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Background and purpose: Quality of hospital wastewater is similar to municipal wastewater however, due to the presence of toxic agents and pathogens in hospital wastewater, if not already treated, it is dangerous to the environment and consequently to human’s health. This research was to study the wastewater treatment and disposal condition and the quality of hospitals effluent of Babol Üniversity of Medical Sciences.
Materials and methods: This cross-sectional descriptive research studied the wastewater treatment and disposal systems condition and effluent quality in Shahid Beheshti, Shahid Yahianejad, Âmirkola children and Âyatollah Roohani hospitals. 72 mixed samples were collected and tested for pH, BÔD5, ÇÔD, TSS and TÇ in the effluents of wastewater treatment plants using the current standard methods.
Results: Mean values of pH, TSS, BÔD, ÇÔD and total coliforms in the inlet and outlet wastewaters from the studied hospitals were 7.5±0.6, 296±151mg/L, 400±173mg/L, 616±252mg/L, 3.1×105MPN/100 mL and 7.4±0.4, 78±36 mg/L, 84±31.5 mg/L, 150±51 mg/L and 831±509 MPN/100 mL, respectively. The mean value of free chlorine residual in outlet wastewater was 0.2 mg/L. Mean removal of TSS, BÔD, ÇÔD and TÇ in outlet %74.3, %79.6, %76.5 and %99.7, respectively.
Çonclusion: The mean value of TSS, BÔD, ÇÔD and TÇ in the outlet wastewater of the studied hospitals exceeded the maximum allowable thereshold of the environmental conservation administration, which indicate the inefficiency of wastewater treatment systems. We conclude that essential considerations must be taken into account to upgrade the studied wastewater treatment systems in terms of design, operation and maintenance.

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Background and purpose: There is no specific standard on the compost maturity time of biosolids of wastewater treatment plants in Ïran therefore, the researchers made an attempt to employ different chemical and biological methods to assess the compost maturity time.
Materials and methods: Ïn this study, the sludge was obtained from the drying beds of South Ïsfahan Wastewater Treatment Plant and was then mixed with sawdust and windrow type of composting was performed to stabilize the sludge. The height, width and length of windrow were 1.2, 1.5, and 2.5 m, respectively. The windrow turning was done manually for 7-10 days.
Results: The results showed that, Ç/N ratio after 100 days of composting reached 15.1 and the NH4/NÔ3 ratio decreased with increase in the time of dewatered sludge compost. The content of volatile solids decreased up to 28.8 percent with composting time and the number of fecal coliforms reached 898 MPN/gram of total solids.
Çonclusion: Thus, biosolids compost in this study was mature and ready for use as an agricultural substrate after 100 days of composting.

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Background and purpose: High concentrations of heavy metals in industrial and domestic wastewater cause adverse effects on the environment and human health. Therefore, removing heavy metals from water resources is considered as a positive step towards sustainable development. Today, application of artificial wetlands to remove pollutants such as heavy metals is increasing due to high costs of construction sites, low operation, maintenance, and energy needs. Materials and methods: This experiential research was carried out in a pilot scale in adjacent of wastewater treatment plant in the campus of Mazandaran University of Medical Sciences. The pilot was composed of four rectangular concrete reactors with 6 × 1.5 × 0.8 m length, width and affective depth. One reactor was used as control. The research was performed in five phases. Different hybrid systems of the reactors (combination of vertical and horizontal with parallel and series flow) were evaluated. The samples were digested using an acid digester and concentrations of lead and cadmium were analyzed using atomic absorption spectrophotometer. The data was analyzed using SPSS. Results: By increasing the hydraulic retention time (HRT) from 2 to 6 days, the mean percentage for removal of studied metals increased to 58 (which was 42 at the beginning). Among the different phases, phase four was more efficient which removed 54% of the heavy metals while the lowest removal percentage was detected in phase one. The average percentage removal of cell output for reed planting and the controls were 65% and 35%, respectively. These differences were statistically significant (P≤ 0.05). Conclusion: The findings of this research showed that combination of DF-UF (down flow-Up flow) reactors was the best condition for the removal of lead and cadmium from subsurface wetlands. The optimal hydraulic retention time was 4 to 6 days and 10 to 20 mm gravel could be more appropriate for the size of gravel in wetland.

