نشریه مهندسی بهداشت محیط
سال هفتم شماره 3 (پیاپی 28، بهار 1399)

Ceftriaxone is an antibiotic which is extensively used to treat a number of various infections. It is mainly accumulated in water and sewage resulting in the environmental and health problems. This study is centered on the evaluation of the efficiency of a photocatalytic process using Fe3O4@SiO2@TiO2 in the removal of ceftriaxone from aqueous solutions.

This research was based on an experimental-practical study.  Fe3O4 @ SiO2 @ TiO2 was initially synthesized via a sol-gel method and characterized by SEM, XRD and EDX analyses. The effects of variables such as pH, catalyst concentration, ceftriaxone concentration, contact time, reusability tests (n=7) and degree of mineralization were separately assessed in a laboratory scale. The concentration of ceftriaxone was measured by HPLC at 240 nm.

Based on the results obtained, the highest process efficiency of 96.7% was obtained under the following optimal conditions: concentration of ceftriaxone 10 mg/L, pH=3, the catalyst dosage of 2 g/L and a time contact of 120 min. At the end of the process, the degree of mineralization was determined to be 83.7%. Additionally, the data regarding the reusability of the nanocatalyst demonstrated that a 5.2% loss in the removal efficiency was observed after 7 times of reuse. Finally, the results revealed that the removal process of ceftriaxone follows the first-order kinetic model.

The results demonstrated that the photocatalytic process using the magnetic nanocatalyst (Fe3O4 @ SiO2 @ TiO2) could be effectively used for the removal of ceftriaxone from aqueous media.

Aniline is a substance used in chemical industries and in various processes such as pesticide production, chemical bleaching, textile dyes, etc. In spite of the negative effects of aniline on the environment due the difficult decomposition of this substance, various methods have been investigated to remove this substance from water resources. The aim of this study was to investigate the efficiency of magnetized carbon nanotubes in the removal of aniline from aqueous solutions.

Fe3O4-CNT magnetic nanoparticles were prepared by co-precipitation method. The morphology of the adsorbent surface, shape and size of CNT-Fe3O4 magnetic nanoparticles was investigated by scanning electron microscopy (SEM) and transfer electron microscopy (TEM). BET analysis was also used to determine the physical properties of the adsorbent such as surface area, size and volume of the cavities and their distribution on the adsorbent. An X-ray diffraction device (XRD) was used to determine the pattern and the purity of the Fe3O4 particles. The synthetic adsorbent properties were analyzed by FTIR technique. In order to optimize the adsorption conditions and determine the optimal values of each of the factors affecting the adsorption process (pH, contact time, adsorbent value, initial aniline error and temperature), adsorption experiments were performed and aniline concentration was determined by spectrophotometric method.

SEM and TEM analyzes showed that the magnetic carbon nanotubes were almost uniform and had an average diameter of 5 nanometers and an average length of 100 nanometers. XRD analysis also showed the stabilization of Fe3O4 on carbon nanotubes. FTIR analysis for the absorption of aniline contaminants on the magnetic carbon nanotubes adsorbent indicated that the aniline contaminant bond has appeared on the adsorbent.

The results of the study showed that magnetic MWCNT adsorbent was able to effectively remove aniline contaminants from aquatic environments. Statistical analysis showed that pH parameters, adsorption concentration, pollutant concentration, temperature and contact time were effective on pollutant removal efficiency.

Organophosphates are one of the most common pesticides in the world. One of the most commonly used toxins in this group is malathion, which is classified by the EPA as Group III carcinogenic substances. Therefore, due to the high consumption of this pesticide and its pathogenicity, it should be eliminated in an appropriate manner. One of the elimination ways is the use of advanced oxidation processes. The aim of this study was to determine the photocatalytic removal of malathion pesticide by g-C3N4/Fe3O4/Ag nanocomposite.

In this study, g-C3N4/Fe3O4/Ag nanocomposites synthesized by hydrothermal method were used for photocatalytic removal of malathion. The variables studied were pH, nanocomposite dose, and contaminant concentration. Furthermore, the radical effects of ammonium oxalate, tert-butanol, and benzoquinone were analyzed on the experiment procedure.

