Investigating the Impact of Organic Loading Rates and Magnetic Nanoparticles on the Performance and Stability of Continuous Stirred Tank Reactors

Research on energy demand is advancing, with the addition of nanomaterials in anaerobic digestion increasing stability, accelerating hydrolysis, and reducing microbial inhibition. However, further research is needed to determine the mechanisms, ideal dosages, and long-term impacts. This work used continuous stir tank reactors (CSTRs) to experimentally examine the biocompatibility of iron oxide nanoparticles (Fe3O4-NPs) at a concentration of 75 mg/L at various organic loading rates (OLRs) of 0.3, 0.8, and 1.3 gVS/L.d (CSTRs). The efficiency of the reactors was observed by considering various parameters, such as pH, soluble chemical oxygen demand (sCOD), TVFA formation and degradation, total solids (TS), and volatile solids (VS) removal, as well as methane (CH4) generation. Hence, it was found that the reactor with added NPs (R1) yielded an optimum 725.9 mL/gVS of CH4 and this was achieved at the lowest OLR of 0.3 gVS/Ld. However, another reactor (R2, without NPs), exhibited more stabilized results, ranging from 372.8 to 424.4 mL/gVS at 0.3 to 1.3 gVS/Ld of OLR, respectively. Therefore, in R1, the maximum removal of sCOD, TVFAs, and VS was achieved at 90%, 74%, and 93%, respectively, as compared to R2.