Impact of co-substrate molecular weight on methane production potential, microbial community dynamics, and metabolic pathways in waste activated sludge anaerobic co-digestion.

Proteins and carbohydrates are important organics in waste activated sludge, and greatly affect methane production and microbial community composition in anaerobic digestion systems. Here, a series of co-substrates with different molecular weight were applied to investigate the interactions between microbial dynamics and the molecular weight of co-substrates. Biochemical methane production assays conducted in batch co-digesters showed that feeding high molecular weight protein and carbohydrate substrates resulted in higher methane yield and production rates. Moreover, high-molecular weight co-substrates increased the microbial diversity, enriched specific microbes including Longilinea, Anaerolineaceae, Syner-01, Methanothrix, promoted acidogenic and acetoclastic methanogenic pathways. Low-molecular weight co-substrates favored the growth of JGI-0000079-D21, Armatimonadota, Methanosarcina, Methanolinea, and improved hydrogenotrophic methanogenic pathway. Besides, Methanoregulaceae and Methanolinea were indicators of methane yield. This study firstly revealed the complex interactions between co-substrate molecular weight and microbial communities, and demonstrated the feasibility of adjusting co-substrate molecular weight to improve methane production process.

Effect of probiotics and synbiotics on complications of wound infection after colorectal surgery: A meta-analysis.

Wound infection is a serious complication that impacts the prognosis of patients after colorectal surgery (CS). Probiotics and synbiotics (Pro and Syn) are live bacteria that produce bacteriostatic agents in the intestinal system and have a positive effect on postoperative wound infections. The purpose of this study was to evaluate the effect of Pro and Syn on complications of wound infection after CS. In November 2023, we searched relevant clinical trial reports from Pubmed, Cochrane Library, and Embase databases and screened the retrieved reports, extracted data, and finally analysed the data by using RevMan 5.3. A total of 12 studies with 1567 patients were included in the study. Pro and Syn significantly reduced total infection (OR, 0.44; 95% CI, 0.35, 0.56; p < 0.00001), surgical incision site infection (SSI) (OR, 0.61; 95% CI, 0.45, 0.81; p = 0.002), pneumonia (OR, 0.43; 95% CI, 0.25, 0.72; p = 0.001), urinary tract infection (OR, 0.28; 95% CI, 0.14, 0.56; p = 0.0003), and Pro and Syn did not reduce anastomotic leakage after colorectal surgery (OR, 0.84; 95% CI, 0.50, 1.41; p = 0.51). Pro and Syn can reduce postoperative wound infections in patients with colorectal cancer, which benefits patients' postoperative recovery.

Effect of freeze-thaw frequency plus rainfall on As and Sb metal(loid)s leaching from the solidified/stabilized soil remediated with Fe-based composite agent.

The composite agent of ferrous sulfate, fly ash, and calcium lignosulfonate (FFC) can remediate the soil contaminated by As and Sb under cyclic freeze-thaw (F-T) via stabilization/solidification (S/S). However, the impact of high-frequency F-T cycles on the leaching behavior and migration of As and Sb in FFC-treated soils remains unclear. Here the leaching concentrations, heavy metal speciation (Wenzel's method), and Hydrus-1d simulations were investigated. The results showed that FFC effectively maintained the long-term S/S efficiency of arsenic remediation subject to an extended rainfall and freeze-thaw cycles, and stabilized the easily mobile form of As. The short-term S/S effect on Sb in the remediated soils suffering from F-T cycles was demonstrated in the presence of FFC. In a 20-year span, the mobility of Sb was affected by the number of F-T cycles (FT60 > FT20 > FT40 > FT0) in soil with a depth of 100 cm. As leaching progressed, FFC slowed the upward proportion of adsorbed As fractions but converted parts of the residual Sb to the form of crystalline Fe/Al (hydro) oxide. Moreover, the adsorption rate and capacity of As also preceded that of Sb. Long-term curative effects of FFC could be observed for As, but further development of agents capable of remedying Sb under cyclic F-T and long-term rainfall was needed. The predictive results on the migration and leaching behavior of heavy metals in S/S remediated soils may provide new insight into the long-term assessment of S/S under natural conditions.

