مجله آب و فاضلاب
پیاپی 132 (فروردین و اردیبهشت 1400)

Hydrogen sulfide (H2S) is a toxic, odorous, colorless, flammable and acidic gas. The main problems of hydrogen sulfide are the threat to health and safety, and causing corrosion and damage to metal installations. This study was conducted to remove hydrogen sulfide from the sour waters of Tabriz refinery and to recycle large amounts of water as well as to reduce air pollution in the refinery. In this experimental and laboratory study, the effect of pH, adsorbent content, initial concentration of pollutant, contact time and temperature on hydrogen sulfide removal process using clinoptilolite adsorbent was investigated. Thermodynamics, kinetics, and isotherms of adsorption process were studied. The results were used to remove H2S from the sour water of Tabriz refinery. The results showed that the optimal values of pH, absorbent value, initial pollutant concentration, contact time and temperature were 3, 1g/100 mL, 50 mg/L, 30 min and 25 oC, respectively. The results of thermodynamic studies showed that the adsorption process was exothermic, irreversible and spontaneous. The experimental data were better fitted to the pseudo-second order kinetics model and Freundlich isotherm model. After passing 100 ml of sour water from the fixed bed at 25 oC and 45 minutes, the removal efficiency was 96.7%. According to the results of this study, the proposed method due to its simplicity and high efficiency and the clinoptilolite due to its cheapness, abundance, ability to resuscitate and increase efficiency by enhancing the amount of clinoptilolite can be considered as an appropriate method and suitable adsorbent to remove hydrogen sulfide from the sour water of refineries and effluents.

One of the oldest methods of producing electrical energy is the use of latent energy in running water, which uses a water turbine to achieve this. It is one of the most important sources of renewable energy and has attracted the attention of many researchers in recent years. In this study, laboratory evaluation of hydraulic performance of a type of water microturbine to convert excess pressure in medium pressure water supply networks into electrical energy usable for sensors or equipment such as flow meters, pressure meters, leak detectors, etc., used to manage energy consumption and intelligent water supply networks is investigated. For this purpose, in three different scenarios, the effect of parameters such as flow rate, pressure and different angles of the guide vane on the microturbine performance and pressure drop was investigated. The results showed that the highest microturbine output power (59.01 watts) and pressure drop rate (9.71 meters H2O) were obtained when the inlet discharge was 42.61 m3/hr and the opening guide vane was 20 degrees. It also has the lowest output power (0.8 watts) and pressure drop rate (4.65 meters H2O) for a flow rate of 46 m3/hr without the guide vane. The coefficient of determination (R2) for the equations of microturbine output power and pressure drop was calculated to be 0.92 and 0.99, respectively.

The scarcity of water resources and the increasing demand for household water, as a result of urban population growth, have made it difficult for the citizens to supply the water they need in metropolises. Therefore, it is necessary to reduce the amount of domestic water consumption in metropolitan areas using management and consumption control strategies. One of the most effective methods to modify the pattern of water consumption is changing the consumers’ behavior for efficient water use. (Social) Media advertising, establishing training programs for consumers (citizens), implementing effective training programs in schools, spreading educational brochures among water consumers and and billboard advertising are the most practical approaches to promote water saving behavior in metropolises. The aim of this study is to rank the mentioned methods in changing the water consumption behavior of the citizens. Evaluation and ranking of these methods are carried out applying the integrated method of Grey Analytic Hierarchy Process (Grey-AHP) and Grey-TOPSIS. In this study, Mashhad metropolis was selected as a case study. The results show that (social) media advertising and and billboard advertising are the most influential approaches for promoting the effective consumption of water in Mashhad. Distributing educational brochures, educational materials in schools, and establishing training programs for citizens are ranked second to fourth, respectively. Practical approaches to promote water saving behavior, which are easier to apply, are more appropriate and have a greater influence on reducing water consumption.

