Removal of tetracycline by ultraviolet/sodium percarbonate (UV/SPC)advanced oxidation process in water.

Tetracycline (TC) was widely used and frequently detected in various water bodies, where the presence of TC posed a significant threat to the health of aquatic organisms. Furthermore, antibiotics were hardly degraded by biological treatment. Thus, in order to enhance the removal of TC, we proposed the use of a novel ultraviolet/sodium percarbonate (UV/SPC) advanced oxidation process and initiated an in-depth study. The study investigated the influence of oxidant dosage, initial pH, UV intensity, and TC concentration on the removal of TC. The results demonstrated that the UV/SPC system efficiently removed TC, with removal efficiency increasing as the SPC concentration increased. Within the pH range of 3-11, TC degradation exhibited minimal variation, indicating the UV/SPC system's strong adaptability to pH variations. The research on the impact of the water matrix on TC removal revealed that HCO3- had an inhibitory effect on TC degradation, while NO3- promoted TC degradation. Additionally, the presence of free radical species (·OH, ·CO3-, ·O2-) were detected and rate constants for the secondary reactions (k·OH,TC = 6.3 × 109 L mol-1·s-1, k·CO3-,TC = 3.4 × 108 L mol-1·s-1) were calculated, indicating that ·OH exhibited a stronger oxidative performance compared to ·CO3-. This study did not only present a novel strategy via UV/SPC to remove TC but also uncovered the unique role of ·CO3- for contaminant removal.

Effect of light intensity and photoperiod on high-value production and nutrient removal performance with bacterial-algal coupling system.

Direct discharge of mariculture wastewater can lead to eutrophication, posing a threat to aquatic ecosystems. A novel Bacteria-Algae Coupled Reactor (BACR) offers advantages in treating mariculture wastewater, which can effectively remove pollutants while simultaneously obtaining microalgal products. However, there is limited information available on how illumination affects the cultivation of mixotrophic microalgae in this bacteria-algae coupling system. Therefore, a combined strategy of photoperiod and light intensity regulation was employed to improve the biological mariculture wastewater remediation, promote microalgae biomass accumulation, and increase the high-value product yield in this study. Optimal light conditions could effectively enhance microalgal carbohydrate, protein, lipid accumulation and photosynthetic activity, with the carbohydrate, protein and lipid contents reached 44.11, 428.57 and 399.68 mg/L, respectively. Moreover, excellent removal rates were achieved for SCOD, NH4+-N and TP, reaching 86.68%, 87.35% and 95.13% respectively. This study proposes a comprehension of BACR processes in mariculture wastewater under different light conditions.

The acceptance of SARS-CoV-2 rapid antigen self-testing: A cross-sectional study in China.

Compared with the nucleic acid amplification test (NATT), the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapid antigen self-testing (RAST) has advantages in speed and convenience. However, little is known about people's acceptance and influencing factors for SARS-CoV-2 RAST. A cross-sectional study was conducted from April 21 to 30, 2022 in China. The χ2 test and multivariate logistic regressions were used to identify the influencing factors. The structural equation model was used to test the extended protective motivation theory (PMT) model hypotheses. Among the total of 5107 participants, 62.5% were willing to accept the SARS-CoV-2 RAST. There were significant differences in acceptance among different residences (p < 0.001), educational level (p < 0.001), occupation (p < 0.001), monthly income (p < 0.001), travel frequency (p < 0.05), and feelings about NATT (p < 0.001). Response efficacy (ß = 0.05; p = 0.025) and self-efficacy (ß = 0.84; p < 0.001) had a positive effect, while response cost showed a negative effect (ß = -0.07; p < 0.001). The public's major concerns about SARS-CoV-2 RAST are its reliability, testing method, price, and authority. Overall, a moderate intention to use SARS-CoV-2 RAST was found among the Chinese population. The extended PMT can be used for the prediction of intention to accept the RAST. We need to take measures to increase people's acceptance of SARS-CoV-2 RAST.

Insight in degradation of tetracycline in mariculture wastewater by ultraviolet/persulfate advanced oxidation process.

