Effect of different concentrations of substrate in microbial fuel cells toward bioenergy recovery and simultaneous wastewater treatment.

Microbial fuel cells (MFCS) is a promising and expanding technology able to eliminate various pollutants of wastewater while converting its chemical energy into power energy using biocatalysts. The potential application of double-chamber microbial fuel cell (DC-MFC) for chemical oxygen demand (COD) removal and generated power from wastewater in the different conditions is investigated. DC-MFC is operated with anaerobic sludge as an active biocatalyst in an anode section, an aerobic cathode section and a Nafion117 membrane as a separator. The performance of the bioreactor is determined with different concentrations of chemical oxygen demand (COD) loadings in the MFC process, in terms of COD removal, power generation and columbic efficiencies. The results illustrated that COD removal efficiency increased at the high concentrations of organic matter. So that at COD concentration of 2000.0 mg/L the highest COD removal efficiency (84%) was obtained. But with increasing substrate initial concentration to 10000.0 mg/L the efficiency decreased to 79%. The important outputs of the system like the highest voltage, maximum generated power, current density, and energy efficiency with the 100,000 mg/L COD are 447 mV, 50.7 mW/m2, 570.0 mA/m2, and 18.6%, respectively. The optical density levels increased due to bacterial growth while pH severely decreased in the anode chamber when using high-concentration substrates in the MFC.

Are photocatalytic processes effective for removal of airborne viruses from indoor air? A narrative review.

A wide variety of methods have been applied in indoor air to reduce the microbial load and reduce the transmission rate of acute respiratory diseases to personnel in healthcare sittings. In recent months, with the occurrence of COVID-19 pandemic, the role of portable ventilation systems in reducing the load of virus in indoor air has received much attention. The present study delineates a comprehensive up-to-date overview of the available photocatalysis technologies that have been applied for inactivating and removing airborne viruses. The detection methods for identifying viral particles in air and the main mechanisms involving in virus inactivation during photocatalysis are described and discussed. The photocatalytic processes could effectively decrease the load of viruses in indoor air. However, a constant viral model may not be generalizable to other airborne viruses. In photocatalytic processes, temperature and humidity play a distinct role in the inactivation of viruses through changing photocatalytic rate. The main mechanisms for inactivation of airborne viruses in the photocatalytic processes included chemical oxidation by the reactive oxygen species (ROS), the toxicity of metal ions released from metal-containing photocatalysts, and morphological damage of viruses.

Electrodisinfection of bacteria-laden in surface water using modified Ti electrode by antimony-and nickel-doped tin oxide composite.

Providing clean and safe drinking water by point of use (POU) disinfection methods has become a critical issue, especially in crises and epidemics. In this study, antimony-and nickel-doped tin oxide electrode (Ni-Sb-SnO2) was employed as an electrode for electro-catalytic disinfection of surface water. The synthetized electrodes were characterized using scanning electron microscope, linear sweep voltammetry and X-Ray diffraction techniques. The results revealed that the highest electrochemical disinfection efficiency was achieved by the Ni-Sb-SnO2 electrode under weak acidic conditions and its performance decreased with increasing pH towards alkaline environment. Based on the results, total coliform (TC) and fecal coliform (FC) were completely removed at current density of 0.67 mA cm-2. Moreover, the electrochemical disinfection of microorganisms showed that the process efficiency was directly proportional to increasing time and at 0.6 C cm-2 of charge passed, 3-log removal of the both indicators occurred after 15 min. The highest removal efficiency of TC and FC was also achieved at 8 mmol of NaCl concentration at <10 min of detention time. The results of this study depicted that the Ti/Ni-Sb-SnO2 electrode provides higher disinfection efficiency for the removal of TC and FC compared with Ti and SS/PbO2 electrodes. Moreover, the proposed system was able to completely eliminate heterotrophic, Streptococcus faecalis and Pseudomonas aerogenes indicators under optimal conditions. Therefore, it can be concluded that the proposed electrochemical system can be efficiency applied as a POU disinfection system for disinfection of water contaminated with microbial indicators, especially for crises and epidemics.

