Co-doping polymethyl methacrylate and copper tailings to improve the performances of sludge-derived particle electrode.

Three-dimensional electrochemical reactor (3DER) is a highly efficient technology for refractory wastewater treatment. Particle electrodes filled between anode and cathode are the core units of 3DER, determining the treatment efficiency of wastewater. However, particle electrodes deactivation due to catalytic sites coverage seriously impedes the continuous operation of 3DER. In this work, granular sludge carbon (GSC) particle electrodes being resistant to deactivation are fabricated by pyrolyzing the mixture of waste sludge, polymethyl methacrylate (PMMA), and copper tailings, whose performances are evaluated by degrading rhodamine B (RhB) wastewater in a continuous-flow 3DER. Results indicate that hierarchical-pore structure comprising macro-, meso-, and micropores is developed in GSC-10-CTs by doping 10 g PMMA and 5 g copper tailings into 100 g waste sludge. PMMA contributes to construct macropores, which is essential for the mass transfer of RhB into GSC particle electrodes of centimeter-size. Copper tailings promote the formation of meso- and micro-pores in GSCs, as well as improving the electrochemical properties. Consequently, GSC-10-CTs packed 3DER exhibits the highest removal efficiency and lowest energy consumption for RhB treatment. In addition, the compressive strength of GSC-10-CTs is enhanced by copper tails, that is crucial to fill into 3DER as particle electrodes. The high-efficient and cost-effective GSC-10-CTs fabricated by waste materials have the potential of substituting commercial granular activated carbon catalysts in the future, consequently promoting the application of 3DER in wastewater treatment.

Insights into thermodynamic mechanisms driving bisphenol A (BPA) binding to extracellular polymeric substances (EPS) of activated sludge.

Bisphenol A (BPA) in wastewater has high risks of causing biological feminization. During the wastewater treatment process, large amounts of BPA are accumulated in activated sludge. However, the mechanisms of BPA interacted with activated sludge are still unclear. Especially, the roles of extracellular polymeric substances (EPS), which are major components of activated sludge, in the removal of BPA have never been concerned. In this study, the binding interactions between sludge EPS and BPA are explored combining fluorescence spectroscopy and dynamic light scattering. The thermodynamic mechanisms driving the binding behavior of BPA to EPS are illustrated by isothermal titration calorimetry. The results indicate that the binding interaction between BPA and EPS is spontaneous. BPA mainly binds with the proteins of EPS by hydrophobic association. The random-coiled structure of EPS transforms into relatively condensed cores after binding with BPA. A neutral pH, high ionic strength, and high temperature promote the binding process, facilitating to stabilize BPA in sludge EPS. This study provides new insights into the roles of sludge EPS in the migration and removal of BPA in activated sludge system.

Enhanced denitrification by nano ɑ-Fe2O3 induced self-assembled hybrid biofilm on particle electrodes of three-dimensional biofilm electrode reactors.

Three-dimensional biofilm electrode reactors (3D-BERs) represent a novel technology for wastewater denitrification. Formation of mature electroactive biofilm on particle electrodes is crucial to realize successful denitrification in 3D-BERs. However, long start-up time and low electroactivity of the biofilm formed on particle electrodes limit the further application of 3D-BERs in wastewater treatment. In this work, self-assembled hybrid biofilms (SAHB) was cultivated on granular activate carbon particle electrodes of the 3D-BER by assembling nano ɑ-Fe2O3 into the biofilm. ɑ-Fe2O3 was selected due to its high affinity to bacterial outer-membrane cytochromes, an important mediator for microbial electron transfer. SAHB formed on particle electrodes were characterized and the denitrification performance of 3D-BERs was also investigated. Results indicate that nano ɑ-Fe2O3 plays positive roles in the start-up of 3D-BER, which captures more microbes into SAHB and constructs thick biofilm on particle electrodes. Special microorganisms with denitrification function related with genera of Hydrogenophaga and Opitutus are distinctively enriched in SAHB. Nano ɑ-Fe2O3 induced SAHB exhibit superior denitrification performance compared to natural biofilm. The average denitrification rate increases from 0.62 mg total nitrogen/L/h for natural biofilm to 1.73 mg total nitrogen/L/h for SAHB, mainly ascribed to accelerated nitrites reduction. Our work provides new technical solution to enhance nitrates removal in 3D-BERs and brings deep insights into application of bio-electrochemical system in wastewater treatment.

Insights into the interactions between triclosan (TCS) and extracellular polymeric substance (EPS) of activated sludge.

Triclosan (TCS) contaminant has aroused wide concerns due to the high risk of converting into toxic dioxin in aquatic environments. During the wastewater treatment process, considerable amounts of TCS are accumulated in activated sludge but the mechanisms are still unclear. Especially, roles of extracellular polymeric substances (EPS), the main components of activated sludge, in TCS removal have never been addressed. In this work, the binding properties of loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS) of activated sludge to TCS are investigated by fluorescence quenching approach. The influences of aquatic conditions including solution pH, ionic strength and temperature on the interactions between EPS and TCS are explored. Possible interaction mechanisms are discussed as well as the corresponding environmental implication. Results indicate that binding processes of EPS to TCS are exothermic mainly driven by the enthalpy changes. The proteins components in EPS dominate the interactions between EPS and TCS by hydrogen bond and hydrophobic interaction. The binding strength could be improved under the condition of weak alkaline and relative high ionic strength. Generally, LB-EPS exhibit stronger binding ability to TCS than TB-EPS under neutral environment, playing more crucial roles in the binding process. This work highlights the important contributions of EPS to TCS removal, that is beneficial to comprehensively understand the migration of TCS in activated sludge system.