Nowadays, provision of sanitary water is one of the main concerns of the world society, and heavy metals are one of the most important pollutants in water resources. Heavy metals, including copper, can enter the food chain and the body of living organisms and can affect humans through toxic and carcinogenic effects. Therefore, in this study, nanoporous SBA-15 functionalized with di and tetra carboxylic acid was synthesized and used for remove copper ions from aqueous solutions. The adsorbents were characterized by scanning electron microscopy, N2 adsorption-desorption measurements and infrared spectroscopy for investigation of porosity and functional groups of mesoporous silica. Flame atomic absorption spectroscopy was used for determination of ions. Effective parameters on removal process including amount of adsorbent, contact time, pH of solution and presence of other metal ions in the medium, were evaluated and optimized. The best removal efficiency with di and tetra carboxylic acid functionalized SBA-15 was obtained at pH>5 with 10 mg of adsorbent in the stirring time of 15 minutes. The recovery of copper from adsorbents was done with 20 ml solution of nitric acid (3 mol/L). Langmuir and Freundlich adsorption isotherms were evaluated for both adsorbents. According to the Langmuier model, the maximum adsorption capacity of 232.56 and 93.46 mg of copper per gram of adsorbent and correlation coefficients (R2) of 0.857 and 0.9688 for di and tetra carboxylic acid functionalized SBA-15 were obtained, respectively. But, the correlation coefficients (R2) obtained from the fitting of the data using the Friendlich isotherm were 0.991 and 0.972 for di and tetra carboxylic acid functionalized SBA-15 silicas, respectively, which indicates that this model is suitable to explaining the behavior of copper adsorption on both adsorbents. Finally, the removal of copper from real wastewater samples was performed. The results indicate that nanoporous SBA-15 silicas functionalized with di and tetra carboxylic acid are desirable adsorbents for copper ions removal.

The entry of herbicides into drinking water supply sources can have devastating effects on human health and the environment. Therefore, removal of them from the aquatic environment is essential, in order to preserve the environment. Therefore, this study was conducted with the aim to investigate the isotherm absorption of graphene oxide modified by organic dendrimers to remove Butachlor toxin from the aquatic environment. In the present study, operating magnetic graphene oxide was produced by absorption of covalent bonds and used as adsorbent. Synthetic adsorbent properties were analyzed by FTIR, XRD, SEM, TEM, TGA, VSM and EDS. Also, the effects of pH parameters, contact time, contaminant concentration, adsorbent amount, temperature and reusability on adsorption absorption capacity were investigated and optimal conditions were determined. The absorption results were described by Langmuir, Freundlich, Temkin and kinetic adsorption models by first-order and quasi-second-order models and thermodynamic equations. The results indicated that functionalized graphene oxide effectively absorbs Butachlor and absorption percentage is significantly affected by the examined parameters. By increasing the time to 45 minutes, increasing the pH to 5, increasing the amount of adsorbent to 3 g/L and the concentration of Butachlor toxin to 10 mg/L and increasing the temperature to 25 ⁰C, the rate of absorption of Butachlor toxin has increased to 95.4%. Toxin absorption increased from 37 to 50 ⁰C, and after ten re-uses of the adsorbent, the absorption rate decreased by only 6.5%. Under optimal conditions, the adsorbent was able to remove 86.3% of Butachlor toxin in the real sample with a standard deviation of 6.06%. The Langmuir isotherm described the absorption process well (R2 = 0.99). Synthesized nano-adsorbent is an efficient, powerful and heat-sensitive adsorbent for removing Butachlor from the aquatic environment.

