Electrical stress and acid orange 7 synergistically clear the blockage of electron flow in the methanogenesis of low-strength wastewater.

Energy recovery from low-strength wastewater through anaerobic methanogenesis is constrained by limited substrate availability. The development of efficient methanogenic communities is critical but challenging. Here we develop a strategy to acclimate methanogenic communities using conductive carrier (CC), electrical stress (ES), and Acid Orange 7 (AO7) in a modified biofilter. The synergistic integration of CC, ES, and AO7 precipitated a remarkable 72-fold surge in methane production rate compared to the baseline. This increase was attributed to an altered methanogenic community function, independent of the continuous presence of AO7 and ES. AO7 acted as an external electron acceptor, accelerating acetogenesis from fermentation intermediates, restructuring the bacterial community, and enriching electroactive bacteria (EAB). Meanwhile, CC and ES orchestrated the assembly of the archaeal community and promoted electrotrophic methanogens, enhancing acetotrophic methanogenesis electron flow via a mechanism distinct from direct electrochemical interactions. The collective application of CC, ES, and AO7 effectively mitigated electron flow impediments in low-strength wastewater methanogenesis, achieving an additional 34% electron recovery from the substrate. This study proposes a new method of amending anaerobic digestion systems with conductive materials to advance wastewater treatment, sustainability, and energy self-sufficiency.

H*ads dynamics engineering via bimetallic Pd-Cu@MXene catalyst for enhanced electrocatalytic hydrodechlorination.

Electrocatalytic hydrodechlorination (EHDC) is a promising approach to safely remove halogenated emerging contaminants (HECs) pollutants. However, sluggish production dynamics of adsorbed atomic H (H*ads) limit the applicability of this green process. In this study, bimetallic Pd-Cu@MXene catalysts were synthesized to achieve highly efficient removal of HECs. The alloy electrode (Pd-Cu@MX/CC) exhibited better EHDC performance in comparison to Pd@MX/CC electrode, resulting in diclofenac degradation efficiency of 93.3 ± 0.1%. The characterization analysis revealed that the Pd0/PdII ratio decreased by forming bimetallic Pd-Cu alloy. Density functional theory calculations further demonstrated the electronic configuration modulation of the Pd-Cu@MXene catalysts, optimizing binging energies for H* and thereby facilitating H*ads production and tuning the reduction capability of H*ads. Noteably, the amounts and reduction potential of H*ads for Pd-Cu@MXene catalysts were 1.5 times higher and 0.37 eV lower than those observed for the mono Pd electrode. Hence, the introduction of Cu into the Pd catalyst optimized the dynamics of H*ads production, thereby conferring significant advantages to EHDC reactions. This augmentation was underscored by the successful application of the alloy catalysts supported by MXene in EHDC experiments involving other HECs, which represented a new paradigm for EHDC for efficient recalcitrant pollutant removal by H*ads.

Advantages of residual phenol in coal chemical wastewater as a co-metabolic substrate for naphthalene degradation by microbial electrolysis cell.

The use of co-metabolic substrates is effective for polycyclic aromatic hydrocarbons (PAHs) removal, but the potential of the high phenol concentrations in coal chemical wastewater (CCW) as a co-metabolic substrate in microbial electrolysis cell (MEC) has been neglected. In this study, the efficacy of varying phenol concentrations in comparison to simple substrates for degrading naphthalene in MEC under comparable COD has been explored. Results showed that phenol as a co-metabolic substrate outperformed sodium acetate and glucose in facilitating naphthalene degradation efficiency at 50 mg-COD/L. The naphthalene removal efficiency from RP, RA, and RG was found to be 84.11 ± 0.44 %, 73.80 ± 0.27 % and 72.43 ± 0.34 %, respectively. Similarly, phenol not only enhanced microbial biomass more effectively, but also exhibited optimal COD metabolism capacity. The addition of phenol resulted in a stepwise reduction in the molecular weight of naphthalene, whereas sodium acetate and glucose led to more diverse degradation pathways. Some bacteria with the potential ability to degrade PAHs were detected in phenol-added MEC, including Alicycliphilus, Azospira, Stenotrophomonas, Pseudomonas, and Sedimentibacter. Besides, phenol enhanced the expression of ncrA and nmsA genes, leading to more efficient degradation of naphthalene, with ncrA responsible for mediating the reduction of the benzene ring in naphthalene and nmsA closely associated with the decarboxylation of naphthalene. This study provides guidance for the effective co-degradation of PAHs in CCW with MEC, demonstrating the effectiveness of using phenol as a co-substrate relative to simple substrates in the removal of naphthalene.

