Oxidation-reduction Potential Research Articles

Removal of tetracycline and chloramphenicol through constructed wetlands: Roles of plants, substrates, and microbial fuel cells

In this study, wastewater was analyzed for the presence of the antibiotics, tetracycline (Tet) and chloramphenicol (Chlor). Additionally, the antibiotic removal capacities of constructed wetland systems, with interacting macrophytes (Lemna gibba and Azolla filiculoides), substrates (sand and silt) and with or without microbial fuel cells (MFCs), were examined. To find the ideal wetland combination, a randomized 23 factorial design was applied, resulting in eight combinations in triplicate. The initial and final concentrations of antibiotics in the aquatic medium and in plants at the end of the experiment were measured with a high-performance liquid chromatography-diode array detector (HPLC-DAD) to verify the absorption rate. The results showed average Tet and Chlor concentration in wastewater samples 4.25 ± 3.95 and 1.87 ± 0.07 μg/L, respectively. All wetland types performed efficiently, removing a maximum of 100% tetracycline and chloramphenicol and a minimum of 99.45% and 97.84% Tet and Chlor, respectively. The average absorption of Tet and Chlor was 3.13 and 0.36 μg/g, respectively, in A. filiculoides; and the average absorption of Tet and Chlor was 2.08 and 0.08 μg/g, respectively, in Lemna. L. gibba had a higher biomass increase and a better relative growth rate than Azolla. In relation to electrical production, at first, all treatments were affected by the antibiotics; however, production increased as time progressed. Finally, the physicochemical parameters that improved with treatment were oxygen, oxidation-reduction potential and pH, whereas conductivity, dissolved solids, and salinity were most influenced by the silt substrate. Overall, although no wetland was ideal, all combinations were efficient at removing antibiotic contaminants.

The Impact of a Pulsed Light Stream on the Quality and Durability of the Cold-Stored Longissimus Dorsal Muscle of Pigs.

The purpose of this study was to investigate the effect of pulsed light application (exposure to a pulsed light beam (PL) of 400 Hz for a period of 60 s, with an energy dose of 600 mW and wavelengths of 660 and 405 nm) on the physicochemical, technological, and sensory properties, as well as the nutritional value and shelf life of cold-storage pig longissimus dorsi muscle. Each muscle was divided into six parts, three of which were control samples, and the rest were exposed to pulsed light. The detailed laboratory tests of the meat were conducted 1, 7, and 10 days after slaughter. The meat was cold stored at +3 °C ± 0.5 °C. The study showed that the application of pulsed light has a favorable effect on lowering the TBARS index, oxidation-reduction potential, and water activity values. In addition, the application of PL had no statistically significant effect on the variation in the perception of selected sensory characteristics of meat. Furthermore, PL processing, as a low-energy-intensive method that can be environmentally friendly and thus have a large potential for implementation, is an innovative way to extend the shelf life, especially of raw meat, without a negative impact on its quality. This is of particular importance for food security (especially in the quantitative and qualitative aspects of food, but also in terms of food safety).

Effect of high hydrostatic pressure processing on the rennet coagulation kinetics and physicochemical properties of sheep milk rennet-induced gels

