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Currently tons of dye produced per year, about the one sixth tons are converted into wastewater in various industries such as textiles and dyeing, which are among the toxic, carcinogenic and mutagenic wastes due to the presence of aromatic rings in their structure. This issue has attracted a lot of attention to the purification of such compounds. Ozone is one of the strong oxidizers which produces non-toxic compounds due to its decomposition. Ozone can convert many organic materials into simpler compounds through both direct and indirect oxidation mechanisms, including degradation of wastewater that contains double bonds components such as aromatic compounds and dyes. The purpose of this study was to investigate modeling, optimization and the interactions between parameters affecting the ozonation process in removal of Acid Orange 7 in order to achieve the highest removal efficiency for the highest possible initial dye concentration under the lowest ozone injection rate, no change in initial wastewater pH and the shortest reaction time by the use of response surface method. The RSM was performed using 4 parameters pH, initial dye concentration, ozone injection rate and time with 5 levels which ends up in 30 experimental tests. The results showed that correlation coefficients and adjusted correlation coefficients were 96.85 and 94.92, respectively, and p-value for model (less than 0.0001) and lack of fit (0.0507) were obtained as significant and non-significant, respectively. These results indicate the consistency and high reliability of the modeling results. Normal error, error independence and variance stability control were also checked which showed that the closeness between the actual and predicted values and the uniform distribution of the results obtained on the normal line indicates the uniform distribution of the error. The results and predictions of the software, the random distribution and distribution of the results indicate the suitability of the assumption considered by the software regarding the stability of the variance. Based on variance stability control, the effect of the experiments on the responses provided by the software. If one of the experiments is outside the range, this experiment will have a negative impact on the overall results of the software. In the case of experiments performed, this control was also well performed. Based on model equation the most important parameters are the injection rate of ozone (Q(O3)), pH, reaction time (T) and initial dye concentration [Dye], respectively, in which all parameters except the initial dye concentration have a positive effect on dye removal efficiency. After the related tests the optimum condition were the initial dye concentration of 480 mg/L, pH of 7.7, ozonation rate of 0.6 L/min and ozonation duration of 60 min which resulted in 90% dye removal efficiency. It was also found that the most effective factors were injectable ozone rate, time, pH, and dye concentration, respectively. The results showed that determining the appropriate domains can be of great importance in achieving the desired results from the response surface method. Also, the ozonation process is able to purify the dye from high initial concentrations to high removal efficiency, indicating the high strength of this applied process in the decomposition of complex organic compounds. Ozonation kinetic rate is based on pseudo first order which was increased from 0.3 to 0.6 by enhancing injected ozone rate from 0.2 to 0.6 L/min respectively and further increase of ozone injection rate didn’t had any effect on its kinetic rate.

There are different methods for soil stabilization, such as using windbreak, planting and use of mulch. The use of new soil stabilization methods, due to reduced environmental impacts, is a suitable alternative for oil mulch. Soil stabilization by using Nano polymer Polylatice creates a uniformly coherent cortex that is resistant to high wind speed and has less environmental degradation effects. In this research, the soil of the Hossein Abad area, near the salt lake of Qom, has been used for wind erosion test to verify the stabilization with the use of nano polymer Polylatice. After passing through a 2 mm sieve, the soils were stabilized with concentrations of 1, 1.5 and 2 L/m2 of Polylatice in trays with dimensions of 80*80*3 cm. These specimens were exposed to wind by three different velocities, including 10, 15 and 20 m/s, during 7 and 30 days and their stabilities were analyzed against wind. The concentration of dust of the Hossein Abad area in the 7 and 30-day stabilization decreased by 60 and 50 times at a wind speed of 20 m/s, respectively and as time passed by after adding mulch, the amount of particles deposited along the channel were also decreased significantly.

The aim of this study was to investigate the removal of acid orange 7 from aqueous solution using a new triple nanocomposite biochar/ZnO/SnO2. In this experimental study, weight percentages of ZnO, weight percentages of SnO2, pH, dye concentration and nanocomposite dosage as effective parameters on removal of acid orange 7 using one factorial method were analyzed. The maximum dye removal efficiency of 96.92% obtained at optimum conditions, 20% weight ratio for ZnO, 5% weight ratio for SnO2, pH = 7.1, 250 ppm dye concentration, 0.5 g/L nanocomposite dose after 60 minute. One of the highlights of the nanocomposite was its high power to remove dyes in a very short time. As after 2 minutes of testing, most of the dye (about 86%) was removed. It was also observed that the nanocomposite had the ability to reduce COD by 77.27% and TOC by 66.6% after 2 hours. Also, nanocomposite was reused until the fourth time, when the efficiency reduction for the first to fourth times was less than 10%. According to the results, the kinetics of the reactions for the nanocomposite were in accordance with the double exponential model and the Langmuir isotherm model was the most consistent with the observed data. Also, according to the thermodynamic studies, the dye adsorption on the surface of the nanocomposite was physical.

The purpose of this study was to compare the performance of Fe2+ activated persulfate and electro-persulfate process in Acid Blue 25 removal from aqueous solution. For this reason, the effects of different parameters including pH, dye, sodium persulfate and ferrous sulfate concentrations were investigated. The removal efficiency of 92% at the time of 60 min was obtained at pH= 3, dye concentration= 50 mg/L, sodium persulfate concentration= 500 mg/L and Fe (II) sulfate concentration= 100 mg/L for Fe2+ activated persulfate system and the removal efficiency of 95% at pH= 5, dye concentration = 200 mg/L, sodium persulfate concentration = 500 mg/L and ferrous sulfate concentration = 100 mg/L for electro-persulfate system by means of graphite materials as the neutral electrodes. COD removal efficiency in Fe2+ activated persulfate and electro-persulfate in the mentioned conditions were 90% and 89% in 180 minutes, respectively. Moreover, the result of process kinetics showed that using electrochemical process improved the reaction velocity from 0.0016 to 0.0487 mg/L/min. The comparison between these two-process showed that using electrochemical process improved dye removal efficiency by 4 times.

The textile industry wastewater causes serious environmental problems due to its high toxicity and color. Therefore, it is necessary to find an effective treatment technology for removing organic dyes from wastewater. Cavitation is one such modern technique which has been considered for the treatment of complex pollutants because of its ability to generate highly reactive free radicals. Up to now, researchers have mostly focused on qualitative interpretations and related scientific techniques, and there has been no quantitative cost analysis for pollutant control in textile industries for decision making purposes. Future studies need to focus on the cost analysis of more processes in textile wastewater treatment, such as advanced oxidation and combined and biological processes. Thus, this research was conducted with the aim of investigating and comparing various single and combined processes using the hydrodynamic cavitation (in a single system and with a specific contaminant) to remove reactive black 5 dye. Hydrodynamic cavitation (HC) was applied by using an orifice plate with a 7 mm hole diameter at the inlet pressure of 4 bars. Single processes, photocatalysis, photolysis, adsorption and combined processes, cavitation + photolysis, cavitation + photocatalyst and cavitation + photocatalysis were investigated in dye elimination and each of them was optimized by changing the various parameters (pH, TiO2 nanophotocatalyst concentration, irradiation power and dye concentration) and their best efficiency was obtained. In addition, considering the cost of energy and the nanophotocatalyst consumed by the processes, along with the process efficiency, processes were ranked by defining the index of efficiency to cost ratio. In the studied processes, efficiency increased as pH reduced, however, in the case of the photolysis process, efficiency increase at the highest level of the basic pH was significantly higher than acidic pH. Increasing the nanophotocatalyst concentration up to an optimum level resulted in efficiency increase. The decolorization rate increased as the irradiation power increased. The processes efficiency decreased with an increase in the initial concentration of the dye. In terms of efficiency, cavitation + photocatalysis, photocatalysis, cavitation + photolysis, photolysis, cavitation + photocatalyst, cavitation and adsorption processes, with the dye removal efficiencies of 83, 60, 52, 49, 43, 38 and 13% were placed first to seventh. This is while, considering both efficiency and cost consumption, photolysis process and then processes of cavitation + photolysis, cavitation and photocatalysis were ranked first to fourth, respectively with the best ratios. Hydrodynamic cavitation is a promising approach for dealing with industrial pollutants and the combination of this process with other advanced oxidation processes yields desirable results. Considering the parameters of energy and the cost of consumed nanophotocatalyst in the comparison of processes is very important and the output efficiency of the process should not be the only criterion. Paying attention to the substantial costs of nanophotocatalysts such as nanotitanium dioxide, combined techniques (e.g., the combination of cavitation with other advanced oxidation processes) lead to less consumption of nanomaterial and lower operational costs and are therefore cost-effective.

