مجله آب و فاضلاب
پیاپی 125 (فروردین و اردیبهشت 1399)

Chlorine is used as the most common disinfectant to prevent microbial growth in water networks. The concentration of chlorine in distribution systems or water conveyance lines is reduced due to two different types of bulk and wall decay. In this study EPANET software is applied to numerically simulate chlorine decay in the Isfahan water supply line from the Baba Sheikhali water treatment plant to Naein. Two methods are applied for simulation and the results are compared to the measurement. In the first method, chlorine simulation was performed taking into account the whole Isfahan water conveyance line as one section (integrated) and determining a bulk decay and wall decay coefficient for the entire conveyance line. In the second method, the line was divided into two sections (bisection) and decay coefficients of chlorine for each section was separately considered. To determine the bulk reaction rate, the bottle tests were performed at 6o and 18o Celsius corresponding to winter and summer. The results indicated that separating the line to two and applying independent coefficients and decay parameters to each part improves the results and the RMSE values are reduced from 0.09 to 0.03 in summer and from 0.064 to 0.025 in winter.  Therefore, dividing the line in two or more sections substantially improves the accuracy of the simulation of chlorine decay.

For better utilization of water distribution networks (WDNs), it is recommended that the existing networks be converted into Distinct Metered Areas (DMAs). Due to the complexity of the old networks, the conversion of these networks into DMA is a costly and sensitive issue. In this paper, a model has been developed to optimize implementation of the old networks into DMA by using the graph theory and water distribution system modeling software (EPANET), while the minimum required standard pressure is met and the number of linked pipes between the proposed areas is minimum. The minimum number of linked pipes will minimize the cost of the needed flowmeters. The developed model has been successfully applied for Poulakis WDN with 30 nodes and 50 pipes in different statuses and for the actual Bushehr WDN with about 3740 nodes and 3980 pipes. The output result shows that the developed model, in a satisfactory way, converts water distribution networks into DMAs with respect to the hydraulic constrainsts.

Nitrate (NO3−) pollution of surface and ground water is a major problem in water quality on the planet. The scientific method of the relations between δ15N-NO3− and δ18O-NO3− to identified the dominant sources of nitrate in groundwater, despite the overlap of nitrate isotopic ranges and the occurrence of nitrate isotopic fractionation, have been used in numerous studies. NH4+ fertilizer, treated wastewater, sewage and manure, Shour River, NO3 in precipitation and soil organic N, are potential sources of nitrate pollution in the study area. To identify different nitrate sources and to estimate their proportional contribution in the groundwater of the Varamin aquifer, a dual isotope (δ15N-NO3− and δ18O-NO3−) method and a Bayesian isotope mixing model for 38 samples in November 2016 have been applied. Based on hierarchical cluster analysis, 38 groundwater samples are classified into three clusters (groups one to three) in terms of hydrochemical properties., the mean values of δ15N–NO3− in groups 1, 2 and 3 are +7.0± 2.1‰, +10.2 ±1.1‰ and +16.1±2.1‰, respectively. The mean of δ18O–NO3− values of the groundwater in groups 1, 2 and 3 are +2.3± 1.9‰, +0.6 ± 0.8‰ and +6.2 ± 1.4‰ , respectively. SIAR model results indicate that the highest contribution in the nitrate pollution of the Varamin aquifer are related to“NH4+ fertilizer” and “manure and sewage” while “soil N” and “NO3− in precipitation” have the lowest influence.

Ethylene dichloride is one of the most important chlorinated hydrocarbons in the petrochemical industry, which is mainly used to produce vinyl chloride monomer, the main precurser of PVC production. Iran is one of the largest PVC producers in the world. During the production of 1000 kg of ethylene dichloride, about 0.4 m3 wastewater is produced containing 50-200 mg / L of ethylene dichloride. In this study, heterogeneous photocatalysis was used for degradation of this chlorinated hydrocarbon. PAni-TiO2 nanocomposite was immobilized on glass beads by a modified dip coating and heat attachment method. The morphology characteristics were confirmed by scanning electron microscope, energy dispersive X-ray spectroscopy and ultraviolet–visible spectroscopy. A pilot scale packed bed recirculating batch photocatalytic reactor was used for conducting photocatalytic experiments. response surface methodology based on central composite design was used to evaluate and optimize the effect of ethylene dichloride concentration, residence time, pH and coating mass as independent variables on the photocatalytic degradation of ethylene dichloride as the response function. Based on the results, actual and RSM predicted results were well fitted with R2 of 0.9870, adjusted R2 of 0.9718 and predicted R2 of 0.9422. Optimum conditions were the ethylene dichloride concentration of 250 mg/L, reaction time of 240 min, pH of 5 and immobilized mass of 0.5 mg/cm2, which resulted in 88.84% photocatalytic degradation. Kinetic of the photocatalytic degradation at optimal condition followed the Langmuir-Hinshelwood first order reaction with k=0.0095 min-1 with R2=0.9455. Complete photocatalytic degradation of ethylene dichloride was achieved after 360 min. Based on the results, it may be argued that the designed and constructed photocatalytic reactor has the potential for industrialization.