Sludge dewaterability improvement with microbial fuel cell powered electro-Fenton system (MFCⓠEFs): Performance and mechanisms.

Throughout the entire process of sludge treatment and disposal, it is crucial to explore stable and efficient techniques to improve sludge dewaterability, which can facilitate subsequent resource utilization and space and cost savings. Traditional Fenton oxidation has been widely researched to enhance the performance of sludge dewaterability, which was limited by the additional energy input and the instabilities of Fe2+ and H2O2. To reduce the consumption of energy and chemicals and further break the rate-limiting step of the iron cycle, a novel and feasible method that constructed microbial fuel cell powered electro-Fenton systems (MFCⓅEFs) with ferrite and biochar electrode (MgFe2O4@BC/CF) was successfully demonstrated. The MFCⓅEFs with MgFe2O4@BC/CF electrode achieved specific resistance filtration and sludge cake water content of 2.52 × 1012 m/kg and 66.54 %. Cellular structure and extracellular polymeric substances (EPS) were disrupted, releasing partially bound water and destroying hydrophilic structures to facilitate sludge flocs aggregation, which was attributed to the oxidation of hydroxyl radicals. The consistent electron supply supplied by MFCⓅEFs and catalytically active sites on the surface of the multifunctional functional group electrode was responsible for producing more hydroxyl radicals and possessing a better oxidizing ability. The study provided an innovative process for sludge dewaterability improvement with high efficiency and low energy consumption, which presented new insights into the green treatment of sludge.

Enhanced dewaterability of food waste digestate by biochar/potassium ferrate treatments: Performance and mechanisms.

The combined process of biochar (BC) and potassium ferrate (PF) offers a fascinating technique for efficient dewatering of digestate. However, the effects of BC/PF treatment on the dewaterability and mechanisms of FWD are still unknown. This study aimed to reveal the impact mechanisms of BC/PF treatment on digestate dewatering performance. Experimental results indicated that BC/PF treatment significantly enhanced the dewaterability of digestate, with the minimum specific resistance to filtration of (1.05 ± 0.02) × 1015 m·kg-1 and water content of 57.52 ± 0.51% being obtained at the concentrations of 0.018 g·g-1 total solid (TS) BC300 and 0.20 g·g-1 TS PF, which were 8.60% and 13.59% lower than PF treatment, respectively. BC/PF treatment proficiently reduced the fractal dimension, bound water content, apparent viscosity, and gel-like network structure strength of digestate, as well as increased the floc size and zeta potential of digestate. BC/PF treatment promoted the conversion of extracellular polymeric substances (EPS) fractions from inner EPS to soluble EPS, increased the fluorescence intensity of the dissolved compounds, and enhanced the hydrophobicity of proteins. Mechanisms investigations showed that BC/PF enhanced dewatering through non-reactive oxygen species pathways, i.e., via strong oxidative intermediate irons species Fe(V)/Fe(IV). BC/PF treatment enhanced the solubilization of nutrients, the inactivation of fecal coliforms, and the mitigation of heavy metal toxicity. The results suggested that BC/PF treatment is an effective digestate dewatering technology which can provide technological supports to the closed-loop treatment of FWD.

Deciphering the role of polystyrene microplastics in waste activated sludge anaerobic digestion: Changes of organics transformation, microbial community and metabolic pathway.

