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Nanofiltration contributes to the development of advanced treatment of wastewater. An antifouling mixed matrix recycled polyethylene terephthalate (rPET) membrane modified by the hydrophilic ZnO/y-FeOOH nanoparticles (NPs) was fabricated via the electrospinning method. The effect of ZnO/y-FeOOH NP

Purpose This paper aims to investigation of processes for Pb2+ elimination from water/wastewater as a significant public health issue in many parts of world. The removal of Pb2+ ions by various nanocomposites has been explained from water/wastewaters. ZnO-based nanocomposites, as eco-friendly nanoparticles with unique physicochemical properties, have received increased attention to remove Pb2+ ions from water/wastewaters. Design/methodology/approach In this review, different ZnO-based nanocomposites were reviewed for their application in the removal of Pb2+ ions from the aqueous solution, typically for wastewater treatment using methodology, such as adsorption. This review focused on the ZnO-based nanocomposites for removing Pb2+ ions from water and wastewaters systems. Findings The ZnO-based nanocomposite was prepared by different methods, such as electrospinning, hydrothermal/alkali hydrothermal, direct precipitation and polymerization. Depending on the preparation method, various types of ZnO-based nanocomposites like ZnO-metal (Cu/ZnO, ZnO/ZnS, ZnO/Fe), ZnO-nonmetal (PVA/ZnO, Talc/ZnO) and ZnO-metal/nonmetal (ZnO/Na-Y zeolite) were obtained with different morphologies. The effects of operational parameters and adsorption mechanisms were discussed in the review. Research limitations/implications The findings may be greatly useful in the application of the ZnO-based nanocomposite in the fields of organic and inorganic pollutants adsorption. Practical implications The present study is novel, because it investigated the morphological and structural properties of the synthesized ZnO-based nanocomposite using different methods and studied the capability of green-synthesized ZnO-based nanocomposite to remove Pb2+ ions as water contaminants. Social implications The current review can be used for the development of environmental pollution control measures. Originality/value This paper reviews the rapidly developing field of nanocomposite technology.

The aim of the present study was to prepare the modified magnetic activated carbon from sawdust (AC/Fe3O4@SiO2-APTMS) as a novel adsorbent for efficient removal of humic acid (HA) from aqueous solu...

Cardboard factory wastewater is usually known by high chemical oxygen demand (COD), color, phenols, lignin, and its derivatives, and usual treatment techniques are not able to treat such wastewaters. This study aimed to investigate the efficiency of ozone-assisted electrocoagulation process (EC/O3) for the treatment of real cardboard wastewater. The parameters influencing COD removal in the EC/O3 process were optimized using response surface methodology. Regard to the statistical model, the optimum conditions were obtained at current density 9.6 mA/cm2, time 20 min, and pH 12. At optimal condition, EC/O3 process removed 74.7% and 97.5% of COD and color, which was higher compared to ozonation and EC processes separately. The COD removal followed pseudo-first-order kinetic with the coefficient correlation of 0.97 and the reaction rate constant of 0.073 1/min. To sum up, the combined electrocoagulation process with ozonation could be used satisfactorily for removing pollutants from real cardboard wastewater.

The feasibility of using intermittent cycle extended aeration system (ICEAS) sludge as a lipid feedstock for biodiesel production was investigated. The main effects of in situ transesterification parameters, reaction temperature (30–70 °C), reaction time (4–24 h), catalyst concentration (1–5% v/v), and proportion of methanol to dry sludge (5–25 ml/g) at five-levels as well as their simultaneous interactions were evaluated to develop an empirical model. Optimized conditions were obtained at 60 °C, 4.65% (v/v) H2SO4, 17.84 h reaction time, and 5:1 methanol to dry sludge proportion (ml/g), leading to a maximum of 18.58% (w/w) biodiesel yield with 94.23% fatty acid methyl ester content. This result was higher in comparison with yields derived from conventional activated sludge, membrane bioreactor and anaerobic-anoxic-oxic processes. The ICEAS technology advantages are owned to its different configurations leading to production of one blended sludge, shorter hydraulic retention time and higher chemical oxygen demand to nitrogen ratios. The predominance of fatty acid methyl esters such as palmitic, oleic, palmitoleic, stearic, linoleic and myristic acid methyl ester, in the obtained biodiesel, indicated suitability of ICEAS sludge as feedstock for biodiesel production.

