approximately 95% compared to 63% attained in control batches, in addition to a 50% enhancement in methane production yield. A biodegradability percentage of 94% was achieved with magnetite NP doses of 50 and 80 mg/L, compared to only 62.7% obtained with control incubation. NZVIs were applied in doses of 20, 40 and 60 mg/L, corresponding to 10.8, 21.5 and 32.2 mg NZVIs/gTS of substrate, respectively. The results have shown that supplementing anaerobic batches with NZVIs revealed insignificant impact, most probably due to the agglomeration of NZVI particles and consequently the reduction in available surface area, making the applied doses insufficient for measurable effect.

Anaerobic Co-Digestion of Kitchen Waste and Blackwater for Different Practical Application Scenarios in Decentralized Scale: From Wastes to Energy Recovery

“…However, in the experimental group with a high concentration of initial TAN in BW, the cumulative methane production was only 160.3 mL/g VS, which was 46.9% lower than the raw BW group. The result shows that reducing the initial TAN concentration of BW to a certain extent is very important to increase methane production, because it is conducive to improve hydrolysis efficiency which is considered the rate-limiting step [35,36] during the anaerobic digestion of solid organic matter.…”

“…Water 2020, 12, x FOR PEER REVIEW 10 of 13 is conducive to improve hydrolysis efficiency which is considered the rate-limiting step [35,36] during the anaerobic digestion of solid organic matter.…”

Fe0-Supported Anaerobic Digestion for Organics and Nutrients Removal from Domestic Sewage

“…This study shows that under the stated experimental conditions (0 ≤ [Fe 0 ] (g/L) ≤ 10, for scrap iron), "cathodic H 2 " [23] from Fe 0 oxidation by water (Equation ( 2)) is highly effective in improving the performance of anaerobic digestion systems for the removal of organics from domestic sewage. Since the proof of concept in 1998 by Till [23] using nitrate as probe substance, an impressive body of research has been devoted to extend the application of Fe 0 -supported anaerobic digestion to wastewater treatment [22,[69][70][71][72][73] and biogas production [22,[74][75][76]. However, related investigations were mostly designed and performed on a pragmatic case-to-case basis [31,77].…”

Perspectives on Potential Applications of Nanometal Derivatives in Gaseous Bioenergy Pathways: Mechanisms, Life Cycle, and Toxicity

“…Intracellular NMDs in the bacterial cell facilitated the oxidation of organic matter by increasing the intracellular electron transfer rate between enzyme groups incorporated in hydrolysis and acidogenesis processes, resulting in the enhancement of overall process efficiency . Furthermore, NMDs tend to attach to the outer microbial membrane of acetogens and/or acidogens . This process promotes the rate of electron transport to enzymes involved in the H 2 -producing process such as ferredoxin oxidoreductase and hydrogenases with the aid of c -type cytochromes …”

“…69 Furthermore, NMDs tend to attach to the outer microbial membrane of acetogens and/or acidogens. 70 This process promotes the rate of electron transport to enzymes involved in the H 2 -producing process such as ferredoxin oxidoreductase and hydrogenases with the aid of c-type cytochromes. 71 Most studies utilized NPs in a certain size range (below 100 nm).…”