The direct discharge of trace amounts of antibiotics in mariculture wastewater results in adverse effect on the ecological environment of receiving waters. Hence, the degradation of tetracycline (TC) in mariculture wastewater by the ultraviolet/peroxydisulfate (UV/PS) process was investigated in this study. The results revealed that 95.73% removal of TC with 5 mg/L dosage was achieved after 30 min UV/PS treatment. Chloride ion (Cl-) in mariculture wastewater slightly inhibited TC degradation by scavenging free radicals. Comparably, bromine ion (Br-) significantly enhanced the removal of TC and even doubled the degradation rate. Reactive bromine species (RBS) made a major contribution to the TC removal, followed by free chlorine and other reactive chlorine species (RCS). The TC degradation pathway revealed that functional group shedding and ring-opening reactions occurred successively. In addition, TC mineralization rate was low within 30 min, causing the inefficient reduction of acute toxicity of TC and its intermediates, which could be improved by optimizing the process parameters. These results indicated that UV/PS is a new alternative process for the harmless treatment of mariculture wastewater containing the antibiotics.

Comparison of primary and secondary sludge carbon sources derived from hydrolysis or acidogenesis for nitrate reduction and denitrification kinetics: Organics utilization and microbial community shift.

Seeking available and economical carbon sources for denitrification process is an intractable issue for wastewater treatment. However, no study compared different types of waste sludge as carbon source from denitrification mechanism, organics utilization and microbial community aspects. In this study, primary and secondary sludge were pretreated by thermophilic bacteria (TB), and its hydrolysis or acidogenic liquid were prepared as carbon sources for denitrification. At C/N of 8-3, the variations of NO3--N and NO2--N were profiled in typical cycles and denitrification kinetics was analyzed. Primary sludge achieved a competitive NOX-N removal efficiency with less dosage than secondary sludge. Fourier transform infrared (FTIR) spectroscopy was introduced to analyze organic composition from functional-group perspective and the utilization of organic matters in different sludge carbon sources was investigated. To further analyze the microbial community shift in different denitrification systems, high-throughput sequencing technology was applied. Results showed that denitrifier Thauera, belonging to Proteobacteria, was predominant, and primary sludge acidogenic liquid enriched Thauera most intensively with relative abundance of 47.3%.

Impact of sulfamethoxazole and organic supplementation on mixotrophic denitrification process: Nitrate removal efficiency and the response of functional microbiota.

Recirculating aquaculture systems (RAS) effluent is characterized by low COD to total inorganic nitrogen ratio (C/N), excessive nitrate, and the presence of traces of antibiotics. Hence, it urgently needs to be treated before recycling or discharging. In this study, four denitrification bioreactors at increasing C/N ratios (0, 0.7, 2, and 5) were started up to treat mariculture wastewater under the sulfamethoxazole (SMX) stress, during which the bioreactors performance and the shift of mixotrophic microbial communities were explored. The result showed that during the SMX exposure, organic supplementation enhanced nitrate and thiosulfate removal, and eliminated nitrite accumulation. The denitrification rate was accelerated by increasing C/N from 0 to 2, while it declined at C/N of 5. The decline was ascribed to which SMX reduced the relative abundance of denitrifiers, but improved the capability of dissimilatory nitrogen reduction to ammonia (DNRA) and sulfide production. The direct evidence was the relative abundance of sulfidogenic populations, such as Desulfuromusa, Desulfurocapsa, and Desulfobacter increased under the SMX stress. Moreover, high SMX (1.5 mg L-1) caused the obvious accumulation of ammonia at C/N of 5 due to the high concentration of sulfide (3.54 ± 1.08 mM) and the enhanced DNRA process. This study concluded that the mixotrophic denitrification process with the C/N of 0.7 presented the best performance in nitrate and sulfur removal and indicated the maximum resistance to SMX.

Regulation of carbon source metabolism in mixotrophic microalgae cultivation in response to light intensity variation.

Microalgae are one of the promising sources for renewable energy production, and the light intensity variation can affect the biofuel generation and carbon assimilation of mixotrophic microalgae. To reveal the response of carbon assimilation to light intensity, the effect of light intensity on the carbon source metabolism of Chlorella vulgaris under mixotrophic cultivation was investigated in this study. Moreover, the optimal carbon source composition for mixotrophic microalgae cultivation was evaluated using bicarbonate (HCO3-) and carbonate (CO32-) as inorganic carbon sources, and glucose and acetate as organic carbon sources. The optimal light intensity for Chlorella vulgaris growth was at the range of 8000-12000 lux. For the accumulation of biochemical components, low light intensity was beneficial to protein accumulation, and high light intensity was advantageous for carbohydrate and lipid accumulation. With HCO3- and glucose, the maximum lipid content reached 37.0% at a light intensity of 12000 lux. The citrate synthase activity was negatively correlated with light intensity, showing an opposite trend to biomass production. High light intensity had a positive impact on Rubisco expression, which promoted the microalgae growth and carbon fixing. The energy produced by heterotrophic metabolic activities increased at low light intensity, and the enhancement of biomass production with high light intensity was mainly caused by the improved photoreaction efficiency during the mixotrophic cultivation.