Sampling and detection of corona viruses in air: A mini review.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a strain of coronaviruses that causes coronavirus disease 2019 (COVID-19). In these days, the spread of the SARS-CoV-2 virus through the air has become a controversial topic among scientists. Various organizations provide standard methods for monitoring biological agents in the air. Nevertheless, there has been no standard recommended method for sampling and determination of viruses in air. This manuscript aimed at reviewing published papers for sampling and detection of corona viruses, especially SARS-Cov-2 as a global health concern. It was found that SARS-Cov 2 was present in some air samples that were collected from patient's rooms in hospitals. This result warrants its airborne transmission potential. However, due to the fact that in the most reviewed studies, sampling was performed in the patient's room, it seems difficult to discriminate whether it is airborne or is transmitted through respiratory droplets. Moreover, some other disrupting factors such as patient distance from the sampler, using protective or oxygen masks by patients, patient activities, coughing and sneezing during sampling time, air movement, air conditioning, sampler type, sampling conditions, storage and transferring conditions, can affect the results. About the sampling methods, most of the used samplers such as PTFE filters, gelatin filers and cyclones showed suitable performance for trapping SARS-Co and MERS-Cov viruses followed by PCR analysis.

Integrated advanced oxidation process, sono-Fenton treatment, for mineralization and volume reduction of activated sludge.

In this work, the efficiencies of Fenton catalytic and sonolysis processes were investigated separately and in combination together for the treatment and reduction of sludge volume. Moreover, the effects of operating parameters such as retention time, initial pH, iron concentration, and H2O2 concentration on COD reduction as well as the proportion of volatile solids to total solids (VS/TS) were studied. Finally, the effects of these processes on the sludge volume index (SVI) and sludge volume reduction (SVR) were evaluated. According to the results, the retention time of 60 min, pH = 3, hydrogen peroxide concentration of 0.13 M/L, and iron concentration of 2 mM/L were achieved as the optimum values. Furthermore, the SVR and SVI removal efficiencies in the Fenton process were 19% and 25%, respectively, but the removal efficiency in sonolysis process was very low and can be ignored. Under optimum conditions in sono-Fenton (SF) process, the SVR and SVI removal efficiencies were 55.7% and 83%, respectively. The results showed that by combining sonolysis and Fenton processes; due to the synergistic effect of ultrasonic waves, Fenton agent, and the production of more hydroxyl radicals; the COD removal efficiency increased to 77%, and the proportion of VS/TS in row activated sludge was reduced from 75% to 26%. Generally, by combining sonolysis and Fenton processes, the removal efficiency increased significantly as compared to separate processes owing to the production of more oxidizing agents and improving mass transfer.

Microwave/H2O2 efficiency in pentachlorophenol removal from aqueous solutions.

BACKGROUND: Pentachlorophenol (PCP) is one of the most fungicides and pesticides. Acute and chronic poisoning from PCP may be occurred by dermal absorption, and respiration or ingestion. With respect to health and environmental effects of PCP, many methods were considered regarding its removal. Microwave assisted other methods are environmental friendly, safety, and economical method, consequently, in this study; microwave assisted with hydrogen peroxide (MW/H2O2) was used for PCP removal from aquatic solutions. METHODS: The possible of PCP removal was considered by application of a modified domestic microwave. PCP removal rate was considered under different factors such as H2O2 dose (0.01, 0.02, 0.1, 0.2, 0.3 mol/L), PCP concentration (100,200, 300, 400, 500, 750, 1000 mg/L), pH (3, 7, 11), energy intensity (180,450, 600 W), COD (344 mg/L), and scavenger testes (0.02 mol/L from each of Tert- butyl alcohol (TBA), NaCl, NaHCO3, and Na2CO3). The concentration changes of PCP were determined using spectrophotometer and HPLC spectra, respectively. RESULTS: The best PCP removal was obtained in condition of pH 11, 0.2 mol/L H2O2, and 600 W energy intensity. Moreover, COD removal in this condition was 83%. Results obtained from radical scavengers indicated that OH° had only an initiator role, and had not a dominant role, and order reaction was in first order. CONCLUSIONS: The results of microwave/H2O2 application showed that this process is suitable for removal of PCP and other chlorinated organic compounds in alkaline pH.

Prediction the groundwater level of Hamadan-Bahar Plain, west of Iran using support vector machines.

