Systematic review and meta-analysis of arsenic concentration in drinking water sources of Iran.

Recent studies have found arsenic contamination of drinking water in some parts of Iran, as in many other countries. Thus, a comprehensive systematic review is necessary to assess the distribution and concentration of arsenic in drinking water sources. For this purpose, articles published from the first identification until December 2023, were retrieved from various national and international databases. Of all the studies examined (11,726), 137 articles were selected for review based on their conceptual relationship to this survey. A review of the extracted studies presented that ICP methods (ICP-MS, ICP-OES, 56%) and atomic absorption spectrophotometry (AAS, 34.1%) were the two most commonly used techniques for the analysis of arsenic in water samples. The order of arsenic content in the defined study areas is descending, as follows: northwest ˃ southeast ˃ southwest ˃ northeast. A review of studies performed in Iran depicted that provinces such as Kurdistan, Azerbaijan, and Kerman have the highest arsenic concentrations in water resources. Accordingly, the maximum concentration of arsenic was reported in Rayen, Kerman, and ranged from < 0.5-25,000 µg/L. The primary cause of elevated arsenic levels in water resources appears to be geologic structure, including volcanic activity, biogeochemical processes, sulfur-bearing volcanic rocks, Jurassic shale, the spatial coincidence of arsenic anomalies in tube wells and springs, and, to some extent, mining activities. The findings of the presented survey indicate that it is essential to take serious measures at the national level to minimize the health risks of arsenic contamination from drinking water consumption.

Degradation of 2,4-dinitrotoluene in aqueous solution by dielectric barrier discharge plasma combined with Fe-RGO-BiVO4 nanocomposite.

2,4-Dinitrotoluene (2,4-DNT) as a priority and hazardous pollutant, is widely used in industrial and military activities. In this study the synergistic effect of Fe-RGO-BiVO4 nanocomposite in a non-thermal dielectric barrier discharge plasma reactor (NTP-DBD) for degrading 2,4-DNT was evaluated. Preparation of the Fe-RGO-BiVO4 nanocomposite was done by a stepwise chemical method depositing Fe and reduced graphene oxide (RGO) on BiVO4. Field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), UV-vis diffuse reflectance spectra (DRS), and energy-dispersive X-ray spectroscopy mapping (EDS-mapping) validated the satisfactory synthesis of Fe-RGO-BiVO4. To find the optimal conditions and to determine the interaction of model parameters, a central composite design (RSM-CCD) had been employed. 2,4 DNT can be completely degraded at: initial 2,4-DNT concentration of 40 mg L-1, Fe-RGO-BiVO4 dosage of 0.75 g L-1, applied voltage of 21kV, reaction time of 30 min and pH equal to 7, while the single plasma process reached a degradation efficiency of 67%. The removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) were 90.62% and 88.02% at 30 min contact time, respectively. Results also indicated that average oxidation state (AOS) and carbon oxidation state (COS) were enhanced in the catalytic NTP-DBD process, which demonstrate the effectiveness of proposed process for facilitating biodegradability of 2,4-DNT.

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study).

BACKGROUND: In this study, the effect of static magnetic fields (SMFs) on improving the performance of activated sludge process to enhance the higher rate of microbial growth biomass and improve sludge settling characteristics in real operation conditions of wastewater treatment plants has been investigated. The effect of SMFs (15 mT), hydraulic retention time, SRT, aeration time on mixed liquor suspended solids (MLSS) concentrations, mixed liquor volatile suspended solids (MLVSS) concentrations, α-factor, and pH in the complete-mix activated sludge (CMAS) process during 30 days of the operation, were evaluated. RESULTS: There were not any differences between the concentration of MLSS in the case (2148.8 ± 235.6 mg/L) and control (2260.1 ± 296.0 mg/L) samples, however, the mean concentration of MLVSS in the case (1463.4 ± 419.2 mg/L) was more than the control samples (1244.1 ± 295.5 mg/L). Changes of the concentration of MLVSS over time, follow the first and second-order reaction with and without exposure of SMFs respectively. Moreover, the slope of the line and, the mean of α-factor in the case samples were 6.255 and, - 0.001 higher than the control samples, respectively. Changes in pH in both groups of the reactors were not observed. The size of the sluge flocs (1.28 µm) and, the spectra of amid I' (1440 cm-1) and II' (1650 cm-1) areas related to hydrogenase bond in the case samples were higher than the control samples. CONCLUSIONS: SMFs have a potential to being considered as an alternative method to stimulate the microbial growth rate in the aeration reactors and produce bioflocs with the higher density in the second clarifiers.