Activated sludge process is commonly utilized for the treatment of wastewater with the benefits of high efficiency and easy operation. However, during the biological treatment of wastewater, huge amounts of waste biomass (called as “waste activated sludge (WAS)”) are inevitably generated in the process. The WAS should be treated in order to reduce the water content of raw WAS, transform the highly putrescible organic matter into stable or inert organic and inorganic residue, and finally condition the residue to meet disposal acceptance regulations. But, WAS treatment and disposal, representing 50–60% of the total operating costs of the wastewater treatment. WAS is produced in massive volumes; specifically, more than 25,000 tons of WAS is produced in Iran per year. Anaerobic digestion is one the most applicable methods in WAS stabilization due to its ability to reduce WAS volume and produce biogases. A mixture of primary and secondary sludge (WAS) passes through anaerobic digestion, but this process is more difficult for WAS than primary sludge. However, the hydrolysis stage limits anaerobic WAS digestion. To optimize the general process of WAS anaerobic digestion and increase hydrolysis performance, it would be possible to pre-treat WAS by various mechanical, thermal, chemical, and biological methods. In this research the influence of ultrasonic bath pre-treatment was studied to observe the effects of ultrasonic density and sonication time on WAS solubilisation. The charactristics of ultrasonic wave producer was surface area of 240×137 mm2, frequency of 40 kHz, power of 265W. The effect of ultrasonic waves with these characteristics on WAS solubilization was investigated for the first time. Increases in soluble chemical oxygen demand and soluble polysaccharide concentration, as well as the decrease in volatile suspended solids, indicate that pre-treatment could cause WAS solubilisation. The cavitation produced by ultrasound waves radiation breaked down the bacterial cell wall and released the intracellular substances into an aqueous phase. Since polysaccharide is one of the main parts of extracellular polymeric substances (EPS), a polysaccharide concentration increase in the solution indicated that ultrasonication disintegrates WAS floc and the EPS value reduced in biological flocculation. Increases in ultrasonic density and sonication time caused more solubilisation, stronger cavitation arised with an increase in ultrasonic density and with increased ultrasonic density; more floc structure disintegration was achieved in less time. The best Pre-treatment efficiency was achieved in ultrasonic density 0.53 W/mL and 20 min. sonication time and it caused 20% increase in biogas production compared to the control sample. In addition to WAS pre-treatment for solubilisation, the ultrasonic bath pretreatment could improve WAS settling properties. After pre-treatment with the lowest energy in experiment rang, the diluted sludge volume index (DSVI) decreased by about 10% compared to the control sample; this reduction continued upon the energy increase. Reduction of EPS from around WAS floc reduced the negative charge of WAS floc and increased the WAS floc’s fall rate. Therefore, DSVI reduction resulting from ultrasonic bath pre-treatment could be due to the EPS concentration reduction around WAS floc. Likewise, the influence of pre-treatment on electrical conductivity was also examined for the first time. Given the change in WAS, electrical conductivity with ultrasonic bath pre-treatment, in addition to other tests like chemical oxygen demand and volatile suspended solids, electrical conductivity could also effectively assess WAS solubilisation.

Acid red 14 is an azo dye which is used widely in textile industry and due to its high consumption, is a serious environmental hazard so that in recent years, a lot of research has been done on the photocatalytic removal of azo dyes from water with nanocomposites. In this research, TiO2/Fe3O4/CNT nanocomposite was synthesized with the sonochemical method and the photocatalytic removal of acid red 14 dye was investigated in a batch reactor by OFAT method. The morphology and structure of the nanocomposite were characterized by FESEM and EDS analysis. The optimum efficiency of 96.53 for AR14 was achieved under following conditions: dye concentration of 50 mg/L, nanocomposite concentration of 0.5 gr/L, Dissolved oxygen concentration of 7.4 mg/L, pH= 7, 120 W/m2 irradiation intensity and the reaction time 6 hours. Also, the removal of photocatalytic dyes by TiO2/Fe3O4 nanocomposite showed TiO2/Fe3O4/CNT nanocomposites had better performance in dye removal than TiO2/Fe3O4 nanocomposite. It was also found that the dye removal mechanism with a regression coefficient of 0.9597 had the most overlap with the pseudo first-order reaction.

Petroleum is the major source of energy and the activities related to the petroleum industry leading to high volumes of wastewater and emissions different pollutants to water systems. According to studies, world oil demand will increase to about 107 million barrels a day over the next two decades, and about 32 percent of global energy will be provided from Petroleum by 2030. Thus wastewater resulting from oil and refinery industry is increasingly rising and discharges into the environment, which is a serious threat to the world's water resources. A large amount of water is used to extract and to refine the petroleum in oil refineries, thus produce the large amounts of wastewater. The wastewaters containing various kinds of pollutants with different concentrations are of environmental problems due to high organic load and hard-biodegradable compounds. With the increasing drinking water standards and environmental stricter regulations relation to discharge of sewage, electrochemical technologies have gained their importance all over the world during the last two decades and now electrochemical processes such as recovery of metals, electrocoagulation, electro-flotation and electro-oxidation can be effective technologies in the field of different wastewater treatment. In the electrocoagulation process by applying an electric current to the cathode and anode electrodes in a conductive solution by dissolving anode, coagulants produced in situ and cause the flocs is that they are floating with bubbles of hydrogen gas generated at the cathode. The metal ion generation takes place at the anode, while hydrogen gas is produced at the cathode. The metal ions form flocculates which trap contaminants while the hydrogen gas floats these particles. In this study, the electrocoagulation process was carried out with the use of a cathode and an anode made of stainless steel to reduce pollution from synthesis wastewater. For this purpose, the various parameters are optimized separately in this system by one factorial method, and then use experiment design methods. The effects of five parameters including the electrode surface, initial COD concentration, current density, pH and NaCl concentration were evaluated in the range of 23.36 to 78.36 cm2, 100 to 2500 mg/L, 2 to 30 mA/cm2, 3 to 11 and 0.3 to 2 g/L, respectively, in the case of electrocoagulation process. The optimum conditions of electrode surface, initial COD concentration, current density, pH and NaCl concentration were achieved 23.36 cm2, 900 mg/L, 20 mA/cm2, 8.5 and 0.5 g/L, respectively, for this process with energy consumption of 7.3 kWh/kg CODRem and electrode consumption of 0.4 Kg Fe/Kg CODRem during 60 minutes. The results of the experimental design of response surface methodology were confirmed the results of OFAT method with acceptable obtained error for the electrocoagulation processes. Based on results from experimental design of response surface methodology in this process, current density, time, pH and concentration of sodium chloride, respectively, were the most influential parameters. Electro-coagulation process seems to be an economic and environmental friendly process to remove the pollutants from wastewater. It has been demonstrated that electrocoagulation process with the use of stainless steel anode and cathode is a very effective and operative method to degrade Petroleum pollution and reduce COD.

