مجله آب و فاضلاب
پیاپی 144 (فروردین و اردیبهشت 1402)

The use of a systematic view has increased to deal with social and environmental problems in recent years. Recently, various models have been developed to address urban water issues. Most of them are focused on runoff and storm water management and few have addressed the problems of the Drinking water system. However, the lack of an effective model that supports complex and multi-objective urban water system in terms of management and decision-making is felt. This article focuses on the importance of a sustainable approach to the conventional approach in urban water management and the need to change attitudes due to the current state of water resources. In this paper a novel system dynamics model has been developed, taking into account the technical, economic, social, environmental and government subsystems that simulate and predict the results of urban water management measures. The results of the implementation of the proposed model on the city of Isfahan showed that the model has a high precision in simulating system condition. The model error rate in simulation of different parameters is less than 5%. Therefore, the model can be used as a tool for analyzing different management strategies before implementing and spending time and cost to assist decision makers.

In the current work, the capability of uncoated titanium anode in the electrochemical treatment of textile wastewater has been investigated with the aim of simultaneously benefiting from electrooxidation and electrocoagulation treatment processes. In the present work, the feasibility of using uncoated titanium anodes for wastewater treatment is studied in an electrochemical pre-pilot set-up with polymeric casing and an electrical supply power of 150 W, operated under galvanostatic regime in batch mode, focusing on the current density as the main subject of assessment, and its performance is evaluated using metrics such as chemical oxygen demand removal and specific energy consumption. A noticeable finding of this work, is the flexibility of the set-up to combine the electrocoagulation and electro-oxidation mechanisms with the current density as the controlling parameter, leading to a remarkable decontamination capability, so that reductions in the total chemical oxygen demand as large as 75–80% in the neutral and 90–95% in the acidic environments were achieved. At low current densities (< 100 μA/cm2), the anodic corrosion was limited and the electro-oxidation was the dominant wastewater treatment mechanism. At high current densities (> 100 μA/cm2), the anodic corrosion was accelerated and the dominant wastewater treatment mechanism was switched to electrocoagulation. Along with the chemical oxygen demand removal capability, the energetic cost-effectiveness of the set-up was a major concern, particularly from the industrial point of view, which was assessed in both neutral and acidic environments, and it was realized optimization occurred at 600 μA/cm2, so that the specific energy consumption and the rate specific energy consumption, were both minimized at this current density, in respective order, 8.9 kWh/kgCOD and 3.52 kWh/kgCOD/h in neutral, and 10 kWh/kgCOD and 2.34 kWh/kgCOD/h in acidic environments.

Leachate production and management is a challenging environmental issue in municipal landfills and depots in Iran. Leachate contains toxic materials, heavy metals, and organic and microbial pollutants on a significant scale. Its uncontrolled entrance into the surface, groundwater, and soils can also substantially inverse impacts on human health and natural habitats. In Mazandaran province, during the last decades, depots and landfilling of municipal and industrial waste have led to environmental degradation in its eco-sensitive natural zones and brought a series of health, social, and security challenges to the region. Due to the region's high precipitation rate and landfills with no cover, these places practically convert into an extensive resource for leachate production. To diminish the environmental impacts, a lot of work has been done in recent years to develop a sort of leakage gathering system and treatment plants in these landfills, based primarily on an overall estimation. In this study, a calculating computer model has been developed for leakage production based on regional climate conditions and the characteristics of municipal waste. This model is different from the HELP model, which is commonly used for sanitary landfills and is specifically developed for the waste depots of the Mazandaran province. In this model, hydrological methods, which are based on the water balance in the landfill sites, were used for the calculation. The developed model was uploaded as an online service for public use. By referring to the internet address provided, the developed model in the landfill part and the leachate section, the amount of produced leachate for the landfill site of Mazandaran province can be calculated. Also, the leachate volume of the Babol Anjilsi landfill has been calculated as a case study. As a result of this study, the lowest and highest amount of the production leachate for hot and dry months of the year (June and July) and for wet and rainy months (October) was about 63.39 and 260.07 cubic meters per day, respectively.

