مجله آب و فاضلاب
پیاپی 124 (بهمن و اسفند 1398)

Increasing water demand in agricultural, urban and industrial sectors and decreasing water resources due to climate change caused serious restrictions in traditional manners of water management especially in arid and semi-arid regions including Central Plateau of Iran. In order to manage water resources effectively, it is essential to consider the socio-economic system and administrative-institutional system, in addition to the natural system. This study aims to investigate the administrative-institutional system of water management in Zayandehrud basin. Quantitative methods generally are used to study water resource systems, but these methods face some challenges such as: the lack of sufficient data, the weakness of the quantitative models in adapting to human systems, and the inability to provide a general picture of the problem; therefore, it’s essential to use of Qualitative methods along with quantitative methods for understanding these systems. The present study tries to understand the most important problems of the administrative-institution of water management system in the Zayandehrud basin using the grounded theory as a systematic qualitative method. The results of this study indicate that the incomplete and misleading information, different understanding of issues, ineffective meetings, conflict of interest, lack of coordination and conflict between organizations, corruptor structure, and weak regulatory system are the problems that caused the current administrative structuer is ineffective. The main causes of these problems are lack of transparency and non-participatory management. These factors, along with the lack of a deterrent mechanism, have led to excessive water allocation and unauthorized exploitation. According to recent 20-years data, the average annual renewable water including transferred water into the basin has been about 2500 MCM while the average annual water consumption has been about 2770 MCM and resulted in a cumulative decrease of 4900 MCM non-renewable water storage. In this paper, only quantitative method of the grounded theory is considered and it is necessary to use a quantitative method in the future to accurately assess the importance of the factors driving the instability of water resources in the Zayandehrud river basin.

Water distribution network one of the most important and most sensitive urban infrastructures which can be recently with regard to population growth and consumers '' needs to increase with challenges such as reducing the pressure and discharge that are all due to unsuitable design and based on economic goals. In order to overcome these problems when designing an urban water distribution system should always be considered reliability of the network. In this research, to optimize the water distribution networks, two main objectives of cost minimization and maximization of network reliability were considered. To calculate network reliability, the Tondini''s Resilience Index and its hydraulic simulation EPANET 2.0 model were used. Then using the second edition of the evolutionary algorithm based on the strength of the Pareto (SPEA2) and creating a dynamic connection with the EPANET 2.0 hydraulic model in the MATLAB software environment, optimizing the multi-objective of the four water distribution networks including Two-Loop, Kadu, Hanoi networks and D zone of Mashhad. Simultaneous optimization of two main objectives including cost minimization and maximization of the Tondini''s Resilience Index led to the production of optimal solutions in the form of the Pareto front. An optimal solution, called Point C, was introduced using Young''s bargaining method from the final Pareto front of in each of the networks. Selected C solution in two-loop,Hanoi and Kadu networks increased 22.91, 17.13 and 7.41 precent, of the network average pressure compared to its lowest cost in this study (point A). Also, the selected C solution in D-zone network of Mashhad, with an increase of 4.23 precent of the network average pressure compared to the initial design of the consulting company (point D), illustrate that the solution designed by the consulting company would be a dominated solution under the final Pareto front of this study. In this research, the Tondini''s Resilience Index illustrate that, based on increasing nodal pressure, it has the ability to increase the reliability of the network, which This causes the network to be in critical condition or failure of the pipes, with high reliability, providing adequate pressure and discharge in other nodes. Also, the satisfactory performance of the SPEA2 multi-objective algorithm in providing the optimal Pareto front for the issues indicated showed that the design pattern developed in this study could be to provide an optimal set of solutions to the employer to select the points in which each two factors of cost and reliability are combined in a favorable situation.