A novel adsorbent of modified nanoclay was synthesized by covering of alum on the montmorillonite nanoclay (Al/nanoclay). Al/nanoclay was applied as an efficient superadsorbent to remove Direct Red 23 (DR23) from colored wastewater. The adsorbent was characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and zeta potential analysis. The effects of various operating parameters, such as contact time, initial dye concentration, adsorbent dose, pH and ionic strength on the performance of adsorption, have been studied. The adsorption experiments showed that pH has an obvious effect on the adsorption efficiency and the highest percentage of DR23 dye removal was observed at pH 2. Zeta potential measurement confirmed that the adsorption mechanism is ascribed to electrostatic interaction between sulfonic groups of the anionic dye and the positive surface charge of the adsorbent. The pseudo-second-order kinetic model and the Langmuir isotherm were found to best describe the DR23 adsorption and the maximum monolayer adsorption capacity at the conditions of pH 2 and the adsorbent dose of 0.05 g/L was 2,500 mg/g. The findings recommend that Al/nanoclay can be successfully used for DR23 dye removal from the colored wastewater.

The objective of this study was to use activated carbon produced from poplar sawdust (ACPSD) as an adsorbent to remove Reactive Black 5 dye from aqueous solution. Investigation of the properties of...

In addition to the large volume, the generated wastewater in paper and cardboard recycling industry contains various organic compounds and dyes. Treatment of these wastewaters is difficult due to t...

The presence of antibiotics in the environment as persistent micropollutants, due to their widespread consumption, has increased the concerns about the harmful effects of these compounds on human and animal health. Advanced oxidation processes are one of the most effective methods to remove these types of organic pollutants. In this study, amoxicillin (AMX) removal in a modified photoelectro-Fenton (PEF) reactor in which porous stainless steel was used as a cathode electrode, and the ability of air injection into its center to produce H2O2 was investigated. A graphite anode electrode equipped with iron rings was used to increase the electrochemical reaction surface and produce iron ions. The effect of current density, time, and electrolyte concentration on AMX removal efficiency was evaluated by Box-Behnken design method. Subsequently, the effect of AMX concentration variable and pH on removal efficiency was investigated. Finally, the chemical oxygen demand (COD) removal efficiency, toxicity, and effluent activity from the PEF reactor were investigated. The results showed that the modified photoelectro-Fenton process could have efficiency of 99% to remove AMX, in 20 min using current density of 36 mA/cm2 and 16 mM/L electrolyte concentration. Reducing pH and AMX concentration increased the removal efficiency. The PEF process can completely remove the COD in 58 min. Also, toxicity studies indicated an effective reduction in the effluent. This modified reactor improves the efficiency of the PEF process, which, in addition to the 99% removal of AMX, provides a proper function for COD removal, reducing the toxicity properties of the effluent

Natural organic materials, principally humic acids cause serious problems in water treatment plants due to combination with chlorine and the formation of carcinogenic disinfection by-products. In t...