BACKGROUND: Water is considered as the main source of life but water resources are limited and nonrenewable. Different factors have caused groundwater to decrease. Therefore, modeling and predicting groundwater level is of great importance. METHODS: Monthly groundwater level data of about 20 years (October 1991 to February 2012) from the Hamadan-Bahar Plain, west of Iran were used based on peizometric height related to hydrologic years. The support vector machine (SVM), a new nonlinear regression technique, was used to predict groundwater level. The performance of the SVM model was assessed by using criteria of R(2), root mean square error (RMSE), means absolute error (MAE), means absolute percentage error (MAPE), correlation coefficient and efficiency coefficient (E) and was then compared with the classic time series model. RESULTS: The SVM model had greater R(2) (=0.933), E (=0.950) and Correlation (=0.965). Moreover, SVM had lower RMSE (=0.120), MAPE (=0.140) and MAE (=0.124). There was no significant difference between the estimated values using two models and the observed value. CONCLUSIONS: The SVM outperforms classic time series model in predicting groundwater level. Therefore using the SVM model is reasonable for modeling and predicting fluctuations of groundwater level in Hamadan-Bahar Plain.

Treatment of waste sludge: a comparison between anodic oxidation and electro-Fenton processes.

BACKGROUND: Electrochemical methods, as one of the advanced oxidation processes (AOPs), have recently been applied to remove different contaminants from water and wastewater. This study compares the performance of anodic oxidation (AO) and electro-Fenton (EF) methods on waste sludge treatment. METHODS: This experimental study was performed on real sludge and the effect of operating parameters such as solution pH, operating time, current density, supporting electrolyte and hydrogen peroxide concentration were investigated in a batch reactor. For determination of oxidation and treatability of the sludge, chemical oxygen demand (COD) and total coliform (TC) removal were examined. Pb/PbO2 and iron electrodes respectively for AO and EF were applied. RESULTS: Experimental data indicated for both AO and EF as the operating time and current density increased, COD removal increased. pH=4.0 and 3.0 and current density=1.75 and 2 A respectively for AO  and EF and the concentration = 57.2 mMol of hydrogen peroxide for EF were measured as the optimum amounts of these variables. The removal efficiency of COD in AO and EF process was 76% and 72%, respectively. Of course, the efficiency of EF in TC removal was better and the percentage of TC removal in 60 min for AO and EF was 99.0% and 99.9%, respectively. The amounts of consumed electrical energy for AO and EF were 8.6 and 28.0 kWh kg-1 COD, respectively. CONCLUSIONS: AO was more effective in treatment and mineralization of waste sludge and TC removal than EF in terms of environmental economical features.

Preparation of an adsorbent from pumice stone and its adsorption potential for removal of toxic recalcitrant contaminants.

BACKGROUND: In recent years, proficient treatment of wastewaters containing recalcitrant and toxic compounds such as phenol has been a challenge. This study introduced and evaluated an efficient option for treating such wastewater. METHODS: This experimental study was performed on phenol removal as a recalcitrant and toxic compound in aqueous solutions in 2011. The pumice stone was collected from a local mine. Collected samples were crushed and granulated using standard sieves (mesh size of 20). CuSO4 was used to modify prepared samples. The chemical composition and the surface area of the modified pumice were evaluated using X-ray fluorescence and N2 gas via Brunauer-Emmett-Teller isotherm and Belsorb software. Different parameters including of pH (3-12), contact time (20-120 min), phenol concentration (25-400 mg/L) and adsorbent dosage (0.25-1 g/L) were examined in a batch reactor. RESULTS: 93.5% of the phenol was removed under optimum experimental conditions of pH 3 and a 0.5 g/L adsorbent dose after 60 min contact time. The experimental adsorption isotherm the best fit with Freundlich equation model. The maximum amount of phenol adsorption onto modified pumice (MP) was 15.8 mg/g. CONCLUSION: Modified pumice is effective adsorbent for the removal of phenol from aqueous solution. Accordingly, it is feasible and promise adsorbent for treating polluted phenol streams.

Catalytic ozonation of phenol using copper coated pumice and zeolite as catalysts.