The effect of the combined system of hydrodynamic cavitation, ozone, and hydrogen peroxide on chlorophyll a and organic substances removal in the raw water.

Increased levels of nutrients and algae can cause drinking water problems in communities. Harmful algal blooms affect humans, fish, marine mammals, birds, and other animals. In the present study, we investigated the use of a combined system [Hydrodynamic Cavitation, Ozone (O3), and Hydrogen Peroxide (H2O2)] on the removal of Chlorophyll a and Organic substances in the raw water was investigated. The Effect of different operating conditions such as pH, cavitation time, pressure, distance, flow rate, ozone dose, and hydrogen peroxide concentration was studied. Utilizing the Taguchi design method, experiments were planned and optimized. The combined system treatment yielded a maximum reduction in Chlorophyll a and Total Organic Carbon (TOC) at an optimum condition of pH 5, cavitation pressure 5 bar, flow rate of 1 m3/h, a distance of 25 cm from the orifice plate, O3 3 g/h and 2 g/l of H2O2 concentrations. The most efficient factor in the degradation of TOC and Chlorophyll a, was cavitation pressure based on the percentage contributions of each parameter (38.64 percent and 35.05 percent, respectively). H2O2 was found to have the most negligible impact on degradation efficiency (4.24 percent and 4.11 percent, respectively).

The best location for the application of static magnetic fields based on biokinetic coefficients in complete-mix activated sludge process.

The use of the kinetic coefficients for the mathematical expression of the biochemical processes and the relationship between the effective parameters is importance. Change of the biokinetic coefficients in the complete-mix activated sludge processes were calculated for 1 month operation of the activated sludge model (ASM) in a Lab-scale in three series. 15 mT intensity of static magnetic fields (SMFs) applied on the aeration reactor (ASM 1), clarifier reactor (ASM 2) and, sludge returning systems (ASM 3) for 1 h, daily. During the operation of the systems, five basic biokinetic coefficients such as maximum specific substrate utilization rate (k), heterotrophic half-saturation substrate concentration (Ks), decay coefficient (kd), yield coefficient (Y) and, maximum specific microbial growth rate (µmax) were determined. The rate of k (g COD/g Cells.d) in ASM 1 was 2.69% and, 22.79% higher than ASM 2 and, ASM 3. The value of Ks (mg COD/L) was 54.44 and, 71.13 (mg/L) lower than the ASM 2 and, ASM 3. The rate of kd ASM 1, ASM 2 and, ASM 3 was 0.070, 0.054 and, 0.516 (d-1). The value of Y (kg VSS/kg COD) in ASM 1 was 0.58% and, 0.48% lower than ASM 2 and, ASM 3. The rate of µmax (d-1) in ASM 1 was 0.197, this value for ASM 2 and ASM 3 were 0.324 and 0.309 (d-1). Related to the biokinetic coefficients analyses the best location for the application of 15 mT SMFs was the aeration reactor, where the present of oxygen, substrate and, SMFs have the greatest impact on the positive changes of these coefficients.

Application of fingernail samples as a biomarker for human exposure to arsenic-contaminated drinking waters.