The effluents of polymerization plants are acidic due to the use of sulfuric acid as flocculation agent and their wastewater contains high amounts of sulfate ions. In wastewater industry, several physical, chemical and biological treatment methods are used. The main purpose of this study is to examine the feasibility of anaerobic biological treatment of sulfate in industrial effluents by using sulfate-reducing bacteria. The research method is quantitative, and experiments and data collection from 2017-2020. The main variables of this research are temperature, effluent pH and the population of microorganisms. Experiments at two temperature levels of 25 and 60 oC and two different pHs, 7.5 and 8.5, were performed and four series of experiments were done. The results showed that by increasing the temperature of the solution from 25° to 60 °C at a concentration of 50 mg/L sulfate ion and a pH of 7.5, microorganisms showed 17.6% better performance. Also, the performance of microorganisms in anaerobic biological treatment at concentration of 50 mg/L of sulfate ion was 45.3% minimum and 49.9% at maximum. Comparison of experimental results at two different pHs of 7.5 and 8.5, indicates that at the same temperatures of 25 and 65°C, with increasing pH, the performance of microorganisms has improved by 16.4%. The efficiency of wastewater treatment increases 19.6% by changing pH from 7.5 to 8.5. Results showed that the correlation between temperature and sulfate ion concentration follows the 1st degree equation. Also, the weak pH environment provides suitable conditions for the removal of ions in the effluents, and the correlation between increasing the pH of the solution and decreasing the concentration of sulfate ions is a 2nd degree equation. Study showed that temperature and pH are the two effective factors in the process of biological treatment of effluents.

Zagros Petrochemical Company, as one of the largest methanol companies in Iran, faces the problem of high levels of turbidity and sulfate and ammonia pollutants in its wastewater. So, it is required to effectively purify this wastewater for reusing in steam production in the methanol unit; also, to bring the amount of pollutants to the required environmental standards. The purpose of the present study is to investigate the coagulation process and compare the effectiveness of six different coagulants, including aluminum sulfate (alum), iron (II) sulfate, chloroferric, polyaluminum chloride and two types of cationic and anionic polyelectrolytes, in reducing the existing amount of turbidity, sulfate and ammonia in the wastewater of this company. During these experiments, the effects of effluent pH and coagulant concentration parameters on the efficiency of reducing the turbidity and the mentioned pollutants has been investigated. According to the results, and considering the long flocculation time, as well as low formation of very small and non-quick precipitating suspended particles, the coagulants alum, chloroferric and iron (II) sulfate do not have a significant effect on the removal of turbidity from the target wastewater sample. Meanwhile, the coagulants PAC, cationic and anionic polyelectrolytes, with low concentrations, are suitably effective, and, in combination with lime, can remove a significant amount of the turbidity (about 99%) and the ammonia (about 60%) from the investigated wastewater. Also, the highest amount of the sulfate reduction (about 45%) is attributed to the alum coagulant. Finally, taking into account the costs, accessibility and compatibility of the wastewater treatment package of the Zagros Petrochemical Company, the coagulant PAC in a concentration of 5 mg/L, in combination with lime at a pH of 12, has been suggested and the mentioned problems were completely resolved.