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Background and purpose: Indirect electro-oxidation method with H2O2 electrogeneration is an electrochemical process for wastewater treatment based on the production of hydroxyl radicals by means of H2O2 generation in the presence of transition metals such as copper. Materials and methods: The electrogenerated hydrogen peroxide process was performed in an open and undivided cell to be assessed for degradation of real textile wastewater using graphite felt (cathode) and Pt (anode) in the presence of copper ions. The effect of major parameters such as dissolved oxygen concentration, initial pH, applied current, copper concentration and time reaction on the decolorization was investigated. Results: 67.9% decolorization and 56.3% chemical oxygen demand (COD) removal were achieved after 210 minutes reaction under the conditions 7.8-7.9 mg/l dissolved oxygen, 250 mA applied current, 7 mM copper concentration and pH=4. Conclusion: The electrogenrated H2O2 process in presence of copper ions could degrade real textile wastewater. Moreover, due to generation of hydrogen peroxide, this process can be economically important.

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Background and purpose: Today, environmental pollution, especially pollution of aquatic ecosystems, humans and other organisms are faced with serious problems. Endocrine disrupting chemicals are one group of chemical compounds that are important because of their significant adverse effects in humans and animals. Therefore, this study aimed to determine the concentration of 4-Nonylphenol, Bisphenol A and Octylphenol compounds in surface sediments of 4 areas in the coastal of Caspian Sea. Materials and methods: Surface sediments samples taken from stations were studied and after preparation (Drying, Extraction, Clean up) the samples were injected into the Gas Chromatography-mass Spectrometry Results: The concentration ranges of 4-Nonylphenol, Octylphenol and Bisphenol A compounds in surface sediment samples were as follows (in ng/gdw): 16.41-174.48, 5.63-41.90 and 0.3-30.66 respectively. The station that is located in the Anzali region showed significant amounts of all three compounds, Because the sources of these compounds there and the stations that are located in Kaporchal and Astara regions showed extremely low concentration. Compare concentrations were abtained from coasals of Caspian Sea with sediment quality standard showed that these compounds have potential to cause negative effects on the organisms in some stations Conclusion: There are concerns about the presence of Estrogen Doubt Compounds in the aquatic ecosystems due to the adverse effects of them in biological communities health even at low concentrations.

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Background and purpose: Mercury is a toxic heavy metal which causes irrevocable intense nerve-recognition disturbance to human. Excess contact to mercury causes diseases like tremor, losing sensation, decreasing vision and hearing or growth. WHO recommended the most amount of mercury absorption about 0.3 mg per week and the most concentration in water about 1µg/L. The purpose of this study was to investigate the efficiency of Lcysteinefunctionalized single-walled carbon nanotubes (SWCNs) in mercury removal from aqueous solutions. Materials and methods: In this study, single-walled carbon nanotubes was used as absorbent. The effects of some parameters such as pH, absorbent dose, contact time and mercury concentration were assessed. All experiments have been done according to standard methods. The sample size was determined by Box-Benkan method. Results: The result showed that absorption rate increased by increasing of pH, contact time and mass CNTs dose. The Hg removal efficiency decreased by increasing of initial Hg concentration.The maximum and the minimum of absorption rate are 95 and 22 percent, respectively. ANOVA showed that RSM has a significant relationship for single-walled carbon nanotubes with linear conditions. Conclusion: The study demonstrated that SWCNT-Cysteine is a well absorbent for Hg removal from aqueous solutions Therefore, it can be effective for the removal of mercury from aqueous solutions.

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Background and purpose: Removal of lead as a toxic metal from contaminated water resources is necessary due to the dangerous effect of lead. One of the most effective methods of removal is the adsorption process. The aim of this study was adsorption and magnetic separation of lead from synthetic wastewater using iron oxide nanoparticles and carbon (ION/C) composite Material and Methods: In this study nanoparticles of iron oxide (ION) were used as a source of iron for magnetic separation of powder activated carbon from solution samples. The physical and surface properties of the adsorbent were studied along with influencing factors (pH, contact time, adsorbent dosage, initial lead concentration, and temperature) on the adsorption process. Kinetic equations and equilibrium isotherms studies were also conducted. Results: The size of ION and specific surface area of ION/C were found to be 30-80 nm and 671.2 m2/g, respectively. We observed that the adsorption process reached equilibrium at 60 min and pH=6and adsorption efficiency increased by increasing the amount of adsorbent and temperature. Maximum adsorption capacity based on Langmuir isotherms was obtained 67.1mg/g at 50 °C. Conclusion: According to this study it is believed that magnetized active carbon by keeping its physical and surface properties could be a suitable method to solve some related problems including separation and filtration.