The best removal efficiency of malathion at pH = 7, the dose of 0.5 g/l, and contaminant concentration 10 mg/l at 60 min was 100%. By increasing the catalyst dose up to 0.5 g/L, the efficiency increased. However, with increasing contaminant concentration, the removal efficiency decreased. Additionally, the removal efficiency of malathion in the presence of ammonium oxalate, tert-butanol, and benzoquinone radicals was 93.36%, 44.78%, and 90.71%, respectively, and the reaction kinetics followed the first equation with R2 = 0.9852. 

Therefore, g-C3N4/Fe3O4/Ag has a high potential for malathion removal moreover can be used to remove various pollutants from aqueous solutions.

Given the increasing use of detergents and the problems of water pollution caused by the release of wastewater containing large amounts of detergents in recent decades, this study aimed to investigate the concentration and health and ecological risk assessment of linear alkylbenzene sulfonate (LAS) as the most important detergent composition in Ekbatan Dam is Hamedan.

31 sampling stations from Ekbatan dam reservoir and Inlet Rivers to Ekbatan dam and overflow dam (Abshineh dam) selected for water sampling. Parameters such as water temperature, pH, EC, TDS, DO and ORP was measured at the sampling site. LAS adsorption was reading through a spectrophotometer (WTW 660) at 650 nm. The pollutant concentration was calculated through the equation of the calibration curve.

The results showed the measured LAS concentration in the range of 0.01-1.4 mg / L. The results of the Spearman correlation test between LAS and water quality factors showed a positive significant relationship between LAS with salinity, TDS and EC at 0.01 level and a negative relationship between LAS and DO at 0.05 levels. The results of the health risk assessment of LAS showed no risk in different age groups. The results of the comparison of LAS concentration with surfactant discharge standard in surface water and irrigation and agricultural applications in Iran showed that the concentration of LAS is below the permissible level (1.5 mg / L) for discharge into surface water. However, in terms of use for agricultural and irrigation purposes, the LAS value at 7 stations was higher than the permissible level (0.5 mg / L).

The results of this study showed that Ekbatan dam and rivers entering the dam are exposed to mild wastewater as a result of human activities. Therefore, it is necessary to take effective and preventive activities to control and reduce pollutants entering this valuable dam.

 In this study, the optimization and prediction of the efficiency of a moving bed biofilm reactor (MBBR) in the treatment of synthetic wastewater containing organic material including aniline was investigated using response surface methodology and artificial neural network.

Modeling results were applied to a 5-liter volume reactor filled with 30%, 50% and 70% LECA lightweight aggregates as a growth medium for microorganisms and biofilm layer formation. In order to determine the optimum conditions in the experiments results and also to predict the tests not performed, three factors were feed levels at levels of 100 to 3000 mg/L, retention time of 8 to 72 hours and filling percentage of 30 and 50 and 70% were performed using RSM. The accuracy of the presented models was evaluated by ANOVA. Prediction of system removal efficiency using radial basis ANN was also investigated.

Process optimization showed that the optimum conditions for maximum removal were at feed rate of 1700 mg/l and 72 hours at 56.82% filling percentage. The results of the process prediction using radial basis ANN also showed that in the best network structure with Radbas and linear functions (Purelin) with R2 = 0.982 can predict the efficiency.

By comparing the radial basis ANN model and RSM and comparing the error rates of these two methods, it can be concluded that the radial base ANN method predicts the data process more accurately and with lower error.

Striving for employment in developing countries, as industries develop, heavy metals are released to the environment continuously. The purpose of this study was to measure heavy metal concentrations and to evaluate dust pollution levels in a number of industries using ecological indices.

This cross-sectional, descriptive-analytical study was conducted in winter by installing 35 dust traps around the industrial Khak-e-chini, Tile and Ceramic, Sand and Gravel and Glass in Ardakan county. The concentration of heavy metals in dust was measured by ICP-MS. The level of dust pollution was assessed using Contamination Factor, Pollution Index, Threshold Pollution Index, New Pollution Index, Vector Modulus of Pollution Index, Weighted Average of Pollution Index, Enrichment Factor, Multi-Element Contamination, Mean Effects Range-Median Quotient, Exposure Factor and Integrated pollution indices and it was zoned in GIS version 10.5.