Purpose The purpose of this paper is to analyze zero valent iron nanoparticles (NZVIs) by a novel green method, taken from Thymus vulgaris (TV) plant extract, were synthesized and applied to degrade reactive black 5 (RB5) azo dye. Design/methodology/approach The optimum conditions for the highest removal of RB5 dye were determined. Characterization of NZVIs was done by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The NZVIs were used for the removal of dye RB5, and the parameters affecting were discussed like pH, initial concentration, contact time and NZVIs dosage. Findings The characterization results of NZVIs by SEM, TEM, FTIR and XRD show that polyphenols, organic acids and proteins reduce not only the green synthesis of NZVIs but also the aggregation of nanoparticles. The maximum dye removal efficiency of 99.6 per cent occurred at pH 4, NZVIs dose of 600 mg/L, and contact time of 5 min. The adsorption of RB5 dye onto the NZVIs surface and scavenging of the azo bond (−N = N) by the strong reduction of NZVIs were the proposed mechanisms for dye removal. The application of NZVIs to treat wastewater containing reactive dye shows high degradation efficiency. Research limitations/implications The findings may greatly benefit the application of the NZVIs taken from Thymus vulgaris (TV) in the fields of dye adsorption. Practical implications The present study is novel because it incorporated the morphological and structural properties of the synthesized NZVIs using a native plant of Iran and studied the capability of green-synthesized NZVIs to remove RB5 as a water contaminant. Social implications The native plant presented here can be developed for reduced environmental pollution before discharge to accepted water. Originality/value The NZVIs is prepared via green-synthesized method, which is prepared with leaves of TV. There are two main innovations. One is that the novel NZVIs is prepared successfully by native plant via green-synthesized method. The other is that the optimized conditions were obtained for the removal of RB5 dye as a water contaminant. Furthermore, to the best of our knowledge, no study has ever investigated the removal of RB5 by NZVIs produced using a native plant in Iran.

In the present study, the efficiency of amine-functioned Fe3O4 magnetic nanoparticles with L-arginine (Fe3O4@L-arginine) for the removal of RB5 azo dye from aqueous solution was investigated. Box–B...

While chlorination is critical for water disinfection, a knowledge gap includes the nature of free residual chlorine (FRC) decay, which was investigated using four physical methods (SSA, SSR with a...

Humic acids are one type of natural organic matter and precursors of chloro organic compounds that cause a major problematic issue for water treatment plants. In the present study, Hyperbranched polyethylenimine (HPEI) was grafted onto Fe3O4 nanoparticles for HA adsorption from aqueous solution. Fe3O4@HPEI nanoparticles were characterized via TEM, SEM, FTIR, XRD, VSM, and BET analysis. The effects of various operational parameters including initial HA concentration, pH, adsorbent dose, contact time and ionic strength on the HA removal were assessed. According to the obtained statistical model, the optimal condition was acquired at the initial HA concentration 79 mg/L, adsorbent dose 0.128 g/L, pH 3 and contact time 29 min, which up to 97.27% HA were adsorbed by Fe3O4@HPEI that was close to the predicted result by the model (95.6%) that confirmed the validity of the selected model. The adsorption data were fitted to the pseudo-second-order kinetic and Freundlich isotherm. Thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. The fabricated Fe3O4@HPEI nanoparticles could be repeatedly utilized as a suitable adsorbent to remove HA from the aqueous environment.

In this research, the adsorption of the Direct Red 23 dye from synthetic textile wastewater using nanoclay was studied in a batch system. The properties of nanoclay were investigated by scanning electron microscope, Fourier transform infrared, and EDX analysis. The specific surface area of the nanoclay was determined using Sear's method. The results revealed that with increasing adsorbent dose and contact time and decreasing pH, ionic strength, and adsorbate concentration, dye removal efficiency has increased. Nanoclay could remove 99.4% dye from the solution containing 50 mg/L dye at 30 min. The results indicated that dye removal followed pseudo-second-order kinetic (R2 > 0.99) and the Langmuir isotherm. According to the findings, nanoclay is an effective adsorbent for direct dye removal from wastewater.

The recent increase in the global consumption of antibiotics has led to faster entry of these pollutants into the environment as well as an increase in public concern about its impact on ecosystem and human health. Generally, due to high toxicity of antibiotics, biological methods are not used to treat these pollutants; therefore, advanced oxidation processes are recommended to treat and reduce the toxicity of the wastewater. In this study, we evaluated the efficacy of photo-oxidation (P) and electro-oxidation (E) processes in the removal of amoxicillin (AMX) from wastewater, either as integrated or separate processes. Moreover, the effect of variables, including current density (2-100 mA/cm2), reaction time (2–120 min), and electrolyte concentration (100–1,000 mg/l) on antibiotic removal efficiency were investigated by Box Behnken design under response surface methodology, and optimal conditions were determined for pollutant removal. Then, the effect of AMX concentration and pH variables on the removal efficiency was investigated. The COD removal efficiency was also evaluated under optimal conditions, and eventually the toxicity and bioavailability of the effluent from the combined Photo-Electro oxidation process (PE) were examined. The optimal conditions for variables, including current density, reaction time, and electrolyte concentration for removal efficiency of 62.4%, were 94 mA/cm2, 95 min and 997 mg/l, respectively. Investigating the Amoxicillin and pH variables showed that by reducing the contaminant concentration and pH, the antibiotic removal efficiency increased. The toxicity and bioavailability of the final effluent show the reduction of both parameters in the PE reactor effluent. The PE process can provide an appropriate function to reduce the toxicity and antibacterial properties of effluent by removing more than 60% of amoxicillin and 30% of COD from wastewater.

