Yunshu Zhang

Bioelectrochemically-assisted anaerobic composting process enhancing compost maturity of dewatered sludge with synchronous electricity generation

Bioelectrochemically-assisted anaerobic composting process (AnCBE) with dewatered sludge as the anode fuel was constructed to accelerate composting of dewatered sludge, which could increase the quality of the compost and harvest electric energy in comparison with the traditional anaerobic composting (AnC). Results revealed that the AnCBE yielded a voltage of 0.60 ± 0.02 V, and total COD (TCOD) removal reached 19.8 ± 0.2% at the end of 35 d. The maximum power density was 5.6 W/m(3). At the end of composting, organic matter content (OM) reduction rate increased to 19.5 ± 0.2% in AnCBE and to 12.9 ± 0.1% in AnC. The fuzzy comprehensive assessment (FCA) result indicated that the membership degree of class I of AnCBE compost (0.64) was higher than that of AnC compost (0.44). It was demonstrated that electrogenesis in the AnCBE could improve the sludge stabilization degree, accelerate anaerobic composting process and enhance composting maturity with bioelectricity generation.

Microbial fuel cell with high content solid wastes as substrates: a review

With the increasing concern about the serious global energy crisis and high energy consumption during high content solid wastes (HCSWs) treatment, microbial fuel cell (MFC) has been recognized as a promising resource utilization approach for HCSW stabilization with simultaneous electrical energy recovery. In contrast to the conventional HCSW stabilization processes, MFC has its unique advantages such as direct bio-energy conversion in a single step and mild reaction conditions (viz., ambient temperature, normal pressure, and neutral pH). This review mainly introduces some important aspects of electricity generation from HCSWand its stabilization in MFC, focusing on: (1) MFCs with different fundamentals and configurations designed and constructed to produce electricity from HCSW; (2) performance of wastes degradation and electricity generation; (3) prospect and deficiency posed by MFCs with HCSWas substrates. To date, the major drawback of MFCs fueled by HCSW is the lower power output than those using simple substrates. HCSW hydrolysis and decomposition would be a major tool to improve the performance of MFCs. The optimization of parameters is needed to push the progress of MFCs with HCSW as fuel.

Analysis of functional genomes from metagenomes: Revealing the accelerated electron transfer in microbial fuel cell with rhamnolipid addition

Extracellular electron transfer is the predominant electricity generation process in microbial fuel cells (MFCs). Our pervious study have proved that the anodic adsorption of rhamnolipid resulted in the Frumkin effect, which enhanced anodic microorganism attachment and accelerated anodic electron transfer. In this study, an in-depth research on the influence of rhamnolipid on functional genes of anodic biofilms metagenomes was carried out to explain its mechanism at the gene level. The result showed that the composition and distribution of functional genes in each dominant genus were different. The category of signal transduction mechanisms was the dominant function category in exoelectrogens, and its relative abundance in the metagenome significantly increased from 4.56 to 5.86% from rhamnolipid addition. Additionally, the metabolic pathway and electron flow analysis revealed that electron flows tend to choose direct electron transfer in the presence of rhamnolipids, and resulting in the increase of Coulombic efficiency from 19.10±0.79% to 27.39±1.07%.

Accelerating anodic biofilms formation and electron transfer in microbial fuel cells: Role of anionic biosurfactants and mechanism

Anodic electron transfer is the predominant electricity generation process of MFCs. To accelerate anodic biofilms formation and electron transfer, 40mg/L, 80mg/L, and 120mg/L of rhamnolipid biosurfactants were added to the anolyte, resulting in an increased abiotic capacitance from 15.12F/m2 (control) to 16.54F/m2, 18.00F/m2, and 19.39F/m2, respectively. Anodic biofilm formation was facilitated after dosing 40mg/L of rhamnolipids on the 7th day after inoculation, resulting in an increased anodic biofilm coverage from 0.43% to 42.51%, and an increased maximum power density from 6.92±1.18W/m3 to 9.93±0.88W/m3. Furthermore, the adsorption of rhamnolipids on the anode caused the Frumkin effect, leading to a decrease of equilibrium potential from -0.43V to -0.56V, and an increase of exchange current density from 5.09×10-3A/m2 to 8.72×10-3A/m2. However, electron transfer was blocked when the rhamnolipid concentration was further increased to 80mg/L, and 120mg/L. Analysis of the anodic bacterial communities revealed that rhamnolipids facilitated the enrichment of exoelectrogen, increasing the total proportion from 65% to 81%. Additionally, biosurfactants were found to have significant impacts on the composition of exoelectrogens.

Acceleration of organic removal and electricity generation from dewatered oily sludge in a bioelectrochemical system by rhamnolipid addition

Conversion of biomass energy of dewatered oily sludge to electricity is the rate-limiting process in bioelectrochemical system (BES). In this study, 2mgg-1 rhamnolipids were added to dewatered oily sludge, resulting in a significant enhancement in maximum power density from 3.84±0.37 to 8.63±0.81Wm-3, together with an increase in total organic carbon (TOC) and total petroleum hydrocarbon (TPH) removal from 24.52±4.30 to 36.15±2.79mgg-1 and 29.51±3.30 to 39.80±2.47mgg-1, respectively. Rhamnolipids can also enhance the solubilization and promote the hydrolysis of dewatered oily sludge with increases in SOCD from 14.93±2.44 to 18.40±0.08mgg-1 and VFAs from 1.02±0.07 to 1.39±0.12mgg-1. Furthermore, bacteria related to substrate degradation were predominant in dewatered oily sludge, and bacteria related to the sulfate/sulfide cycle were significantly enriched by rhamnolipid addition.