Effect of external carbon addition and enrofloxacin on the denitrification and microbial community of sequencing batch membrane reactor treating synthetic mariculture wastewater.

The effect of sequencing batch membrane bioreactor (SMBR) on external carbon addition and enrofloxacin was investigated to treat synthetic mariculture wastewater. Anoxic/anaerobic and low COD/TN can improve the ammonia oxidation of the system, and the NH4+-N removal efficiency above 99%. External carbon was added and an anoxic environment was set to provide a suitable environment for denitrifying bacteria. When the external carbon source was 50-207 mg/L, the TN removal efficiency (31.82%-37.73%) and the COD of the effluent (28.85-36.58 mg/L) had little change. The partition resistance model showed that cake deposition resistance (RC,irr) and irreversible resistance (RPB) were the main components. And with the increase in cleaning times, the fouling rate of membrane components accelerated. Enrofloxacin can promote the TN removal efficiency (45.66%-93.74%) and had a significant effect on TM7a, Cohaesibacter, Vibrio and Phaeobacter.

Metagenomic analysis and nitrogen removal performance evaluation of activated sludge from a sequencing batch reactor under different salinities.

The effect of salinity on the nitrogen removal performance and microbial community of activated sludge was investigated in a sequencing batch reactor. The NH4+-N removal efficiency was over 95% at 0-4% salinity, indicating that the nitrification performance of activated sludge was slightly affected by lower salinity. The obvious nitrite accumulation was observed with the increment of the salinity to 5%, followed by a notable decline in the nitrogen removal performance at 6% salinity. The salinity inhibited the microbial activity, and the specific rate of nitrification and denitrification was decreased by the increasing salinity obviously. Additionally, the lower activity of superoxide dismutase and peroxidase and higher reactive oxygen species content in activated sludge might account for the deteriorative nitrogen removal performance at 6% salinity. Metagenomics analysis revealed that the genes encoding the ABC-type quaternary amine transporter in the ABC transporter pathway were abundant in the activated sludge at 2% and 4% salinity, and the higher salinity of 6% led to the loss of the genes encoding the p-type Na+ transporter in the ABC transporter pathway. These results indicated that the salinity could weaken the ABC transporter pathway for the balance of osmotic pressure in activated sludge. The microbial activity and nitrogen removal performance of activated sludge were decreased due to the unbalanced osmotic pressure at higher salinity.

Mariculture wastewater treatment with Bacterial-Algal Coupling System (BACS): Effect of light intensity on microalgal biomass production and nutrient removal.

Mariculture wastewater generated from the mariculture industry has increased public concern due to its impact on the sustainability of aquatic environments and aquaculture practices. Herein, the Bacterial-Algal Coupling System was applied for mariculture wastewater treatment. Microalgae growth in heterotrophy and mixotrophy (2000-8000 lux) was first compared. The best microalgal growth and nutrient removal were obtained at 5000 lux, where biomass productivity of microalgae was 0.465 g L-1 d-1, and 98.1% of chemical oxygen demand, 70.7% of ammonia-nitrogen, and 90.0% of total phosphorus were removed. To further understand the nutrient removal through microalgae cultivation, the enzyme activities involved in the Calvin cycle and the Tricarboxylic Acid cycle at different light intensities were determined. Under mixotrophic cultivation, there was a coordination between photosynthesis and heterotrophic metabolism in the agal cell, which resulted in a high algal biomass production and removal efficiency of nutrients. This study provided a novel insight into the bioremediation of mariculture wastewater and microalgae cultivation.

Enhanced in-situ electro-generation of H2O2 using PTFE and NH4HCO3 modified C/PTFE electrode for treatment of landfill leachate.