BACKGROUND: Catalytic ozonation has recently been applied as a new method of contaminant removal from water and wastewater. In this study, copper coated pumice and zeolite were used to catalyze the ozonation of phenol as a target pollutant from aqueous solutions. METHODS: The pumice and zeolite stone were modified by CuSO4 (1N). Modified pumice and zeolite were characterized by Adsorption/Desorption Porosimetry (BET) and Scanning Electron Microscope analyses. Ozonation and catalytic ozonation experiments were performed in a 1 L semi-batch reactor containing a prepared phenol solution. The efficiency of catalytic ozonation was investigated by different variables: pH value, contact time, initial phenol concentration, catalyst dose, and radical scavenger. RESULTS: Experimental data indicated that as the pH solution increased, phenol removal increased. pH = 8 was measured as the optimum pH. The removal efficiency in single ozonation process (SOP) was 32% and in the catalytic ozonation process (COP) using modified zeolite and pumice was 51% and 63%, respectively. Moreover, these processes showed a great ability to mineralize phenol (up to 30%). Using the radical scavenger determined the indirect oxidation as the main pathway of phenol removal in both catalytic processes. CONCLUSION: The copper modified zeolite and pumice had good performance to remove phenol through catalytic ozonation method.

Kinetic and isotherm of hexavalent chromium adsorption onto nano hydroxyapatite.

BACKGROUND: Hexavalent chromium (Cr (VI)) is an important contaminant in surface and groundwater and its removal from contaminated water and wastewater has received interest in recent years. This study aimed to explain the removal process of Cr (VI) from aqueous solution using nano hydroxyapatite (n-HAp) as an adsorbent material. METHODS: Cr (VI) removal experiments with the prepared n-HAp were carried out as the batch test in 100 ml flask while agitating on the shaker. The influence of pH (3 toll), contact time (3-60 min), Cr (VI) concentration (1 to 2 mg/L) and adsorbent dosage (0.025 to 1 g/L) were explored. Three isotherms models and eight kinetics models were used to evaluate the experimental data, respectively. For validation of kinetic and isotherm data, correlation coefficient, sum of square errors (SSE) and normalized deviation were used. RESULTS: The removal efficiency of Cr (VI) was improved an increase in Cr (VI) and n-HAp concentration. The results best fitted with Langmuir model and the pseudo-second-order rate reaction. Analysis of data with Dubinin Radushkevich isotherm showed that the adsorption of Cr (VI) onto synthetic n-HAp is a chemisorption process. CONCLUSION: The n-HAp as an ecofriendly compound is effective adsorbent for the removal of Cr (VI) from aqueous solution. Accordingly, n-HAp is feasible and promise adsorbent for treating polluted Cr (VI) groundwater.

Nitrate removal from drinking water by point of use ion exchange.

BACKGROUND: A laboratory study was conducted to investigate the ability of a special type of strongly basic resin MP500WS for the removal of nitrate from different waters. METHODS: Two different types of Point-of-Use (POU) devices containing an identical resin were used. MP500WS known as macro porous was used in POU devices for removal of high concentrations of nitrate and sulfate ions from water. Sulfate and chloride ions are considered the most important interferences in the treatment process of nitrate by most anion exchange resins. RESULTS: The results obtained by treatment of water samples having different ranges of nitrate (20 to150 mg/L), sulfate (50, 100 and 800 mg/L) and chloride (50 and 500 mg/L) have shown that the method was suitable for delivering water with NO(3) concentrations in less than its maximum contaminant level (MCL=45 mg/L) as long as the initial NO(3), SO(4) and Cl concentration has remained in less than 150, 100 and 500 mg/L, respectively. CONCLUSION: For this purpose, POU systems that utilize a suitable tested resin may be considered as an economical and effective alternative to conventional systems. This study shows this strategy very effective for nitrate reduction to acceptable levels when macro porous type strongly basic resin is used as the resin.

Correlation between asthma and irritable bowel syndrome in a general population in Iran in 2003.

BACKGROUND: Associations have been reported between irritable bowel syndrome (IBS) and asthma. AIMS: To explore the inter-relations between these conditions in a general population sample. SUBJECTS: A randomly selected community sample of 5492 adults. METHODS: All of the subjects were invited for a medical interview. Those subjects suspected to have either asthma and/or IBS underwent spirometry with post-bronchodilator test if indicated. The labeling of subjects as having IBS was based on Rome II criteria. RESULTS: 4762 subjects agreed to take part (86.7% response). Prevalence rates for IBS, and currently active asthma were 7.1% and 3.8%, respectively. Logistic regression showed independent associations between IBS and most asthma symptom categories. There was no significant independent association between IBS and chronic bronchitis. The odds ratio with 95% confidence interval (CI) for IBS and current asthma was 1.79 (1.06-3.03). CONCLUSIONS: These observations indicate the necessity of further community-based studies to elucidate the possible common pathogenic mechanisms involved in two disease entities.