One of the pillars of any country’s development is access to safe water and sanitation, so it is important to execute water and wastewater projects in the shortest possible time. In this regard, considering the emergence of various methods of partnership, choosing the right approach has become one of the most important issues in this industry. Therefore, a proper investment method in this field has always been the concern of decision makers. Using the database of partnership projects and data mining algorithms in the water and wastewater sector, we have designed a model to predict a proper way for public-private partnership projects. In this research, CRISP data mining method was applied to the data from 176 projects. After understanding and identifying the data, they were cleaned by deleting outliers and noisy data, and missing values were replaced. Then, the process of data classification was performed using decision tree and machine learning algorithms, and necessary analysis was performed. Also, the indicators of PPP were extracted and prioritized. K-fold cross validation method is used for validation and dividing the data. Based on the modeling and considering the data preparations and data mining methods, the stacking method is suitable for predicting and determining the type of public-private partnership contract in the implementation of each project of water and wastewater industry, which has an accuracy of 86.27%. In the pre-processing section, the combined COF method for deleting outliers and entropy factors for feature selection was used. Using the model, the success rate of each project can be predicted and an appropriate PPP contractual template for any water and wastewater project can be proposed. In addition, by entering the information of each new project, the impact of the improvement of each indicator can be easily examined.

Groundwater contaminant transport modeling is a useful tool for identifying how pollutants fate and transport in porous aquifer environments. These models include several parameters, which are often estimated based on personal judgment or in the best case, based on limited field measurements. Therefore, the input data of simulation models are not accurate and contain several errors. The purpose of this study is parameter uncertainty and sensitivity analysis in the groundwater solute contaminants transport modeling using probability theory. First, governing equations for groundwater flow and solute contaminant transport have been presented. Then, using MOFLOW for modeling groundwater flow and MT3DMS for modeling solute contaminant transport in a hypothetical problem and using effective parameters in a case study (Qazvin plain), uncertainty analysis through the Monte Carlo method was done. To illustrate the uncertainty analysis, the Complementary Cumulative Distribution Functions (CCDF) of Chloride and Nitrate graphs have been computed. Then using random samples, generated in uncertainty analysis step, local and global sensitivity analysis of solute transport model parameters have been determined. 

Using maximum concentration of solute contaminant as a model output, the results of the local sensitivity analysis show that the most sensitive parameters are hydraulic conductivity (K), decay rate constant (λ), porosity (θ), distribution coefficient (Kd), and dispersivity (D) respectively. While using time to maximum concentration as output variable, leads to the following order of sensitivity: K, Kd, θ, D, and λ. On the other hand, the global sensitivity analysis using maximum concentration shows that the order of sensitivity is: K, λ, θ, D, and Kd, and using time to maximum concentration it is: K, Kd, D, λ, and θ respectively. According to the CCDF of Chloride, concentrations of 5%, 50% and 95% equal 205.5, 196 and 185.4 mg/L respectively. Also, according to the CCDF of Nitrate the concentrations of 5%, 50%, and 95% equal 56, 54.125 and 51.5 mg/L respectively. All five parameters are sensitivite in solute transport modeling. The local and global sensitivity analysis show more or less the same results. In general, the sensitivity ranking of parameters is K, λ, Kd, θ, and D.