The effects of high hydrostatic pressure on the constituents and coagulation ability and their effect on cheese production of sheep milk have not been studied in detail. The objective of this work was to evaluate the effect of high hydrostatic pressure processing on the coagulation kinetics and physicochemical properties of sheep milk and to explore how such treatment could improve the cheesemaking process. Five batches of milk were tested: 1 untreated control batch and 4 batches each subjected to a different pressure (150, 300, 450, or 600 MPa) for 5 min at 10°C. As treatment pressure increased, values of electrical conductivity and oxidation-reduction potential were found to decrease. However, no significant reduction in pH was recorded. Treatment pressures >300 MPa produced milk with lower lightness (luminosity) and a more yellow and green hue. Pressures >150 MPa resulted in micellar fragmentation, as well as significant increases in particle size, viscosity, and water-holding capacity as a consequence of the denaturing of soluble proteins. High-pressure treatments increased the solubility of colloidal calcium phosphate, leading to a considerable increase in the concentration of minerals in the serum phase. The highest concentrations of calcium and phosphorus in the rennet whey of milk were reached at 300 MPa. Curd coagulation time was reduced by 28% at pressures >300 MPa, and an increase in the curd firming rate was observed. As treatment pressure increased to 450 MPa, the firmness, elasticity, and the percentage creep recovery of gels increased, whereas values of compliance and fracture strain were reduced. Thus, we can conclude that 300 MPa is the optimum treatment pressure for milk intended for cheesemaking by enzymatic coagulation. This pressure produced milk with optimal coagulation kinetics and water-holding properties with the least loss of fat and protein to the whey.

The Influence of CO2 Injection into Manure as a Pretreatment Method for Increased Biogas Production

Manure is considered a by-product or organic waste in cattle, pig, chicken or other animal breeding farms, which can be a valuable product as compost or feedstock for biogas production. The production of biomethane from biogas always copes with the formation of carbon dioxide (CO2) as a by-product. This CO2 may be recycled through the feedstock as a pretreatment to maximize homogeneity, and improve biogas yield and biogas quality. The CO2-pretreatment process of cow manure (CoM), chicken manure (ChM) and pig manure (PM) was performed in the continuously fed agitated reactor at 25 °C temperature and ambient barometric pressure. Biogas yield and composition exploration were performed in an anaerobic continuous feeding digester with controlled mesophilic (37 °C) environmental conditions. The CO2 pretreated PM, CoM and ChM yielded 234.62 ± 10.93 L/kgVS, 82.01 ± 3.19 L/kgVS and 374.53 ± 9.27 L/kgVS biomethane from feedstock volatile solids, respectively. The biomethane yield from CO2 pretreated CoM, ChM and PM achieved was higher over untreated manure by +33.78%, +28.76% and +21.78%, respectively. The anaerobic digestion process of tested feedstocks was stable, and the pH of the substrate was kept steady at a pH of CoM 7.77 ± 0.02, PM 8.07 ± 0.02 and ChM 8.09 ± 0.02 during all the experiment. The oxidation-reduction potential after pretreatment was within the optimal range (−255 ± 39.0 to −391 ± 16.8 mV) for anaerobic digestion. This process also had a positive effect on the energy generated from the feedstock, with ChM showing the greatest increase, from 2.38 MJ/kg to 3.06 MJ/kg.

Antifungal activity of 40 plant essential oil components against Diaporthe fusicola from postharvest kiwifruits and their possible action mode

The antifungal activity of essential oils is closely related to their components and contents. The study aimed to explore the structural activity of essential oil (EO) components against Diaporthe fusicola and modes of action. The results showed most of the tested compounds showed inhibitory effects on the growth of D. fusicola and carvacrol was the strongest one with half maximal effective concentration (EC50) of 11.21 μL/L. The chemical structures of the tested compounds had great influences on their antifungal activity, in which the presence of CHO group, CC group or Ar-OH group in any EO components significantly increase the antifungal potency, but the increment of carbon chain length of saturated fatty aldehyde decreased antifungal activity. In order to analyze the antifungal action mode of EO components, the correlations between EC50 and oxidation-reduction potential (ORP), cell-membrane permeability and respiration inhibition of the tested compounds were further evaluated. The results showed antifungal activities of these EO components seemed to be accomplished by increase of cell membrane permeability and inhibition of the respiration of D. fusicola. The levels of increased membrane permeability, inhibited respiration and ORP of chemicals were all significantly correlated with EC50. This results indicated the action mode of these EO components against D. fusicola may be associated with the increment of cell membrane permeability and respiration inhibition via disrupting redox homeostasis in fungal cells, and oxidation-reduction property could be used as a secondary indicator for screening the antifungal agent from EO components.