Enhancing degradation of organic matter in microbial electrolytic cells coupled with anaerobic digestion (MEC-AD) systems by carbon-based materials.

Currently, little information is available on relative contributions among biochar (BC), activated carbon (AC), magnetic BC (MBC), and magnetic AC (MAC) to enhance the effectiveness of a microbial electrolytic cells coupled with anaerobic digestion (MEC-AD) system and the impact of carbon-based materials on microbial community. In this study, six anaerobic reactors were constructed to demonstrate the effects of different carbon-based materials on organic matter elimination in the MEC-AD system. Remarkably, the reactor containing MBC exhibited a significant increase in organic removal, achieving 95.0 % chemical oxygen demand (COD) eradication. Additionally, the MBC-added MEC-AD reactor yields acetic acid at a rate 2.9 times higher than that of the BC-added reactor. Electrical stimulation enriched electro-producing bacteria such as Pseudomonas (18.1 %) and Gordonia (6.8 %), which were further promoted by the addition of MBC, indicating that the microbial communities cultivated with the MBC could provide the necessary microbiome for the MEC.

Atomic hydrogen-mediated enhanced electrocatalytic hydrodehalogenation on Pd@MXene electrodes.

In this study, a Pd@MXene catalyst was synthesized to enhance the electrocatalytic hydrodehalogenation (ECH) of emerging halogenated organic pollutants (HOPs) by improving the dispersibility, catalytic activity, and stability of palladium (Pd). The average size of Pd nanoparticles (NPs) was reduced to 3.62 ± 0.34 nm with a more intensive peak of Pd (111), which facilitated atomic hydrogen (H*) production. The Pd@MX/CC electrode demonstrated superior ECH activity for diclofenac (DCF) degradation, with a reaction rate constant (kobs) 2.48 times higher than that of Pd/CC (without MXene). The satisfactory ECH performance of Pd@MX/CC remained consistent within a wide range of initial DCF concentrations (5-100 mg/L), and no significant ECH attenuation was observed even after up to 10 batches. Furthermore, the high activity of Pd@MX/CC was also observed in the ECH of other halogenated organic pollutants (levofloxacin, tetrabromobisphenol A, and diatrizoate). Density functional theory (DFT) calculations revealed that electronic configuration modulation of the Pd@MXene catalyst optimized binging energies to H* , DCF, and dechlorinated products, thereby enhancing the ECH efficiency of DCF.

Evaluation of the respective contribution of anode and cathode for triclosan degradation in a bioelectrochemical system.

In this work, the bioelectrochemical system (BES) is a feasible alternative for successfully degrading typical refractory emerging contaminant triclosan (TCS). A single-chamber BES reactor with an initial TCS concentration of 1 mg/L, an applied voltage of 0.8 V, and a solution buffered with 50 mM PBS degraded 81.4 ± 0.2% of TCS, exhibiting TCS degradation efficiency improvement to 90.6 ± 0.2% with a biocathode formed from a reversed bioanode. Both bioanode and biocathode were able to degrade TCS with comparable efficiencies of 80.8 ± 4.9% and 87.3 ± 0.4%, respectively. Dechlorination and hydrolysis were proposed as the TCS degradation pathway in the cathode chamber, and another hydroxylation pathway was exclusive in the anode chamber. Microbial community structure analysis indicated Propionibacteriaceae was the predominant member in all electrode biofilms, and the exoelectrogen Geobacter was enriched in anode biofilms. This study comprehensively revealed the feasibility of operating BES technology for TCS degradation.

Metatranscriptomic insights into the microbial electrosynthesis of acetate by Fe2+/Ni2+ addition.

