Performance and mechanism of the long-term vanadium(V) remediation by immobilization of rice washing waste

There is an urgent need to develop more efficient microbial technologies suitable for heavy metal stressed environments, especially in the case of vanadium (V) contamination. In this study, rice washing waste (RWW) was utilized as both the carbon and microbial sources immobilized together with sludge to treat V-containing wastewater. Continuous flow reactors were operated, V(V) removal efficiencies (30 d) with polyvinyl alcohol (PVA) and chitosan as embedded carriers, achieving 9.0% and 79.4%, respectively. A superior V(V) removal performance (91.5%) was achieved in the continuous flow reactors with chitosan-based immobilized materials after 70 d. The presence of V was detected on the surface and within the material, indicating that both adsorption and microbes were able to contribute to V(V) remediation. Model fitting results indicated that the V(V) adsorption by researched materials followed Langmuir isotherm and Second-order reaction kinetics (R2=0.9145). An increase in the fraction of functional microbes as unclassified_f_Comamonadaceae and unclassified_f_Enterobacteriaceae were observed in response to V(V) stress. This study demonstrated that RWW can serve as a suitable carbon and microbial source for long-term operation enhanced V(V) removal by immobilized together with sludge, thereby unveiling a new method for processing both food and V contaminants.