Cyclodextrins are categorized into three groups of alpha, beta, and gamma, according to the number of their own glucose units of 6, 7 and 8 units. These ring compounds have two surfaces of hydrophilic and hydrophobic to trap compounds with different polarities. twofold behavior of cyclodextrins has attracted the attention of the various industries, including pharmaceuticals, medicine and cosmetics. Metal cations are one of the sources of pollution of industrial and mining wastewater. In this work, the theory of the interaction of Cu1+ metal cation with alpha, beta, and gamma cyclodextrin has been studied. The structure and stability energy of these compounds are investigated using the Density functional theory and the B3LYP method with a base set of 6-31g (d, p) in the gas phase and solution. Using the NBO calculations, the active site of these compounds was determined for interaction with metal cation. The calculations showed that the distribution of charge on the glucopyranose oxygen atoms as the constructors of each constructor is approximately the same. Also, the corresponding complexes were optimized using the computational level and the Chelating ability of each of these rings oligosaccharides comparison has been made. Using the NBO calculations, the active site of these compounds was determined for interaction with metal cation. The calculations showed that the distribution of charge on the glucopyranose oxygen atoms as the constructors of each constructor is approximately the same. Also, the corresponding complexes were optimized using the computational level and the Chelating ability of each of these rings oligosaccharides comparison has been made.

Phosphorus is recognized as a nutrient in aquatic environments, but increasing its concentration in water resources causes the occurrence of eutrophication in water and, as a result, causes the death of aquatic organisms. Therefore, removal of phosphate from water is very important. In this research, in order to remove phosphate from water resources, the baffled subsurface-flow constructed wetland was used. In order to increase the efficiency of the wetland system, experiments were designed in 3 different phases. In the first phase, in the form of batch experiments, the composite performance of cheap materials such as zeolite, bentonite and pumice aggregates (The stabilization of nanoparticles of zeolitebentonite on the surface of Pumice aggregates) to absorb phosphate and select the preferred candidate for placement in the wetland was investigated. In the second phase, in the form of pot experimentation, the performance of native plants of khuzestan province such as salicornia, Typha, and Juncus, In order to uptake phosphate and select the best candidate for cultivation in the bed of the wetland was investigated. Finally, in the third phase, with the placement of the selected bedding and plant (selected from previous experiments) in the wetland system, experiments were carried out to study the effect of parameters such as the percentage of optimum mix of Selected bed with gravel, hydraulic residence time and temperature changes on the phosphate removal efficiency. The results showed that among absorbent materials and candidate plants for placement and cultivation in the wetland, the maximum capacity to absorb and accumulate phosphate by Pumice aggregate coated by zeolite nanoparticles (1.08 mg/g) and salicornia (9.68 mg/g of plant dry weight) was observed. In this experiment, The use of a combination of 10% of the selected bed with 90% of the gravel was obtained as the best and most economical option for removal of phosphate. Also, the efficiency of removal of phosphate in the 1-day hydraulic residence time was achieved at the highest intensity (99.60%) and was selected as the optimum time to remove phosphate. Finally, the results of the effect of temperature changes on the efficiency of the wetland system showed that the removal efficiency from March 2018 (20 °C) to July 2018 (40 °C) increased to about 1 percent, which indicates the effect of temperature changes on the performance of the wetland system. According to the results, in the case of adequate land availability, the use of subsurface-flow constructed wetland systems to wastewater treatment of agricultural and industrial units is very convenient and cost-effective.

The effluent from the active sludge treatment plant of Qom Shokoohiyeh industrial flows into surface water and reuse of water in industrial process is necessary. The aim of this study was to investigate the efficiency of aluminum sulfate, chlorofluorocarbons and poly aluminum chloride in removing turbidity and other parameters in industrial wastewater before entering RO in Shokoohiyeh Qom industrial refinery. This study was applied in a laboratory scale using a jar-test and experiments based on varying concentrations of coagulants (200, 400, 700, 800, 1000, 1200 mg/L) and pH=2.4.6.7.8.10 has been done. Steady mixing, slow mixing and stagnation have been performed and factors such as turbidity, pH, COD, BOD5, EC, SVI and TSS have been investigated. Coagulants are effective in removing turbidity. The highest removal rate was for polyvinyl chloride (95%) and the least amount of turbidity removal was in chlorofacry (50%). The highest and lowest levels of pH were detected at pH=2 (72%) and pH=8 (10%), respectively. The lowest BOD5 removal efficiency in poly aluminum chloride was 88% at pH=4 and the highest removal rate of BOD5 was found in chloroformate coagulant with pH=4 (96%). The highest COD reduction was observed in poly aluminum chloride at pH=9 (89%) and the lowest COD reduction was observed at a concentration of 800 mg/L alum with 34%. The highest reduction in electric conductivity in poly aluminum chloride with 87% and the lowest amount of electrical conductivity reduction occurred at a concentration of 500 mg per liter of alum with 12%. The highest total removal of suspended solids in chlorofacrylic coagulant was 88% and the lowest amount was removed in chloroform with up to 18%. The maximum amount of sludge deposited at  pH=9 (240 mg/L) in aluminum chloride and the lowest amount of sludge deposited at pH=2 (5 mg/L). The use of coagulant materials can increase the purification efficiency, eliminate opacity and return water to the cycle. PAC and Alum coagulant have high efficiency in removing turbidity and other wastewater treatment parameters that can be used to treat wastewater for RO systems.

