Search

Oxygen vacancy rich TiO2 catalysts were placed in the back of a non-thermal plasma reactor to convert harmful ozone molecules into reactive oxygen species, which exhibited superior catalytic activity in the degradation of toluene.

The effect of cost-effective combined pretreatment on rice straw for lignin solubilization and the recovery of biomethane.

Graphene-based catalysts have been widely applied for catalytic ozonation. However, as it is difficult to obtain graphene with high structural precision, it is currently unfeasible to comprehend the relationships between the intrinsic structure of the layered carbon catalysts with its catalytic activities. Here, an advanced plasma-assisted etch strategy was used to fine tune the ozonation activity of monolayered graphene films by tailoring the defect types. Raman mapping indicated that the defects of the as-prepared monolayered graphene films were predominantly sp3, vacancy, and boundary-type defects, respectively. The roles and contributions of these active defects in manipulating the oxidative potential of monolayered graphene films were revealed by quenching experiments, electron paramagnetic resonance results, and density functional theory calculations. The catalytic results showed that the monolayered graphene films with boundary-like defects exhibited the best catalytic performance toward the degradation of sulfamethoxazole. This work contributes new insights into the design of high-efficiency carbonaceous catalysts by structuring additional defective sites.

Clean water shortages require the reuse of wastewater. The presence of organic substances such as humic acids in wastewater makes the water treatment process more difficult. Humic acids can significantly affect the removal of heavy metals and other such toxins. Humic acids is formed by the decomposition and transformation of animal and plant remains by microorganisms, and naturally exists in soil and water. It is necessary to degrade and remove humic acids from wastewater. As it seriously human health, effective technologies for removing humic acids from wastewater have attracted great interest over the past decades. This study compared existing techniques for removing humic acids from wastewater, as well as their limitations. Physicochemical treatments including filtration and oxidation are basic and key approaches to removing humic acids. Biological treatments including enzyme and fungi-mediated humic acids degradation are economically feasible but require some scalability. In conclusion, the integrated treatment processes are more significant options for the effective removal of humic acids from wastewater. In addition, humic acids have rich utilization values. It can improve the soil, increase crop yields, and promote the removal of pollutants.

Energy crisis and increasing rigorous management standards pose significant challenges for solid waste management worldwide. Several emerging diseases such as COVID-19 aggravated the already complex solid waste management crisis, especially sewage sludge and food waste streams, because of the increasingly large production year by year. As mature waste disposal technologies, landfills, incineration, composting, and some other methods are widespread for solid wastes management. This paper reviews recent advances in key sewage sludge disposal technologies. These include incineration, anaerobic digestion, and valuable products oriented-conversion. Food waste disposal technologies comprised of thermal treatment, fermentation, value-added product conversion, and composting have also been described. The hot topic and dominant research foci of each area are summarized, simultaneously compared with conventional technologies in terms of organic matter degradation or conversion performance, energy generation, and renewable resources production. Future perspectives of each technology that include issues not well understood and predicted challenges are discussed with a positive effect on the full-scale implementation of the discussed disposal methods.

A novel tubular bioreactor-enhanced floating treatment wetland (TB-EFTW) was developed for the in situ treatment of high nitrate river water. When compared with the enhanced floating treatment wetland (EFTW), the TB-EFTW system achieved 30% higher total nitrogen removal efficiency. Further, the average TN level of the TB-EFTW effluent was below the Grade IV requirement (1.5 mg/L) specified in Chinese standard (GB3838-2002). Microbial analysis revealed that both aerobic and anoxic denitrifying bacteria coexisted in the new system. The relative abundance of aerobic and anoxic denitrifiers were 42.69% and 22% at the middle and end of the tubular bioreactor (TB), respectively. It is reasonable to assume that effective nitrogen removal can mainly be attributed to the addition of solid carbon source and the spatial difference in DO distribution (oxic-anoxic areas in sequence) inside the TB. The initial investment cost and operating costs associated with the TB-EFTW system are approximately 14,000 and 3500 yuan per 1000 m