The entry of toxic organic pollutants and resistant to biodegradation has increased the concern about human health. The use of advanced oxidation (AO) processes to degrade these pollutants has been developing. One of the AO processes is based on the use of hydrogen peroxide in removing resistant organic pollutants.This study aimed to develop a new reactor capable of producing H2O2 in the solution. Therefore, a porous electrode made of stainless steel with the capability of air injection in the electrode center was used. The 30 cm rod graphite electrodes were also used as an anode electrode in a 4000 ml reactor. The effects of variables, including current density (30–40 mA/cm2), time (10–30 min), and electrolyte concentration (12–17 mM/L) on the amount of H2O2 production were evaluated by Box behenken design under response surface methodology using Design expert software. The results of this study showed that H2O2 can be produced at the electrode surface of porous cathode under optimal conditions of 36 mA/cm2 current density, 16 mM/l electrolyte concentration, in 23 min, and in the amount of 34 ppm. Using a porous cathode electrode causes the maximum contact among the solution, water, and air, and increases the production of H2O2.The release of resistant organic compounds to the waste water is a serious problem to the environment. By the application of the Electro-oxidation (EO)reactor with the ability to produce H2O2, this issue is resolved. Furthermore, this technique is applied for non-selective degradation of the toxic organic compounds. • The electro-oxidation process is a useful method for destruction of persistent organic matter from wastewater. • Due to use of porous cathode in this method, contact between the electrode and the sewage is at its maximum level which increases the efficiency and speed of sewage treatment. • This method can produce H2O2 as a high potential oxidant that can reduce persistent organic properties of sewage and make the wastewater suitable for biological treatment. Method name: Advanced Oxidation Process (AOP), Electro-oxidation (EO), Electrochemical Oxidation Processes (EOP), Keywords: Box Behnken design, Electro-oxidation process, Hydrogen peroxide, Modeling, Porous electrode

This study aimed to investigate the effect of exposure to pesticides and the prevalence of type 2 diabetes (T2D). In a cross-sectional study with a population of 9088, the data were collected through Persian Adult Cohort Questionnaire in Shahedieh area of Yazd, Iran. Based on the results, variables such as age, gender, body mass index, physical activity, and education level in the studied population had a significant association with the prevalence of diabetes. Although the obtained data in this study did not show a relationship between exposure to pesticides and the risk of developing T2D, further prospective studies are needed to determine the association between exposure to pesticides and the development of T2D.

Introduction: Water quality is essential for industries because they play an important role in countries’ economic development. Groundwater is one of the most widely used resources, and when the ionic constituents were increasing higher than the allowable limit, it increases the cost of maintenance and production in the industries. Materials and Methods: In order to evaluate groundwater corrosiveness and scaling potential in Zahedan City, 29 groundwater wells and GIS-based geostatistical mapping techniques were analyzed clemically. The physicochemical parameters were invetsiagted and the most popular corrosion and scaling indices were determined as Langelier Index (LI), Aggressive Index (AI), Ryznar Index (RI), Puckorius Index (PI), and Larson–Skold Index (LS). Using ArcGIS 10.6.1 software, the zoning maps were plotted for LI, AI, RI, PI, and LS indices. Results: The results showed that total dissolved solids (TDS) and electrical conductivity (EC) values in all of the samples exceeded the World Health Organization (WHO) drinking water standard. AI values of 58.62% samples showing moderate corrosiveness, and the remaining 17 samples have a scaling nature with very less corrosivity. Based on the LI values, 55.2% of samples have a corrosive nature. Concerning RI values, 59% of the samples have a corrosive tendency. According to the PI values, the entire groundwater of this region has a significant corrosive tendency, and 96% of samples exceeded the LS > 1.2, showing a high rate of localized corrosion. Conclusion: The zoning and spatial analysis of water quality showed that water quality was treated for industrial purposes in the entire studied region.