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Background and purpose: Heavy metals such as chromium, nickel, and zinc are the most common contaminants found in the plating wastewater that cause environmental pollution due to non-biodegradability. This study investigated the removal of chromium, nickel, zinc and turbidity from wastewater of plating and galvanized industries by electrocoagulation technology. Material and methods: This study was conducted at laboratory scale using four parallel aluminum electrodes (5cm × 10cm dimensions, 1 mm thickness). In each electrode, 6 holes (0.7 cm) were considered. Wastewater samples were first collected as grab sampling and finally changed to combined samples. This study was performed in pH= 3 and pH= 7.2 for plating wastewater and pH= 9 for galvanized wastewater and reaction times of 20, 40, 60 and 80 minutes. Results: Nickel and chromium contents in plating wastewater were 45 and 50 mg/l, respectively. Zinc concentration in galvanized wastewater was determined 210 mg/l. Turbidity in plating and galvanized wastewaters were 250 and 200 NTU, respectively. The maximum removal of nickel and chromium was observed in contact time= 80 min and pH=4, while it was seen in pH=9 for zinc (98 %, 95.6%, and 94%, respectively). The maximum removal of turbidity in Ni – Cr wastewater and galvanized wastewater was 97% and 95.3%, respectively. Conclusion: Electrocoagulation technology was found as an effective, economical and rapid method for infiltration of toxic wastewater in plating and galvanized industries.

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Background and purpose: In Electro/Fe2+/persulfate process, persulfate radicals are produced as powerful oxidizing agents which increase the efficiency of this process. The aim of this study was to investigate the efficiency removal of COD, TSS and dye from industrial effluent in Buali industrial area in Hamedan. Materials and methods: In this study, the batch experiment was performed using a reactor equipped with four iron electrodes. We studied the effects of some operating parameters including pH (3-11), divalent iron ion dose (0.1 to 0.5 g/L), concentration of persulfate anion (0.5-2 g/L) and direct current electric rate (1-5 A) in removal of COD, TSS and dye from wastewater. The COD, TSS and dye measurement was done according to the standard methods. Results: The results showed that under optimum conditions (pH: 3, Fe+2 dosage: 0.1 g/L and density: 5A) the removal efficiencies of process in COD, TSS and dye were 91.6, 73.5 and 93.1%, respectively. By making changes in the parameters, the efficiency of process also changed. The removal efficiency of single application of electrooxidation was 58.2%, 52.2% and 68% for COD, TSS and dye, respectively. Conclusion: The electro/Fe2+/persulfate process showed acceptable performance in removal of COD, TSS and dye. Therefore, this process could be used as a pretreatment unit to reduce the load of raw wastewater pollution before entering the conventional treatment units. Furthermore, the assessment of synergistic effects of persulfate revealed that single application of electrochemical degradation in optimum conditions had a much lower efficiency compared to electro/Fe+2/persulfate process.

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Background and purpose: Wastewaters are the most important sources of antibiotics entrance into the aqueous environments. Conventional wastewater treatments cannot eliminate these micropollutants and antibiotic resistant bacteria. The aim of this study was to determine the antibiotic resistance pattern in bacteria isolated from untreated sewage and effluent of municipal wastewater treatment plant in Tabriz. Materials and methods: In this cross sectional study, in addition to counting the number of different types of bacteria in raw sewage and municipal wastewater effluent, various bacteria including Enterobacteriaceae and Staphylococcus, Bacillus and Pseudomonas were identified using specific mediums, API E20 kits and biochemical tests. Susceptibility test of bacteria to antibiotics was determined by Kirby-Bauer's disc diffusion. Results: The results showed lower than one log removal efficiency for coliforms bacteria by the wastewater treatment plants. The difference in the number of colonies apart from staphylococci was not significant in wastewater influent and effluent. Aeromonas and staphylococci were the most frequent bacteria in wastewater influent and effluent, respectively. Enterobacteriaceae were generally more sensitive than other bacteria. Resistance to antibiotics was found to be higher in the penicillin member of antibiotics. Resistant to four antibiotics including cephalexin, ampicillin, methicillin and amoxicillin were between 60 to 100%. The resistance of all species increased in the effluent of wastewater treatment plant. Conclusion: Growth and survival of antibiotic resistant bacteria increases in wastewater treatment plants and conventional treatment processes do not demonstrate enough efficiency for removal of these strains.