As important components of enzymes and coenzymes involved in energy transfer and Wood-Ljungdahl (WL) pathways, Fe2+ and Ni2+ supplementation may promote the acetate synthesis through CO2 reduction by the microbial electrosynthesis (MES). However, the effect of Fe2+ and Ni2+ addition on acetate production in MES and corresponding microbial mechanisms have not been fully studied. Therefore, this study investigated the effect of Fe2+ and Ni2+ addition on acetate production in MES, and explored the underlying microbial mechanism from the metatranscriptomic perspective. Both Fe2+ and Ni2+ addition enhanced acetate production of the MES, which was 76.9% and 110.9% higher than that of control, respectively. Little effect on phylum level and small changes in genus-level microbial composition was caused by Fe2+ and Ni2+ addition. Gene expression of 'Energy metabolism', especially in 'Carbon fixation pathways in prokaryotes' was up-regulated by Fe2+ and Ni2+ addition. Hydrogenase was found as an important energy transfer mediator for CO2 reduction and acetate synthesis. Fe2+ addition and Ni2+ addition respectively enhanced the expression of methyl branch and carboxyl branch of the WL pathway, and thus promoted acetate production. The study provided a metatranscriptomic insight into the effect of Fe2+ and Ni2+ on acetate production by CO2 reduction in MES.

Evaluation of the effect of biofilm formation on the reductive transformation of triclosan in cathode-modified electrolytic systems.

The performance of electrochemical reduction is often enhanced by electrode modification techniques. However, there is a risk of microbial colonization on the electrode surface to form biofilms in the treatment of actual wastewater with modified electrodes. In this work, the effects of biofilm formation on modified electrodes with reduced graphene oxide (rGO), platinum/carbon (Pt/C), and carbon nanotube (CNT) were investigated in triclosan (TCS) degradation. With biofilm formation, the TCS degradation efficiencies of carbon cloth (CC), rGO@CC, Pt/C@CC, and CNT@CC decayed to 54.53 %, 59.77 %, 69.19 %, and 53.97 %, respectively, compared to the raw electrodes. Confocal laser scanning microscopy and microbial community analysis revealed that the difference in biofilm thickness and activity were the major influencing factors on the discrepant TCS degradation rather than the microbial community structure. The electrochemical performance tests showed that the biofilm formation increased the ohmic resistance by an order of magnitude in rGO@CC, Pt/C@CC, and CNT@CC, and the charge transfer resistance was increased by 2.45, 3.78, and 7.75 times, respectively. The dechlorination and hydrolysis governed the TCS degradation pathway in all electrolysis systems, and the toxicity of electrochemical reductive products was significantly decreased according to the Toxicity Estimation Software Tool analysis. This study presented a systematic assessment of the biofilm formation on modified electrodes in TCS reduction, and the undisputed experimental outcomes were obtained to enrich the knowledge of implementing modified electrodes for practical applications.

A feasibility investigation of a pilot-scale bioelectrochemical coupled anaerobic digestion system with centric electrode module for real membrane manufacturing wastewater treatment.

The large-scale application of bioelectrochemical coupled anaerobic digestion (BES-AD) is limited by the matching of electrode configuration and the applicability of real wastewater. In this study, a pilot-scale BES-AD system with an effective system volume of 5 m3 and a 1 m3 volume of a carbon fiber brush electrode module was constructed and tested for treatment of the membrane manufacturing wastewater. The results showed that the BOD5/COD of the wastewater was increased from 0.238 to 0.398 when the applied voltage was 0.9 V. The pollutants such as N, N-Dimethylacetamide and glycerol in wastewater were degraded significantly. The microorganisms in the electrode modules were spatially enriched. The fermenters (Norank_f__ML635J-40_aquatic_group, 6.55 %; unclassified_f__Propionibacteriaceae, 5.25 %) and degraders (Corynebacterium, 29.31 %) were mostly enriched at the bottom, while electroactive bacteria (Pseudomonas, 29.39 %, Geobacter, 7.86 %) were mostly enriched at the top. Combined with the economical construction and operation cost ($1708.8/m3 and $0.76/m3) of the BES-AD system.

The microbial synergy and response mechanisms of hydrolysis-acidification combined microbial electrolysis cell system with stainless-steel cathode for textile-dyeing wastewater treatment.