This study evaluated the relationship between arsenic uptake via drinking water ingestion and arsenic concentration in fingernails as a biomarker for human exposure. For this purpose, we collected fingernail samples from 40 healthy participants of arsenic-affected rural regions of Kaboudrahang County, the west of Iran. A total of 49 fingernail samples were also collected from individuals who lived in areas where contamination of drinking water sources with arsenic had not been reported. It was found that the fingernails arsenic contents in 50 and 4.08% of the samples collected from arsenic-contaminated and reference villages were higher than the normal arsenic values of nails (0.43-1.08 µg/g), respectively. Based on the results of adjusted multiple linear regression, a significant association was found between groundwater and fingernails arsenic concentration (p < 0.001). Moreover, a statistically significant association was shown between arsenic in the fingernail samples and gender (p = 0.037). Fingernails arsenic contents were not significantly affected by other variables including age, smoking habits, and BMI (p > 0.05). In light of the results of this study, the use of biological indicators such as fingernail tissues due to easier sampling and less risk of external contamination is suitable for assessing exposure to heavy metals in contaminated areas.

Effect of household processing on pesticide residues in post-harvested tomatoes: determination of the risk exposure and modeling of experimental results via RSM.

This study aimed to investigate the acute and chronic hazard quotients of chlorpyrifos and diazinon for tomatoes in preharvest and postharvest conditions, and to evaluate the relationship between the main variables, including temperature and contact time and pesticide dissipation at different conditions using response surface methodology for the first time. The qualification analyses were conducted by a gas chromatography-tandem mass spectrometry. The Monte Carlo simulation technique was utilized to evaluate the variability and uncertainty and achieve more accurate results in the health risk assessment process. A quadratic model and the second-order polynomial analysis were employed to investigate the mutual effect of time and temperature on removing diazinon and chlorpyrifos. Based on findings, the chronic hazard quotient values of chlorpyrifos and diazinon residues ranged from 0.43 - 1.33 to 0.13 - 2.27 for boiling, 0.65 - 1.49 to 3.05 - 7.15 for room condition, and 0.63 - 1.92 to 3.28 - 7.47 for refrigerator condition, respectively. According to the Monte Carlo simulation, the hazard quotient and estimated daily intake values were more affected by the consumption rate, pesticide concentration, and body weight. The results of response surface methodology showed that the effect of temperature variations on the dissipation of both pesticides was more than that of contact time variations.

Deterministic and probabilistic human health risk assessment approach of exposure to heavy metals in drinking water sources: A case study of a semi-arid region in the west of Iran.

In the current study, the concentration of heavy metals (Ba, Mn, Pb, and Cd) in drinking water resources of 328 villages in Hamadan Province were measured using ICP-OES apparatus during two dry (September 2018) and wet (April 2019) seasons. The assessment of the non-carcinogenic risk of selected heavy metals was conducted based on the recommendations of the USEPA. Also, sensitivity analysis and uncertainty of the effective variables were performed using Monte-Carlo simulations. Based on the results, Mn level in drinking water samples ranged 0.08-25.63 µg/L and 0.08-20.03 µg/L in dry and wet seasons, respectively. Similarly, Ba levels in water samples ranged 0.15-70.13 µg/L and 0.84-65 µg/L. Also, Cd and Pb concentrations in all sampling sites were below the limits of detection (LOD) of the ICP-OES apparatus. The hazard index (HI) values for adult and children were 2.17 × 10-3 and 3.29 × 10-3, respectively, which show a lack of non-carcinogenic risk for the examined heavy metals (Mn and Ba) to the local inhabitants. The results of the sensitivity analyses for adults and children revealed that two variables including metal concentration and ingestion rate of drinking water (IR) had the highest positive effects on the non-carcinogenic risk estimates. It was also found that there was no significant non-carcinogenic risk for the local residents in the studied area due to drinking water consumption.

The relationship between chronic exposure to arsenic through drinking water and hearing function in exposed population aged 10-49 years: A cross-sectional study.

