WATER AND WASTEWATER
Year:2018 | Volume:29 | Issue:2 |Papers Count:13

Monoaromatics of Benzene, Toluene, Ethyl Benzene and Xylene which are abbreviated as BTEX, are among the most important environmental pollutants. Due to high solubility of BTEX in water, it is emitted to the aquatic environment with a very high speed. Absorption by carbon nanotubes is be regarded as one new treatment method. The aim of this study was to investigate the removal of BTEX from aqueous solutions through adsorption by single wall carbon nanotubes coated with Zinc oxide nanoparticles. The prepared nanoparticles were characterized by FT IR, XRD, FESEM and EDAX. First, the pHZPC was determined. Then, the effect of different operating parameters such as the amount of sorbent, contact time, pH, temperature and ionic strength were studied through batch method in order to obtain optimal conditions for the absorption process. The optimum conditions for BTEX removal from aqueous solution by ZnO/SWCNTs was obtained as following: pH=6, contact time=20 min, adsorbent concentration=300 mg/L, amount of sorbent=10mg, T=20° C and salt concentration= 2g/L. The results showed that single wall carbon nanotubes coated with zinc oxide effectively absorbs BTEX from water and it has a good potential for treating wastewater contaminated with petroleum.

Heavy metals are recognized as one of the most toxic groups. They enter the food chain through the waste disposal into the water and environment. This study was carried out with the aim of investigating cadmium ions removal from aqueous solution using conocarpus nanostructure. For this purpose, conocarpus was grinded to nano-size by the ball mill. The effect of experimental parameters such as pH, time, adsorbent dosage and initial concentration of cadmium were studied in batch system. The PSA, FTIR and SEM tests were used to determine the absorbent characteristics. The imaging of adsorbent indicated that surface of conocarpus had many deep pores, which represents the better adsorption of cadmium. 8. 5% of adsorbent particles were in the range of nanoparticles and 91. 5% of them were in the range of nanostructure. The results showed that optimum pH for cadmium adsorption is 6 and the maximum removal efficiency and adsorption capacity of cadmium are 80. 9% and 0. 86 mg/g., respectively. Comparing the adsorption isotherm and kinetics models showed that the Langmuir and Ho models, with R2 values of 0. 998 and 0. 990 respectively, had a better fitting and description of adsorption data than other models. The study showed that conocarpus nanostructure is an effective adsorbent for cadmium removal from aqueous solution.

In this paper, a new method for preconcentration and measurement of trace amounts of nickel in aqueous samples by magnetic solid phase extraction (MSPE) via magnetic carbon nanotubes (Mag-CNTs) was developed. In order to increase selectivity, Y-Furildioxime was used as chelating agent. In order to do extraction, optimum amount of ligand was added to the nickel sample and pH was set on 9, then 7 ml. of adsorbent was added and stirred for 15 minutes. After that, aqueous phase and adsorbent were separated by a strong magnet. Finally, the absorption was measured via flame atomic absorption spectrometry by analyte elution from the absorbent with an appropriate solution. Parameters affecting the extraction and preconcentration of nickel were investigated and optimized. Under optimum conditions, the calibration curve was linear in concentration range from 2. 5 to 375 Zg L-1 and the detection limit was 0. 8 Zg L-1 of nickel. The method was applied for determination of nickel in aqueous samples. The relative efficiency values of nickel measurement in aqueous samples were from 98. 7% to 102. 1%. Results indicated that Mag-CNTs can be used as an effective and inexpensive absorbent for preconcentration and extraction of nickel from actual samples.