Microplastics are ubiquitous in the natural environment, which inevitably affect the relevant biochemical process. Nevertheless, the knowledge about the impacts of microplastics on organics transformation and corresponding microbial metabolism response in anaerobic environment is limited. Here, polystyrene (PS) microplastics were selected as model microplastics to explore their potential impacts on organics transformation, microbial community and metabolic pathway during sludge anaerobic digestion system operation. The results indicated that the PS microplastics exhibited the dose-dependent effects on methane production, i.e., the additive of 20-40 particles/g TS of PS microplastics improved the maximum methane yield by 3.38 %-8.22 %, whereas 80-160 particles/g TS additive led to a 4.78 %-11.04 % declining. Overall, PS microplastics facilitated the solubilization and hydrolysis of sludge, but inhibited the acidogenesis process. Key functional enzyme activities were stimulated under low PS microplastics exposure, whereas were almost severely inhibited due to the increased oxidative stress induced from excess PS microplastics. Microbial community and further metabolic analysis indicated that low PS microplastics improved the acetotrophic and hydrogenotrophic methanogenesis, while a high level of PS microplastics shifted methanogenesis from acetotrophic to hydrogenotrophic pathway. Further analysis showed that the reacted PS microplastics exhibited greater toxicity and ecological than the raw PS microplastics due to that they are more likely to adsorb contaminants. These findings revealed the dosage-dependent relationships between microplastics and organics transformation process in anaerobic environments, providing new insights for assessing the impact of PS microplastics on sludge anaerobic digestion.

A review of application of combined biochar and iron-based materials in anaerobic digestion for enhancing biogas productivity: Mechanisms, approaches and performance.

Strengthening direct interspecies electron transfer (DIET), via adding conductive materials, is regarded as an effective way for improving methane productivity of anaerobic digestion (AD). Therein, the supplementation of combined materials (composition of biochar and iron-based materials) has attracted increasing attention in recent years, because of their advantages of promoting organics reduction and accelerating biomass activity. However, as far as we known, there is no study comprehensively summarizing the application of this kind combined materials. Here, the combined methods of biochar and iron-based materials in AD system were introduced, and then the overall performance, potential mechanisms, and microbial contribution were summarized. Furthermore, a comparation of the combinated materials and single material (biochar, zero valent iron, or magnetite) in methane production was also evaluated to highlight the functions of combined materials. Based on these, the challenges and perspectives were proposed to point the development direction of combined materials utilization in AD field, which was hoped to provide a deep insight in engineering application.

Performance of high solids enzymatic hydrolysis and bioethanol fermentation of food waste under the regulation of saponin.

Bioethanol recovery from food waste through high solids enzymatic hydrolysis (HSEH) and high solids bioethanol fermentation (HSBF) alleviate the energy crisis. However, this cause decreased glucose and bioethanol yields due to the high solids content. In this study, saponin was introduced into food waste HSEH and HSBF systems to enhance the product yields. Under the regulation of saponin, the substrate released >90% of the theoretical reducing sugar. The glucose concentration increased by 137.41 g/L after 24 h of HSEH with 2.0% saponin. The bioethanol titer reached 73.2 g/L (1.0%-saponin). Untargeted metabolomics illustrating that saponin had higher antifungal properties at lower concentrations (0.5%-saponin) that caused a decrease in bioethanol yield. The addition of saponin concentrations of 1.0%∼3.0% promoted HSEH, HSBF, and the metabolism of Saccharomyces cerevisiae; thus, 1.0% was suggested for practical use. This study deepened the understanding of saponin in enhancing HSBF and provides theoretical support for further application.

Remediation of Cu, Cr(VI) and Pb polluted soil with industrial/agricultural by-products in seasonally frozen areas.

Soils contaminated with potentially toxic elements (PTEs) may face serious environmental problems and pose health risks. In this study, the potential feasibility of industrial and agricultural by-products as low-cost green stabilization materials for copper (Cu), chromium (Cr(VI)) and lead (Pb) polluted soil was investigated. The new green compound material SS âˆ¼ BM âˆ¼ PRP was prepared by ball milling with steel slag (SS), bone meal (BM), and phosphate rock powder (PRP) which had an excellent stabilization effect on contaminated soil. Under 20% SS âˆ¼ BM âˆ¼ PRP addition into the soil, the toxicity characteristic leaching concentrations of Cu, Cr(VI) and Pb were reduced by 87.5%, 80.9% and 99.8%, respectively, and the phytoavailability and bioaccessibility of PTEs were reduced by more than 55% and 23%. The freezing-thawing cycle significantly increased the activity of heavy metals, and the particle size became smaller due to the fragmentation of the soil aggregates while SS âˆ¼ BM âˆ¼ PRP could form calcium silicate hydrate by hydrolysis to cement the soil particles, which inhibited the release of PTEs. Different characterizations indicated that the stabilization mechanisms mainly involved ion exchange, precipitation, adsorption and redox reaction. Overall, the results obtained suggest that the SS âˆ¼ BM âˆ¼ PRP is a green, efficient and durable material for remediation of various heavy metal polluted soils in cold regions and a potential method for co-processing and reusing industrial and agricultural wastes.