It has been documented that arsenic has a potential risk to human health and identified as a risk factor for hearing impairment. However, there are few studies that confirm the ototoxic effect of arsenic, especially on the human auditory system. Therefore, the current study was conducted to investigate the correlation between auditory thresholds at different frequencies (0.25, 0.5, 1, 2, 4 and 8 kHz) and arsenic levels in drinking water samples. A total of 240 people, divided into two equal groups: exposed and reference, were selected for the auditory tests. It should be noted that, at frequencies from 0.25 to 1 kHz, no hearing loss was observed in the both groups. Based on the results, no significant correlations (p > 0.05) were found between hearing thresholds and confounding variables including gender and BMI. However, smoking and age are known to be the main variables for hearing loss in univariate regression analysis. In the case of age, the hearing loss risk in the older participants was increased compared with the younger participants (4 kHz (OR =1.09; 95% CI: 1.04, 1.13) and 8 kHz (OR =1.12; 95% CI: 1.06, 1.18)). Smoking habits had significant associations with hearing loss risk at 4 kHz (OR = 3.48; 95% CI: 1.47, 8.22) and 8 kHz (OR = 3.01; 95% CI: 1.14, 7.95). The multivariate regression analysis showed that age, smoking status, and exposure to arsenic were significantly associated with increased risk of hearing loss. Moreover, no statistically significant correlation (p˃0.05) was observed between arsenic exposure and hearing loss in the logistic regression model compared to the reference group. These outcomes suggest that further investigation and cohort studies with a larger number of participants should be conducted to find an association between arsenic exposure and hearing loss in general population.

Moving-bed biofilm reactor combined with three-dimensional electrochemical pretreatment (MBBR-3DE) for 2,4-D herbicide treatment: application for real wastewater, improvement of biodegradability.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide that is considered as a carcinogenic and highly toxic contaminant, and due to its biological and chemical stability, its degradation is very difficult. Therefore, this study aimed to investigate a hybrid system's efficiency of three-dimensional electrochemical (3DE) process and a moving bed biofilm reactor (MBBR) in removing 2,4-D herbicides from aqueous solutions. In this experimental study, the electrochemical degradation of 2,4-D herbicide in a 3DE process with a G/ß-PbO2 anode was first investigated as a pretreatment process. Then, in the post-treatment stage, MBBR with continuous flow was used. The amount of aeration in the MBBR reactor was 4 L min-1, and the amount of dissolved oxygen (DO) was in the range of 3-5 mg L-1. The effect of various parameters such as hydraulic retention time (HRT) and filling ratio were investigated. The amount of sewage injection was set between 0.001-0.004 L min-1. Routine microbiological biochemical tests were used to detect bacteria. BOD5/COD, COD/TOC, AOS, and COS ratio parameters were used to determine the biodegradability of 2.4-D due to the effluent of the 3DE process. The results showed that with increasing current density, decreasing pH, decreasing herbicide concentration and increasing electrolysis time, the herbicide degradation efficiency increased by 3DE pretreatment process. Based on the results of MBBR post-treatment process efficiency, with increasing HRT and filling ratio, the herbicide removal efficiency increased. According to the results, the highest removal efficiencies of 2,4-D and COD herbicides were obtained during HRT of 24 h, and the filling ratio of 70% were 97.33% and 88.95%, respectively. The consortium of 2,4-D degrading bacteria identified in this study included E. coli, Enterobacter spp., Bacillus spp., Alcaligenes spp., Proteus spp., Acinetobacter spp., Pseudomonas spp., Arthrobacter, and Brevundimonas vesicularis. In the MBBR biological process, the reaction kinetics followed the Grau second-order model (R 2 = 0.98). In general, the results showed that the combined process of 3DE with G/ß-PbO2 anode and MBBR biological process has relatively high efficiency in 2,4-D herbicide degradation and can be used as a suitable complementary treatment method in wastewater containing non-degradable compounds such as phenoxy herbicides, e.g., 2,4-D should be used.

Thermochemical degradation of furfural by sulfate radicals in aqueous solution: optimization and synergistic effect studies.