Many pollutants in industrial wastewaters, such as dyes, can't be removed easily by the conventional physical, biological and chemical purification processes, because of their complexity and intractability. Therefore, it is necessary to find an effective treatment technology that can degrade complex bio-refractory molecules or can breakdown them into smaller molecules which can be further degraded by conventional methods. Cavitation is one such recent technique which has been extensively studied for the treatment of complex wastewater due to its ability of generating highly reactive free radicals. Hydrodynamic cavitation has a potential of application on larger scale due to its capability in generating hydroxyl radicals at ambient condition, easy scale up and less material cost making it more economical to employ. The purpose of this study was application of hydrodynamic cavitation process for removing Reactive Black 5 and optimization the affecting parameters (pH, inlet pressure, hole diameter and initial concentration of dye) based on the amount of efficiency and energy consumption. Material and methods: In this research, removal of Reactive Black 5 with the use of hydrodynamic cavitation process was studied. 8.25 liters of colored solution was examined in each test. The cavitation was produced by orifice plate and pump. In order to optimize process, various trials were performed in pH of 3 to 11 and also using different orifice plates with hole diameter of 2, 3, 5 and 7 mm at inlet pressures of 2, 3, 4 and 5 bar and dye concentration of 30, 50 and 100 ppm. Due to the constant voltage of urban electricity, the electric current was measured as an indicator of energy consumption by ammeter. According to the results by reducing the pH, dye removal was increased and orifice plates with larger hole diameter in upper pressures had better efficiency. It was observed that increasing the initial concentration of dye resulted in decreasing dye removal efficiency. The orifice with 7 mm hole diameter at 5 bar inlet pressure yielded the highest efficiency, but by involving the amount of energy consumed and considering the process efficiency to energy consumption, the orifice with 7 mm hole diameter at 4 bar inlet pressure was chosen as the best. The pH of 3, orifice with 7 mm hole diameter at 4 bar pressure and initial concentration of 30 ppm (with regards to pump energy consumption obtained from measuring the electrical current and the efficiency of process) were selected as optimum conditions. In these conditions after 120 minutes, 38.21% dye removal was obtained using hydrodynamic cavitation. Hydrodynamic cavitation has a potential of application on larger scale due to its capability in generating hydroxyl radicals at ambient condition. It was found that the energy consumption was an effective factor in selecting the optimum conditions. By reducing the initial dye concentration and pH, dye removal was increased and orifice plates with larger hole diameter in upper pressures had better efficiency.

High salinity wastewater is one of the main environmental issues. Using biological treatment systems to treatment this kind of wastewater is hard due to loss of microorganisms. Phytoremediation is one of the main methods to treat this type of wastewater, which is an environmental friendly and a low cost process. In this research we aim to study operation of two plants, including chrysopogon zizanioides known as Vetiver grass and Cyperus alternifolius know as umbrella, to simultaneous removal of salinity and organic loading. We assume five different combination of wastewater which are called statistical treatments and characterized by different amount of salinity and COD. Statistical treatments contain wastewater with Electrical conductivity 0,2.5,5,7.5,10 (ds/m) and 0,75, 150, 250, 300 (mg/L) COD respectively. Pure water is used as control treatment. Results show that in reactors with low level of salinity, both plants have better operation in removing of salinity and organic loading. For electrical conductivity above 5 and 7.5 ds/m, signs of salinity stress including Chlorosis and withering seen in leaves of both plants. For chrysopogon zizanioides, different statistical treatments results in different removal of organic loading range from of 60 to 12 percent. Salinity removal is ranged from 53 to 4 percent. For Cyperus alternifolius reduction in organic loading and salinity are respectively varied from 49 to 5 and 20 to 1 percent. Results of this study in laboratory scale shows that using phytoremediation method in constructed wetland for different combination of salinity and organic loading results in 17 and 15 percent reduction in salinity and wastewater for each unit of chrysopogon zizanioides and Cyperus alternifolius respectively. By increasing the level of salinity the trend of electrical conductivity is decreased. For the wastewater with 2.5 ds/m electrical conductivity, the most absorbing salinity absorbing is seen for both plants, which is 53 percent for chrysopogon zizanioides and 30 percent for Cyperus alternifolius. Reduction in capability of absorbing salt occurred for both plants due to completeness of salt aggregation capacity of the plant. By increasing the electrical conductivity of wastewater solution, wither and reduction in operation of the plant is seen as well. Increasing the salinity level results in decreasing the trend of organic loading reduction. COD removal for chrysopogon zizanioides is greater than Cyperus alternifolius in all reactors, which is related to natural characteristics of this plant, higher tolerance of salinity fluctuations and different phytoremediation mechanism. In statistical analysis of morphological characteristics of plants, the statistical population is all plants for different combination of wastewater and statistical controls. For each plant, results of different statistical treatments are compared to each other. The null hypothesis for independent tests assumes that the waste water treatment doesn’t have effect on morphological characteristics of the plant. So, rejecting this hypothesis means that all combination of wastewater doesn’t have the same effect on morphological characteristics. This hypothesis is considered separately for each of morphological characteristics by use of two sided independent sample T-test. These characteristics included dry weight, mean leaf area, mean stem diagonal and root volume. Results indicate that increasing salinity will affect the morphological characteristics with 95% confidence. Fitting the generalized linear regression shows that existing of organic loading doesn’t have meaningful effect on morphological characteristics, and level of salinity of wastewater affect the growing characteristics of the plant.

Surfactants are considered as chemical combinations with many environmental impacts such as eutrophication, foam generation, and oxygen reduction. This experimental study is conducted to evaluate the removal of Sodium dodecyl benzene sulfonate (SDBS) using unipolar electro-flotation and electro coagulation system. The experimental set up was installed as a cubic shape with effective volume of 735 ml and stainless steel mono-polar electrodes arranged in a horizontal fashion. Parameters evaluated individualy for the overall system optimization include: distance between electrodes (0.5-1.5 cm), surfactants initial concentration (50-1000 mg/L), pH (3-11), current density (0.5–1.5 A), and electric conductivity (950-3500 S/cmμ). Results obtained during the 1 hr operation time showed that the optimum surfactant and COD removal efficiency were about 94 and 90 percent, respectively. This optimum removal eficciencies were accomplished under the following condition: pH=8, distance between electrodes =1 cm, initial surfactant concentration = 750 mg/L, current density = 1 A, and EC = 1440 μS/cm . In addition, the energy consumption and anode dissolution were 45.03 kWh/kg and 1.04 kg Fe/kg for SDBS removal, respectively. In conclusion, the results obtained in this study support the application of electro-flotation and electro coagulation as an appoperiate system for the removal of surfactants such as detergent.

Pigments such as Chlorophyll and Carotenoid are of particular interest due to their antioxidant and therapeutic properties. Spirulina is a great source to commercial pigments production due high pigment percentage and simple extraction processes. The aim of this study was chlorophyll and carotenoid optimization of spirulina biomass by innovative photobioreactor. In this experimental study, by designing and constructing an innovative photobioreactor for the elimination of some defects of commercial open cultures, spirulina combined culture was investigated. Using RSM-CCD method, the effect of circulation cycle factors, control volume, and irradiance intensity on total value of pigments were evaluated. The data were analyzed by SPSS 16, using linear regression. The highest amount of total Chlorophyll (3.63mg/l) was obtained in Test No. 7 with the shortest circulation cycle (2hr) and control volume of 30%. In this situation, total carotenoid was 0.90mg/l and the whole amount of two pigments was maximum. But, the highest amount of total carotenoid (1.59mg/l) was obtained in the least control volume (20%), circulation cycle of 9.5hr, and light intensity of 10500Lux. In order to attain the highest level of chlorophyll, the optimal irradiance intensity to increase the biomass and the short-range circulation cycle to increase content are the top priority. But, to attain the maximum level of carotenoid, long-range circulation cycle to increase biomass and irradiance intensity at high level to increase content is predominate. The importance of the effect of increasing irradiance intensity on the increase of carotenoid content as well as the reduction of the circulation cycle on the increase of chlorophyll content is greater than its negative effect on the dry weight of biomass and results in an increase in the pigmentation.