Microbial electrolysis cell (MEC) has been existing problems such as poor applicability to real wastewater and lack of cost-effective electrode materials in the practical application of refractory wastewater. A hydrolysis-acidification combined MEC system (HAR-MECs) with four inexpensive stainless-steel and conventional carbon cloth cathodes for the treatment of real textile-dyeing wastewater, which was fully evaluated the technical feasibility in terms of parameter optimization, spectral analysis, succession and cooperative/competition effect of microbial. Results showed that the optimum performance was achieved with a 12 h hydraulic retention time (HRT) and an applied voltage of 0.7 V in the HAR-MEC system with a 100 µm aperture stainless-steel mesh cathode (SSM-100 µm), and the associated optimum BOD5/COD improvement efficiency (74.75 ± 4.32 %) and current density (5.94 ± 0.03 A·m-2) were increased by 30.36 % and 22.36 % compared to a conventional carbon cloth cathode. The optimal system had effective removal of refractory organics and produced small molecules by electrical stimulation. The HAR segment could greatly alleviate the imbalance between electron donors and electron acceptors in the real refractory wastewater and reduce the treatment difficulty of the MEC segment, while the MEC system improved wastewater biodegradability, amplified the positive and specific interactions between degraders, fermenters and electroactive bacteria due to the substrate complexity. The SSM-100 µm-based system constructed by phylogenetic molecular ecological network (pMEN) exhibited moderate complexity and significantly strong positive correlation between electroactive bacteria and fermenters. It is highly feasible to use HAR-MEC with inexpensive stainless-steel cathode for textile-dyeing wastewater treatment.

FexN produced in pharmaceutical sludge biochar by endogenous Fe and exogenous N doping to enhance peroxymonosulfate activation for levofloxacin degradation.

For preparing high performance biochar to be applicated in persulfate-based oxidation treatment of wastewater, the feasibility of deriving Fe-N biochar from pharmaceutical sludge by endogenous Fe and exogenous N doping was investigated. With exogenous urea doping, FexN contained biochar (PZBC800U) was successfully derived from endogenous Fe(OH)3 contained pharmaceutical sludge. PZBC800U effectively activated peroxymonosulfate (PMS) to remove 80 mg·L-1 levofloxacin (LEV) within 90 min. The main mechanism of PMS activation by PZBC800U for LEV degradation was revealed as non-radical pathways dominated by 1O2 generation and direct electron transfer. The formation of FexN combined with the increase of pyridinic-N in the biochar changed the electronic structure, improved the electron transfer ability, and thus achieved the excellent PMS activation capacity of the biochar. The vital function of endogenous Fe(OH)3 was verified by comparing PZBC800U to Fe leached and extra Fe added controls. A total of 18 intermediates in the degradation of LEV were identified, and degradation pathways were proposed. Combined with the average local ionization energy calculation, the priority of piperazine breakage during LEV degradation was experimentally proved and mechanistically elucidated. This study provides a new insight into FexN biochar preparation from pharmaceutical sludge and the mechanisms of its excellent PMS activation performance for LEV degradation.

Understanding the effects of sludge characteristics on the biosorption of triclosan.

On account of hydrophobic nature, the adsorption process on solids is considered as the major pathway for triclosan (TCS) removal in wastewater treatment plants. In this work, four sludge sources (primary sludge, thickened sludge, dewatered sludge, and anaerobic digested sludge) were collected to evaluate the adsorption performance of TCS. The solid-liquid distribution coefficients of TCS were increased with total solids increasing of primary sludge, thickened sludge, and dewatered sludge, whereas decreased in anaerobic digested sludge. Results further revealed differences in sludge floc sub-structures of TCS adsorption. The residues contained most of adsorbed TCS in all sub-structures, while distinguished in various extracellular polymeric substances (EPS). The major contributor of EPS sub-fractions to TCS adsorption was identified as tightly bound EPS in thickened sludge and soluble EPS in anaerobic digested sludge. Based on the excitation-emission matrix spectra and Fourier infrared spectrum results, the protein-like and humic acid-like substances were closely related to the TCS adsorption, and hydrogen bond, hydrophobic interaction, and electrostatic interaction were considered as the dominant mechanisms. This study comprehensively reveals the effects of sludge sources and sub-structures on TCS adsorption, which improves the understanding of interaction and migration processes between TCS and sludge.

Alkalinity regulation in a sulfur autotrophic denitrifying filter substantially reduced total dissolved solids and sulfate in effluent.

Sulfur autotrophic denitrification (SAD) filters are considered a promising technology due to their stable and excellent performance in nitrogen removal, affordable costs, and operational advantages. In this work, a novel operational strategy that employed sodium bicarbonate as an alkalinity source in the autotrophic denitrification filter (S-SAD) was established. With the sufficient supply of alkalinity, the S-SAD reached an excellent denitrification performance (98.01%±0.43%) with a nitrate concentration of 10 mg/L in influent and hydraulic retention time of 3 hrs. The total dissolved solids increment and sulfate concentration in effluent were significantly reduced by one-third, compared with that of the traditional SAD process under the same conditions. The analysis of microbial community indicated that Thiobacilhus, typical species with the functions of simultaneous sulfur oxidation and denitrification, was evidently enriched in the S-SAD. Thus, this present work demonstrated a feasible, relatively cost-effective and environmentally friendly approach to operate SAD towards further application.