In this study, thermochemical degradation of furfural by sulfate radical has been investigated to find the best-operating conditions. For this purpose, the response surface methodology (RSM) based on central composite design (CCD) was applied to optimize the five independent variables of thermally activated persulfate (TAP)/nZVI oxidation process including pH, PS concentration, furfural concentration, nZVI dosage, and heat. The ANOVA results ("P > F value" < 0.0001 and [Formula: see text] = 0.9701) showed the obtained quadratic model is acceptable to predict furfural removal. Based on the reduced quadratic model PS concentration, nZVI dosage, and heat revealed the positive effects on removal efficiency, while pH and furfural concentration had a negative effect. Accordingly, 98.4% of furfural could be removed within 60 min of reaction under the optimum conditions: pH 5.26, PS concentration of 20.52 mM, furfural concentration of 84.32 mg/L, nZVI dosage of 1.15 mg/L, and a temperature of 79 °C. In such circumstances, the furfural removal efficiency for TAP, PS/nZVI, PS, and nZVI was 94.5, 9, 3, and 2%, respectively. Therefore, based on the synergy index (SI) values, the combination of PS, nZVI, and heat can lead to a synergistic effect in the performance of the thermochemical process.

Parameter optimization and degradation mechanism for electrocatalytic degradation of 2,4-diclorophenoxyacetic acid (2,4-D) herbicide by lead dioxide electrodes.

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most commonly used herbicides in the world. In this work, the electro-catalytic degradation of 2,4-D herbicide from aqueous solutions was evaluated using three anode electrodes, i.e., lead dioxide coated on stainless steel 316 (SS316/ß-PbO2), lead dioxide coated on a lead bed (Pb/ß-PbO2), and lead dioxide coated on graphite (G/ß-PbO2). The structure and morphology of the prepared electrodes were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The process of herbicide degradation was monitored during constant current electrolysis using cyclic voltammetry (CV). In this study, the experiments were designed based on the central composite design (CCD) and were analyzed and modeled by response surface methodology (RSM) to demonstrate the operational variables and the interactive effect of three independent variables on 3 responses. The effects of parameters including pH (3-11), current density (j = 1-5 mA cm-2) and electrolysis time (20-80 min) were studied. The results showed that, at j = 5 mA cm-2, by increasing the reaction time from 20 to 80 min and decreasing the pH from 11 to 3, the 2,4-D herbicide degradation efficiency using SS316/ß-PbO2, Pb/ß-PbO2 and G/ß-PbO2 anode electrodes was observed to be 60.4, 75.9 and 89.8%, respectively. Moreover, the results showed that the highest COD and TOC removal efficiencies using the G/ß-PbO2 electrode were 83.7 and 78.5%, under the conditions pH = 3, electrolysis time = 80 min and j = 5 mA cm-2, respectively. It was also found that G/ß-PbO2 has lower energy consumption (EC) (5.67 kW h m-3) compared to the two other studied electrodes (SS316/ß-PbO2 and Pb/ß-PbO2). The results showed a good correlation between the experimental values and the predicted values of the quadratic model (P < 0.05). Results revealed that the electrochemical process using the G/ß-PbO2 anode electrode has an acceptable efficiency in the degradation of 2,4-D herbicide and can be used as a proper pretreatment technique to treat wastewater containing resistant pollutants, e.g., phenoxy group herbicides (2,4-D).

Ultrasound-assisted sorption of Pb(ii) on multi-walled carbon nanotube in presence of natural organic matter: an insight into main and interaction effects using modelling approaches of RSM and BRT.