The increasing development of microalgae applications has led to the concentration of new multidisciplinary studies to facilitate commercial cultivation of these organisms due to cost reduction and productivity enhancement. The aim of this study was the growth and quality optimization of Spirulina biomass by changing the dilution of medium and using the aeration cycle. In this experimental study, the effect of concentration of Zarrouk medium (0 to 100% dilution) and aeration cycle on specific growth rate and dry weight, as well as the content of chlorophyll and carotenoids of Spirulina were investigated, using response surface method, central design. A total duration of 16 hours was aerated in any 24-hour period; the interval time between these aerated periods varied between 1 to 8 hours. The data were analyzed by SPSS 16 software, using multiple regression test. Findings: The highest biomass (0.659mg/ml) was obtained at 80% concentration of culture media and aeration cycle of 2.75 hours and the highest specific growth rate (0.230 daily) was obtained at 60% concentration and aeration cycle of 4.5 hours. The highest aeration cycle (8 hours) resulted in a significant and simultaneous increase in the content of chlorophyll and carotenoids (11.65 and 2.67 mg/g, respectively). The growth and quality optimization of Spirulina biomass can be accomplished by changing the dilution of the medium and using the aeration cycle.

Special properties and various applications of Spirulina species have led to the growing focus of biotechnology to the cost effective cultivation. Open ponds used in the most commercial cultivation have many deficiencies such as risk of contamination, lack of light penetration, inefficient mixing and low productivity. In this study, an innovative reactor was designed and manufactured. By adding a control area, it was possible to control some environmental conditions for a limited amount of open pond volume. The conventional pumping system was replaced by a new elevator system to reduce the damage of to the fragile cells. The baffles structure and aeration from bottom, contributed to better mixing system. The effect of tree factors (Circulation Cycle (Cir. Cyc.), Control Volume (Con.Vol.) and Irradiance Intensity (Irr. Int.) in units of hours, percentage and Lux respectively) on the quantity of biomass (Specific Growth Rate (SGR, day-1) and fifth and seventh day dry weight (g/L)) were evaluated using RSM-CCD. The maximum biomass dry weight (0.915 g/L) was achieved in longest circulation cycle (12 hours), 30% Con. Vol. and 7000 Lux light intensity. The optimal irradiance intensity to achieve the highest biomass was 8700 Lux. According to the results, due to the great influence of Con. Vol. and Cir. Cyc., it is possible to increase the productivity and enhance the culture dry weight by controlling a limited amount of ponds volume (20%), subject to economic considerations. These successful results can provide the context using a control zone for several open ponds to improve the overall efficiency.

Due to the potential contamination of groundwater and surface water in the vicinity of the consumer dye industry, removal of this dyestuff waste is an environmental priority. Water clarity and solubility of gases in the presence of even a small amount of dye is reduced. If there are colored substances toxic to lower layers light penetration in the water is low. In addition, photosynthesis of aquatic plants and the amount of dissolved oxygen is so low that aquatic animals are destroyed. Dyes are stable compounds that are not easily biodegradable, and azo dyes are considered especially carcinogenic. Dye removal via various methods of physical, chemical, biological or a combination of them is possible that can be noted on physical methods such as adsorption, membrane filtration and ultrasonic waves, chemical methods, such as ion exchange, electrolysis, coagulation and flocculation, canonical and advanced oxidation, and biological methods, using algae, fungi and bacteria.Chemical coagulation is a common method of wastewater containing dye. High levels of dissolved solids and sludge in purified effluent are the disadvantages of chemical coagulation. In recent years, because of the versatility and compatibility with the environment, the electrochemical method as an effective method for treating wastewater of containing dye industries is taken into consideration. In the electric coagulation, production happens in the place of coagulant materials that are the result of dissolution metal anode (steel) by passing an electric current.If we put sewage between the positive anode and negative cathode that are plugged to electricity, an electric field is established because of the electrical conductivity of the solution. By electrolysis of water, tiny bubbles of oxygen and hydrogen are produced and they move upwards and form a blanket on the surface. Bubbles bring suspended particles to the surface and form a sludge layer that is mechanically collected.Expected use of electric flotation process simultaneously with electric coagulation eliminates the requirement of gravity sedimentation unit for the separation of the clots, resulting in the separation of both emissions and reducing the cost of the filtration.Studies in the field of electrochemical dye degradation based on electric coagulation and flotation property of the produced bubble are rarely used. In this study, reactors designed in a manner intended to electric coagulation properties and electric flotation can be used simultaneously. In addition, this study is a used innovation, such as the use of grille stainless steel electrodes with horizontal arrangement.In this research, the electrode-related parameters affecting the performance of the electric coagulation and flotation system, including the surface, distance, type, and shape of electrodes, were investigated. In addition, the influences of each of these parameters on the removal efficiency of Acid Red 14 from synthetic wastewater, energy and the anode consumption were determined and their values were optimized.The surface of electrode equal to 20.5 cm2, the distance between the electrodes equal to 0.5 cm, and stainless steel as type of electrode and a grid shape electrode (mesh generator) were chosen as optimized.Under optimal conditions in about 20 minutes, 100% dye removal efficiency with special energy consumption equal to 6.2 kWh/kg was obtained. Dye removal with the anode consumption equal to 4.4 kg Fe/kg and sludge TSS 17000 mg/L was also obtained.According to electric coagulation and flotation benefits such as the ability to fully automatic exploit, easy control of parameters involved in the process, safe operation conditions and very high tolerance to organic, hydro and toxins shocks and considering the importance of reducing the cost using systems with less material and energy and TSS consumption, use of this method for filtrating or pre- filtrating is suggested prior to supplementary filtration of industrial wastewater containing dye. The advantages of this method compared to other methods of dye removal are as follows: simple equipment, high speed and short retention time to remove pollutants, easy navigation, and low amount of chemicals, and low produced sludge which has high sedimentation or floating rate with low amount of water.

In this study, a baffled photocatalytic reactor was used to treat wastewater containing azo dye. The baffles made of Plexiglas covered by TiO2 nanomaterials placed vertical in the reactor, were used. Using this reactor could enhance in the wastewater passage time, decrease in contact distance due to existence of the colored wastewater and the effect of preventing the passage of UV ray, bring about turbulence in the current, prevent from short circuit phenomenon, increase at the current length, and cause enhancement in effective surface against the relatively low occupancy level that make it possible to construct this kind of reactors in larger scales. The dimensions of the Reactor were 20 cm*25 cm*50 cm and the baffle dimensions used in the reactor were selected 20 cm*12 cm. The photocatalyst particles were fixed on baffles and then the experiments were conducted based on the experimental design by Design Expert software. In order to ensure adequate waste water to pass from the photoreactor, the rotary flow regime was used in the original design. In the research, Methyl orange one of the anionic dyes with the chemical formula C14H14N3NaO3S was used. This azo dye was the kind of amino benzene and has a functional azoic group (-N = N-) and cofactors NaSO3 and now widely used in dyeing textile, wood, paper, leather and printing applications. In order to investigate the effect of the main factors and optimizing colored wastewater treatment process by using TiO2 nanoparticles in the baffled reactor Response Surface Methodology, central composite design (CCD), was used. Based on the results, reducing the pH and initial dye concentration had synergetic effect on color and COD removal simultaneously. The effect of pH less than 5 and less than 75 mg/L concentrations are more rapidly. This phenomenon was a result of amphoteric behavior of TiO2 and the weakening of oxidation ability of the produced holes in alkaline conditions. The pH of the solution influence on how the TiO2 surface is ionized and leads to amphoteric behavior the TiO2 nanoparticles under different conditions and this behavior changes the oxidation ability of the process. Another reason for this phenomenon could be described as the reduction in light penetration due to increased dye concentration in the solution and the more dye adsorption on the surface of TiO2 causes a part of UV energy is absorbed by the molecules of the dye. Although Methyl orange is an anionic dye with the negatively charged sulfonic group thus in high pH, hydroxyl radicals lose the chances of reaction with the trapped dye quickly. At the same time reducing the pH and increasing the reaction time also increases the efficiency of COD and color removal and enhanced for the pH below 4 and after 6.5 hours for dye removal and at pH below 5 and after 8 hours for COD removal. This was due to increased opportunities for photocatalytic activity in acidic pHs reduce the initial dye concentration and increase the reaction time had amplified effect in efficiency of decolorization and reduction of COD. The rate of the phenomena was more obvious for the dye concentration less than 50 mg/L and after 8.5 hours. The results showed that the color removal efficiency was more than COD removal efficiency. The most noticeable reason for this phenomenon is the breaking of the colored azoic bond and producing colorless intermediate products that decrease removal efficiency during tests. The maximum amount of COD and color removal when the 50 mg /L initial dye concentration and at the pH= 5 were 98.81 and 69.7 percent, respectively, after 9.5 hours. The results data comply with reduced quadratic model with a correlation coefficient (R2) 94.95 and 95.30 percent for color and COD removal respectively that validate the model results. Laboratory assessment also indicated that due to the very small difference between the results of the represented model and the experimental data, the model was consistent with acceptable confidence level.