(Bio)dissolution of arsenopyrite coupled with multiple proportions of pyrite: Emphasis on the mobilization and existential state of arsenic

The formation of arsenic-bearing acid mine drainage (AMD) via the oxidation of arsenopyrite refuse ore has attracted significant attention. Pyrite, as main a concomitant mineral, is a crucial factor that affects the (bio)dissolution of arsenopyrite, but there are still some points on the detailed action mechanism under normal environmental conditions that need further study. In this study, the effect mechanism of pyrite with a systematic pyrite content (0, 10, 25, 50, 75, 90, and 100 wt %) on arsenopyrite oxidation and arsenic release in the presence of Acidithiobacillus ferrooxidans was investigated. The X-ray diffraction (XRD), scanning election microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical analyses were also carried out. Results showed that the existence of pyrite and Acidithiobacillus ferrooxidans significantly accelerated the dissolution of arsenopyrite and the oxidation of As (Ⅲ) to As (Ⅴ), resulting from the galvanic effect, an increase in the Fe3+/Fe2+ ratio and the oxidation–reduction potential (Eh) value, and a decrease in pH level. As the detected main intermediate products, element sulphur was considered as the dominating obstructive factor during arsenopyrite oxidation, while the added pyrite could accelerate its oxidation. Moreover, a close relationship between different mineral proportions and the galvanic effect was also observed and discussed. Finally, suggestions on AMD governance and source control are proposed.

Temporal Stability of Salmonella enterica and Listeria monocytogenes in Surface Waters Used for Irrigation in the Mid-Atlantic United States

Enteric bacterial pathogen levels can influence the suitability of irrigation water sources for fruits and vegetables. We hypothesize that stable spatial patterns of Salmonella enterica and Listeria monocytogenes levels may exist across surface water sources in the Mid-Atlantic U.S. Water samples were collected at four streams and two pond sites in the mid-Atlantic U.S. over 2 years, biweekly during the fruit and vegetable growing seasons, and once a month during nongrowing seasons. Two stream sites and one pond site had significantly different mean concentrations in growing and nongrowing seasons. Stable spatial patterns were determined for relative differences between the site concentrations and average concentration of both pathogens across the study area. Mean relative differences were significantly different from zero at four of the six sites for S. enterica and three of six sites for L. monocytogenes. There was a similarity between the mean relative difference distribution between sites over growing season, nongrowing season, and the entire observation period. Mean relative differences were determined for temperature, oxidation-reduction potential, specific electrical conductance, pH, dissolved oxygen, turbidity, and cumulative rainfall. A moderate-to-strong Spearman correlation (rs > 0.657) was found between spatial patterns of S. enterica and 7-day rainfall, and between relative difference patterns of L. monocytogenes and temperature (rs = 0.885) and dissolved oxygen (rs = -0.885). Persistence in ranking sampling sites by the concentrations of the two pathogens was also observed. Finding spatially stable patterns in pathogen concentrations highlights spatiotemporal dynamics of these microorganisms across the study area can facilitate the design of an effective microbial water quality monitoring program for surface irrigation water.

The Effect of Extraction Methods on Phytochemicals and Biological Activities of Green Coffee Beans Extracts.