This study centers on the controllable synthesis, characterization, and application of a novel magnetic bio-metal-organic framework (Bio-MOF) for the adsorption and subsequent removal of arsenic from aqueous solutions. Zinc ions and carnosine (Car) were exploited to construct the Car-based MOF on the surface of magnetite (Fe(3)O(4) NPs). The Magnetite precoating with Car led to an increase in the yield and the uniform formation of the magnetic MOF. The prepared magnetic Bio-MOF nanoparticles (Fe(3)O(4)-Car-MOF NPs) had semi-spherical shape with the size in the range of 35–77 nm, and the crystalline pattern of both magnetite and Car-based MOF. The NPs were employed as an adsorbent for arsenic (As) removal. The adsorption analyses revealed that all studied independent variables including pH, adsorbent dose, and initial arsenic concentration had a significant effect on the arsenic adsorption, and the adsorption data were well matched to the quadratic model. The predicted adsorption values were close to the experimental values confirming the validity of the suggested model. Furthermore, adsorbent dose and pH had a positive effect on arsenic removal, whereas arsenic concentration had a negative effect. The adsorption isotherm and kinetic studies both revealed that As adsorption fitted best to the Freundlich isotherm model. The maximum monolayer adsorption capacity (94.33 mg/g) was achieved at room temperature, pH of 8.5 and adsorbent dose of 0.4 g/L. Finally, the results demonstrated that the adsorbent could be efficiently applied for arsenic removal from aqueous environment. [Image: see text]

In this work, the optimum condition for the adsorption of Reactive Blue 19 dye onto Fe3O4 functionalized with hyperbranched polyethylenimine (Fe@HPEI) was determined using response surface methodology. The properties of synthesized magnetic Fe@HPEI nanoparticles were ascertained using FTIR, SEM, TEM, VSM and zeta potential measurement. The experimental adsorption data indicating the positive effect of adsorbent dose and contact time, and the negative effect of pH, initial dye concentration and ionic strength on dye adsorption. At optimal condition; pH 3.4, contact time 25 min, adsorbent dose 0.4 g/L and initial dye concentration 113 mg/L, Fe@HPEI nanoparticles removed dye up to 99.27%. The maximum experimental dye adsorption was near to the predicted value of 100%, which confirmed the reliability of the selected statistical model. The dye adsorption data were fitted well to Langmuir isotherm and pseudo-second-order kinetic, and the maximum adsorption capacity was 500 mg/g. Totally, Fe@HPEI as an effective superadsorbent can be repeatedly utilized for the adsorption of dye from the aqueous environment.

The aim of this research was to evaluate the efficiency of electrocoagulation (EC) for the removal of natural organic matter (NOM) by using iron (Fe) and aluminum (Al) electrodes. The effects of several operational parameters such as initial pH (3–10), time of electrolysis (5–30 min), initial concentration of organic matter (10–50 mg NOM/L), current density (0.25–1.25 mA/cm2), type of electrode material (n = 4, 2 sides × 11 cm × 10 cm, wall thickness = 2 mm, distance between each electrode = 5 mm), and type of connection of electrodes (bipolar and monopolar configurations) were explored for the removal of NOM from synthetic humic acid solution in a 2 L laboratory-scale EC cells (A s/V = 0.110 cm−1). The optimum conditions for the process were identified as pH = 3 and 7, electrolysis time = 20 and 10 min for Fe and Al electrodes, respectively. Using both electrodes at current density = 0.25 mA/cm2 and initial concentration of organic matter = 50 mg/L, a NOM removal efficiency of almost 100% could be achieved in the bipolar mode. Based on the optimum conditions, specific reactor electrical energy consumptions were 14.90 kWh/kg Al (or 0.092 kWh/m3) and 2.88 kWh/kg Fe (or 0.11 kWh/m3). Specific electrode consumptions were obtained to be 0.0062 and 0.0382 kg/m3, and operating costs of the EC system were preliminary estimated at 0.057 and 0.119 $/m3 for Al and Fe electrodes, respectively.

