مجله آب و فاضلاب
پیاپی 134 (امرداد و شهریور 1400)

Antibiotics, which are extensively produced and used all over the world, are considered as emerging contaminants. These organic compounds cannot be efficiently removed by traditional methods applied in wastewater treatment plants. Continuous discharge of antibiotic-containing wastewaters into the aquatic environments can lead to long-term adverse effects on aquatic life and human health. Rifampin is the most widely used antibiotic for treatment of tuberculosis. For this reason, its removal from water and wastewater is of high importance. Electrocoagulation is an advanced treatment method which has been effectively applied for removal of complex organic compounds such as chemical drugs. The main aim of the present study is to investigate the techno-economic aspects of the EC process for removal of RIF antibiotic from aqueous solution. In this study, effects of different parameters including initial pH, voltage, stirring speed, initial RIF concentration, reaction time, inter-electrode distance (die), shape of electrodes and their arrangement inside the reactor were evaluated on RIF removal efficiency using the EC process and its operating costs. The EC process was induced in batch mode using a 1 L reactor and synthetic RIF containing solution. The experiments were designed by one-factor-at-a-time method and relative standard deviation was used to compare the grade of the effect of the parameters on removal efficiency and operating costs of the process. Based on the obtained results, under optimal conditions, i.e., initial pH of 5, die of 1 cm, voltage of 20 volt, stirring speed of 200 rpm, initial RIF concentration of 10 mg/l, reaction time of 30 min and hole-punched shape electrodes in horizontal arrangement, the removal efficiency and the operating costs of the process reached about 92.49% and 89 US$/kg RIF removed, respectively. According to RSD values, among all the parameters investigated, reaction time, initial RIF concentration, voltage and initial pH were distinguished as the most effective ones on both RIF removal efficiency and operating costs. Generally, results of the study showed that the EC process has a high ability for removal of RIF antibiotic from water.

In urban water distribution networks, as the age of the pipes increased, the rates of pipe breakage and water losses increased which causes financial losses to the water and sewerage company. Therefore, to reduce the number of breaks and leaks in pipes, worn pipes should be replaced. Replacing old pipes is an expensive and costly procedure. Thus, it may be more economical to replace the pipe at the appropriate time. In this research, the urban water supply network of Hamedan was simulated by using system dynamics approach. Then the optimal time for pipe replacement was estimated by using analytical solution of the net present value equation and the combined method of system dynamics-net present value. Also, in order to improve the financial balance of Hamadan Water and Sewerage Company, the optimal price of drinking water was determined by using the Powell optimization algorithm method. Dynamic simulation was performed in VENSIM. To test the model, the simulated data were compared with the observed data collected from the water and sewerage organization of Hamedan over the period 2014 to 2018. To statistical analysis and calculating statistical, the root mean square error, standard error and correlation coefficient (R2) were used. Base on the results, for the Benefit-Cost variable, the RMSE index was calculated to be 0.006, the SE to be 0.010 and the R2 to be 0.991. Comparison of the standard error showed that the difference between the observed and simulated values of the standard error of the Benefit-Cost variable is less than about one percent. The result indicate that the presented model has the very high accuracy. Base on the results of the study, the optimal time for pipe replacement is 2041. Finally, the results of this study show that the financial balance of the company can be increased by determining the optimal price of drinking water. However, the level of social welfare can be improved by increasing the renewal coefficient of pipes. Therefore, the system dynamics method and Powell algorithm can be used to determine the optimal scheduling of water pipe replacement, to reduce losses to water and sewage companies and to reduce the number of failure of water supply pipes.