Thermophilic solid-state anaerobic digestion (SS-AD) of agricultural wastes, i.e., corn straw, cattle manure, and vegetable waste, was carried out in this study. The effects of temperature (40-60°C), initial solid content (ISC, 17.5-32.5%), and C/N ratio (15-32 : 1) on biogas production were evaluated using a Box-Behnken experimental design (BBD) combined with response surface methodology (RSM). The results showed that optimization of process parameters is important to promote the SS-AD performance. All the factors, including interactive terms (except the ISC), were significant in the quadratic model for biogas production with SS-AD. Among the three operation parameters, the C/N ratio had the largest effect on biogas production, followed by temperature, and a maximum biogas yield of 241.4 mL gVS-1 could be achieved at 47.3°C, ISC = 24.81 % , and C / N = 22.35 . After 20 d of SS-AD, the microbial community structure under different conditions was characterized by high-throughput sequencing, showing that Firmicutes, Bacteroidetes, Chloroflexi, Synergistetes, and Proteobacteria dominated the bacterial community, and that Firmicutes had a competitive advantage over Bacteroidetes at elevated temperatures. The biogas production values and relative abundance of OPB54 and Bacteroidia after 20 d of SS-AD can be fitted well using a quadratic model, implying that OPB54 and Bacteroidia play important roles in the methanogenic metabolism for agricultural waste thermophilic SS-AD.

The construction of a nonthermal plasma (NTP)-catalysts system is an efficient strategy for purifying organic waste gas. Up to now, developing stable, efficient, and environmental-friendly catalyst...

Excessive nitrogen emission is a common problem in the secondary effluents of rural wastewater treatment facilities. Nitrogen could be removed by constructed wetlands and ecological floating beds, but these techniques have low purification capacity in practice. Here, a novel tubular reactor-enhanced ecological floating bed was developed to enhance nitrogen removal of secondary effluents. We tested the feasibility of this system during a long-term operation. Results show that our system achieves a removal efficiency of secondary effluent N of 82.2% for 30 days after start-up and then maintains this efficiency for an additional 220 days. Dissolved oxygen was reduced from 2.92 to 0.23 mg L−1, and the CODCr/TN (C/N) ratio increased from 2.6 to 13.1 along the reactor channel. This finding is explained by the synergy between the unique tubular reactor configuration and the mixed filler: palm fiber and bagasse. This environment enhances the spatial distribution of nitrifiers and denitrifiers along the channel, which was further demonstrated by scanning electron microscopy and high-throughput sequencing.

Biohydrogen production from seagrass (SG) has gained much attention due to their chemical composition (carbohydrate rich biomass). In this study, an attempt was made to enhance the biohydrogen production from sea grass through novel ozone coupled rotor-stator homogenization (ORSH). The efficiency of the homogenization pretreatment was evaluated in terms of seagrass lysis and biohydrogen generation. Initially, sea grass was subjected to rotor-stator homogenization (RSH) to optimize its power input (5.4–19.1 W) and energy spent (0–1285 kJ/kg TS). RSH consumes specific energy of 510 kJ/kg TS to achieve seagrass lysis of 10.45%, whereas ORSH achieved 23.7% of seagrass lysis at less energy (212.4 kJ/kg TS) input. The outcome of the present study reveals ORSH reduced 58.3% of energy input and increased 55.9% of SG lysis when compared with RSH. Hence, a considerable amount of energy could be saved through this combinative pretreatment. Biohydrogenesis was done to evaluate and compare the biohydrogen production potential of ORSH sample. Higher ultimate biohydrogen production was achieved by ORSH (90.7 mL/g COD) than RSH (39.6 mL/g COD). A higher energy ratio of 1.17 could be achieved through ORSH.

Wastewater treatment is an essential aspect of the earth's sustainable future. However, different wastewater treatment methods are responsible for carbon discharge into the environment, raising environmental risks. Hence, such wastewater treatment methods are required that can minimize carbon release without compromising the treatment quality. Microbiome-based carbon sequestration is a potential method for achieving this goal. Limited studies have been carried out to investigate how microbes can capture and utilize CO

Granule formation, microstructure and microbial spatial distribution are crucial to granule stability and nitrogen removal. Here, an upflow blanket filter (UBF) reactor with porous fixed cylinder carriers was fabricated and operated for 234 days to investigate overall performance and the formation mechanism of anammox granules. Results showed that the UBF performed the highest nitrogen removal efficiency of 93.19 ± 3.39% under nitrogen loading rate of 3.6 kg-N/m

The objective of the present study is to improve the biohydrogen production from marine macroalgae (Ulva reticulate) by acidic - hydrogen peroxide (H2O2) induced microwave (AHMW) pretreatment. Higher soluble chemical oxygen demand (SCOD) release of 1450 mg/L and its liquefaction rate of 30.2% was achieved in microwave (MW) pretreatment with treatment time period of 15 mins. Varying concentration of H2O2 from 0.003 to 0.03 g/g TS were used in the optimal microwave power (40%) to enhance the organic release in H2O2 induced microwave pretreatment (HMW). Maximum liquefaction of 33.9% was obtained at the H2O2 concentration of 0.024 g /g TS. The combined HMW pretreatment under acidic (pH 4–6.5) show synergistic effect on organic release. At optimal pH 5, AHMW pretreatment shows the SCOD release of 1850 mg/L with its liquefaction of 38.5% at time of 10 min. Therefore, AHMW pretreatment significantly reduce the treatment time and increase liquefaction when compared to MW and HMW. The maximum biohydrogen production was observed as 92.5 mL H2/g COD in AHMW pretreatment.