Heavy metals are introduced in human tissue through breathing air, food chain and human skin. They can cause damage to the nervous system and internal organs. In the present study, sixty street dust samples were collected from the central area of Tehran and were digested in the laboratory to determine the content of Zn, Ni, Cd, Cr, Cu and Pb, using inductively coupled plasma optical emission spectrometry (ICP-OES). The level of contamination with the analyzed metals was determined according to the following indices: geo-accumulation index (I geo), enrichment factor (EF), pollution index (PI), integrated pollution index (IPI) and potential ecological risk index (RI). The average concentration of heavy metals found was in the order of Zn > Cu > Pb > Ni > Cr > Cd. The average I geo values for Cd, Cr, Cu, Ni, Pb and Zn were 1.53, −1.88, 2.68, −0.67, 1.62 and 2.70, respectively. Among the investigated heavy metals, zinc and copper had the maximum average EF values and were placed into the “very severe enrichment” class. Potential ecological risk factor (E r) also indicated that Cd had the highest risk, and it was classified as of considerable potential ecological risk. Therefore, it is necessary to pay more attention to the appearance of Cd in the human environment. The calculated potential ecological risk index values also illustrated that the street dust samples presented a “moderate ecological risk.” The calculated IPI values showed that the pollution levels of the street dust samples ranged from high to extremely high.

This study aimed to investigate the removal of Reactive Blue 19 from colored wastewater using Fe3O4 magnetic nanoparticles modified with L-arginine (Fe3O4@L-arginine). In order to investigate the effect of independent variables on dye removal and determining the optimum condition, the Box–Behnken Design (BBD) under Response Surface Methodology (RSM) was employed. Fe3O4@L-arginine nanoparticles were synthesized and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and vibrating sample magnetometer. Applying Fe3O4@L-arginine nanoparticles for dye removal showed that; by increasing adsorbent dose and decreasing pH, dye concentration, and ionic strength dye removal has been increased. In the optimum condition, Fe3O4@L-arginine nanoparticles were able to remove dye as high as 96.34% at an initial dye concentration of 50 mg/L, adsorbent dose of 0.74 g/L, and pH 3. The findings indicated that dye removal followed pseudo-second-order kinetic (R2=0.999) and Freundlich isotherm (R2=0.989). Based on the obtained results, as an efficient and reusable adsorbent, Fe3O4@L-arginine nanoparticles can be successfully applied for dye removal from colored wastewater.

In this study, the efficiency of Integrated Fixed-film Activated Sludge (IFAS) system in synthetic greywater treatment and nutrients removal was studied in duration of 105 days according to different Organic Loadings Rates (OLRs). The study was operated in pilot-scale and OLRs of 0.11–1.3 gCOD/L.d. Scanning Electron Microscope (SEM) image showed that the biofilm with a proper thickness was formed on IFAS reactor’s media. The results indicated that the best removal efficiency of BOD5, COD, and TSS were 85.24, 92.52 and 90.21%, respectively, in an organic loading of 0.44 gCOD/L.d. Then, with the OLR increased, the removal efficiencies of BOD5, COD, and TSS increased as long as the organic loading reached 0.44 gCOD/L.d. But with the OLR increased more, the removal efficiency of these parameters decreased. The ANOVA statistical test results showed that the mean difference of removal efficiency in organic loadings for BOD5 (p ≤ 0.001) and COD (p = 0.003) was significant, while it was insignificant for TSS (p = 0.23). The best removal efficiencies of Total Nitrogen (TN) and Total Phosphorus (TP) were 89.60 and 86.67%, respectively, which were obtained at an OLR of 0.44 gCOD/L.d. By increasing OLR up to 0.44 gCOD/L.d, removal efficiencies of TN and TP increased, while the removal efficiency decreased with the OLR increased more, and this difference was statistically significant (p = 0.021). Finally, the results showed that the IFAS system provided a proper efficiency in treatment of the synthetic greywater and it could be used in a full scale.