Large and complex infrastructural projects, especially water and wastewater projects always exposed to various internal and external risks. Given the increasing volume and complexity of rural water and wastewater projects, the constraints on funding and resources required their success in identifying, assessing, prioritizing and managing these risks. In this research, using research literature, checklist, experts, and expert opinions, the risks in rural and rural sewage projects in Gilan identified based on the 10 areas of the project management knowledge standard. The ranking indexes in this study include two parts of the primary and secondary indices: 16 effective risk factors among 60 risks, using the initial indicators based on the probability of occurrence and the degree of risk impact on the initial indexes of the project (time, cost, quality, performance) Determined. In the next step, based on additional indicators, the amount of exposure to risk, the level of manageability, the proximity of the occurrence of risk, the socio-economic effects and the environmental impacts (which are proportional to the climate and geographical area studied), are used by two methods of fuzzy topsization and hierarchical analysis Fuzzy has been evaluated for project risks. Finally, by integrating the results with simple averaging, the final ranking of the risks specified. The result of the research showed that the risk of insufficient funding at the due time chosed as the most important risk. In addition, the risk of non-payment of time claims of contractors and work force with a mean score of 2 and the risk of not using feedback results in quality control and implementation with a mean score of 3.5 were in the next priorities. The results of the research show that the rural water and Wastewater Company of Guilan should be adopt special measures for the required budget in order to manage the identified risks, and to conduct more detailed studies of validation in various projects in the preparatory phases. . It also pledges to pay in due time claims and analysis in control and quality and implementation.

Nowadays water pollution is one of the most important problems in different societies. This problem increases with the development of countries. Existence of various dyes in waters is one of these important pollutions so adsorption can be used as an important method to eliminate dyes from waters. In this research, the adsorption of Malachite Green on odorant Do Ghazal tea waste was studied. The study of this issue was performed in laboratory’s temperature, with variation of different parameters like pH, adsorption time, amount of adsorbent and dye concentration. The results of the experiments show that the adsorption efficiency increases with more adsorbent addition, higher pH levels and time enhancement. Also the reduction of dye concentration causes better adsorption efficiencies. Moreover the study on isotherms of adsorption process confirmed that the adsorption obeys the Freundlich model. The results of this study show that the efficiency of Malachite Green elimination in aqueous solutions on odorant Do Ghazal tea waste was higher than 95%. An artificial neural networks (ANN) model was developed to predict the performance of the decolorization efficiency by the adsorption process based on the experimental data. A comparison between the predicted results of the designed ANN model and experimental data was also conducted. The ANN model yielded a determination coefficient of R2=0.9981. The model can describe the decolorization efficiency under different conditions. Odorant Do Ghazal tea can be used as a low cost and available adsorbent to removal of organic pollutants from contaminated waters. Artificial neural networks can be employed as an appropriate method for adsorption process modeling too.

Removal of contaminants by adsorbent is a useful and effective way to remove heavy metals from wastewater and aqueous samples. Mercury is one of the heavy metals that is toxic to humans, animals and the environment. In this study, magnetic multi-walled carbon nanotube (MMWCNT) composite was synthesized and used to remove Hg(II) from aqueous solutions. This work was conducted on a laboratory scale and based on the design of experiment by the surface response methodology (RSM) and based on Box-Behnken design, and the effects of independent variables including pH, adsorbent dose, initial concentration of Hg and contact time in different levels were evaluated with the help of Design-Expert Stat-Ease Inc software. The properties of this magnetic adsorbent were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The results show that the adsorption of Hg(II) on magnetic MWCNT composite is strongly dependent on contact time and adsorbent dosage. The highest efficiency of removal mercury was about 85% and that occurred when pH=6, dose of adsorbent= 0.6 g/L, initial concentration of Hg(II)=10 ppm and contact time=150 minutes. The adsorption isotherm data were better fitted by Freundlich model, while kinetic data can be characterized by the pseudo-second-order rate kinetics. In general, it can be concluded that magnetic MWCNT adsorbent has a very high ability to remove mercury.

Heavy metals are among the environmental pollutants that human exposure to some of them through water and food can cause chronic and dangerous poisoning. The problem of poisoning drinking water to arsenic is a pervasive problem and has been seen in almost all countries, whether developed or developing, which endangered the lives of many people. In the present study, the removal of arsenic from water using iron / N-isopropyl acrylamide / chitosan nano-adsorbent was studied and evaluated. In this research, a magnetic nanoparticle was used to absorb arsenic, which is an innovative method. In order to increase the absorption capacity, we use polymer grafting operations on the surface of the nanoparticles, which will greatly increase the specific surface of the adsorbent. In fact, by placing polymers on the adsorbent, the combined desire increases. The results show that synthesized nano-adsorbants have the ability to absorb arsenic at different concentrations. But its concentration varies in different concentrations. Langmuir, Freundlich, Tamkin and Dobbin Radhushev isotherms were fitted with arsenic adsorption at 45 °C, pH = 7.5 at different concentrations. And the results show that a high (R = 0.995) R2 value for Langmuir model confirms that this model is suitable for fitting experimental data. The percentage of arsenic removal in optimal conditions at pH= 7.5, the amount of adsorbent 10 mg, contact time 60 min, temperature 45 °C and concentration of 10 μg/ml was 82.2%.