Although oily sludge has tremendous resource recovery value, its high water content has hindered its treatment and reuse. This study systematically explored the technical feasibility of using Fe(II)-activated persulfate oxidation (Fe 2+ /S 2 O 8 2− ) to enhance the dewaterability of oily sludge. To identify the main factors controlling sludge dewatering, this study measured changes in chemical oxygen demand, ammonia nitrogen (NH 4 + -N) and extracellular polymeric substances (EPS). Results showed that at 0.1 mmol-Fe 2+ /g-VSS and 0.08 mmol-S 2 O 8 2− /g-VSS, capillary suction time (s) was reduced by roughly 36.1% within 1 min and dewaterability was strengthened strongly. Sulfate radicals originating from Fe 2+ /S 2 O 8 2− oxidized a large amount of EPS, leading to liberation of EPS-bound water. A similar declining trend in NH 4 + -N was evident as a result of the strong oxidizing ability of sulfate radicals. Further analysis via scanning electron microscopy and thermogravimetric-Fourier transform infrared spectrometry revealed that Fe 2+ /S 2 O 8 2− oxidation destroyed the water-oil-gel-like structure of the oily sludge, thereby accelerating the separation of solids and water while reducing CO 2 emissions during the subsequent pyrolysis. Therefore, oily sludge dewatering was enhanced significantly by the Fe 2+ /S 2 O 8 2− process.

Anaerobic co-digestion has attracted much attention due to its unique advantages compared with the anaerobic mono-digestion. In this work, the synergistic effect and biodegradation kinetics of sewage sludge (SS) and food waste (FW) were studied during anaerobic co-digestion. Biochemical methane potential (BMP) assay and three kinetic models were used to detect and analyze methane production potential during co-digestion under different ratios of SS and FW. The SS:FW ratios of 0.5:0.5 showed very high methane recovery, with the methane productivity increasing by 4.59 times (50.30 ± 10.37 mL/g-VS/day), the lag-phase shortening by 11.53 times (0.182 day) and the hydrolysis rate increasing by 3.88 times (0.334/day) compared with the SS mono-digestion. Moreover, correlation model parameter analysis indicated the Cone model has the best fitness to the experimental data. These results confirmed the superiority of co-digestion and the existence of synergy, which can greatly accelerate the biodegradation process and more effectively recover bioenergy.

Two types of novel municipal sewage sludge (SS) combined TiO2 photocatalysts (ST1 and ST2) were synthesized through calcination treatment under different atmospheres (air and N2). The morphology, structure, and chemical states of photocatalysts were characterized by SEM, XRD, EDS, FT-IR, Raman UV–Vis, BET, and TG-IR. The results showed that ST2 consisted of a mesoporous graphene-like structure (20.02 nm) displayed exhibited better visible light photocatalytic performances and the highest BET surface area and pore volume (92.97 m2 g−1 and 0.46 cm3/g). The doping of Carbon and transition metals (Al, Mg) in TiO2 strengthened visible-light response by lowering the band gap. The photocatalytic ability is evaluated in the degradation of tetracycline, which is a typical antibiotic in the aquatic environment. The ST2 photocatalytic efficiency under visible light than that of ST1 and TiO2. The enhancement is formed together by porous surface and lower band gap of ST2, which could offer more active sites and facilitate faster electron-hole pair separation. In addition, the sludge-TiO2 calcination in N2 (ST2) has the potential to reduce CO2 emission while recovering more energy from the sludge, which turned out to be a more cost-effective way to reutilization of sewage sludge compared with that of calcination in air.

Ferrous persulfate (Fe(II)/S2O82–) oxidation has gained much attention due to its outstanding oxidizability and high efficiency in upgrading waste activated sludge (WAS) dewaterability. Even though...