In this study, the carbon black/polytetrafluoroethylene (C/PTFE) electrode was prepared under the best conditions, and then it was modified by PTFE and NH4HCO3 to make a PTFE-C/PTFE electrode. PTFE-C/PTFE electrode was used to enhance H2O2 in-situ electro-generation and the electro-peroxone process (EPP) treatment of leachate. Various analytical methods results were applied to prove that the PTFE-C/PTFE electrode greatly improved the performance of H2O2 generation and electrode stability. The effects of initial pH, current intensity, ozone flow and Cl- concentration on the removal of NH4+ and chemical oxygen demand (COD) from landfill leachate were studied in the EPP with PTFE-C/PTFE as cathode (MEPP) by one factor at a time (OFAT) method. The initial pH value 7.5, current intensity 300 mA, ozone flow 875 mg/h and Cl- concentration value 4198 mg/L were selected as the best operating parameters. A response surface methodology based on box-behnken design (BBD) was employed to optimize running conditions of the MEPP of leachate. After optimization, Mineralization efficiency of the NH4+ and COD was obtained to be 79.83% and 52.14%, and biochemical oxygen demand (BOD5)/COD ratio increased to 0.38 after 4 h. The removal curves of NH4+ and COD in the MEPP conforms to the zero-order and first-order reaction kinetics, respectively. Three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) analysis shows that MEPP has a good removal effect on organics in leachate. Energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis were carried out for the cathode sediment, which was mainly magnesium ion silicate precipitation and NaCl.

Impact of carbon/nitrogen ratio on the performance and microbial community of sequencing batch biofilm reactor treating synthetic mariculture wastewater.

The differences of cultured organism species, aquaculture model and supervisor mode lead to different carbon/nitrogen ratios in mariculture wastewater. Therefore, the performance, microbial community and enzymatic activity of sequencing batch biofilm reactor were compared in treating synthetic mariculture wastewater at different chemical oxygen demand/nitrogen (COD/N) ratios. Compared with COD/N ratio of 6, the ammonia-oxidizing rate and nitrite-oxidizing rate at COD/N ratio of 5, 4 and 3 increased by 3.66 % and 3.08 %, 11.19 % and 14.95 %, and 24.50 % and 32.54 %, respectively. Similarly, the ammonia monooxygenase and nitrite oxidoreductase activities increased by 3.50 % and 6.76 %, 11.09 % and 16.22 %, and 25.43 % and 39.19 % at COD/N ratio at 5, 4 and 3, respectively. However, the denitrifying rate and denitrification enzymatic activity declined with the decrease of C/N ratio from 6 to 3. The production, protein content and polysaccharide content of loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS) reduced with the decrease of COD/N ratio from 6 to 3. The abundance of nitrifying genera increased with the decrease of COD/N ratio from 6 to 3, whereas most of denitrification genera displayed a decreasing trend. The microbial co-occurrence pattern, keystone taxa and significant difference were altered with the decrease of COD/N ratio. Among the keystone taxa, Thauera, Denitromonas, Nitrosomonas and Denitratisoma had a close link with nitrogen transformation. The present results can provide some theoretical basis for evaluating the effect of carbon/nitrogen ratio on the nitrogen removal of biological wastewater treatment systems.

Comparison of the effects of salinity on microbial community structures and functions in sequencing batch reactors with and without carriers.

This study investigated and compared the microbial communities between a sequencing batch reactor (SBR) without carriers and a hybrid SBR with addition of carriers for the treatment of saline wastewater. The two systems were operated over 292 days with alternating aerobic/anoxic mode (temperature: 28℃, salinity: 0.0-3.0%). High removal efficiency of chemical oxygen demand (COD) and total inorganic nitrogen (TIN) was achieved in both the SBR (above 86.7 and 95.4% respectively) and hybrid SBR (above 84.4 and 94.0%) at 0.0-2.5% salinity. Further increasing salinity to 3.0% decreased TIN removal efficiency to 78.4% in the hybrid SBR. Steep decline of biodiversity and relative abundance of ammonia-oxidizing bacteria (AOB) contributed to the worse performance. More genera related to sulfide-oxidizing and sulfate-reducing bacteria were detected in the hybrid SBR than the SBR at 3.0% salinity. The abundance of halotolerant bacteria increased with the salinity increase for both reactors, summing up to 25.5% in the suspended sludge (S-sludge) from the SBR, 28.9 and 22.9% in the S-sludge and biofilm taken from the hybrid SBR, respectively. Nitrification and denitrification via nitrate was the main nitrogen removal pathway in the SBR and hybrid SBR at 0.0 and 0.5% salinity, while partial nitrification and denitrification via nitrite became the key process for nitrogen removal in the two reactors when the salinity was increased to 1.0-3.0%. Higher abundance of anaerobic ammonium-oxidizing (ANAMMOX) and sulfide-oxidizing autotrophic denitrification (SOAD) bacteria were found in the hybrid SBR at 3.0% salinity.