IntroductionThe aim of this study was to evaluate the efficiency of electrochemical systems for removing of Acid red 14 contaminants, in which electrical coagulation and flotation methods by steel electrodes, are used simultaneously. It is expected that, simultaneously using of electrical flotation and electrical coagulation process eliminate gravity sedimentation unit for the separation of the clot, and result both in the separation of emissions and reducing the cost of the treatment. Researches in the field of electrochemically dye removing methods, are based on electrical coagulation, and flotation property of bubbles are rarely used. In this research, innovations such as gridded horizontal were used to improve the performance of flotation. The impact of key parameters on electrochemical system performance including current density and initial dye concentration was examined and optimized based on the amount of energy consumption and anodes consumption and ensuring the proper functioning in terms of coagulants and bubbles. In optimum conditions, in order to evaluate the performance of coagulation and flotation process in treating of real wastewater plants, electrochemically treatment of the actual colored wastewater was evaluated.
Materials and methodsCubic Plexiglas electrochemical cells with small dimensions of 15×7×7, with a pureed volume of 735 ml was used for electrical coagulation and electrical floatation process. Two mesh stainless steel 316 electrodes with a purity of 99%, with horizontal monopole arrangement was used as the anode and cathode in the reactor. Because hydrogen gas at the cathode, play a key role in floating suspended particulates, current flow was introduced in a way that, the cathode and anode was placed on top and down, respectively.
Acid red 14 dyestuff, which was used as the main contaminants to create artificial wastewater, is anionic and has an Azo group with chemical formula of C20H12N2Na2O7S2 and molecular weight of 502.4 gr/mol. In addition, in order to evaluate the effectiveness of the system in optimal conditions, discoloration of real wastewater were studied.
In order to determine the optimal electrical current density and optimal initial concentration of dye by using of single-element method, synthetic wastewater was prepared with desired specifications.
Results and discussionIn order to determine the optimal amount of electrical current density, experiments are performed in different electric current densities when other affecting parameters considered to be constant. According to the observations, by increasing the amount of electric current, the speed of dye removal is increased. This is because, production speed of coagulants and hydrogen and oxygen gases has been increased by increasing current density, which leads to coagulation, flocculation and faster separation of contaminants. The specific energy consumption and reduction of the anode metal mass are evaluated as a criteria for better comparison of the economic and environmental terms according to which, by removal efficiency of 99% in 10, 20, 30 ,40 and 50 mA/cm2 electrical current densities and for kg dye removal, energy consumption is respectively 3.57, 3.22, 3.19, 2.52 and 2.26 kWh and anode consumption rate is 0.4, 0.34, 0.63,0.54 and 0.67 kg Fe/kg Dye Removed, respectively. Finally, the optimal electrical current density was selected equal to 20 mA / cm2 (0.4A) according to the results, in which 99% of dye was removed in less than 20 minutes, and the amount of specific energy consumption was 3.22kWh / kg Dye Removed, anode’s consumption was 0.34kg Fe/kg Dye Removed and the TSS of sludge was 3820mg/L.
Various experiments with different concentrations of dye take place in order to determine the optimal value of this parameter with optimized electrical current density where other parameters were kept constant. According to these tests, dye removal rate decreased with increasing initial concentration and more time is required in order to get fixed removal efficiency. This is because at a constant electric current density, the produced coagulant metal hydroxide is constant with time and this amount of metal hydroxide is not sufficient to coagulation and flocculation greater amount of pollutants. It should be noted that at very high concentrations (500mg/L) dye removal process go slower but the performance is much better in compare with other studies. By comparing of energy and anode’s consumption with efficiency of dye removing in terms of time, the optimum concentration was selected equal to 250 mg/L, in which 99% of dye was removed in less than 30 minutes, and the amount of specific energy consumption, anode’s consumption and TSS of sludge were 1.9kWh/kg Dye Removed, was 0.95kg Fe/kg Dye Removed and 3700mg/L, respectively .
Using the optimal conditions obtained from previous experiments, to evaluate the performance of coagulation and electrical flotation process in real waste water treatment, real sewage electrochemical treatment for actual dyeing is considered, in which, after 30 minutes treatment by removal efficiency of 63%, the primary COD equal to 803 mg/L reached to 296 mg/L. In synthesized sample, after 30 minutes treatment with removal efficiency of 79%, the primary COD magnitude decreased from 278 to 58mg/L. This amount is lower than the standard limit of discharge to surface water and catchy wells. After 30 minutes treatment with removal efficiency of 77%, the color of actual wastewater decreased from 1.5 Gardner in the beginning to 2.1Gardner. The energy and anode’s consumption in actual wastewater treatment for removing of 63% of COD in 30 minutes, were 3.11 kWh/kg COD Removed and 0.565 kg Fe/kg COD Removed respectively. These values for synthetic wastewater with removal efficiency of 79% in the same time were 2.10kWh/kg COD Removed and 1.38kg Fe/kg COD Removed, respectively.
ConclusionElectrical coagulation and flotation has the advantages of low sludge production, in comparison with similar methods and fully automatic and continuous operation is possible. The parameters involved in the process can be controlled easily and the safety of equipment is high. Tiny bubbles with the same size are produced and there is a little or no need to add chemicals. Also, very high tolerance against organic, hydraulic and toxins shocks and reduced number of processing plants and thus reducing the required surface for treatment plant and reducing in operating costs are another advantages of this method.
By increasing of electrical current density, production speed of coagulants and gases were increased, which lead in faster coagulation, flocculation and flotation. However, when electrical current density is increased in very high rate, the amount of iron in the separated sludge is increased with high speed. Increasing of iron clots in the water containing sludge, in spite of their high volume, and because of lightness, reduce the TSS of separated sludge and therefore the ability of system in flotation and separation of clots is reduces.
Due to the limited amount of coagulants produced at a time of electrolysis and consistency of electrical current density, with increasing of initial concentration of dye (from 50 to 500mg/L), the removal efficiency was decreased. However, according to the amount of energy used and the high dissolution of anode at lower concentrations, concentration of 250 mg / L was chosen as the optimal concentration.
Anode consumption and the need for its renewing and cathode corrosion are the disadvantages of this method. However, according to results, 99% of dye was removed in less than 30minutes, where specific energy consumption was 1.9kWh/kg Dye Removed, the anode’s consumption and the TSS of sludge were 0.95kg Fe/kg Dye Removed and 3700mg/L, respectively. These results proved the ability of electrical flotation and coagulation methods in treatment of wastewater containing dye, with low consumption of materials and energy. The proper functioning of this procedure in real waste water treatment, which are containing different combinations of colored dyes, suggest that, this method can be used for wastewater treatment in dyeing industry, textile and other industries. In addition, low sludge produced in this treatment reduces sludge’s treatment, disposal, and its relative problems costs. As a result, using of this method as an alternative option to conventional methods is considerable.