Enhancing of pretreatment on high solids enzymatic hydrolysis of food waste: Sugar yield, trimming of substrate structure.

The development of high solids enzymatic hydrolysis (HSEH) technology is a promising way to improve the efficiency of bioenergy production from solid waste. Pretreatment methods such as ultrasound (USP), freeze-thaw (FTP), hydrothermal (HTP), and dried (DRD) were carried out to evaluate the effect and mechanism of the pretreatment methods on the HSEH of FW. The reducing sugar of HTP and DRD reached 94.75% and 94.92% of the theoretical value. HTP and DRD could reduce the crystallinity of FW. DRD resulted in lower alignment and the occurrence of fractures of the substrate and exposed the α-1,4 glycosidic bond of starch. The high destructive power of HTP and DRD reduced the obstacles caused by the high solid content. Moreover, DRD consumed only 27.62% of the total energy of HTP. DRD could be a promising pretreatment methods for glucose recovery for its high product yield, significant substrate destruction, and economic feasibility.

Carbonate-bound Pb percentage distribution in agricultural soil and its toxicity: Impact on plant growth, nutrient cycling, soil enzymes, and functional genes.

Metals pollution of lead in agricultural soils is a serious problem for food safety. Therefore, we investigated the toxic effects of carbonate-bound fraction Pb on agricultural soil from various aspects. The results revealed that a higher carbonate-bound fraction of Pb had more toxic effects on wheat growth, as evidenced by higher malondialdehyde (3.17 µmol g-1 FW) and lower catalase levels (9.77 µg-1 FW min-1). In terms of nutrient cycling, soil nutrients including carbon, nitrogen, and phosphorus would slow down transformation rates in high concentrations. Compared to carbon, nitrogen and phosphorus were more likely to be affected by the initial carbonate-bound fraction at the earlier stage. Increased Pb dosage may reduce the soil enzymes activity such as urease (119-50 U g-1) and phosphatase (3191-967 U g-1), as well as the functional genes of nitrogen degradation related nirK, nisS, and carbon related pmoA. Correlation analysis and structural equation modeling indicated that carbonate bound Pb could regulate nutrients cycle via functional genes inhibition, soil enzyme activity reduction and wheat growth suppression in agricultural soil. Our findings will help with polluted agricultural soil monitoring and regulation through microbial activity to ensure food safety.

Investigation of electrochemical properties, leachate purification, organic matter characteristics, and microbial diversity in a sludge treatment wetland- microbial fuel cell.

Sludge treatment wetland-microbial fuel cell (STW-MFC) is a unique sludge treatment process that produces bioelectricity, but its technology is still in its infancy. This study investigated the electrochemical properties, organic matter characteristics, leachate purification, and microbial community structure of STW-MFCs as affected by electrode location. When electrodes were placed in the filler layer, the STW-MFC system presented a higher power generation capacity (maximum output power density: 0.498 W/m3; peak cell voltage: 0.879 V) and organic matter degradation efficiency. The hydrophilic fraction was the main dissolved organic carbon fraction in sludge extracellular biological organic matter (EBOM) and leachate dissolved organic matter (DOM). Aromatics were mainly concentrated in the hydrophobic acid fraction. The UV-254 content of sludge EBOM decreased mainly in the hydrophilic and transphilic acid fractions. The excitation-emission matrix analysis showed that tryptophan-like protein was more easily eliminated than tyrosine-like protein. In addition, there was a strong correlation between voltage and NH4+ removal efficiency; a negative correlation between total chemical oxygen demand (TCOD), total nitrogen (TN), and total phosphorus (TP) removal efficiency, and a negative correlation between pH and TN, TP, and NH4+ removal efficiencies. High-throughput sequencing showed that the system was most abundant in Thermomonas, Geothrix and Geobacter when the electrodes were placed in the filled layer, while the levels of genes for membrane transport, carbohydrate metabolism and energy metabolism functions were higher than in other systems. This work will support STW- MFC widespread implementation by illuminating the underlying mechanics of different anode positions.