In order to strengthen in situ nitrogen removal of urban landscape water, a novel pilot-scale tubular bioreactor-enhanced floating treatment wetland (TB-EFTW) was constructed, and the long-term performance and responsible microbial mechanisms were investigated in this study. The results showed that the system could remove 81.5% nitrogen from the landscape water after 240 days' operation. Moreover, the contribution rate of plant absorption to nitrogen was low (8.3%), which indicated that microbial biotransformation rather than plant absorption played a more key role in nitrogen removal in TB-EFTW system. The declining dissolved oxygen (DO) concentration along the axial direction of tubular bioreactor (TB) resulted in the sequential bacterial community of nitrifying, aerobic denitrifying, and anoxic denitrifying bacteria in the front, middle, and final part of TB. High-throughput sequencing results demonstrated that the internal environment of the system realized the coexistence of nitrifying, aerobic denitrifying and anoxic denitrifying process. The reason was mainly because that oxic-anoxic (O-A) areas were formed in sequence along the axial direction of tubular bioreactor. Overall, a unique advantage in nitrogen removal was achieved in TB-EFTW, which could provide important references for in situ treatment of urban landscape water. PRACTITIONER POINTS: TB-EFTW strengthened nitrogen removal for in situ urban landscape water treatment. Microbial conversion played a key role in nitrogen removal of the TB-EFTW system. The unique distribution of oxic-anoxic (O-A) areas was formed in sequence along the TB. Nitrification, aerobic, and anoxic denitrification were synergistically involved in the TB.

Given the aggravated greenhouse effect caused by CO2 and the current energy shortage, CO2 capture and reuse has been gaining ever-increasing concerns. Microbial Electrolysis Cells (MECs) has been considered to be a promising alternative to recycle CO2 bioelectrochemically to low-carbon electrofuels such as CH4 by combining electroactive microorganisms with electrochemical stimulation, enabling both CO2 fixation and energy recovery. In spite of the numerous efforts dedicated in this field in recent years, there are still many problems that hinder CO2 bioelectroconversion technique from the scaling-up and potential industrialization. This review comprehensively summarized the working principles, extracellular electron transfers behaviors, and the critical factors limiting the wide-spread utilization of CO2 electromethanogenesis. Various characterization and electrochemical testing methods for helping to uncover the underlying mechanisms in CO2 electromethanogenesis have been introduced. In addition, future research needs for pushing forward the development of MECs technology in real-world CO2 fixation and recycling were elaborated.

This study reports the result of sodium citrate induced exopolymer extraction on the photocatalytic thin film (TiO2) pretreatment efficiency of waste activated sludge (WAS). TiO2 is immobilized through DC spluttering method followed by annealing process. The exopolymer removal of 94.2% by sodium citrate (0.05 g/g SS) promotes better disintegration. This TiO2 thin film efficiently extricate the intracellular components of exopolymer extracted sludge at 50 min increasing the solubilization to 19.33%. As a result, the exopolymer extracted sludge shows high methane generation (0.24 gCOD/gCOD) than the other (pretreated sludge without exopolymer removal – 0.12 gCOD/gCOD and raw sludge without treatment – 0.075 gCOD/gCOD). The methane generated in sodium citrate induced TiO2 thin film pretreated sludge is 398.99 kWh. In cost analysis, it gives net cost of −57.46 USD/ton of sludge. In addition, the proposed method also accounts 51.3% of solid reduction.

Sludge management represents a critical challenge because of complex compositions and poor dewaterability. Fe

Bioelectrochemical regulation represents a newly emerging strategy to enhance anaerobic digestion (AD) of biowastes. Herein, a novel microbial electrolysis cell (MEC) system, equipped with a pair of carbon brush anode and hybrid Ti/RuO

CO2 bioelectromethanosynthesis represents a promising strategy for the capture and utilization of CO2. In such process, the continuous generation of electron (e-) and proton (H+) in anodic oxidation are of prime importance for the efficient cathodic CO2 electroreduction and process stability. Proton transfer, however, is very easy to be hindered due to the fouling of proton exchange membrane (PEM). In this study, an artificial channel in microbial electrolysis cell (MEC) was proposed to strengthen the transport of protons from anodic to cathodic compartment, and H+-rich anolyte was semi-continuously circulated to the cathodic chamber to provide protons for CO2 electroreduction. The results indicated that the daily CH4 yield in cathode with anolyte circulation (18.5 mL/d·L-reactor) was 5.4-fold higher than that without circulation (2.9 mL/d·L-reactor). Meanwhile, efficient anodic biodegradation of organic components was observed with COD, proteins and polysaccharides removal of up to 95.6 ± 1.9%, 96.3 ± 3.7% and 99.1 ± 0.2% respectively, which supplied a continuous e-/H+ donor for CO2 electroconversion. 16S rRNA gene pyrosequencing analysis identified a large number of proteins-utilizing Bacteroidetes (14.11%) and polysaccharides-consuming Thermotogae (18.49%) in anodic biofilm, conductive to the biodegradation of organic components. Moreover, a high abundance of Methanobacterium (81.07%) was detected to prevail in cathodic biofilm, demonstrating the occurrence of highly enhanced CH4 bioelectrosysthesis. The syntrophic and symbiotic relationship was established in the dual-bioelectrode system, creating a beneficial environment and an energy-efficient approach for biowaste refinery and CO2 electromethanosynthesis.