The petroleum refineries, water are used for different purposes, such as extraction of contaminants. Some of these pollutants such as petroleum and Methyl Tertiary Butyl ether (MTBE) can be noted that have less biodegradability than other organic compounds. Discharge of these pollutants into water, and the presence of them in drinking water make huge environmental concerns.
A sequencing airlift reactor (SBR) along with an internal riser is called sequencing batch airlift reactor (SBAR); it has a similar structure to SBR and purifies wastewater with a certain temporal cycle in a single reactor. The SBAR system, which is used along with granules to treat wastewater, is known as granule sequencing batch airlift reactor (GSBAR). Using this system for biodegrading requires a high concentration of biomass (aerobic granules. In recent years, several studies have been conducted on the use of aerobic biogranules. Mousavi et al., examined the removal of phenol with an initial concentration of 1000 mg/L from saline wastewater using GSBAR with aerobic granules 2 mm in size. The results indicated that 99% of phenol was removed. Bao et al., studied the effect of temperature on the formation of aerobic granules and on the removal of nutrients by SBAR system. The granules had an average diameter of 3–4 mm, density of 1.036 g/mL, sludge volume index of 37 mL/g, and sedimentation rate of 18.6–65.1 cm/min. The input load rate of COD, NH4–N, and PO4–P was 1.2–2.4, 0.122, and 0.012–0.024 kg/m3/day, respectively and the removal efficiency at low temperatures was 90.6–95.4, 72.8–82.1, and 95.8–97.9%, respectively. Taheri et al., examined the formation of aerobic granules in SBR for treating saline wastewater. In this study, the granules were 3–7 mm in size, had a fall speed of 0.9–1.35 cm/s, and density of 32-60 g/L. Using aerobic granules with a diameter of 1–2 mm to biologically restore 2, 4-di-chlorophenol with an initial concentration of 4.8 mg/L, Wang et al., achieved the removal efficiency of 95% and 94% for COD and di-chlorophenol, respectively. Siroos Rezaei et al. reported that COD removal efficiency of synthetic wastewater was 95% with the glucose carbon source in six 4-h cycles with a loading rate of 1500 mg/L in SBAR system using aerobic granules. The new granules had different diameters in the range of 0.5–5 mm, high sedimentation ability, and SVI of 100 mL/g. Ghaderi et al., investigated the performance of the biofilm reactor and SBR in removing formaldehyde from wastewater. The results revealed that removal efficiency of CODs less than 200 mg/L was 100% and removal efficiency of CODs between 200–450 mg/L was 90% after 48 h. The aim of this study was evaluating the ability of SBAR system in quick produce of granules and achieving high removal of petroleum and MTBE in a short time. For this purpose, 2 similar SBAR systems with Circular cross-section were used. Outer Cylinder's diameter and length was respectively 8cm and 110 and the internal riser's diameter and length was respectively 4 cm and 90 cm. In the first system (R1) petroleum was treated in 6 hours and in the second system (R2) MTBE wastewater was treated in 4 hours. In COD equivalent to 600 mg/L, the removal efficiency of R1 and R2 were equal to 81.1 and 84.2%. These values were respectively 82.8 and 90% in COD equivalent 500 mg/L. Consider to granules changes, optimal COD was respectively equivalent to 600 and 500 mg/L in R1 and R2. By reducing retention time to 5 and 3 hours in R1 and R2, removal efficiency of pollutants in optimal COD of each system was respectively 77.8 and 90 %. The first granules were observed in the seventh day of operating system. During this period, the size of the granules increased to 1.3 and 0.6 mm in R1 and R2. Density and velocity of the granules were in the range of 0.0252-1.1998 gr/mL and 3.02-3.32 cm/s in R1 and 0.05-0.06502 gr/mL and 0.4-0.9 cm/s in R2. SVI was in the range of 42-65 mL/g, pH and DO was in the range of 6.8-7.2 and 2-6 mg/L and ORP was always above 100 mV.

The use of different synthetic dyes in textile industries has increased in recent decay, resulting in the release of dye-containing industrial effluents into natural aquatic ecosystem. Since most of dyes are usually very recalcitrant to microbial degradation, therefore dye removal from effluent is a main concern in many studies. Different process was used for the treatment of dye effluent. In the last few years, studies were focused on advanced oxidation process (AOPs) methods such as UV-ZnO, UV-H2O2, UV-O3 and UV-TiO2. Photocatalytic process such as UV-ZnO is an efficient method that treats non-degradable wastewater by active radicals. The photocatalysis needs a photo-reactor that contacts reactant, products and light. In recent years, different types of photo-reactors have been used for wastewater treatment. In some reactors, nano-photocatalysts are utilized in slurry form, and the other particles are coated on bed. In Photocatalytic reactors with fixed bed, nano-photocatalysts are immobilized on bed and do not need the separation unit, but the main disadvantage of this photo-reactors is the low mass transfer rate between wastewater and nano-photocatalysts. Consequently, Different optimal photo-reactors were developed for increasing mass transfer rate. In this study, a novel photocatalytic cascade disc reactor coated with ZnO nano-photocatalysts was applied and in order to increase mass transfer rate artificial roughness were created on the surface of disks. Applying artificial roughness changes mass transfer rate by providing vertical mixing, creating secondary currents and increasing the Reynolds number. This photo-reactor has a number of advantages that include eliminating the need for catalyst separation units as the catalyst is immobilized, creating the flow mixing by non-mechanical method, increasing the transport of oxygen from the gas phase to the photocatalyst surface by providing the flow cascade pattern. The photo-reactor was used in order to remove Reactive Yellow 81 (RY81) dye from textile industry effluent, by means of UV-ZnO process. RY81 is a reactive dye composed of 10 Benzene rings and two –N=N azo bonds. The effect of different operational parameters such as initial Concentration of dye, pH, Catalyst surface loading and flow rate in removal efficiency was investigated, and the optimal value of those parameters were 50 mg/L, 8, 40 gr/m2 and 80 cc/s, respectively. A rate equation for the removal of RY81 was obtained by mathematical kinetic modeling. The Langmuir-Hinshelwood kinetic model is one of the most common kinetic models that are used for studying the kinetics of heterogeneous photo-catalysis. The results of reaction kinetic modeling indicate the conformity of removal kinetics with Langmuir-Hinshelwood model, and the constants kL-H and Kads were obtained 7.17 mg L-1 hr-1, 0.122 mg-1 L, respectively.
One way of inserting various operational parameters to a rate equation is regression analysis. Therefore, in this study, nonlinear regression model was developed for prediction pseudo- first order rate constant as a function of initial concentration of dye, pH, catalyst surface loading and flow rate. This equation could properly predict (R2=0.95) the removal rate constant of RY81 removal in the photocatalytic cascade disk reactor under different operational conditions and a good consistency was observed between the calculated results and experimental findings.

Effluents bearing petroleum hydrocarbons must be treated prior to release into the environment due to the high toxicity of these compounds and the consequent hazards they pose to the receiving environment. The moving bed biofilm reactor (MBBR) is one of the several biofilm systems used in treating different types of wastewater that offers a good resistance to both toxic and hydraulic shocks. This study investigates the roles of the three air stripping, adsorption, and biodegradation mechanisms in the biofilm reactor using polyethylene sponge strips used as the biomass to treat the effluent from Tehran Refinery. Based on the results obtained, the optimum values of loading rate, retention time, and media filling ratio were equal to TPH=278 mg/L (COD=1000 mg/L), 22 hours, and 50 percent, respectively. Laboratory studies confirmed that each of the three mechanisms of air stripping, adsorption, and biodegradation may be involved in the removal of petroleum hydrocarbons by the MBBR system depending on hydrocarbon concentrations. More specifically, biological degradation was the dominant removal mechanism with lower loading rates (TPH=57 mg/l with a COD equal to 200 mg/l) while stripping became the dominant mechanism at higher loading rates (TPH=278 mg/l with a COD equal to 1,000 mg/l). It was found that under optimum conditions and at TPH=278 mg/L (and COD=1,000 mg/l), stripping removed 58%; biodegradation, 29%; and adsorption, 13% of the petroleum hydrocarbon content. It was observed that the removal of petroleum hydrocarbons by stripping and adsorption processes took place within the first process hour at the latest.