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Background and purpose: Pulp and paper industries produce large quantities of effluent that release various pollutants daily. Among various methods for treating such effluents, anaerobic biosorption process is of interest because of lower need to mechanical energy, boigasses production, high organic loading rate (OLR), low sludge production, and resistant system. OLR is one of the most important effective hydrodynamic parameters. In this study, the effect of OLR was investigated on anaerobic biosorption reactor in treating pulp and paper effluent.

Materials and methods: A 1.96L effective volume cannon pilot was used and wastewater was injected by pumping to the bed of the reactor. Temperature and pH were maintained about 30±2°C and 6.8-7.2, respectively. The effect of OLR on efficiency of system was studied in 1-12 kgCOD/m³.d. All experiments were performed under steady state conditions using procedures outlined in Standard Methods.

Results: In OLR 7kgCOD/m³.d and upflow velocity of 0.56m/h the system was able to reduce over 80% of COD concentration after 33-39h. No significant increase was observed in efficiency of the system at more OLRs, so it was selected as optimum loading rate. System efficiency was found to have a direct relation with decrease of upflow velocity and increase of HRT. The gas generation rate was 0.32 m³/kg COD removed.

Conclusion: According to this study, anaerobic biosorption system satisfactorily treated pulp and paper mill effluent and could perform this close to wastewater discharge standards established by national guidelines.

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Background and purpose: 2, 4-dinitrophenol (DNP) are carcinogenic and non-biodegradable pollutants that exist at high concentration in wastewater of chemical industries. In this study, treatment and removal of organic materials (COD) in wastewater was carried out by catalytic ozonation process (COP) using carbon Nano-composite catalysts.

Materials and methods: This study was conducted in cylindrical 250 mL semi-continuous reactor and the effects of several parameters including pH of the solution (4-10), the amount of catalyst concentrations (0 to 4 g/L), reaction time (0 to 60 min), and saturated catalyst was studied on treatment of high concentration of DNP and the COD removal efficiency. Also, the kinetics were compared with single ozonation (SOP).

Results: Removal efficiency of high concentrations of DNP (1500 mg/L) and kinetics of the COP process catalyst concentration of 4 g/L was 83% (0.0241 min^-1) while the results in SOP were 50% (0.0108 min^-1). The optimum pH was 6 with the reaction time of 60 min. However, the removal efficiency of COD at initial concentration of 610 mg/L in the SOP process was 61% which increased to 92% after addition of the catalyst. The main mechanism of process was chemical oxidation and a small share (3%) was due to adsorption.

Conclusion: The results showed that COP and this new catalyst effectively and quickly removed high concentrations of DNP and COD. This method is believed to be economic due to the short time of ozonation, recovery and reuse of the catalyst.

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Background and purpose: Laundry is one of the main wastewater producing units in hospitals. Most of detergent materials are hardly degradable and cannot be broken fast in the conventional treatment facilities. This research aimed at studying the possibility of hospital laundry wastewater pretreatment by electrocoagulation method using aluminum electrodes.

Materials and methods: Using composite sampling method, a total of 72 samples was taken from the effluent of a hospital laundry wastewater in Gorgan. The samples were analyzed according to standard methods of water and wastewater examination. After determining the quality of raw laundry wastewater, the wastewater was treated by electrocoagulation method with aluminum electrodes in different circumstances of pH, voltage and times. Process efficiency concerning the removal of COD, color, phosphate and surfactant was examined.

Results: In this study the mean density of COD, phosphate and surfactants in hospital laundry waste water were 848.8 ± 109.4, 1.03 ± 0.06 and 4.81 ± 0.93 mg per liter, respectively and the mean concentration of color was 759.3 ± 152.8 TCU. In optimal conditions, this process could remove 86, 98.8, 94.98, and 66.6% of COD, color, phosphate and surfactant, respectively. The efficiency removal of all parameters increased as the voltage and the contact time increased.

Conclusion: This study showed that laundry waste water was highly polluted and electrocoagulation process could be an efficient procedure in its pre-treatment.

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Background and purpose: Phytoremediation (constructed wetland) is one of the most appropriate technologies for wastewater treatment. The aim of this study was to evaluate the efficiency of the combined anaerobic and phytoremediation systems for sanitary wastewater treatment.

Materials and methods: This experimental study was performed during nine months to measure some parameters including COD, BOD₅, TSS, turbidity, total coliform, and intestinal nematode using combined anaerobic and phytoremediation systems. The samples of wastewater were randomly taken twice per month from the influent and effluent of the septic, wetland and control system. The parameters were measured based on both the Bailenger and standard methods for extermination of water and wastewater. The results were then compared with the Iranian effluent standards for irrigation.