Given the increasing consumption of potable water in the world, efforts to adopt new solutions for the obtainment of the right amount of desirable water is essential. One of the chief issues facing the majority of industries including water industry is corrosion and sedimentation. The present study was conducted to address the corrosion and sedimentation of drinking water supply and distribution reservoirs in the city of Sough, Kohgiloye-Boyer-Ahmad province. Through descriptive analysis, the Langelier, Raisner, Pokorius, and aggressive indices to determine the corrosion and sedimentation potential of the water supply network were used. This study was aimed measure chemical and physicochemical information of 84 water samples from wells, water reservoirs and allocated water supply network of the area. The samples were collected and analyzed from 2007 to 2016 by the provincial Water and Wastewater Company. The results indicated that the mean indices were -0.589±0.63 (low to moderate corrosion), 8.470±0.797, (low to moderate corrosion), 7.472±0.228 (low to moderate corrosion), respectively and 12.015±0.227 (mild aggressive or very corrosive) respectively. The water supply sources under investigation had low to moderate corrosion and little tendency to develop eggshell sedimentation. The water supply sources of the study area had low to moderate corrosion and had a slight tendency for eggshell sedimentation. Drinking water allocated to Sough water supply network in the direction of joint drinking water transmission of Dehdasht and Sough within 17 km of joint water supply from Sepah Tapeh reservoir (Dehdasht and Sough joint) is separated and directed, within 15 km by the transfer line and pump station, to Sough city. The average values of corrosion and sedimentation indices of the city of Sough water supply and distribution network (Lanzeley, Reisner, Pokoris and aggressive) were 0.63, 6.8, 7.28 and 12.8, respectively which indicate tendency toward sedimentation, relative tendency toward CaCO3, and non-aggressiveness. Despite the fact that the average pH of the joint water resources of both cities was 7.78. In summer, the water pH of Sough allocated water network increased to 8.5. Values and mean values of corrosion and sedimentation indices of Sough water supply network during hot seasons of the year show that the water of this network tends to precipitate. The findings also suggest that the average water temperature of the allocated water supply network in these 15 kilometers of transition which includes the transmission line and surfaced metal reservoirs had an increase in temperature around 10 °C. This temperature rise was due to the environment temperature (above 48 °C), the hot water in metal reservoirs and the surfaced steel transmission line in water supply network components. This physical change of water temperature is the main factor behind sedimentation.

Contamination of drinking water is known as a major threat of water security around the world. As contamination enters a water distribution network, it spreads rapidly into the network and poses health and safety risks to the community. Using a set of sensors to report the concentration of chlorine or any other chemical, useful observations can be made to detect, identify and manage pollution. Based on these observations, location, concentration and start time of contamination can be determined and decision makers can be informed. In this paper, a simulation-optimization approach is used to solve the problem of contamination source characterization in which the EPANET software is used as a simulator and the Genetic Algorithm is used as an optimizer. The model developed in this paper is implemented on EPANET example 3. Modeling of water distribution networks uses information as input data which can cause error in model simulation. Pipe roughness and chlorine deterioration rate are among these inputs. The model has been implemented to find the location, start time and concentration of inlet pollution and the effect of pipe roughness and chlorine deterioration rate on the model responses have been investigated. The pollution entry scenario is applied to the network and the model presented is accurate in finding the location and time of the contamination. As the variables increase, the model accurately estimates the location and time of entry of the contamination but does not have complete accuracy in estimating the concentration of contamination, which is calculated with standard deviation of σ = 4.8% -8.1%.

Arsenic in water is one of the highly toxic elements which has harmful influences on the human health and ecosystems. To address this problem, single-walled carbon nanotubes modified with poly (allylamine hydrochloride) (PAH/Ox-SWCNT) composite were synthesized and applied as an adsorbent for arsenic removal from aqueous solution in this study. The properties of PAH/Ox-SWCNT nanocomposite were characterized using scanning electron microscopy, Thermogravimetric, Fourier-transform infrared spectroscopy, and X-ray powder diffraction analysis. Batch experiments were executed to determine the ability of PAH/Ox-SWCNT to adsorb As from solution under various operational conditions. The experimental data were fitted by pseudo-first-order kinetic and pseudo-second-order kinetic models by nonlinear regression analysis using Mathematica software. Langmuir and Freundlich models were employed to describe the adsorption equilibrium isotherms. The removal percentage of As increased with initial solution pH from 3 to 7 while it decreased with the initial concentration of As. Moreover, the enhancement of contact time caused better adsorption efficiencies. The percentage removal of As using 10 mg of synthesized nanocomposite was more than 90% at pH=7 and contact time of 30 min. The adsorption experimental data had better agreement with pseudo-second-order kinetic and the Freundlich isotherm models. The maximum adsorption capacity of PAH/Ox-SWCNT was 275.07 mg/g at 298 K. The As removal percentage after eight adsorption-desorption cycles was higher than 65%. All results implied that the synthesized PAH/Ox-SWCNT could potentially be a promising adsorbent in arsenic water remediation.