The objectives of the present study consisted of identifying the impact of extraction methods and parameters held over the phytochemistry and biological activities of green coffee beans. Extraction processes belonging to two categories were performed: classical methods-maceration, Soxhlet extraction, and such innovative methods as turboextraction, ultrasound-assisted extraction, and a combination of the latter two. Total polyphenolic and flavonoid content, as well as in vitro antioxidant activity of the resulted extracts were spectrophotometrically determined. Extracts displaying the highest yields of bioactive compounds were subjected to High Performance Liquid Chromatography-Mass Spectrometry analysis. The extracts with the best phytochemical profiles were selected for biological activity assessment. In vivo, a model of plantar inflammation in Wistar rats was used to determine antioxidant activity, by evaluating the oxidative stress reduction potential, and anti-inflammatory activity. In vitro antimicrobial activity was also determined. The Soxhlet extraction and ultrasound-assisted extraction gave the highest bioactive compound yields. The highest total polyphenolic content was 2.691 mg/mL gallic acid equivalents and total flavonoid content was 0.487 mM quercetin equivalents for the Soxhlet extract subjected to 60 min extraction time. Regarding the antioxidant activity, ultrasound-assisted extraction reached the highest levels, i.e., 9.160 mg/mL Trolox equivalents in the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay and 26.676 mM Trolox equivalents in the FRAP (Ferric Reducing Antioxidant Power) assay, at a 30 min extraction time and 50 °C extraction temperature. The 60 min Soxhlet extract reached the highest level for the ABTS+ (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay, 16.136 mM Trolox equivalents, respectively. Chlorogenic acid was present in the highest concentration in the same Soxhlet extract, 1657.179 µg/mL extract, respectively. Sterolic compounds were found in high concentrations throughout all the analyzed extracts. A proportional increase between yields and extraction parameter values was observed. Increased inhibition of Gram-negative bacteria was observed. The finally selected Soxhlet extract, that of 60 min extraction time, presented a significant in vivo antioxidant activity, with a slight anti-inflammatory activity. Antioxidant levels were elevated after 2 h of extract administration. Pro-inflammatory cytokine secretion was not influenced by the administration of the extract.

Performance Evaluation of Hydroponic Wastewater Treatment Plant Integrated with Ensemble Learning Techniques: A Feature Selection Approach

Wastewater treatment and reuse are being regarded as the most effective strategy for combating water scarcity threats. This study examined and reported the applications of the Internet of Things (IoT) and artificial intelligence in the phytoremediation of wastewater using Salvinia molesta plants. Water quality (WQ) indicators (total dissolved solids (TDS), temperature, oxidation-reduction potential (ORP), and turbidity) of the S. molesta treatment system at a retention time of 24 h were measured using an Arduino IoT device. Finally, four machine learning tools (ML) were employed in modeling and evaluating the predicted concentration of the total dissolved solids after treatment (TDSt) of the water samples. Additionally, three nonlinear error ensemble methods were used to enhance the prediction accuracy of the TDSt models. The outcome obtained from the modeling and prediction of the TDSt depicted that the best results were observed at SVM-M1 with 0.9999, 0.0139, 1.0000, and 0.1177 for R2, MSE, R, and RMSE, respectively, at the training stage. While at the validation stage, the R2, MSE, R, and RMSE were recorded as 0.9986, 0.0356, 0.993, and 0.1887, respectively. Furthermore, the error ensemble techniques employed significantly outperformed the single models in terms of mean square error (MSE) and root mean square error (RMSE) for both training and validation, with 0.0014 and 0.0379, respectively.

Influence and mechanism of the vertical distribution of Cu, Cd, and Pbat a simulated sediment-water interface covered by degradable microplastics.

Currently research on microplastics in the environment focuses on non-degradable microplastics with little attention to research on degradable microplastics. This study involved a 400-day experiment in a simulated lake environment of three degradable microplastics, poly(ε-caprolactone) (PCL), polybutylene succinate (PBS), and poly(butylene adipate terephthalate) (PBAT) at the sediment water interface. Results showed that (1) for the three microplastics, Cd concentration showed a large change from 0 to 20mm in the water above the sediment interface; the adsorption of Cd, Pb, and Cu in a diffusive gradients thin film (DGT) device are the highest in PBAT micro plastic, followed by PCL and then PBS. (2) Diffuse flux (J) of the three degradable microplastics indicated that Cu, Cd, and Pb in the sediments come from the overlying water that was added to the simulation experiment. (3) Fourier transform infra-red spectroscopy (FTIR) for investigating the adsorption capacity of Cu, Cd, and Pb in the three degradable microplastics showed the absorption peak intensity increased and widened, and some adsorption sites changed. (4) Correlation analysis showed that the factors which most influenced diffusion flux for both water and sediments are oxidation-reduction potential (ORP), followed by organic matter (OM), pH, and electrical conductivity (EC).