Results: The results showed that by using the hybrid process of anaerobic and phytoremediation systems, the COD and TSS removal rates reached 80% each and the turbidity and BOD₅ removal rates were reported to be 90%. The removal efficiencies of total coliform and intestinal nematode were 99, 999% and 100%, respectively. In this study, the quality of the treated wastewater was found to be acceptable according to the Iranian effluent standards for irrigation.

Conclusion: The combined anaerobic and phytoremediation systems can be used as an efficient process for wastewater treatment.

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Background and purpose: Estrogen is a steroid hormone that enters water sources through urban and hospital waste water and is a serious threat to aquatic organisms, especially fish, and human health. The aim of this study was to evaluate the performance of municipal and hospital waste water treatment, especially biological treatment in removal of estrogenic compounds.

Materials and methods: Estrogens in aqueous samples were determined by tracking. Fifty six samples were obtained from various locations in Ahwaz municipal wastewater treatment plant and hospital waste water treatment facilities within 8 months. The samples were analyzed using Electrochemiluminescence (ECL). The results were reported in units of ng/L.

Results: The average influent and effluent hormone levels in municipal wastewater treatment plant were 58.8 ng/ L and 5.4 ng/L, respectively. In hospital treatment plant the average influent estrogen level was 61.8 ng/L and the average effluent level was 10.8 is ng/L. The results showed that biological treatment using activated sludge can remove significant amounts of estrogen and could reduce its level to a value lower than international standards.

Conclusion: The removal mechanism of estrogen in biological treatment system, especially activated sludge are adsorption and biological degradation. Secondary treatment of wastewater is effective in reducing hormones that could be due to wastewater biological treatment.

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Background and purpose: Molasses is colored, toxic and non-biodegradable compound which is found in the wastewater of fermentation industries. This study investigated the kinetic and efficiency of molass dye removal and mineralization in the yeast wastewater using nanocomposite catalysts in ozonation process.

Materials and methods: The catalytic ozonation process (COP) of colored effluent of biological treatment of yeast production factory was carried out using semi-continuous flow cylindrical reactor and the effects of operational parameters such as initial pH value (4-10) and reaction time (5-60 min) on removal efficiency of dye and mineralization were investigated. After determining the kinetic parameters of reaction, the effects of some other parameters such as adsorption and reuse of the catalyst were calculated and the efficiency was compared with single ozonation process (SOP) and granular carbon as catalyst.

Results: The removal efficiency of dye of molass factories effluent and its kinetic, at the condition of initial dye concentration 4521 ADMI, catalyst concentration 2 g/L and 60 min reaction time were 95% and 0.045 min^-1, respectively; while these parameters in SOP and granular activated carbon as catalyst were 71% with 0.018 min^-1 and 86% with 0.028 min^-1, respectively. But, the mineralization and its kinetic in COP were 74% and 0.023 min^-1, respectively, in which initial TOC was decreased from 510 mg/L to 132 mg/L.

Conclusion: The nanocomposite was found to have the best efficiency in dye degradation and TOC removal and it is easy to recover and reuse over and over by magnet. The main mechanism of dye degradation in COP was chemical oxidation and less occurred by adsorption.

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Background and purpose: Dyes from textile industry are amongst the major pollutants of the environment that are harmful for both human health and the environment. Azo dyes constitute the largest and the most important class of commercial dyes, accounting for 50% of all commercial dyes. This study investigated the efficacy of Cr-doped ZnO nanoparticles in removal of reactive black 5 (RB5) dye from aquatic solutions in presence of solar radiation.

Materials and methods: An experimental laboratory study was done by designing the surface-answer test. Cr-doped ZnO nanoparticles were synthesized using co-precipitation method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for characterization of the nanoparticles prepared. Effects of parameters such as pH, nanoparticle dosage, initial RB5 concentration, and contact time on the removal efficiency of RB5 were studied. The remaining concentration of RB5 was analyzed by UV/VIS spectrophotometer at a wavelength of 597 nm. Finally, the statistical analysis of the model was conducted by ANOVA.

Results: Results showed that removal efficiency increased by increasing nanoparticle dosage and contact time. Also, we found that removal efficiency decreased by increasing the initial dye concentration and pH. The optimum condition for dye removal was obtained at pH 4, nanoparticle dosage of 1.75 g/L, initial dye content of 112.5 mg/L, and 75 min contact time. In this condition the efficiency removal and desirability were 75.41 and of 0.905, respectively.