Heavy metals are environmental pollutants that nowadays a lot of efforts are made to remove them. In this research, the sawdust modified with diethylenetriamine as an effective adsorbent for Fe (III) removal from water samples was conducted. First, the sawdust was modified by diethylenetriamine. SEM analysis showed that the particle surface is changed by modification. Then the effective factors in Fe (III) removal such as pH, adsorbent dose, shaker speed and contact time were studied and optimized. The optimum conditions were employed for various Fe (III) concentrations (20– 300 mg L-1) and in all cases, the removal rate was significant. The adsorbent has high capacity for Fe (III) removal in a way that it removed more than 95. 0± 0. 3 % of Fe (III) (50 mg/L) by 1. 5 g/L of adsorbent in 15 minutes. The Langmuir and Freundlich isotherms were applied to the adsorption process and their constants were evaluated. The adsorption equilibrium data fitted well to Langmuir isotherm. The maximum Langmuir adsorption capacity of Fe (III) ions was 200. 0 mg/g. According to kinetics experiments of Fe (III), the adsorption process had more conformity to pseudosecond-order kinetic model. This method was successfully applied for Fe (III) removal from potable water, well water, river water and industrial wastewater samples.

One of the chemical oxidation method for water and wastewater treatment is to use potassium ferrate. The aim of this study was to optimize the potassium ferrate consumption for wastewater treatment in carpet industries using central composite design and response surface methodology. The samples of this experimental study were collected from a carpet factory monthly and during two seasons. Measuring of the studied parameters were carried out based on the standard reference method for experiments in water and wastewater. To determine the optimized conditions for removing COD, color, turbidity and TSS by potassium ferrate, the central composite design and response surface methodology were used. The results showed that two independent variables of pH and potassium ferrate concentration and their interaction had a significant effect on removing COD, turbidity, color and TSS variables. The optimum condition for removal of these four pollutants were 160mg/l for consumption dosage of potassium ferrate and 4. 5 for pH. In such condition the removal percentage of COD, turbidity, color and TSS were 86%, 85%, 84% and 83% respectively. In addition, the results indicated that the quadratic model has a good fitting to the experimental data. Potassium ferrate is recommended as an effective compound for reducing COD, color, turbidity and TSS from wastewater produced in textile industries especially in carpet industries. This process can be applied as a preliminary treatment and in cases where biological treatment is the main treatment, it could be used as a supplementary treatment.

Prediction of water consumption and its effective factors is an important step in water crisis management. Studies showed that meteorological parameters are considered as the most important factor for short-term prediction of water consumption. In this research, cluster-based sliced inverse regression method was used to identify the meteorological variables affecting the household water consumption in Qom. In addition to dimension reduction, this method can be used to remove collinearity. The data consisted of seven meteorological parameters and monthly household water consumption from 2001 to 2013. Data analysis indicated that instead of seven primary variables, only two new components which are linear combinations of independent variables can be used. The negatively charged maximum wind speed and relative humidity (0. 757 and 0. 4) of the first component, and the negatively charged average minimum temperature (0. 753) and positively charged average air temperature (0. 634) of the second component had the greatest impact on the components. The regression analysis indicated that the average minimum temperature coefficient 0. 018, the maximum wind speed coefficient-0. 004, and determination coefficient 0. 92% are significant. Comparing the method proposed in this paper with the usual method of principal component analysis (PCA) for multivariate data analysis indicated that cluster-based sliced inverse regression has fewer errors. Moreover, noticing the impact of collinearity on the outputs of neural networks, the method proposed in this paper had better performance than the usual methods and consequently predicts water consumption.

The aim of this study is to identify domestic water consumption among citizens of Ilam using a segmentation approach based on demographic variables. Water consumption pattern in this study was investigated with a cognitive-behavioral approach. The research population of this study consisted of domestic water consumers in Ilam. From this population a sample of 313 individuals selected through multistage cluster sampling to respond the research questionnaire. Data collection tool in this study was a researcher-made questionnaire. The questionnaire’ s reliability was confirmed through Cronbach’ s alpha test with a confirmed 0. 78 coefficient. Its validity also approved by using factor analysis. In order to cluster water consumers, the two-stage clustering method was applied. The results indicated the existence of five clusters from the aspects of and demographic properties among domestic water consumers. The consumers who were placed in high-consumption clusters had lower education level. The results also indicated that unemployed individuals are usually placed in highconsumption clusters.