Water meters, as one of the most important components of the urban water distribution network, like other mechanical equipment, are gradually degraded and lose their desired efficiency. The poor performance of the water meter for estimating the amount of subscribers’ water consumption has a negative effect on planning for the provision of water production resources and also causes financial losses to water and wastewater companies. Therefore, in the present study, the accuracy of measurement of domestic water meters including 2 new meters (Baylan and Talayeh) and 7 used meters (about 35 years old) has been experimentally investigated in the range of water consumption rates of evaporative coolers (up to the start-up flow-rate). For this purpose, each of the above meters is separately installed on the test bench and placed in the water flow path in series with an ultrasonic test meter (owned by South Khorasan Province Water and Wastewater Company) and a digital turbine meter (owned by the project manager). Then, the flow rate shown by each of these three meters (apparent flow rate) was simultaneously read and compared with the actual flow rate (measured by a calibrated container and a stopwatch). Therefore, in the range of flow rates of evaporative coolers,  the error of meter operation in measuring the correct amount of water consumption (or unaccounted-for water) and the values of Root-Mean-Square Error can be determined. The results showed that the best operating range of domestic meters is between 15 and 22 liters per hour and RMSE values for this range of rates for the two new meters of Baylan and Talayeh are 7.79 and 3.61 liters per hour, respectively. Also, the start-up flow-rate values for Baylan and Talayeh meters were measured at 13.8 and 7.7 liters per hour, respectively, which are closely similar to the results of other researchers. In addition, by changing the network’s water pressure by means of a pressure regulating valve, the effect of this parameter on the accuracy of the meters is evaluated. Moreover, the effect of changing the parameters such as altitude, dry-bulb temperature, and relative humidity on water consumption of an evaporative cooler with a capacity of 7500 m3/h was theoretically investigated for 4 cities of South Khorasan province. Through psychrometric calculations, it was observed that the highest consumption of water cooler occurred in conditions of high dry temperature, low relative humidity, and higher air pressure (Tabas city) at the rate of 56.39 L/h.

In recent years, because of excessive and unregulated use of antibiotics, the threat of acquisition of antibiotic resistance by pathogens is growing. Hospitals are hotspots for antimicrobial-resistant bacteria (ARB) and will be ejected from hospitals via wastewater systems. The aim of this study was the frequency assay of qnr plasmid’s genes in quinolone resistant Entrobacteriaceae strains isolated from urban and hospital wastewaters. A total of 99 Entrobacteriaceae strains were isolated from urban and hospital wastewater in Alborz province during the spring of 2019. Bacterial strains were identified by standard microbiological and biochemical tests. The antimicrobial susceptibility test to ciprofloxain, levofloxacin, ofloxacin, norfloxacine and nalidxic acid was determined by Kirby-Bauer method and the frequency of quinolone resistance genes (qnrA, qnrB, qnrS) was investigated by PCR. Among the organisms cultured, Escherichia coli was the most common organism followed by Escherichia coli (inactive) and Citrobacter freundii. The most antibiotic resistance was observed against nalidixic acid.  Most of the isolates (61%) harboured the qnrA gene. qnrB and qnrS genes were found in 31% and 8% of isolates respectively. One isolate has both qnrA and qnrB genes. Most of the strains that contain qnrA and qnrB genes were isolated from hospital and urban wastewater respectively. Antimicrobial resistance should now be seen as an environmental pollutant and new wastewater treatment processes must be assessed for their capability in eliminating antimicrobial-resistant bacteria, especially from hospital effluents. Also, unregulated use of antibiotics should be stopped.