Conclusion: Removal of textile dyes was found to be quick and effective when using Cr-doped ZnO nanoparticles. Also, designing and performing the experiment (in low frequency) can help in optimizing the efficiency removal of pollutant from aqueous media.

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Background and purpose: 2,4 dichlorophenol is one of the most important components of organochlorine. High resistance against degradation, creating odor and taste in water, high toxicity and being carcinogen have made this pollutant a great concern. Current study batch was done to investigate the adsorption of 2,4 dichlorophenol onto Magnetic Graphene Oxide Particles (MGO NPs).

Materials and methods: The adsorption behavior of 2,4-dichlorophenol was studied in a series of batch experiments as a function of pH (3-11), contact time (0-120 min), and pollutant concentration (10-125 mg/L) at three different adsorbent dosages (0.1-1 g/L). Finally, pseudo-first-order, pseudo-second-order kinetic, Langmuir and Freundlich isotherm models and adsorption thermodynamic were studied in optimized conditions.

Results: The results revealed in optimized conditions (pH=5, contact time=15 min, pollutant concentration= 10mg/l and adsorbent dose=0.75 g/l) maximum adsorption capacity and removal efficiency of 2,4-dichlorophenol were 84.74 mg/g and 100%, respectively. Langmuir isotherm (R²=0.9987) and pseudo-second-order (R²=0.9992) models were proved to be the best in describing the adsorption data. The thermodynamic parameters showed that the adsorption process was endothermic (ΔG= 57.7 to 119.15) and spontaneous (ΔG= -1.15 to -9.44).

Conclusion: MGO NPs have extended capabilities such as easy and rapid separation from sample and high potential in removing 2,4 dichlorophenol, so, it can be introduced as an appropriate adsorbent for removal of this pollutant from water and wastewater.

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Background and purpose: The aim of this study was to evaluate the quality of wastewater treatment plant effluent in Qazvin (Alvand) industrial area for discharge into the environment and reuse.

Materials and methods: The study was conducted over a period of nine months in 2015-2016. Ninety samples of wastewater were collected to determine the concentrations of BOD₅, COD, TSS, TC, FC, and heavy metals (lead, cobalt, and Cd). The levels of pollutants were evaluated according to the standards of Iran Environmental Protection Agency for discharge to the environment and reuse.

Results: The mean concentration of COD in the effluent during autumn, winter and spring were 145.20±52.66 mg/L, 316.50±279.80 mg/L, and 177.00±124.2mg/L, respectively. The average concentration of BOD₅ were found to be 79.40±26.76 mg/L, 154.25±122.86mg/L, and 72.00±13.74 mg/L in autumn, winter, and spring, respectively. The mean values for total coliform and fecal coliform were 6×10² MPN/100 mL and 6.21×10² MPN/100 mL, respectively. The average lead and cobalt concentrations were found to be 0.21±0.11 mg/L and 0.004±0.003 mg/L, respectively. The cadmium concentration was reported to be minimal.

Conclusion: Current results showed that the wastewater quality conformed with EPA's standards for reuse, but the use of wastewater for agriculture, due to the biological and cumulative effect of some elements, should be done based on health principles.

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Background and purpose: Using catalysts to enhance the efficiency of the ozonation process (known as catalytic ozonation process) has received much attention in recent years. This study aimed at examining the overall feasibility of using catalysts ozone as catalyst in ozonation process for decolorization and mineralization of a real textile wastewater in presence of persulfate.

Materials and methods: This experimental study was conducted on a laboratory scale reactor using a semi-batch mode. The effect of persulfate, ozone flow rate, reaction time and catalytic dose in dye and COD was investigated in an optimal state of textile wastewater. To obtain optimization test, the experiment was performed by fractional factorial method at three-level factorial (3k−p) with a high resolution (VI).

Results: In this study, 15 min contact time (P = 0.006) and 0.5g/L dose of catalyst (P=0.029) had the best effect on color removal. Moreover, the interaction of these parameters were found to be significant (P= 0.025). The optimum condition for color removal was achieved at 15 min reaction time, ozone flow rate of 2 L/min, 1.5 mM persulfate and catalyst dosage of 0.5 g/L. Optimum efficiency removal for color and COD in textile wastewater were 96% and 75%, respectively.

Conclusion: Application of nano-magnesium oxide with ozone in presence of persulfate showed synergistic effect and buffering property in decolorization and mineralization of textile wastewater. It also increases the efficacy of color removal and improves mineralization so, there would be no need for pH adjustment.