Water quantity-quality equitable allocation model in river-reservoir systems provides the possibility of decision making on the amount of allocated water by considering the hydrological, economical, and environmental effects. Water allocation is done according to three criteria, namely equity, efficiency, and sustainability by considering uncertainties in hydrological parameters. In this method, at first a water quantity-quality allocation model was developed in GAMS optimization model based on the mentioned three criteria. Scenarios were built based on scenario optimization technique by identifying the uncertainties in the model inputs. Water was allocated using the initial model for each sub-scenario. Afterward, water allocation in each scenario was obtained by the tracking model. To assess the applicability of the proposed method, it was applied to Roodbal river basin in south-east of Fars province, south of Iran. After analyzing basic data, upstream inflow and TDS concentration were identified as the uncertain input and the most critical quality parameter respectively. Due to the existing uncertainty, three scenarios of wet, normal and dry year were built. The results of using the proposed model showed that 100 percent of the users’ demands are supplied in wet and normal years and 61 percent in dry years. The volume of reservoir was always more than minimum volume (35 MCM) and TDS concentration was lower than 1000 mg/L (TDS water quality standard). The value of these three criteria were also at their highest possible. Based on the results of the model, the Roodbad River-Reservoir system faces no problem in supplying agricultural water demands in wet and normal years. Therefor, water can be stored in wet and normal years to be used during dry years. In dry years, water is allocated to the users in a way that the mentioned criteria have the maximum values and the reservoir storage doesn’ t reach the minimum value except for the last month of the optimization period.

Under transient flow condition, the behavior of water conveyance system varies according to their characteristics. In the present study, the pressure was measured using a fast and sensitive pressure gauge in Bukan and Piranshahr water conveyance system. The pressure simulation was conducted using Bentley Hammer software. The friction head loss was calculated by different methods. The results showed that Unsteady Vitkovsky method had minimum error comparing with other methods. Wave velocity increase had direct effect on maximum pressures while velocity decrease affected minimum pressures. In a shorter water conveyance system, the reduction of wave velocity had direct effect on maximum pressure. Destruction to the long conveyance system was more probable and maximum and minimum pressures occurred during the first period. Shorter conveyance system had more pressure fluctuations and the minimum pressure did not occur in the first period. Coincidence of periods happened at the beginning and continued untill the end of data recording in the longer conveyance system. However, as time passed by, such coincidence did not occure in shorter conveyance system.

In recent years, with growing population and industrialization of the world, desalination techniques have developed drastically to supply the rising needs of coastal cities to fresh water. The brine is the second product of the producing fresh water process in the desalination facilities, that is usually discharged into the sea through marine outfalls (surface and submerged). The main purpose of the outfall is to enhance the dilution and reduce the impact on the local environment. In this study, in order to investigate the impact of the shape of the surface discharge channel, rectangular and trapezoidal sections with the equivalent diameter were used to discharge wastewater with negative buoyancy into stagnant and non-stratified water bodies. Experiments have been carried out in a dark room and processed using digital analysis. The location of plunge point, impact point and the dilution in this point, and the location of the ultimate point and dilution at this point were the flow characteristics studied in this research. According to the shape impact and less hydraulic conflict with the surroundings, trapezoidal section had better geometric characteristics compared to rectangular section. Results of the experiments were presented in the form of non-dimensional diagrams and equations. Finally, statistical indices such as Root Mean Square Error (RMSE) and R-Square (R2) were used to verify the accuracy of the presented dimensionless equations. The results indicated that the closer the shape of surface channel discharge is to the best hydraulic cross section (semicircular), the better geometric and mixing characteristics would be obtained for the flow along near-field area. In this way, prediction of flow characteristics and design of actual samples of these outfalls will be possible.