Pyrolyzing pharmaceutical sludge to biochar as an efficient adsorbent for deep removal of fluoroquinolone antibiotics from pharmaceutical wastewater: Performance and mechanism.

This study explored the impact of pyrolysis parameters and modification methods on the characteristics of pharmaceutical sludge biochar, and investigated its capacity and mechanisms for levofloxacin (LEV), a typical fluoroquinolone antibiotics, adsorption. The results showed that SBET of the biochar was improved with temperature increase, but decreased when temperature reached 900 °C. Under the optimal pyrolysis condition of 800 °C and 90 min, the biochar possessed the highest SBET of 264.05 m2 g-1, excellent iodine value of 401.41 ± 3.84 mg∙g-1 and phenol adsorption of 57.36 ± 3.39 mg∙g-1. Among KOH, ZnCl2, and CO2 modifications, ZnCl2 modification achieved the highest phenol adsorption of 123.40 ± 4.65 mg g-1, with a significantly improved SBET of 534.91 m2 g-1. The maximum LEV adsorption capacity of ZnCl2 modified biochar, PZBC800, reached 159.26 mg g-1, which overwhelmed the reported sludge biochars. BET, zeta potential, FT-IR, XPS, and Raman analysis, along with quantum chemistry calculation, revealed that pore filling, hydrogen bonding, π-π interaction, surface complexation, and electrostatic interaction were the main mechanisms for the excellent LEV adsorption performance of PZBC800. Deep removal (99.9%) of Fluoroquinolones (FQs) from pharmaceutical wastewater was also achieved by PZBC800 adsorption. The study promoted the development of pharmaceutical sludge biochar preparation and its application in advanced treatment of FQs pharmaceutical wastewater.

Bioelectrochemical systems with a cathode of stainless-steel electrode for treatment of refractory wastewater: Influence of electrode material on system performance and microbial community.

The large-scale application of the bioelectrochemical system (BES) is limited by the cost-effective electrode materials. In this study, five kinds of stainless-steel materials were used as the cathode of the BES coupled with anaerobic digestion (BES-AD) for the treatment of diluted N, N-dimethylacetamide (DMAC) wastewater. Compared with a carbon-cloth cathode, BES-AD with a stainless-steel cathode had more engineering due to its low cost, although the operating efficiencies were slightly inferior. Stainless-steel mesh with a 100 µm aperture (SSM-100 µm) was the most cost-effective electrode and the implanted BES exhibited better COD removal efficiency, electrochemical performance and biodegradability. Analysis of microbial community revealed the synergetic effect between exoelectrogen and fermentative bacteria had been strengthened in the SSM-100 µm cathode biofilm. Function analysis of the microbial community based on PICRUSt predicted metagenomes revealed that the metabolic pathways of xenobiotics biodegradation and metabolism in the SSM-100 µm cathode were stimulated.

Recent advancements in azo dye decolorization in bio-electrochemical systems (BESs): Insights into decolorization mechanism and practical application.

Recent advances in bio-electrochemical systems (BESs) for azo dye removal are gaining momentum due to having electrode biocarrier and electro-active bacteria that could stimulate decolorization via extracellular electron transfer. Enhanced decolorization performance is observed in most laboratory studies, indicating the great potential of BESs as an alternative to the traditional biological processes or serving as a pre-/post-processing unit to improve the performance of biological processes. It is proven more competitive in environmental friendly than physicochemical methods. While, the successful application of BESs to azo dye-containing wastewater remediation requires a deeper evaluation of its performance, mechanism and typical attributes, and a comprehensive potential evaluation of BESs practical application in terms of economic analysis and technical optimizations. This review is organized to address BESs as a practical option for azo dye removal by analyzing the decolorization mechanisms and involved functional microorganisms, followed by the comparisons of device configurations, operational conditions, and economic evaluation. It further highlights the current hurdles and prospects for the abatement of azo dyes via BES related techniques.

Algae biochar enhanced methanogenesis by enriching specific methanogens at low inoculation ratio during sludge anaerobic digestion.