Removal of petroleum hydrocarbons from synthetic contaminated water using with photocatalytic process was conducted in the presence of nano TiO2 immobilized on the concrete plates. The solar photoreactor was consisted of storage tank of 60 L with floating pump, cascade system with 5 concrete steps, a 5 L weir on the top of the stairs and metalic chassis. The UV-A radiation of the sunlight was used instead of UV-A lamps as the irradiation source. The optimum parameters were pH of 5, TiO2 mass loading of 60 grm-2, UV equivalent irradiation time of 200 min, initial concentration of 100 mgL-1 and H2O2 concentration of 2000 mgL-1.The results demonstrated that under optimal conditions removal efficiency of chemical oxygen demand (COD), total petroleum hydrocarbons (TPH) and poly aromatic hydrocarbons (PAHs) were 70.48%, 67.63 % and 84.75% respectively. Also the results of GC-FID analysis indicated that most of PAHs were eliminated and only non-toxic aliphatic hydrocarbons were remained.

In this study, the effects of fly ash $(X_1)$, kaolinitic clay $(X_2)$, micro-silica $(X_3)$ content and water-to-solid ratio $(X_4)$, electrical potential gradient $(X_5)$ and polarity reversal period $(X_6)$ on the solidification and stabilization of Synthetic waste containing lead, zinc and arsenic were investigated. The data were analyzed using the central composite design which is the most commonly used response surface methodology RSM design (using a mixture design of a constrained triangular surface) and ANOVA. Optimum formulations were simulated using a desirability function. pH and compressive strength tests were performed on 86 specimens. The specimens with the highest and lowest compressive strengths were selected for Toxicity characteristics leaching procedure (TCLP) and scanning electron microscopy (SEM) to evaluate the leaching behavior of lead, zinc and arsenic and monitoring hydration progress, respectively. The experiments were arranged according to a full factorial design, which also allowed deriving predictive models for unconfined compressive strength and pH as affected by Synthetic waste content as well as variables type and dosage. Among the variables tested, polarity reversal period (less than 32.5min) and micro-silica (more than 7.5 % wt.) were found to affect mechanical strength far more positively compared to the other species used, at the same time ensuring low metal release from the material. On the other hand, the use of polarity reversal period more than 32.5 min and micro-silica less than 7.5% wt. were observed to cause a significant increase in metal leaching. The result indicates that the extensive accumulations of calcium aluminate hydrates (CAH) which are the main products of tri-calcium aluminate (C3A) and calcium silicate hydrate (CSH) were identified as the main hydration products. The formation of $NaCaAsO_4$.$7.5H_2O$ and portlandite were the main phase controlling $As^{5}$ and heavy metal solubility in cement-treated Synthetic wastes. The optimal conditions obtained from the compromise of the two desirable responses, pH and compressive strength of specimens, were lead, zinc and arsenic concentration in TCLP leachate 0.4 mg/L, 0.393 mg/L and 0.146 mg/L, respectively. pH and compressive strength of specimens in the optimal condition were 57.56 Mpa and 9.82, respectively.

Everyday million liters of color wastewater are produced in different industries and cuases environmental problems. The textile industry significantly affects the environment, producing high volume of wastewater from water and chemicals used in processes including sizing, washing, bleaching, dyeing, printing, and finishing. The wastewater contains salts, acid, or alkali, washing solvents, other chemicals, intermediates, and residue dyes. In the presence of toxic colored substances in water light fails to penetrate the waters lower layers and consequently the photosynthesis of water plants and the level of dissolved oxygen decreases, and results in the death of aquatic life. Dyes are stable compounds that are not easily biodegradable; especially Azo dyes which are considered to be carcinogens that pollute the surface and groundwater.
Generally, the physical, chemical and biological methods or a combination of them have been used for treating textile wastewater can be mentioned as membrane filtration, and ultrasonic waves, electrocoagulation, adsorption, Fenton, photo-Fenton, ion exchange, electrolysis, coagulation, conventional, and advanced oxidation and photo-catalytic process.
In recent years, the ability of advanced oxidation processes in treating various hazardous wastes has brought this technology to the forefront of research. Among advanced oxidation processes, application of heterogeneous photo-catalysis by using semiconductors has been proved to be real interest as an efficient tool for degrading both aquatic and atmospheric organic contaminants. Semiconductors are photo-reactive metal oxides for contaminants eradication that refer to photo-catalysts. These methods mineralize and converse pollutants into CO2, H2O and inorganic ions, by the action of hydroxyl radical, which acts as a nonselective and strong oxidant of organics.
Because of the excellent properties and wide applications on nanomaterials, recent years, researchers start to focus on the nano-zinc oxide granule size lies in the 1-100 nms, because of having nanophase structure and char acteristics, it gets the surface effect and bulk effect and gains some special capabilities (on magnetism, light, electric and sensitivity etc.) and many new usages.
Photocatalytic reactors for water and wastewater treatment can be classified to slurry and immobilized systems. In the slurry reactors, the nano particles are freely dispersed in the water phase and consequently the photo-catalyst is fully integrated in the liquid mobile phase. Whereas the immobilized catalyst reactor design features a catalyst anchored to a fixed support and dispersed on the stationary phase.
The mail aim of this sudy was to compare removal efficiency of acid orange 7, one of the high consumed textile dyes, in slurry and immobilized methods using photocatalyst UV/ZnO process.
Methods and materials: In this study, after detrmination of the maximum absorption wavelength of acid orange 7 (Table 1), the initial experiments were done to determine the main role of photocatalyst process (Figure). Then the effect of different amounts of dye concentration and catalyst, pH, irradiation power and energy consumption were investigated and optimized for both slurry and immobilized systems by changing one papramter and keepig the others constant.
The Water Sealer Method (WSM) was used to immobilize the nano ZnO powder on concrete surface. The process began by complete mixing of 100 mL of selected concrete sealer (colorless liquid) with measured amounts of ZnO. To the cured concrete surface of one reactor, 10 mL of 10% (by mass) ZnO sealer solution was prepared and put into ultrasonic cleaner (Fungilab UE-6SFD) for 5 min to ensure the complete separation of nano particles. Then the solution was applied and allowed to be cured for at least 3 d.
Table 1 Characteristic of Acid Orange 7
Structure
Formula C16H11N2NaO4S
Molar mass 350.3243
λmax 487 nm
Solution pH 3
Slurry and immobilized photo-catalyst reactors
According to the Beer Lambert law, by measuring the absorbance of samples at the maximum absorption wavelength of the dye (487 nm) in a spectrophotometer, dye concentration and removal rate (Eq. 1) were calculated, where CR was color removal efficiency (%), C0 represented initial dye concentration, and C indicated instant dye concentration. In order to eliminate flocs errors, samples were filtered and centrifuged prior to placing them in the spectrophotometer.
(1)
The main equipments used in this study include a Kern PLS 360-3 digital scale with 0.001 accuracy and Metrohm 691 pH meter. The amount of dye in solution was measured by using a Hach DR-4000 spectrophotometer at a wavelength of maximum absorption of acid orange 7 (485 nm) and the calibration curve of dye concentrations, respectively. All experiments were performed according to the method of analysis of water and wastewater and repeated at least 3 times.
In summary, acid orange 7 could be successfully degraded and mineralized by nanophotocatalysis in both slurry and immobilized ZnO nanoparticle photocatalytic reactors.
The experiments in optimum conditions in both slurry and immobilized methods were shown that in pH of 7, catalyst concentration of 80 gr/m2 (10.32 gr/L) and 32 Watt UVc lamps, over 95 and 35 percent of 50 ppm dye was removed in slurry and immobilized methods, respectively. The amount of COD removal was higher in the slurry method (Table 2).
Table 2- Comparison of optimum conditions in the studied systems
Immobilized System Slurry System parameter
80 gr/m2 10.32 gr/L Catalyst Concetration
50 50 Dye Concentration (ppm)
7 7 pH
32 32 Power (Watt)
375 56 Time
4 6 COD Removal after 60 minutes
35 45 COD Removal after 375 minutes