Effect of salinity and pH on dark fermentation with thermophilic bacteria pretreated swine wastewater.

The utilization of swine wastewater is affected by salinity and pH owing to the extensive use with seawater instead of domestic water as swine farm flushing water in coastal city. Therefore, swine wastewater pretreated with thermophilic bacteria was used as fermentation substrate in this work, the effects of salinity and pH on dark fermentation under mesophilic condition were investigated. The research showed that 1.5% salinity and pH 6.0 were the optimal conditions for hydrogen production with swine wastewater. The activity of hydrogenogen was inhibited at 3.5% salinity and pH 5.0. Soluble organic matter in substrate was accumulated under high salinity and alkaline conditions. The utilization of carbohydrate during dark fermentation was up to 61.1% at 1.5% salinity and 51.5% at pH 9.0. Enhancing of salinity and pH had an advantage in accumulation of total soluble metabolites. Acetate was the main metabolite during dark fermentation, and 1.5% salinity contributed to the formation of butyrate.

Effects of transient 3-chloroaniline shock loading on the performance, microbial community and enzymatic activity of sequencing batch reactor.

Chloroanilines from industrial wastewater can produce adverse effects on biological wastewater treatment systems due to their potential biotoxicity. The performance, nitrogen removal rate, microbial community and enzymatic activity of a sequencing batch reactor (SBR) were evaluated under transient 3-chloroaniline shock loading. After 40 mg/L 3-chloroaniline shock loading of 24 h on day 9, the chemical oxygen demand (COD) removal efficiency decreased from 90.71% on day 8 to 80.57% on day 11, and the NH4+-N removal efficiency reduced from 98.96% on day 8 to 35.51% on day 12. Subsequently, the COD and NH4+-N removal efficiencies gradually recovered to normal value. Compared with the absence of 3-chloroaniline shock loading, the ammonia-oxidizing rate (SAOR), nitrite-oxidizing rate (SNOR), nitrite-reducing rate (SNIRR) and nitrate-reducing rate (SNRR) decreased by 66.19%, 14.49%, 16.20% and 49.38% on day 11, respectively, and then they gradually recovered to normal value. The SAOR, SNOR, SNIRR and SNRR displayed the similar varying trends to the activities of ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase, respectively. The appearance of 3-chloroaniline promoted the microbial reactive oxygen species production and lactate dehydrogenase release. The transient 3-chloroaniline shock loading distinctly impacted the microbial richness and diversity. The present research results can provide theoretical basis and technical support for evaluating the effects of transient 3-chloroaniline shock on biological wastewater treatment systems, which is beneficial to take reasonable preventable measures to decrease the adverse effects on the bioreactor performance.

Accelerating waste sludge hydrolysis with alkyl polyglucose pretreatment coupled with biological process of thermophilic bacteria: Hydrolytic enzyme activity and organic matters transformation.

A novel pretreatment method combining thermophilic bacteria (TB) with alkyl polyglucose (APG) was employed to pretreat waste sludge for enhancing the sludge hydrolysis. TB combined with APG pretreatment was effective in the releasing of soluble chemical oxygen demand (SCOD), protein and carbohydrate in extracellular polymeric substances (EPS) when the dosage of APG was below 0.1 g/g TSS. The enhancement of SCOD, carbohydrates and protein in dissolved organic matter (DOM) was promoted by the synthetic effect of APG and TB, which provides more carbon and energy source to the subsequent biochemical processes in sludge digestion. Excitation-emission matrix (EEM) fluorescence spectroscopy revealed that the combined pretreatment was beneficial for the decrease of non-biodegradable materials and the increase of biodegradable materials in DOM, resulting in the enhancement of the biodegradation of waste sludge. The combined use of TB and 0.4 g/g TSS APG achieved the maximal activities of protease (1.8) and α-glucosidase (1.9), and the activities of protease and α-glucosidase were positively correlated to the dosage of APG. The combined pretreatment was advantageous for the sludge reduction and sludge stabilization.

The influence of Fe2+, Fe3+ and magnet powder (Fe3O4) on aerobic granulation and their mechanisms.