In real-scale applications, where NPs are injected into the aqueous environment for remediation, they may interact with natural organic matter (NOM). This interaction can alter nanoparticles' (NPs) physicochemical properties, sorption behavior, and even ecological effects. This study aimed to investigate sorption of Pb(ii) onto multi-walled carbon nanotube (MWCNT) in presence of NOM. The predominant behavior of the process was examined comparatively using response surface methodology (RSM) and boosted regression tree (BRT)-based models. The influence of four main effective parameters, namely Pb(ii) and humic acid (HA) concentrations (mg L-1), pH, and time (min) on Pb removal (%) was evaluated by contributing factor importance rankings (BRT) and analysis of variance (RSM). The applicability of the BRT and RSM models for description of the predominant behavior in the design space was checked and compared using statistics of absolute average deviation (AAD), mean absolute error (MAE), root mean square error (RMSE), and multiple correlation coefficient (R 2). The results showed that although both approaches exhibited good performance, the BRT model was more precise, indicating that it could be a powerful method for the modeling of NOM-presence studies. Importance rankings of BRT displayed that the effectiveness order of the studied parameters is pH > time > Pb(ii) concentration > HA concentration. Although HA concentration showed the least effect in comparison with three other studied parameters theoretically, the experimental results revealed that Pb(ii) removal is enhanced in presence of HA (73% vs. 81.77%), which was confirmed by SEM/EDX analyses. Hence, maximum removal (R% = 81.77) was attained at an initial Pb(ii) concentration of 9.91 mg L-1, HA concentration of 0.3 mg L-1, pH of 4.9, and time of 55.2 min.

Electrodegradation of 2,4-dichlorophenoxyacetic acid herbicide from aqueous solution using three-dimensional electrode reactor with G/ß-PbO2 anode: Taguchi optimization and degradation mechanism determination.

This study aimed to investigate the electro-degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solution using two and three-dimensional electrode (2D and 3D) reactors with graphite(G)/ß-PbO2 anode. To increase the degradation efficiency, affecting parameters on the electro-degradation process were investigated and optimized by adopting the Taguchi design of experiments approach. The structure, morphology and electrochemical properties of the electrodes were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), linear sweep voltammetry and cyclic voltammograms. The controllable factors, i.e., electrolysis time, 2,4-D initial concentration, solution pH and current density (j) were optimized. Under optimum conditions, the 2,4-D degradation efficiency was 75.6% using 2D and 93.5% using 3D electrode processes. The percentage contribution of each controllable factor was also determined. The pH of the solution was identified as the most influential factor, and its percentage contribution value was up to 39.9% and 40.4% for 2D and 3D electrode processes, respectively. Considering the parameters of the kinetics, it was found that the degradation of 2,4-D and removal of COD using the G/ß-PbO2 electrode obey the pseudo-first order kinetics. In addition, the mineralization pathway of 2,4-D at G/ß-PbO2 electrode was proposed. The results also demonstrated that the 3D electrode process with G/ß-PbO2 anode can be considered as a useful method for degradation and mineralization of 2,4-D herbicides from aqueous solution.

Evaluation of Autothermal Thermophilic Aerobic Digester Performance for the Stabilization of Municipal Wastewater Sludge.

BACKGROUND AND OBJECTIVE: Sludge stabilization process in terms of operational, environmental and economic indexes is the most important stage of treatment and its disposal. This study was aimed to determine the performance of Autothermal Thermophilic Aerobic Digestion (ATAD) system as one of the low-cost and biocompatible methods of sludge treatment. MATERIALS AND METHODS: This study has been done using a laboratory scale Autothermal Thermophilic Aerobic Digestion (ATAD). The reactor was consisted of two polyethylene tanks with a final capacity of 100 L for each tank. Both tanks with all fittings were installed on a metal frame. The variables of study were temperature, dissolved oxygen, pH, volatile organic compounds, total solids, COD and the number of Ascaris eggs and fecal coliforms per gram of dry matter of the sludge. The temperature was measured hourly and the pH and dissolved oxygen were measured and controlled twice per day. One-way ANNOVA was applied to analyze reasults. RESULTS: According to the results, the temperature of sludge increased from 11.7-61.2°C by biological reactions. Pathogen organisms were reduced from 80×106 to 503 in number during 72 h. After 6 days pathogen organisms and Ascaris eggs were removed completely. Volatile organic compounds and COD were reduced 42 and 38.3% respectively during the 6 days. CONCLUSION: It is concluded that the performance of ATAD in removing organic compounds from wastewater sludge were desirable. Resulted sludge from stabilization process were appropriate for use in agriculture as a soil supplement and met the indexes of class A sludge according to EPA's standards (CFR 40 Part 503).