Wastewater network is an inseparable part of urban life. Due to importance of this network as one of the urban infrastructure, the failure of this system will lead to stopping service, causing many social, economic and environmental consequences. Hence, assessing the wastewater networks condition and its failure is an important approach for managing it. Generally, failure of system means any condition which is lead to stopping service. In general, artificial intelligence methods are used as a low-cost method to predict failure. In this research, genetic programming (GP) is used to predict the number of blockage (hydraulic failure) in the wastewater network and its results are compared with the results of the artificial neural network (ANN). As a case study, here, a part of Isfahan wastewater network is investigated. The parameters such as age, pipe length, slope and depth as input data and the number of blockage are considered as the output data of the model. In this research, the number of blockage data in the wastewater network at 1394 and 1395 are used, in which the 70% of the data is used for training and 30% for the test. These data are classified in three way leading to three model. In the first model, data are classified based on the slope and in two other models the data are classified according to the cover depth. The results show that all models predicts the number of blockage with good accuracy. In addition the accuracy of the result of GP model is better than the ANN model. For example, for GP model, the values of R2 and RMSE for the second model at the training stage are 0.97 and 0.8 and at the test stage are equal to 0.94 and 0.69, respectively. However these values for ANN model are 0.96 and 0.95 at the training stage and 0.87 and 0.96 at the test stage respectively. These results show the superiority of the GP model in comparison with ANN model in which the results of second proposed model are better. The results of these proposed model can be used for preventive maintenance, prioritization of sewage network repairs and inspections, and finally to prevents the occurrence of suddenly accidents.

In recent years, excessive usage of surface and underground water resources has exerted great stress on Iran's water resources. A survey of water use trends in the past years and forecasts of water needs in the coming years, makes undesirable  perspective for the imbalance between water demand and resources in the near future. Planning for the exploration and use of unconventional water resources, such as gray water and sullage reuse, will greatly help to balance water shortage. In this research, sewage of swimming pools has been investigated because it is a type of urban sewage that has high technical, economic and environmental potential for implementation of urban sullage recycling project. A case study was carried out on 10 public swimming pools in Tehran to determine the volume and 7 pools for qualitative investigation on sewage of different parts of swimming pools. The results indicate that pools have a high quality and high volume wastewater that cause conceivable potential for recycling. For example, the average COD of the tested samples was 153 ppm and the maximum was 246 ppm, which is equivalent to organic load of weak urban wastewater. This wastewater also meets the standards of landscape irrigation in most of parameters, and in the other parameters such as organic load of some samples has a small variance from these standards, which could be met with a simple treatment unit like a depth filtration and an activated carbon. In addition, an average of 120 cubic meters of sullage per day is generated in each aquatic center complex, which is more than the production of gray water in a 700 people capacity residential complex. Reuse of this sullage, in addition to reducing transportation costs and load of centralized treatment plants, will reduce the pressure on water resources of our country by supplying water for non-potable purposes such as irrigation of landscaping.

Water Pipe Line are the lines that take water from different resources and transfer it to drinking needed nodes, industry or agriculture. Because of the intense shortage of water resources especially in the eastern and central reigns of our country, in the recent years some plans have been proposed for water transferring among basins. These projects not only have led to a lot of social conflict in the area that these project have been done but also causes some subversive acts along the pipe lines and dependent installation. So finding suitable location for pipe lines from the passive defense point of view will be very important. In this research a method for finding suitable location for great pipe lines according to different criteria such as privacy, access, military, economic, population, geology, geomorphology, climate and hydrology is introduced. Each criteria is classified to several subgroups. So all the subgroups are done quantification in software of Arc-GIS9.3. Then with super position of above layers, the planed area and high risk places are coloured and determinedon the map. The results shows that the route which has the best access and the least intersection with Faults, agricultural areas, rivers and gas pipe lines with 374 kilometers lengths are selected as the best options.