Mechanisms, performance, and the impact on microbial structure of direct interspecies electron transfer for enhancing anaerobic digestion-A review.

Direct interspecies electron transfer (DIET) has been received tremendous attention, recently, due to the advantages of accelerating methane production via organics reduction during anaerobic digestion (AD) process. DIET-based syntrophic relationships not only occurred with the existence of pili and some proteins in the microorganism, but also can be conducted by conductive materials. Therefore, more researches into understanding and strengthening DIET-based syntrophy have been conducted with the aim of improving methanogenesis kinetics and further enhance methane productivity in AD systems. This study summarized the mechanisms, application and microbial structures of typical conductive materials (carbon-based materials and iron-based materials) during AD reactors operation. Meanwhile, detail analysis of studies on DIET (from substrates, dosage and effectiveness) via conductive materials was also presented in the study. Moreover, the challenges of applying conductive materials in boosting methane production were also proposed, which was supposed to provide a deep insight in DIET for full scale application.

Effect of optimized intermittent mixing during high-solids anaerobic co-digestion of food waste and sewage sludge: Simulation, performance, and mechanisms.

Inadequate mixing has been proven to be a major cause of anaerobic digester failure. This study revealed the mechanism of mixing intervals on high-solids anaerobic co-digestion (HS-AcoD) of food waste (FW) and sewage sludge (SS). Optimized intermittent mixing time (15 min/h) was determined through computational fluid dynamics (CFD) simulation. Experimental results indicated that the simulated intermittent mixing could shorten digestion time and increase cumulative methane output (366.8 mL/gVS) compared with continuous mixing and unmixing. Mixing could considerably accelerate substrate solubilization and hydrolysis. Maximum rates of acidogenesis (53.35 %) and methanogenesis (49.41 %) were observed with an optimized intermittent mixing (15 min/h). Vigorous mixing induced apoptosis and disrupted syntrophic metabolism, whereas intermittent mixing promoted the syntrophic metabolism between Syntrophomonas and Methanobacterium, and led to an enrichment of genes involved in acidogenic and methanogenic pathways. These findings have important implications for the development of an optimized intermittent mixing strategy for maximizing HS-AcoD efficiency of FW and SS.

Insights into high-solids anaerobic digestion of food waste enhanced by activated carbon via promoting direct interspecies electron transfer.

High-solids anaerobic digestion (HS-AD) of food waste frequently confronted the acidification and failure under high organic loading rates (OLRs). Results indicated powdered activated carbon (PAC) addition significantly enhanced methane production and process stability than granular activated carbon, and columnar activated carbon at higher OLRs via accelerating the propionate consumption. Potential direct interspecies electron transfer (DIET) partners, including various syntrophic oxidation bacteria and methanogens, were enriched with the activated carbon (AC) addition. Furthermore, DIET contribution to methane production was 35% by PAC, predicated by the modified Anaerobic Digestion Model No.1 (ADM1). This study deeply elucidated the DIET mechanism and offered the potential foundations for the selection and applications of AC-based materials in HS-AD of food waste.

Effects of organic loading rates on high-solids anaerobic digestion of food waste in horizontal flow reactor: Methane production, stability and mechanism.