Comparing the performance of granular coral limestone and Leca in adsorbing Acid Cyanine 5R from aqueous solution.

The effect of granular coral limestone and Leca as adsorbents for removing Acid Cyanine 5R (AC5R) from aqueous solution was studied. The optimum pH and adsorbent particles size in both adsorbents were determined to be 3 and 297 µm, respectively. The optimum dosages of coral limestone and granular Leca were 0.150 and 0.145 g/mg of dye, respectively. Also, results have shown that the adsorption efficiency by both coral limestone and Leca increased with the decreasing adsorbent particles size. Moreover, under similar conditions, the maximum removal efficiency by granular coral limestone and Leca was 94% and 88%, respectively. The results revealed that the performance of granular coral limestone was better in AC5R removal than that of Leca granulated under such condition. In total, granular coral limestone and Leca act as suitable adsorbents for removing dye pollutants from an aqueous solution.

Study of the efficiency of moving bed biofilm reactor (MBBR) in LAS Anionic Detergent removal from hospital wastewater: determination of removing model according to response surface methodology (RSM).

Detergents are considered one of the important pollutants in hospital wastewater. Achieving efficient and bio-friendly methods for the removal of these pollutants is considered as a concern for environmental researchers. This study aims at studying the efficiency of a moving bed biofilm reactor (MBBR) system for removing linear alkyl benzene sulfonate (LAS) from hospital wastewater with utilization of response surface methodology (RSM). The present study was carried out on a reactor with continuous hydraulic flow using media k1 at pilot scale to remove detergent from hospital wastewater. The effect of independent variables including contact time, percentage of media filling and mixed liquor suspended solids (MLSS) concentration of 1000-3000 mg/l on the system efficiency were assessed. Methylene blue active substances (MBAS) and chemical oxygen demand (COD) 750-850 mg/l were used by closed laboratory method in order to measure the concentration of LAS. The results revealed that the removal efficiency of LAS detergent and COD using media k1, retention time of 24 hours, and MLSS concentration of around 3,000 mg/l were 92.3 and 95.8%, respectively. The results showed that the MBBR system as a bio-friendly compatible method has high efficiency in removing detergents from hospital wastewater and can achieve standard output effluent in acceptable time.

Determination of Pesticides Residues in Cucumbers Grown in Greenhouse and the Effect of Some Procedures on Their Residues.

BACKGROUND: The objective of this study was to determine the residual concentrations of ethion and imidacloprid in cucumbers grown in greenhouse. The effect of some simple processing procedures on both ethion and imidacloprid residues were also studied. METHODS: Ten active greenhouses that produce cucumber were randomly selected. Ethion and imidacloprid as the most widely used pesticides were measured in cucumber samples of studied greenhouses. Moreover, the effect of storing, washing, and peeling as simple processing procedures on both ethion and imidacloprid residues were investigated. RESULTS: One hour after pesticide application; the maximum residue levels (MRLs) of ethion and imidacloprid were higher than that of Codex standard level. One day after pesticide application, the levels of pesticides were decreased about 35 and 31% for ethion and imidacloprid, respectively, which still were higher than the MRL. Washing procedure led to about 51 and 42.5% loss in ethion and imidacloprid residues, respectively. Peeling procedure also led to highest loss of 93.4 and 63.7% in ethion and imidacloprid residues, respectively. The recovery for both target analytes was in the range between 88 and 102%. CONCLUSION: The residue values in collected samples one hour after pesticides application were higher than standard value. The storing, washing, and peeling procedures lead to the decrease of pesticide residues in greenhouse cucumbers. Among them, the peeling procedure has the greatest impact on residual reduction. Therefore, these procedures can be used as simple and effective processing techniques for reducing and removing pesticides from greenhouse products before their consumption.