Recent advances in constructed wetlands methane reduction: Mechanisms and methods.

Constructed wetlands (CWs) are artificial systems that use natural processes to treat wastewater containing organic pollutants. This approach has been widely applied in both developing and developed countries worldwide, providing a cost-effective method for industrial wastewater treatment and the improvement of environmental water quality. However, due to the large organic carbon inputs, CWs is produced in varying amounts of CH4 and have the potential to become an important contributor to global climate change. Subsequently, research on the mitigation of CH4 emissions by CWs is key to achieving sustainable, low-carbon dependency wastewater treatment systems. This review evaluates the current research on CH4 emissions from CWs through bibliometric analysis, summarizing the reported mechanisms of CH4 generation, transfer and oxidation in CWs. Furthermore, the important environmental factors driving CH4 generation in CW systems are summarized, including: temperature, water table position, oxidation reduction potential, and the effects of CW characteristics such as wetland type, plant species composition, substrate type, CW-coupled microbial fuel cell, oxygen supply, available carbon source, and salinity. This review provides guidance and novel perspectives for sustainable and effective CW management, as well as for future studies on CH4 reduction in CWs.

Supplemental oxygen did not significantly affect two-year mortality in patients at-risk for cardiovascular complications undergoing moderate- to high-risk abdominal surgery–A follow-up analysis of a prospective randomized clinical trial

BackgroundIn relatively healthy middle-aged patients, recent studies have shown that supplemental oxygen did not significantly increase one-year mortality after noncardiac surgery. If supplemental oxygen influences long-term mortality, specifically in elderly patients with cardiovascular risk-factors, remains unknown. Thus, we evaluated the effect of supplemental oxygen on two-year mortality in patients with cardiovascular risk factors undergoing moderate- to high-risk major abdominal surgery.MethodsThis is a follow-up study of a prospective, randomized, double-blinded, clinical trial. Two hundred fifty-eight patients, who were at least 45 years of age and at-risk for cardiovascular complications were randomly assigned to receive 80 vs. 30% oxygen during surgery and for the first two postoperative hours. Vital status was obtained from all patients 2 years after surgery using the national registry. Preoperative and postoperative maximum concentrations of NT-proBNP, Troponin T (TnT), Copeptin, von Willebrand Factor (vWF), static oxidation-reduction potential (sORP) and oxidation-reduction potential capacity (cORP) were tested for association with two-year mortality.ResultsThe median age of patients was 74 years (25th-75th percentile 70–78 years). 25.8% (95% CI: 17.3–32.4%) of patients in the 80% oxygen group and 22.3% (95% CI: 14.8–29.1%) in the 30% oxygen group died within 2 years after surgery. No significant difference in two-year mortality was found between patients, who received 80% oxygen concentration, versus patients, who received 30% oxygen concentration (estimated hazard ratio 1.145; 95% CI 0.693–1.893; p = 0.597). Preoperative Copeptin concentrations and postoperative maximum vWF activity were significantly associated with two-year mortality (p < 0.001).ConclusionOur results are consistent with previous studies, that showed that supplemental oxygen did not increase long-term mortality. Therefore, it is becoming more evident that supplemental oxygen may not have a significant effect on long-term outcome in patients undergoing major abdominal surgery.

Bacterial community structure in geothermal springs on the northern edge of Qinghai-Tibet plateau.