Purified terephthalic acid (PTA) wastewater with properties of poor biodegradation and high toxicity is produced from refining and synthesis of petrochemical products. In this study, a lab-scale hollow fiber membrane bioreactor (HF-AnMBR) fed with synthetic PTA wastewater was operated over 200 days with stepwise decreased hydraulic retention time (HRT) to investigate the long-term performance, membrane fouling mechanism and microbial community evolution. Results showed that a stable chemical oxygen demand (COD) removal rate of 65.8 ± 4.1% was achieved at organic loading rate of 3.1 ± 0.3 g-COD/ L -reactor/d and HRT 24 h, under which the methane production rate reached 0.33 ± 0.02 L/ L -reactor/d. Further shortening HRT, however, led to the decreased COD removal efficiency and low methane bioconversion. A mild membrane fouling occurred due to the production of colloidal biopolymers and the interaction between increased colloidal substances secreted/cracked by microorganisms and membrane interface. Further 16S rRNA analysis indicated that microbial diversity and richness had changed with the variation of HRT while Methanosaeta, and Methanolinea species were always the dominant methanogens responsible for methane production. The results verify that HF-AnMBR is an alternative technology for PTA wastewater treatment along with energy harvesting, and provide a new avenue toward sustainable petrochemical wastewater management.

Bioeletromethanogenesis, as a cutting-edge option to capture CO2 and produce multi-carbon biofuels, has received extensive attraction. However, how electroactive biofilm (EAB) as the biocatalyst drives CO2 electromethanogenesis is still not well recognized. In this study, a two-chamber bioelectrochemical cell equipped with a hybrid skirt-shaped cathode was constructed and the electrocatalytic performance of EAB and the electron shuttling mechanisms involved in extracellular electron transfer (EET) were systematically studied. The EAB colonizing on biocathode showed an excellent cathodic electrocatalytic activity and the minimum charge transfer resistance. The CH4 production rate of 298.0 ± 46.7 mL/L/d was obtained at the cathodic potential of −1.0 V vs. Ag/AgCl with the highest Coulombic efficiency of 75.8 ± 9.9%. The gel-like extracellular polymeric substances, secreted by EAB, facilitated the adhesion/aggregation of microbes and EAB development. Further analysis suggested that CO2 electromethanogenesis exhibited a positive association with Methanobacterium (54.4%) in EAB. Moreover, metagenome analysis confirmed the presence of direct EET-related genes (i.e., hdrA, ehaA, and ehbC), which accelerated the formation of corresponding functional protein complexes (particularly heterodisulfide reductase A, HdrA) and electron exchange. The mechanism for electron shuttling process in catalyzing CO2 electromethanogenesis was further proposed. This study provides a new insight into direct extracellular electron transfer (DEET) mechanisms of CO2 electromethanogenesis, and is useful for promoting EAB electrocatalytic activities and CO2 emission reduction and reuse.

Significant advances in the design of bioelectrochemical systems (BES) have promoted these applications to be seen as contemporary biotechnological platforms. However, notable issues in system architecture are still to be addressed and overcome, in particular concerning the membrane separators, which rely widely on polymers. These architectural components play a key-role in facilitating the transport of ions (i.e. protons) between the (compartments containing the) electrodes and therefore, their properties substantially influence the overall BES performance. This article aims presenting an up-to-date survey on the important accomplishments and promising outlooks with polymer-based membranes (both porous/non-porous, charged/uncharged) applied in BES (first and foremost microbial fuel cells, MFCs) that could drive this technology towards enhanced efficiency. Because of the interdisciplinary concept of BES, it attracts attention from scientists and engineers involved in environmental biotechnology, microbial electrochemistry and applied material sciences and as a result, this review paper would target the audience of these fields with particular interest on the progress with membrane separators fabricated with various polymeric materials.