The loss of drinking water from water distribution network is one of the problems of Water and Sewage Companies worldwide, which reduces a remarkable part of the company's profit. Therefore, the aims of this research are: determination of strategies and their evaluating criteria for the loss management in water distribution network, prioritization of those strategies and criteria as well as selection of the most effective strategy. This study is a practical research and data gathering was performed via researcher-made questionnaires on snowball sampling based on the idea of 10 experts employed in Water and Sewage Company of Isfahan province. Four strategies of water loss management of water distribution network assessed in questionnaires were selected based on the recommendations of International Water Association, American Water Works Association and the regulations of the non-revenue water committee by the deputy directorate and under supervision of the Water and Wastewater Company of Iran, 2020. Data gathering and analyzing were carried out using paired comparison matrix and analytic hierarchy process by the Expert-choice software. The calculated inconsistency ratio of questionnaires was determined to be 0.02, and therefore the most effective strategy of water loss management of Isfahan water distribution network was determined to be the pressure drop strategy with weight of 0.400. Three other strategies of active leak detection weight 0.259, network repair weight 0.175, and speed and quality of emergencies weight 0.167, were prioritized in the next ranks, respectively. Likewise, the criteria of financial supply weight 0.463 in the first rank, the criteria of technical supply weight 0.289 in the second rank, the criteria of training update weight 0.146 in the third rank, and the criteria of legal supply weight 0.102 in the fourth rank, were prioritized. By increasing the ratio of circular intubation in water distribution network and construction of water storage tanks in the northwestern heights of Isfahan, it is practical to develop the pressure drop strategy in flat districts of Isfahan city leading to the minimum water loss of Isfahan distribution network.

The water supply network is one of the most critical infrastructures of human societies, which could cause illness or death in many consumers due to its expanding nature. Water pollution is one of the ways of spreading biological pollutants among the population, which is known as bioterrorism today. Biological contamination usually occurs with the use of pathogens and biotoxins. Therefore, recognizing the vulnerable stages of the water supply network against various pollutants is of particular importance. In this research, in the first stage, a selection of five pathogens (Bacillus anthracis, Cryptosporidiosis, Francisella tularensis, Vibrio cholerae, Shigella) that are more likely to pollute water sources have been made. Thus, employing each component of the water supply system (including raw water source (dam)), Raw water storage tank, water treatment plant, treated water transmission line, treated water tanks, and distribution network (30 scenarios) were defined. In the next step, using multi-criteria group decision-making and employing three main criteria (vulnerability of each water supply stage, the amount of contaminant damage power, the amount of contaminant risk in each of the water supply stages) and their sub-criteria, the weight of each criterion was determined from the perspective of decision-makers by utilizing GFDM software. After analyzing the scenarios, the risk level of each scenario was ranked. Scenario 26 created the most risk, which consists of introducing the pathogen Bacillus anthracis into the distribution network. The entry of contamination into the distribution network due to high availability and lack of subsequent treatment steps, as well as the slight chance of preventing the contaminant from reaching consumers, can cause many diseases and deaths. Furthermore, it has a high resistance against chloride and is stable in water, so the entry of this contaminant into the distribution network can be dangerous. Considering the existing conditions, recognizing and calculating the risk of different scenarios can lead to readiness and increase the speed of action in response to possible biological attacks.

Considering lead’s toxicity and its characteristics as a serious environmental pollutant, to protect the human population’s health and the ecosystem it is necessary to stop this heavy metal from entering water resources and the environment through industrial wastewater. Therefore, the present study was carried out to manage lead elimination from aqueous solutions using NiO nanocomposites immobilized on graphene. To determine the effective factors in the elimination process, some parameters including contact time (20, 30, 15, 5, 10, 3 min), adsorbent dosage (0.1, 0.05, 0.2, 0.01g), initial concentration of the lead solution (5, 10, 20, 50, 100, 200, 300, 800, 1000 mg/L) and pH (2, 4, 5, 6, 7) were investigated at room temperature, 40 ˚C and 55 ˚C. Based on the results, the amount of lead eliminated by graphene-immobilized nickel oxide nanoparticles reached its maximum value under the optimum conditions of 20 min contact time, 0.05g adsorbent, 5ppm initial concentration, and 55 ˚C temperature. In addition, the experimental data were analyzed using Langmuir, Freundlich, and Dubinin-Radushkevich isotherms of the adsorption process and the results indicated maximum compliance with the Langmuir isotherm, with a maximum adsorption capacity of 2000 mg/g. These findings show that lead absorption is an endothermic reaction. The graphene/NiO magnetic nanocomposite made in this way has many pores and a high specific area (196.5 m2/g), which makes it an ideal adsorbent for removing lead(II) ions from aqueous solution. The maximum absorption capacity obtained from the said adsorbent was 2000 mg/g, which is much higher than other common adsorbents. Among the advantages of this method, we can point out the very high absorption capacity, the simplicity of separating the adsorbent from the solution, and the fast duration of the absorption equilibrium (up to 20 min).