In order to reveal the composition of the subsurface hydrothermal bacterial community in the zones of magmatic tectonics and their response to heat storage environments. In this study, we performed hydrochemical analysis and regional sequencing of the 16S rRNA microbial V4-V5 region in 7 Pleistocene and Lower Neogene hot water samples from the Gonghe basin. Two geothermal hot spring reservoirs in the study area were found to be alkaline reducing environments with a mean temperature of 24.83°C and 69.28°C, respectively, and the major type of hydrochemistry was SO4-Cl·Na. The composition and structure of microorganisms in both types of geologic thermal storage were primarily controlled by temperature, reducing environment intensity, and hydrogeochemical processes. Only 195 ASVs were shared across different temperature environments, and the dominant bacterial genera in recent samples from temperate hot springs were Thermus and Hydrogenobacter, with both genera being typical of thermophiles. The correlation analysis showed that the overall level of relative abundance of the subsurface hot spring relied on a high temperature and a slightly alkaline reducing environment. Nearly all of the top 4 species in the abundance level (53.99% of total abundance) were positively correlated with temperature and pH, whereas they were negatively correlated with ORP (oxidation-reduction potential), nitrate, and bromine ions. In general, the composition of bacteria in the groundwater in the study area was sensitive to the response of the thermal storage environment and also showed a relationship with geochemical processes, such as gypsum dissolution, mineral oxidation, etc.

Methodology for In Situ Microsensor Profiling of Hydrogen, pH, Oxidation-Reduction Potential, and Electric Potential throughout Three-Dimensional Porous Cathodes of (Bio)Electrochemical Systems.

We developed a technique based on the use of microsensors to measure pH and H2 gradients during microbial electrosynthesis. The use of 3D electrodes in (bio)electrochemical systems likely results in the occurrence of gradients from the bulk conditions into the electrode. Since these gradients, e.g., with respect to pH and reactant/product concentrations determine the performance of the electrode, it is essential to be able to accurately measure them. Apart from these parameters, also local oxidation-reduction potential and electric field potential were determined in the electrolyte and throughout the 3D porous electrodes. Key was the realization that the presence of an electric field disturbed the measurements obtained by the potentiometric type of microsensor. To overcome the interference on the pH measure, a method was validated where the signal was corrected for the local electric field measured with the electric potential microsensor. The developed method provides a useful tool for studies about electrode design, reactor engineering, measuring gradients in electroactive biofilms, and flow dynamics in and around 3D porous electrodes of (bio)electrochemical systems.

Assessment of Drinking Water Quality and the Efficiency of the Two Water Treatment Plants in UP, India

This study presents the analysis of the water quality and efficiency of two water treatment plants (370 MLD Palra Reservoir and 310 MLD Conventional Water Treatment Plant). These facilities are catering the water demand of Agra city, having a population of about 2.5 million people. Results have shown that the canal water in Pahansu at Bulandshahr District from the Ganga River has mainly two physical concerns; turbidity and total suspended solids. Other parameters like TDS (Total Dissolved Solids), Hardness, Alkalinity, ORP (Oxidation Reduction Potential) and E.C (Electrical Conductivity) were also measured, but their concentration met the BIS recommended values for mentioned water quality parameters. During the study, it was found that the average TSS concentration at Palra reservoir is 468 mg/l, and the same is removed by about 50% with the help of the sedimentation process. The initial turbidity level is about 10.55 NTU, whereas, after sedimentation, it is 9.12 NTU. After primary treatment, the raw water is conveyed to the 310 MLD Conventional Water Treatment Plant at Sikandara Agra through an under-gravity pipeline traversing 134kms. The Conventional Water Treatment Plant involves Coagulation, Flocculation, Sedimentation, Filtration and Disinfection Processes. Raw water at the inlet has turbidity and TSS around 16.9 NTU and 187 mg/l, respectively. About 50% turbidity removal and 70% TSS removal occur in the clari-flocculator, and the remaining get removed during the rapid sand filtration process, thus, giving final water free from turbidity and TSS. Other parameters of the treated water, like pH, Alkalinity, Hardness, TDS etc., are well within the prescribed limits.