Carbon materials are promising in improving the performance of anaerobic digestion, however, interactive mechanisms between the carbon-based enhancement and operating parameters remained unclear. Using anaerobic digested sludge as inoculum, the effects of Taihu blue algae biochar (ABC) on methanogenesis at different inoculation ratios were investigated during sludge anaerobic digestion. Results showed that ABC enhanced methane productions at the lower inoculation ratios (4% and 1%, v/v), but not at the higher ratio (10%, v/v). Mechanism analysis demonstrated methanogenic improvements at the lower inoculation ratios were not owing to initial organic loading rate increments. Otherwise, ABC addition at the lower inoculation ratios were more favorable for the enrichment of Methanosarcina than the higher ratio, which might be benefit for methanogenesis through directed interspecies electron transfer. Thus, for the improvement of sludge anaerobic digestion, the microbial enrichments at different inoculation ratios would be more important than the merely biochar addition.

Anaerobic biodegradation of levofloxacin by enriched microbial consortia: Effect of electron acceptors and carbon source.

For improving the understanding of anaerobic degradation mechanism of fluoroquinolone antibiotics (FQs), the degradation of a representative FQs, levofloxacin (LEV), by six enriched anaerobic consortia were explored in this study. The effect of sulfate and nitrate as the electron acceptor and glucose as the carbon source on LEV anaerobic degradation were investigated. Addition of glucose and nitrate alone deteriorated LEV removal from 36.5% to 32.7% and 29.1%, respectively. Addition of sulfate slightly improved LEV removal to 39.6%, while simultaneous addition of glucose and sulfate significantly enhanced LEV removal to 53.1%. Twelve biodegradation intermediates were identified, which indicated that cleavage of piperazine ring is prior to that of quinolone ring, and hydroxylation, defluorination, demethylation, and decarboxylation were the primary steps of LEV anaerobic degradation. Lactobacillus, unclassified _f_Enterobacteriaceae, and Bacillus were enriched by simultaneous addition of glucose and sulfate, with relative abundance of 63.5%, 32.7%, and 3.3%, respectively. The predicted high gene abundance of xenobiotics biodegradation & metabolism, carbohydrate metabolism, and assimilatory sulfate reduction in the consortium, indicated a co-metabolism between carbohydrate metabolism, sulfate metabolism, and LEV degradation under glucose and sulfate added condition. The study revealed that simultaneous addition of glucose and sulfate is the favorable condition for LEV anaerobic degradation.

Damage of anodic biofilms by high salinity deteriorates PAHs degradation in single-chamber microbial electrolysis cell reactor.

The anaerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) in high salinity wastewater is rather hard due to the inhibition of microorganisms by complex and high dosage of salts. Microbial electrolysis cell (MEC), with its excellent characteristic of anodic biofilms, can be an effective way to enhance the PAHs biodegradation. This work evaluated the impact of NaCl concentrations (0 g/L, 10 g/L, 30 g/L, and 60 g/L) on naphthalene biodegradation and analyzed the damage protection mechanism of anodic biofilms in batching MECs. Compared with the open circuit, the degradation efficiency of naphthalene under the closed circuit with 10 g/L NaCl concentration reached the maximum of 95.17% within 5 days. Even when NaCl concentration reached 60 g/L, the degradation efficiency only decreased by 10.02%, compared with the MEC without additional NaCl. Confocal scanning laser microscope (CSLM) proved the superiority of the biofilm states of MEC anode under high salinity in terms of thicker biofilms and higher proportion of live/dead bacteria cells. The highest dehydrogenase activity (DHA) was found in the MEC with 10 g/L NaCl concentration. Moreover, microbial diversity analysis demonstrated the classical electroactive microorganisms Geobacter and Pseudomonas were found on the anodic biofilms of MECs, which have both PAHs degradability and the electrochemical activity. Therefore, this study proved that high salinity had adverse effects on the anodic biofilms, but MEC alleviated the damage caused by high salinity.

Effects of co-pyrolysis of rice husk and sewage sludge on the bioavailability and environmental risks of Pb and Cd.

In this study, biochars were produced by co-pyrolysis of rice husk and sewage sludge, the environmental risk of heavy metal (Pd and Cd) in the biochars was assessed. Co-pyrolysis resulted in a lower yield but a higher C content compared with sewage sludge pyrolysis alone, the relative contents of Pb and Cd in biochars were declined. Co-pyrolysis process transformed the bioavailable heavy metals into stable speciation. The environmental risk assessment codes of Pb and Cd were reduced by 1-2 grades. The co-pyrolysis technology provides a feasible method for the safe disposal of heavy metal-contaminated sewage sludge.