The need to separate acetone from waste water of industrial units such as dyeing, ink production, glazing, etc. has encouraged researchers to propose various separation methods for this purpose. Among different separation techniques, the pervaporation has been considered as a promising one due to its low energy consumption, operational simplicity and environmental compatibility. In this paper, the removal of acetone from water solution using the prepared polydimethylsiloxane/PEBAX/titania nanocomposite membrane by the pervaporation method has been investigated. After the fabrication of the membranes, they were characterized by various analyses including scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, and contact angle to study morphology, chemical bonds changes, crystalline structure, thermal resistance, and hydrophobicity feature of the resultant membranes, respectively. Designing the experiments by Taguchi technique, the effect of three variables: feed concentration (4, 8 and 12 wt.%), titania nanoparticles content (0.0, 0.75 and 1.5 wt.%), and operating temperature (27, 37 and 47 °C) on the separation efficiency of acetone from water was surveyed. The characterization membranes’ results are indicative of a proper distribution of the nanoparticles in the membranes matrices, dense structure of the membranes, the existence of expected functional groups in the membranes, as well as the increased hydrophobicity of the membranes. The FTIR outcomes confirm the presence of PEBAX, polydimethylsiloxane, along with the titania nanoparticles in the fabricated membranes. Besides, the semi-crystalline structure of the membranes which is affirmed by the XRD analysis exhibits the existed crystalline and amorphous parts in their bodies. The SEM photos displays PEBAX-based selective layer with its defect free and dense structure, along with the polydimethylsiloxane-based support layer containing the titania nanoparticles. The obtained results of this study indicated that with raising the titania nanoparticles loading, the separation efficiency of acetone from the water solution firstly increased due to the improved hydrophobicity of the membranes resulting from the well-dispersed titania nanoparticles and then decreased because of the aggregated nanofillers. Moreover, the results exhibited that there is a direct relation between the acetone concentration in feed and the acetone separation efficiency. It was also shown that the as the operating temperature is enhanced from 27 to 37 °C, the separation efficiency increases remarkably, while it does not change significantly at the temperature more than 37 °C. The pervaporation experiments revealed the maximum acetone/water separation efficiency of 90.11% for the membrane embedded with 0.75 wt. % of the titania nanoparticles at 37 °C and 12 wt. % of feed concentration.

Water and wastewater companies play a vital role in society as providers of drinking water services. Therefore, measuring the efficiency of these companies is an action that can help in the optimal allocation of water distribution among customers. Therefore, the present study was conducted to evaluate the efficiency of water and sewage companies in Markazi province. For this purpose, the interval fuzzy data envelopment analysis method was used. The basic premise of this method, unlike the traditional method of data envelopment analysis, is uncertainty about inputs and outputs. Given that uncertainties in the real world are inevitable, the need to use models that have the ability to control this uncertainty is strongly felt. Hence, a successful method is to use fuzzy data envelopment analysis method. The results of evaluation related to seventeen water and wastewater companies in Markazi province showed that Arak, Khomein, Delijan, Saveh, Komeijan, Mamooniyeh, Mahallat and Naragh by obtaining the efficiency range (0.83, 1),  have the highest level of technical efficiency. In addition, among the units under study, Ghargabad Water and Wastewater Company has the lowest level of technical efficiency with an efficiency range of (0.56, 0.46). There is also an excess of consumption over the research findings in the use of all inputs. Therefore, it was suggested that with the correct and optimal use of production inputs and less use of resources, the amount of efficiency can be improved to reach the efficiency frontier.

A realistic understanding of aquifer vulnerability to seawater intrusion is one of the important prerequisites for coastal aquifer management. The GALDIT method is a proper tool that, despite considering the qualitative, hydrogeological, and geological characteristics of the aquifer, has not considered the role of aquifer surface recharge. The Qom-Kahak study area is a part of the salt lake catchment, which is located in the arid and desert part of central Iran. Due to the shortage of surface and groundwater resources in the region, some of the drinking and industrial needs of Qom city are met from water outside the study area. This study, by adding the aquifer surface recharge parameter introduces the GALDITR model to evaluate the Qom aquifer vulnerability to saltwater intrusion from the Salt Lake. Then, the analytical hierarchy process method is used to review the weight of GALDITR model parameters according to the characteristics of the studied aquifer. Based on the obtained results, the high rank of the aquifer surface recharge parameter in a large part of the aquifer led to an increase in the area of moderate vulnerability of the GALDITR model compared to the GALDIT method. In the GALDITR-AHP model, the parameters of distance from the shore, groundwater level above the lake, and the impact of seawater intrusion gained more weight than other parameters, respectively. With increasing the low vulnerability area in the GALDITR-AHP model, the aquifer vulnerability near Qom city decreased. The vulnerability index of GALDITR-AHP, GALDITR, and GALDIT models showed the highest correlation with chloride ion values at observation points, respectively. The results showed that areas with high and moderate vulnerability in the eastern part of Qom aquifer covering about 14 % of the total aquifer area are more prepared for seawater intrusion and can be considered as the expansion of seawater wedge for monitoring and optimal management of coastal aquifer.