Analisis Porositas, Tekstur, dan Morfologi Karbon Tempurung Nipah Hasil Pirolisis Suhu Tinggi Untuk Anoda Baterai Sekunder

Lithium-ion batteries are the recent main store of electrochemical energy that have been widely used for electronic equipment, electric vehicles, and also renewable energy storage such as wind and solar. Lithium-ion batteries have many electrochemical advantages but lithium availability in nature is reduced very quickly and its distribution is uneven throughout the world. Sodium is attractive as an alternative to lithium insertion for secondary batteries because of its abundant availability and oxidation reduction potential to standard hydrogen electrodes only 0.3 volts higher than lithium. This study aims to synthesize hard carbon from nipah shell biomass using thermal methods of low-temperature pyrolysis (lower than 200 oC) followed by high-temperature pyrolysis (higher than 1000 oC). Characterization is carried out by iodine number analysis to determine porosity and SEM-EDX to determine texture and morphology. The result of the analysis of carbon iodine number is 346.86 mg/g while SEM-EDX analysis showed that carbon has a structure similar to a combination of graphene and nano-tube carbon.

Study on Growth Influencing Factors and Desulfurization Performance of Sulfate Reducing Bacteria Based on the Response Surface Methodology.

Sulfate reducing bacteria (SRB) can simultaneously and efficiently remove SO4 2- and heavy metal ions from acid mine drainage (AMD). Environmental factors have a great influence on AMD treated by SRB metabolic reducing sulfate. Providing a suitable growth environment can improve the effect of SRB on AMD. In this paper, the wet soil around the tailings reservoir was used as seed mud to enrich SRB. Based on the single factor experiment method and the response surface methodology (RSM), the effects of temperature, environmental pH value, S2- concentration, and COD/SO4 2- on the growth of SRB were analyzed. The effects of environmental factors such as temperature and pH on the desulfurization performance of SRB were investigated. The results showed that the growth curve of SRB was "S" type. SRB was in the logarithmic phase when cultured for 14-86 h, with high activity and vigorous growth metabolism. When the temperature is 32∼35 °C, the activity of SRB is the highest. With the gradual increase of the S2- concentration in the culture system, SRB activity will be inhibited and even lead to SRB cell death. The environmental pH value that SRB can tolerate is 5∼8, and when the environmental pH value is 7∼8, the SRB activity is the strongest. The chemical oxygen demand (COD)/SO4 2- that is most suitable for SRB growth is 2. The optimal growth conditions of SRB obtained from RSM were as follows: culture temperature at 34.74 °C, initial pH being 8.00, and initial COD/SO4 2- being 1.98. Under these conditions, the OD600 value was 1.45, the pH value was 9.37, the oxidation reduction potential (ORP) value was -399 mV, and the removal percentage of SO4 2- was 88.74%. The results of RSM showed that the effects of culture temperature, environmental pH, and COD/SO4 2- on the desulfurization performance of SRB were extremely significant. The order of affecting the removal of SO4 2- by SRB was environmental pH > temperature > COD/SO4 2-.

Promoted electron transfer in Fe2+/Fe3+ co-doped BiVO4/Ag3PO4 S-scheme heterojunction for efficient photo-Fenton oxidation of antibiotics