Mean heavy metal concentrations in dust were measured in the form of Zinc (3310.54 mg/kg)> Pb (137.28 mg/kg)> Copper (63.65 mg/kg)> Nickel (45.91 mg/kg)> Arsenic (35.12 mg/kg> cobalt (13.73 mg/kg)> molybdenum (4.40 mg/kg). In all sampling stations CF index of lead, arsenic and zinc elements was in very high pollution class and PI index in severe pollution class. Zinc metal showed very high enrichment at 30 stations. For environmental protection user, zinc element PIT index in all sampling stations was very severe in the pollution class. Also, all stations were in severe pollution class based on the IPI index. Based on MERMQ index the heavy metals at 32 stations had 76% toxicity and based on PIN index were in polluted class. Highest values of MEC (3.43) and PIvector (35.93) indices were obtained at S1 and S15 stations, PIwAvg (42.27) at S1 and S12 and ExF (117.11) at S1 stations.

Based on results of zoning a number of pollution indices, dominant downwind in region plays has important role in increase of concentration of heavy metals in downstream stations the industries.

The presence of corrosive anions in industrial wastewater can have many environmental and economic problems.

In this study, layered magnesium–aluminum oxide was synthesized which has an extra positive charge and was used for adsorption of chloride ions from waste-water of lead and zinc industry.

 The synthesized crystalline material was investigated by X-ray diffraction spectroscopy, Scanning electron microscopy- energy dispersive spectroscopic analysis. X-ray diffraction spectroscopy results showed that there was no difference in the crystalline structure before and after chloride ion adsorption. Scanning electron microscopy- energy dispersive spectroscopic analysis showed the condensation of adsorbent after chloride ions adsorption and EDX analysis confirmed the presence of chloride and precipitation of Ca2+ ions after adsorption. Measurement of zeta-potential for synthesized layered magnesium–aluminum hydroxide confirmed the positive surface charge. Isotherm studies have shown the compatibility of experimental data with the Langmuir model, which indicates the interaction between adsorbent and chloride ions, the maximum adsorption capacity for the synthesized adsorbent with Mg / Al ratio of 4 was determined 153.8 mg/g at 60 ° C. The obtained values showed the intercalation rate follows pseudo-second-order. The experimental data confirmed adsorption capacity has been increased with increasing the adsorbent dosage from 1.5 to 4.5 gr and the equilibrium time increased from 90 min. to 4 h from 1.5 g adsorbent to 4.5 g. Thermodynamic studies revealed the adsorption occurs spontaneously and positive entropy changes indicated strengthening the interaction between adsorbent and chloride ions with increasing the temperature from 25 to 60°C.

Finally, it can be concluded synthesized double layered Al-Mg hydroxide can be a good candidate to reduce chlorine ions from lead and zinc Industry wastewaters.

Atmospheric deposition has a significant influence on environmental pollution and human health because of its role on transport mechanisms. The aims of this study were the determination of Concentrations, Sources and Ecological Risks of trace elements in atmospheric deposition of Karaj City, Iran.

18 atmospheric deposition samples were collected from the flat roof of buildings in six districts and then, the concentration of elements including Cu, Zn, Cr, Ni, Li and other (Co and Pb) were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), respectively. Pearson Correlation, One-Way ANOVA and Factor Analyses were used to identify probable sources of the trace elements.

The mean concentrations of Pb, Zn, Cu, Cr, Ni, Co, and Li were 184.73, 931.75, 94.61, 98.79, 83.90, 21.05 and 24.71 μg/g, respectively. Also, the result showed the Enrichment Factors (EF) of Pb and Zn were high; Cr, Ni, and Cu were moderate while Co was unpolluted. Based on statistical analyses, trace elements could be originated from several anthropogenic (Vehicular Sources, Industrial Emissions and Fossil Fuel Combustion) and natural sources. Zn and Cu showed the highest concentrations at high-traffic stations, especially at Karkhene-Ghand located in city center. Maximum concentrations of Cr, Ni, and Co were observed at Fardis Station closed to Karaj Power Plant. Industrial Stations including Kamalshahr, Mohammadshahr, and Mahdasht had the most amount of Pb. Finally, Risk index (RI) showed all studied stations had low potential risk except of Kamalshar with a considerable risk.

Karaj has influenced by several anthropogenic sources of environmental pollution that are created many human health problems and the pollutants have increased with the population density. Therefore, we would have suggested the continuous monitoring of trace elements, especially Pb and Zn to control of the emission sources.