This study aimed to develop an aerobic granular sludge and understand the granulation process of the multi-iron ions. Four sequencing batch reactors (SBRs) were applied to elucidate the effect of Fe2+, Fe3+ and Fe3O4 addition on aerobic granulation. The results confirmed that the start-up time of aerobic granulation with Fe3O4 addition (11 days) was notably less than that with Fe2+ (16 days) and Fe3+ (27 days) addition. Larger granules achieved with Fe3O4 addition with a sludge volume index (SVI30) of 28.50 mL/g and settling velocity of 49.68 m/h. Scanning electron microscope (SEM) analysis further revealed that the presence of mineral crystal in the granule core with Fe2+ and Fe3O4 addition accelerated the granule formation and maintained the stability of the structure. Extracellular polymeric substances (EPS) were studied using three-dimensional-excitation emission matrix (3D-EEM) fluorescence spectra technology to gain a comprehensive view of the interactions between EPS and Fe2+, Fe3+ and Fe3O4. Around 94.76% and 97.68% removal rate was noted for COD and ammonia in the granulation process. Finally, the dominant functional species involved in biological nutrients removal and granule formation were identified by high throughput sequencing technology to assess the effects of Fe2+, Fe3+ and Fe3O4 to granule at the molecular level.

Salinity effect on simultaneous nitrification and denitrification, microbial characteristics in a hybrid sequencing batch biofilm reactor.

The effect of increasing salinity on nitrogen removal via simultaneous nitrification and denitrification, microbial activities and extracellular polymeric substances (EPS) were investigated in a hybrid sequencing batch biofilm reactor filled with soft combination carriers. In the influent salinity range from 1.0 to 2.0%, average COD, NH4+-N and TN removal efficiencies were higher than 97.1, 97.8 and 86.4% at the steady state. When salinity was increased to 2.5 and 3.0%, ammonium oxidation was obviously inhibited in the reactor. For both suspended sludge (S-sludge) and biofilm, specific ammonium oxidation rate, specific nitrite oxidation rate, specific oxygen uptake rate and dehydrogenase activity reduced with the increase of salinity. The quantity of total EPS increased with the increase of salinity from 1.0 to 2.0%. Generally, humic substances were the dominant composition of EPS in both S-sludge and biofilm, with the percentages of 43.9-54.0 and 43.8-64.6% in total EPS.

Effect of magnesium oxide nanoparticles on microbial diversity and removal performance of sequencing batch reactor.

The performance, microbial enzymatic activity and microbial community of a sequencing batch reactor (SBR) have been explored under magnesium oxide nanoparticles (MgO NPs) stress. The NH4+-N removal efficiency kept relatively stable during the whole operational process. The MgO NPs at 30-60 mg/L slightly restrained the removal of chemical oxygen demand (COD), and the presence of MgO NPs also affected the denitrification and phosphorus removal. The specific oxygen uptake rate, nitrifying and denitrifying rates, phosphorus removal rate, and microbial enzymatic activities distinctly varied with the increase of MgO NPs concentration. The appearance of MgO NPs promoted more reactive oxygen species generation and lactate dehydrogenase leakage from activated sludge, suggesting that MgO NPs had obvious toxicity to activated sludge in the SBR. The protein and polysaccharide contents of extracellular polymeric substances from activated sludge increased with the increase of MgO NPs concentration. The microbial richness and diversity at different MgO NPs concentrations obviously varied at the phylum, class and genus levels due to the biological toxicity of MgO NPs.

Microbiological aspects of thermophile pretreatment of activated sludge inhibiting electricity generation of microbial fuel cell.

Thermophile pretreatment of activated sludge greatly improves the biodegradability of sludge, but whether the pretreated products are suitable for the electricity generation of microbial fuel cells (MFCs) is still little known. In this study, municipal activated sludge pretreated by a thermophilic bacterium and heating, respectively, was separately fed into the MFCs. The performance of MFCs was examined and changes of anodic microbial communities were investigated with scanning electron microscopy and 16S rRNA gene high-throughput sequencing on the Illumina Miseq platform. The results showed that MFCs fed with heating-pretreated sludge performed preferably and the power density reached 0.91-2.86 W/m3. MFC anodes were covered with considerable Geobacter spp. However, the bioaugmentation of sludge with the thermophile was not able to support a high potential output although the pretreatment significantly increased the soluble chemical oxygen demand. The maximum power density approached 0.20 W/m3 even when the anolyte was regularly changed. It was observed that amending pH did not improve the performance of MFC. Investigation on this anodic microbial community found that the relative abundance of Lactobacillus spp. exceeded 91%. Consequently, the thermophile-pretreated products stimulated the growth of non-exoelectrogens and finally the niches of anodic biofilm were completely occupied by Lactobacillus spp.