According to studies, nearly 15 percent of synthetic dyes enter wastewater during production and consumption operations annually, which is very dangerous and causes many problems for the environment. Thus, removing these compounds is mandatory. NZVI can be used in detoxification of many environmental pollutants, as a reducing agent and catalyst. In order to develop the technology of NZVI, bimetallic nanoparticles are prepared by deposition of a noble metal, such as nickel, over iron nanoparticles. In this study, as a simple and applicable method in the laboratory, bimetallic nanoparticles, Fe-Ni, were made using the method of chemical deposition of iron chloride (FeCl3.6H2O) by a strong reducer, sodium bohr hydride (NaBH4), under nitrogen gas. To ensure the size and nature of the nanoparticles, SEM and XRD experiments were performed. Then, the nanoparticles were used in a slurry system to remove the azo dye (ccid red 14). To achieve optimum conditions during the experiments, the parameters of the dye initial concentration, nanoparticle dosage, pH, elapsed time from creation to implementation of the nanoparticles, shaking speed and temperature were investigated. Then, to identify other eective factors, a control experiment was performed under the optimal conditions and it was found that ethanol, nickel, and light do not have any eect on dye removal. The reducer, however, was able to remove the dye completely. Also, the use of nickel with 3 wt% iron increased dye removal eciency by 14.65%. According to the survey conducted, optimal conditions were obtained when the tests were performed at temperatures of 25  20C with newly synthesized nanoparticles that have 0.05 gr/L concentration with an initial concentration of dye equal to 200 mg/L and pH of 7.5 and a beginning mixer time of two minutes. These nanoparticles had very high activity, so, removal e- ciency after 2, 30 and 240 minutes, was 79.39, 90.52 and 94.42 percent, respectively. Finally, LC-Mass experiments indicated that after 4 hours of reaction, the azo band in the dye was broken.

Water scarcity has led to the search for alternative water resources. One solution is the recycling of wastewater for irrigation. Wastewater treatment is often based on biological systems such as activated sludge or other engineered units in urban areas. In rural areas, low-cost, environmentally-friendly alternative treatments such as constructed wetlands (CW), are more common. CWs are man-made planted systems that utilize natural processes to improve water quality for human benefit. Salinity in treated wastewater is often increased, especially in arid and semi-arid areas.
Phytoremediation is the use of plants to remove or control of soil and water pollution. Soluble salts, heavy metals, oil and oil derivatives and radioactive substances are pollutants that have been removed using phytoremediation from different environments. In the past two decades, the use of phytoremediation was thrived in the treatment of urban and industrial wastewater and also the treatment of contaminated shallow soil. The sun is the main supplier of energy and is a clean source of energy in terms of creating secondary materials arising from the treatment. Plants use three organs, root, stem and leaves to absorb various pollutants from soil or water. By transferring the pollutant to its tissues, the plant can collect the pollutants from artificial pond cumulatively.
The purpose of this study was to compare the performance of two plants in simultaneous removal of organic matter and salinity of wastewater. In order to have a close estimation of the saline wastewater characteristics, both saline and organic matters were used. A comparison was also done on morphological characteristics of two plants affected by salinity tensions and organic matter in continuing. The results of this study can help the researchers to treat saline wastewater biologically and economically, lateral goals such as creating beauty, producing feed for livestock and also preventing soil erosion.
Setting up sector includes: the preparation of the mature plant, making the laboratory pilot, preparing artificial wastewater, determining the different concentrations of wastewater, determine the number of plants in each tank, transfer plant to pilot and ultimately add wastewater to the reactor. In order to ensure the effectiveness and safety of plants, rooted plants with a life of at least two months were needed. Therefore, by referring to the vetiver farm belonging to the Iranian Association of promotion and development of Vetiver plant in Tankabon, the required plant was prepared. Swamp palm was provided from the center of Oxus houseplants and transferred to the laboratory. Pilot has 17 batch reactors with a volume of 1.7 liters and was made of Plexiglas according to Figure 1. The aim of this pilot is to create the proper context for simulation of artificial wetlands, existing multiple tanks in order to apply different levels of salinity and different amounts of organic matter to each plant and also compare the amount of removal in tanks containing plant against the control tanks. The pilot was set on the basis of permanent flooding. In this way the platform holder was used that usually kept a plant and directly floated on the reinforced solution. An air pump which has also pumped air into air rocks and created tiny air bubbles in solution, take the required oxygen to plant root. Aeration in addition to supply required root oxygen, also provided mixing in the solution. To measure the parameters, the spectrophotometer system Hach model DR 4000, digital scales PJ300 model manufactured by Mettler by precision of 0.001 hot, EC meter Martini model of MI 805 was used. Stem diameter measurement was done with Vernier caliper with precision of 0.01 cm and measuring leaf area with measuring system of leaf area DeltaT area meter mk2. ATF was used to dry the leaf. In order to make the electrical conductivity in the solution, NaCl was used and to meet required COD of the starch, ultrapure Merck Company used and to prepare solutions, distilled water twice distilled used. Plants were fed with liquid fertilizer Pokon made in Holland. Experiment was done with three replications.
Figure 1. Used pilot in research a) air pump b) reactors with plant c) control reactor
Five wastewaters with different amounts of electrical conductivity and organic matter were produced artificially in the laboratory. Their characteristics are shown in Table 1. Both swamp palm and Vetiver plant in addition to treatment with 5 mentioned wastewaters were irrigated with distilled water as the control. 5 of the reactors without plant was irrigated with mentioned wastewater to be investigate the effect of aeration in reducing the amount of electrical conductivity and COD parameters. In every reactor, the amount of 5 mL liquid fertilizer to provide nutrients and maintain the ratio of NPK at 5: 7: 7 required of plant was added. As long as fertilizing was enough for a period of two months of plant growth. This amount was selected based on the company of making fertilizer. Table 2 provides the reactor arrangement and placement of the plant and control reactors.
Table 1. Amount of salinity and COD in different solutions
Electrical conductivity COD (mg/L) Number
Table 2. Ordering reactors and wastewater and each reactor plant
To investigate the obtained results of removing organic matter and salinity, experiments were done at 5 reactors containing Vetiver plant and control (without plant) during four periods, respectively, 10, 15, 15 and 20 days with the specifications listed in reactors containing wastewater in Table 1.
Discussion & The obtained results of this research in laboratory scale showed that using phytoremediation method in artificial wetland, in different levels of salinity and organic matter, on average, for every single plant and vetiver 17%, and per unit of swamp palm plant have had 15% salinity reduction and wastewater in following. Other results are as follows:The process of reducing the amount of electrical conductivity in both species reduced with increasing salinity levels. The highest amount of salt intake by plant of swamp palm in the electrical conductivity was observed 2500 micro Siemens per centimeter and about 30% and about 53% for Vetiver.
The process of reducing organic matter in both species reduced with increase in salinity level with the highest efficiency of COD reduction by plant of swamp palm in the electrical conductivity was observed 0 and organic matter mg / L 300 about 50% and for Vetiver plant about 58%.
Comarison of COD and Electrical Conductivity Removal
Based on the measurement results and the importance of plants, the highest level of leaf area, dry weight and diameter of stem was obtained in vetiver plant and the highest root velum in swamp palm plant. All of these characteristics according to salinity tolerance by the plant, since the transfer to pilot have increased the toxicity and wilting in the mentioned plants and since then has remained static or due to loss of plant and destruction of associated tissue was reduced. Chlorosis in Vetiver plants shows the accumulation of salt in the root that indicates the process of root phytoremediation in this plant. Creating Toxic effects on palm leaves and also the tiller of the plant in salinity before the drought threshold acts as a control on dilution mechanism in phytoremediation of swamp palm. This mechanism was observed in Vetiver due to observing green tillers.
By changing the rinsing characteristics of plant and also destroying the balance of plant enzymes, the electrical conductivity of solution causes reduction in the amount of water taking, drought of plant and results in the lack of transfer of pollutants from the flooding environment into the tissues of plant. Finally, Vetiver plant was diagnosed in comparison to swamp palm for phytoremediation of saline wastewater with appropriate organic matter.