A Fe2+/Fe3+ co-doped BiVO4/Ag3PO4 S-scheme heterojunction catalyst was synthesized by a simple hydrothermal method and applied to achieve efficient photo-Fenton for antibiotics degradation (99.70 %). The co-doping of Fe3+/Fe2+ highlighted red shift of optical absorption edge (535–800 nm) and adjustable band structure of BiVO4/Ag3PO4. The collaborative system of photocatalytic and Fenton could maintain high catalytic activity and stability in the treat of simulated actual water and high efficiency within wide pH conditions (3–7). The degradation experiments were employed to show removal efficiency on tetracyclines and quinolones antibiotics including tetracycline (TC), ciprofloxacin (CIP), doxycycline (DO), levofloxacin (LEV), norfloxacin (NOR), and enrofloxacin (ENR). Mechanism exploration elaborated that the m-FBVO/APO composites with dominant Fe2+ preserved both high oxidation potential (<−0.33 eV vs NHE) and reduction potential (>2.45 eV vs NHE) through the constructed BiVO4/Ag3PO4 S-scheme heterojunction. Efficient e−/h+ pairs separation was further achieved through Fe3+/Fe2+ pairs cycling. And degradation pathway of TC was mainly investigated to verify its mineralization. This work provides a new sight towards catalytic mechanisms in heterogeneous photo-Fenton degradation systems.

Transition of source/sink processes and fate of ammonium in groundwater along with redox gradients

Ammonium (NH4+) retention/removal processes in groundwater are of great interest because of the continuous increase in nitrogenous compound loading due to anthropogenic activities. However, the transition of multiple co-occurring transformation processes that determine the fate of NH4+ in groundwater along a redox gradient remains underexplored. We selected a high nitrogen (N) groundwater system in the western Hetao Basin, China, to identify and quantify NH4+ source and sink processes, including mineralization, dissimilatory nitrate reduction to ammonium (DNRA), nitrification, and anammox, to better understand the dynamics of NH4+. Based on redox-sensitive parameters, that is, the oxidation-reduction potential (ORP) and NH4+ and nitrate (NO3−) contents, etc., the groundwater system was classified into three zones from upstream to downstream: zone I (oxidizing), zone II (moderately reducing), and zone III (strongly reducing). Using the 15N tracing technique, we found that NH4+ was mainly produced by mineralization while < 2% was produced by DNRA throughout the study area. Mineralization increased downstream because the supply of biodegradable N-containing compounds was augmented, which created a strong redox gradient to host a serial reaction chain. In zone I, NH4+ was mainly transferred to NO3− via nitrification, whereas in zones II and III, NH4+ was mainly transferred to N2 via anammox. The average NH4+ production/consumption ratios (P/C) in zones I, II, and III were 0.7, 6.9, and 51.1, respectively. Obviously, the NH4+ purification ability can only exceed the supply under aerobic conditions, thus suggesting that NH4+ will accumulate without limitation and be retained in strongly reducing groundwater. The situation of NH4+ accumulation would deteriorate over space and time in groundwater as human activities increase without an additional artificial supply of oxidants. The results provide mechanistic insights for quantitatively comprehending the dynamics and fate of NH4+ in groundwater, shedding light on groundwater NH4+ mitigation techniques.

Anti-scaling performances of different aged landfill leachates on PPR and ABS pipe materials.

Landfill leachate, because of its complex components, may cause pipe clogging during its collection and transportation, and pose a threat to the environment. This study considers two typical drainage pipe materials, i.e., polypropylene-random (PPR) and acrylonitrile-butadiene-styrene (ABS), to discriminate their anti-scaling performances through a landfill leachate immersion experiment. The results show that both PPR and ABS pipe materials immersed in the younger-aged leachate are prone to scaling. The mass concentrations of Ca2+ in the leachate play a key role in scale formation, followed by Mg2+, pH, oxidation-reduction potential (ORP), dissolved oxygen (DO), and Cl-. In particular, Ca2+, pH, and DO show a positive relationship in scaling, while Mg2+ acts in a negative relationship. Calcium carbonate is the major constituent of the scales, accounting for 72.3% of the total. The scaling on the surface of the PPR pipe material is more serious than that of the ABS pipe material, revealed by the corresponding weight increment that is 33% higher than that related to ABS during the experimental period. It is thus indicated that ABS has better anti-scaling performance, which may be an optional material selected for the system design of leachate collection and transportation.