To maximize the methane production efficiency of high-solids anaerobic digestion (HSAD) of food waste (FW), a horizontal flow reactor was operated under mesophilic, semi-continuous condition at organic loading rates (OLRs) ranging from 1.00 to 13.80 kg-VS/(m3 d). The gas production, substrate transformation, and microbial community characteristics of the horizontal flow HSAD reactor were evaluated. The results indicated that the methane yield (0.173-0.516 L/(g d)) fluctuated with the increasing OLR, volumetric methane production rate (0.25-5.69 L/(L d)) increased with increasing OLR, and the volatile solids (VS) reduction rate ranged between 83.30% and 93.05%. The relationship of biogas or methane production with OLR and HRT in the horizontal flow HSAD reactor were characterized with an empirical equation. The concentrations of soluble COD and volatile fatty acid exhibited significant fluctuations, and free ammonia-nitrogen peaked at the OLR of 13.80 kg-VS/(m3 d). Microbial community analysis revealed that the methanogenic metabolic pathway changes along the propelling direction of the horizontal flow HSAD reactor from CH3COOH and H2/CO2 pathways to CH3COOH, H2/CO2, and H2/methyl co-dominant pathways. These results provide theoretical support for stable methane production from FW and deeper insight into horizontal flow HSAD for FW treatment.

Effects of substrate type on variation of sludge organic compounds, bioelectric production and microbial community structure in bioelectrochemically-assisted sludge treatment wetland.

A bioelectrochemical assisted sludge treatment wetland (BE-STW) is a promising technology used in the elimination of organic compounds and recovery of bio-energy. In this study, four BE-STW systems were constructed to investigate the effects of some substrates (i.e. graphite particles, zeolite, ceramsite, and gravel) on organic compounds biodegradation and transformation, electricity production, and anodic bacterial community. The maximum output voltages were 0.939, 0.870, 0.741 and 0.835 V, and the maximum power densities were 0.467, 0.143, 0.110, and 0.131 W/m3 for the graphite particles (BS-GP), zeolite (BS-Z), ceramsite (BS-C), and gravel (BS-G) systems, respectively. Also, the dissolved organic carbon (DOC) removal rates were 61.84%, 28.54%, 25.56%, and 18.34% in BS-GP, BS-G, BS-Z, and BS-C, respectively. The degradation of aromatic compounds in sludge extracellular biological organic matter (EBOM) was mainly due to the decrease of hydrophilic fraction (HPI) and transphilic acid fraction (TPI-A) contents. Moreover, aromatic proteins were preferentially removed in BS-Z. For BS-C, the tyrosine-like proteins and humic acid-like substances in TPI-A were totally removed. An excitation-emission matrix (EEM) analysis showed that the fluorescent intensity of the humic acid-like substances was the lowest in BS-GP, and no fluorescence peaks of fulvic acid-like substances were observed. Finally, at the genus level, Longilinea, Terrimonas, Ottowia, and Saccharibacteria_genera_incertae_sedis were the dominant bacteria in BE-STW, and Methylophilus was also only detected in BS-GP. These results confirmed that substrate materials have a significant impact on the preferentially degraded organic matter in BE-STWs, which can provide a theoretical basis for the practical application of STW in the future.

Insight into the organic matter degradation enhancement in the bioelectrochemically-assisted sludge treatment wetland: Transformation of the organic matter and microbial community evolution.

Sludge treatment wetland (STW) has been widely used to dewater and mineralize the various sludge, but the low degradation ability of organic matter can limit its application. Bioelectrochemistry has been proven to accelerate the degradation of organic compounds and recover bioenergy from the sludge. In this study, a bioelectrochemical-assisted sludge treatment wetland (BE-STW) system was constructed to determine the most common types of degraded organic matter and the functional bacterial community. It was found that the bioelectrochemistry process contributed to a further removal of the total chemical oxygen demand (TCOD) by 19% (±0.6) and the additional soluble chemical oxygen demand (SCOD) value was 64.10% (±0.63), with a voltage output of 0.961 V and a power density of 0.351 W/m3. The hydrophilic and hydrophobic acid fractions of the sludge were preferentially removed in BE-STW. The tryptophan-like protein and fulvic acid-like substances were totally removed, whereas, the hydrolysis of aromatic organic compounds in the neutral and hydrophobic acid fractions was enhanced. Also, the enrichment of Longilinea and Methylophilus improved the hydrolysis of organic matter. Moreover, the high relative abundance of Thauera, Dechloromonas, and Syntrophorhabdus could accelerate the degradation of aromatic compounds in the BE-STW system. The bacteria from the genus Geobacter was predominantly detected (2.48%) in the anodic biofilm on BE-STW. The results showed that bioelectrochemistry could improve the sludge stabilization degree in STW, accelerate the organic matter degradation and hydrolysis efficiency, and harvest bioelectricity, simultaneously. This technology can provide a new pathway to increase the efficiency of the traditional STW systems.