Nowadays, lack of water resources has become a crisis in many countries around the world including our country, Iran. In the current situation, minimizing the waste of water is vital. Continuous reverse osmosis system, the most widespread technology for water desalination, wastes large amounts of fresh feed water as high salinity brines. Hydraulic parameters and deposition of salts on the membranes are the most important factors limiting the maximum achievable recovery rates in RO systems. Closed circuit RO technology by modifying the operational mode of continuous RO system to a cyclic semi-batch process, reduces limitations of the maximum possible recovery and can decrease the amount of water waste by 90%. Due to the lack of experience and knowledge about CCRO technology in Iran, the main goal of the present study is the performance evaluation of CCRO systems in Iran's water desalination plants. For this purpose, two industrial RO systems, located in central and northwestern Iran, were selected as case studies. For the first time, according to the real feed water matrix, the maximum achievable recovery of systems was investigated by changing continuous RO to CCRO systems. The results revealed that implementing CCRO systems could significantly decrease brine production rate 74 to 89%. However, the electrical energy consumption of the systems increased reasonably 8 to 36%. For high salinity feed water (1st case study), the maximum allowable operating pressure of membrane 41.4 bar limited the recovery of CCRO system to 88.7%. For the system with low salinity feed 2nd case study, the recovery was limited to 96.6% due to restriction in the maximum permeate flowrate per element (1.58 m3h-1). In this case, the saturation levels of silica and sulfate salts were much higher than the permissible levels. Therefore, dosing a suitable antiscalant and high volumes of sulfuric acid were necessary to control the scaling. However, acid and antiscalant demands were reduced by a decrease in CCRO recovery rate.

Produced water is the largest waste stream in the oil and gas industry. It is a mixture of inorganic and organic pollutants. The harmful effects of discharging untreated produced water on the environment and public health is a challenging concern. Nowadays, the integration of advanced oxidation process and biological treatment is of interest to the researchers. Investigating the relationship between AOP pretreated effluent and subsequent bioreactor performance can help to optimize these systems. In this research, biological treatment was first examined without pretreatment, and it was found that biological degradation alone is incapable of treating the sample, so the integrated method of electro fenton-biological treatment was studied. Electro fenton performed the pretreatment and bioreactor did the final treatment. Synthesized MCNT-Ce/WO3/GF cathode and the MWCNT/GO/Fe3O4 heterogeneous catalyst were used in the electro fenton process. BTEX removal test - as a produced water simulant - was done using aerobic granules bioreactor, electro fenton and their combination, respectively. After optimizing the pH and time variables, in order to study the interactive effects of temperature, catalyst load, applied current and electrodes distance, a Box-Behnken experimental design and response surface methodology were used to optimize the performance of proposed system. The experiment carried out in the calculated optimal conditions for the electro-fenton degradation process (temperature 30 °C, catalyst load 250 mg/L, current density 170 mA/m2 and electrode distance 1.5 cm). The BOD/COD ratio and COD removal was found to be 0.41 and 56.5%, respectively. In these conditions, effluent entered the granular bioreactor and the final COD removal of the sample was done up to 94%. Real produced water was fed into the electro-fenton reactor and its effluent was introduced to the aerobic granular bioreactor, results showed that integrated electro fenton-bioreactor removes organic pollutants up to 92.7± 0.2% and keeps the characteristics of the treated produced water within the environmental standard range.