Introduction: The problem related to water pollution of nitrates and nitrites is both an issue in Iran and also most parts of the world. Studies to evaluate the acute and chronic effects of nitrate and nitrite have demonstrated that different concentrations of these compounds in water and food have been causing multiple diseases. Methods: In this paper, researchers reviewed published articles and research from 1950 to 2016 in English and Farsi, according to key words “nitrate”, “nitrite”, “water”, “food” and “health effects”, retrieved from databases, such as Medline, Scopus, Pub Med, and scientific information database (SID). Results: Consumption of drinking water and food containing high concentrations of nitrate and nitrite could cause diseases, such as cancer, methemoglobinemia, and enlargement of the thyroid gland and diabetes mellitus. The positive effects of low concentrations of nitrates and nitrites include a protective effect on the cardiovascular system, regulatory role in blood pressure, and homeostasis (also static) of the vessels Conclusions: As different concentrations of nitrates and nitrites have beneficial and undesirable effects on human health and regarding the high cost of treating water contaminated with nitrite and nitrate, more investigations should be done in setting the standards and levels of parameters used in drinking water.

In this study, dye removal from synthetic colored wastewater using electrocoagulation process was studied. Acid Red 73 was used as model dye compound. The effects of operational parameters, such as current density, reaction time, initial dye concentration, electrolyte concentration, initial pH, and polyaluminum chloride (as a coagulant), on dye removal were investigated. The cost of wastewater treatment at optimal condition was investigated. The results showed that electrocoagulation process was able to remove 99% dye and 88% chemical oxygen demand. Using polyaluminum chloride as a coagulant had significant impact on improving process efficiency, time, and cost reduction. It can be concluded that electrocoagulation was a very effective and fast method to remove acid dye from colored wastewater.

In this study, the efficiency of Moringa stenopetala seed extract was compared with alum and M. stenopetala-alum hybrid coagulant to remove Direct Red 23 azo dye from textile wastewater. The effects of parameters such as pH, coagulant dose, type of salt used for the extraction of coagulant and initial dye concentration on dye removal efficiency were investigated. Moreover, the existing functional groups on the structure of M. stenopetala coagulant (MSC) were determined by Fourier transform infrared spectroscopy, and the morphology of sludge produced by MSC, alum, and hybrid coagulant was characterized by scanning electron microscopy. Ninhydrin test was also used to determine the quantity of primary amines in the MSC and Moringa oleifera coagulant (MOC). According to the results, with increasing the coagulant dose and decreasing the initial dye concentration, dye removal efficiency has increased. The maximum dye removal of 98.5, 98.2, and 98.3 % were obtained by using 240, 120, and 80 mg/L MSC, alum and hybrid coagulant at pH 7, respectively. The results also showed MSC was much more effective than MOC for dye removal. The volume of sludge produced by MSC was one fourth and half of those produced by alum and hybrid coagulant, respectively. Based on the results, hybrid coagulant was the most efficient coagulant for direct dye removal from colored wastewater.

In this research, the efficiency of electrocoagulation treatment process using aluminum electrodes to treat synthetic wastewater containing Reactive Red198 (RR198) was studied. The effects of parameters such as voltage, time of reaction, electrode connection mode, initial dye concentration, electrolyte concentration, and inter electrode distance on dye removal efficiency were investigated. In addition, electrical energy consumption, electrode consumption, and operating cost at optimum condition have been investigated. The results showed that dye and chemical oxygen demand removals were 98.6 and 84%, respectively. Electrode consumption, energy consumption and operating cost were 0.052 kg/m 3 , 1.303 kWh/m 3 and 0.256 US$/m 3 , respectively. Dye removal kinetic followed first order kinetics. It can be concluded that electrocoagulation process by aluminum electrode is very efficient and clean process for reactive dye removal from colored wastewater.