Removal trend of amoxicillin and tetracycline during groundwater recharging reusing: Redox sensitivity and microbial community response.

The abundant existence of antibiotics within the effluent of wastewater treatment plant seriously threatened their safety recharging. To investigate the fate and biodegradation of those toxic antibiotics within the soil aquifer system, typical antibiotics of amoxicillin (AMX) and tetracycline (TC) were selected and their removal mechanisms were investigated. Experimental results revealed that totally 93.4% and 87.2% of the AMX and TC recharged (10 µg/L) were, respectively, removed within 1 m depth column operation. Specifically, the aerobic biodegradation, abiotic processes and anoxic/anaerobic microorganism contributed as higher as 37.5%, 33.7% and 28.8% of the AMX reduction, via the controlling tests of NaN3 inhibition and soil sterilisations. By contrast, the percentage contribution of the TC was aerobic (54.3%) ˃abiotic processes (32.7%) ˃anoxic/anaerobic (13.0%), a higher aerobic degradation whereas weaker anoxic/anaerobic microorganism. Column systems (CSs) were constructed to study the effect of redox conditions (methanogenic, sulfate-reducing, nitrate-reducing, aerobic) on antibiotics degradation, and microbial community results revealed that Verrucomicrobia, Actinobacteria, Deinococcus-Thermus and Armatimonadetes contributed to the aerobic biodegradation of TC. For comparison, AMX could be efficiently degraded under nitrate reduction (19.95%) > sulfate reduction (16.64%) > methanogenic (9.53%), and Actinobacteria, Bacteroidetes and Verrucomicrobia were the dominant bacteria for AMX degradation. This study provided optimal directions for antibiotics removal within the groundwater recharging systems and is conducive to obtain highly value-added reclaimed water.

Simulation and prediction of electrooxidation removal of ammonia and its application in industrial wastewater effluent.

A FLUENT software able to predict and assess the electrooxidation of ammonia from the simulation of ammonia concentration and flow field distribution was developed in this study. The flow field-based models of ammonia removal were simulated and modified through the experimental results. The parameter of reaction constant k is corrected to 0.00195, and the modified model fitted well with experimental values, with the error less than 4%. The electrode depth of 4 cm was assessed to be optimal for ammonia removal based on the comparison of the simulation results on ammonia concentration and flow field distribution. The prediction result applied in the industrial wastewater treatment indicated that complete could be achieved at 0.27 Ah/L, and about 50% of total nitrogen was removed at 0.8 Ah/L. About 7% of chloride ions were converted into inorganic by-products, indicating low biological toxicity and risk on environment. The energy consumption increased with the promotion of removal efficiency of total nitrogen, requiring 5.4 kWh/m3 to remove 50% total nitrogen at 0.8 Ah/L. The results show the practicability and feasibility of this FLUENT software tool on the simulation and prediction of electrooxidation process, which can provide the simulation parameter settings for the subsequent application. PRACTITIONER POINTS: A FLUENT software based on the simulation of ammonia concentration and flow field distribution was able to predict and assess ammonia electrooxidation. A modified model is provided with a rate constant k of 0.00195 and the distinction of 4% with experimental results. The optimal electrode depth was predicted to be 4 cm via the obtained model. Complete ammonia and about 50% of total nitrogen could be at 0.27 Ah/L and 0.8 Ah/L, receptively. About 7% of chloride ions were converted into inorganic by-products in industrial wastewater with high chloride.