Recently, aerobic granular sludge reactors have been extensively studied as a new technology for wastewater treatment. In this study, a mathematical model has been developed and compared with the experimental results to study the microbial distribution and overall conversions performance of the reactor at different conditions such as dissolved oxygen concentrations and COD, nitrogen and phosphorus loading rates. A laboratory reactor with working volume of 3 L was operated in sequencing batch mode. A model was developed using Aquasim software to investigate the structure and performance of the reactor at different dissolved oxygen concentrations and COD, nitrogen and phosphorus loading rates. The model results showed that the majority of the microorganisms inside the biofilm are phosphate accumulating organisms. Total COD and P-removal under the laboratory conditions at a dissolved oxygen (DO) concentration of 100% was reached, but the obtained N-removal was not sufficient. Therefore, the N-removal at lower oxygen concentrations was studied. The optimum value for nitrogen removal was obtained (more than 98%) with a DO concentration of 40-45% and 35% by simulation and in the laboratory reactor, respectively. The model describes the experimental data at different COD, nitrogen and phosphorus loading rates, sufficiently well. The results of the experimental data and model were in a good agreement. Therefore, the model can be used for process understanding and optimization of this complex system.

Today the Phytoremediation is used as an effective and in expensive method for filtering water from contaminated areas. In this study, to absorb nickel two types of plants, Egyptian lotus and Cyprus alternifoliusare used. For this, ponds with Egyptian lotus and Cyprus alternifolius are used which nickel-ion concentrations are 2, 5, 10 and 15 mg/L and pHs are 5.5, 6.5, 7.5 and 8.5. The test temperature is constant at 25oC. The best absorption after 20 days was determined for Egyptian lotus plants at a concentration of 2 ppm and pH=5.5 and for the Cyperus alternifolius plant at a concentration of 2 ppm and pH=6.5. Adsorption isotherm studies with Langmuir and Freundlich models shows that nickel-ion adsorption behavior for Cyprus alternifolius and Egyptian lotusis followed by Freundlich and Langmuir isotherms respectively. Roots, leaves and stems analysis after nickel absorption with atomic absorption spectroscopy shows that for both plants roots have the most share as for Cyprus alternifolius and Egyptian lotus is 79.9 and 86.39 percent respectively.

One of the most important ways to manage consumption is to reduce non-revenue water and losses in urban and rural water supply systems. The inaccuracy of the meters can have direct impact on the evaluation of loss water control programs as well as resource conservation programs thereby leading to incorrect decisions. In this paper, for numerical simulation of the effect of direct pump installation on the performance of domestic water meters, a turbine water meter of multi-jet production type is selected. It is assumed that the values of the mechanical brake torque on the impeller, such as the bearing friction drag torque, and magnetic magnitude is insignificant and can be considered as zero. The input and output flow are the fully developed in the water meter where K-ω-SST turbulent model is selected and the rotational speed of the impeller is collected at different flow rates. Comparing the numerical solution results with the manufacturer's practical experiments data, reveals the maximum error of 9.66%. Thus, the model can be used to evaluate the effect of direct pump installation on the performance of domestic water meters. As a real-world case, the water meter performance when the centrifuge pump is directly inserted into the outlet of the water meter is simulated and the results were compared with the non-pumped state. the behavior of the water meter when the pump is installed at the outlet of the water meter differs from the non-pumped mode in different flow rates. This difference is due to the change in the flow profile and the angle of impact of the water with the impeller. The results indicate that in high flow rates (more than 536 L/h) with the other same conditions, rotational speed of the impeller is less than the non-pumped state with the maximum decrease of 17% and thus the meter has a negative error measurement. However, in low flow rates (less than 75 L/h) the rotational speed of the impeller is increased almost twice more than the non-pumped state causing enlargement in meter's orders of error measurement.