One of the most important problems in the process of wastewater treatment by the complete mix activated sludge method is the production of a large volume of sludge, which poses many problems in the management and conditioning of sludge. Since about 60% of the operating costs of wastewater treatment plants are related to sludge management, so any modified process that can produce less sludge can be effective in reducing costs and better sludge management. The use of magnetic fields to treat wastewater has been considered by researchers in recent years due to the lack of application of chemicals in these processes. This study considered the use of MFs strength in the range of 0.19 to 3.21 mT on diluted sludge volume index for 30 minutes. The rate of reduction of this index in the case samples compared to the control samples from 10 to 100 mL/g was different. During this period, the difference between the temperatures of the case samples compared to the control samples was statistically significant and was estimated from 0.4 to 20 °C. The difference between mean pH of the case and control samples was significant but the dissolved oxygen concentration of them, similar to other variables’ factors that affect the process, was not statistically significant (p> 0.05).

Due to environmental issues caused by pollution of water resources with organic pollutants, research to provide effective methods for removing these pollutants has received considerable attention. In the present work, the application of Metal Organic Frameworks for the photocatalytic treatment of wastewater containing organic pollutants was studied. Due to the high porosity, suitable band gap, good thermal and chemical stability, ZIF-67 was selected for photocatalytic removal of organic pollutants from wastewater. The ZIF-67 photocatalyst was synthesized and characterized by XRD, FTIR, BET, ICP and UV-DRS techniques. To study the photocatalytic activity of ZIF-67, degradation of methylene blue as an organic model compound has been performed and the effects of catalyst loading, dye concentration and pH on MB removal were studied. Also, the effect of zinc addition to ZIF-67 strucure on the performance of photocatalytic activity was studied. According to the BET results, the specific surface area of catalyst was measured about 1750 m2/g which indicates the high porous structure of ZIF-67. A catalyst loading of 0.5 g/L resulted in 68% removal of MB with initial concentration of 15 ppm after 2 hours of exposure. By addition of zinc to the structure, Zn/Co-ZIF was synthesized and not only showed better crystallization, but also photocatalytic activity increased to 79%. Also, increasing pH and catalyst loading resulted in higher removal efficiency. Both ZIF-67 and Zn/Co-ZIF structures exhibited higher activity in the basic environment (pH 8-12). Although increasing catalyst loading increases removal efficiency, it entails the increase of turbidity which could affect the removal efficiency inversely for higher values. Band gap measurements by UV-DRS analysis indicated that both ZIF-67 and Zn/ZIF-67 can be active under visible light irradiation, and hence may be applicable for degradation of organic pollutant in wastewater.

On the eve of the year 2021, about a century has passed since the establishment of municipalities, and more than half a century has passed since the establishment of development planning laws and the beginning of the implementation of urban planning projects. The purpose of creating these laws and establishing structures and organizations to implement them was to monitor the creation and development of cities to provide suitable conditions for citizens in life. The results of the implementation of urban development projects show that these projects, despite spending a lot of money and energy, in many cases do not achieve their goals. Despite these problems, for many years, the lack of coordination of organizations related to urban management, the lack of appropriate methods for preparing and implementing urban plans and the lack of technical and financial capacity in the organs have been raised as important issues in project inefficiency. But the importance of not paying attention to the infrastructure that can affect urban management and planning has been overlooked and among all the factors, water has the most fundamental role as the main source of life and the basis of development. This grounded theory method first examines the causes and known factors of inefficiency of urban planning in Iran, explains the relationship between this issue and the critical factors of inefficiency and then identifies the effect of paying attention to the pivotal role of water in eliminating many of these factors , By presenting a local model for using the basics of water-sensitive city design in urban planning, offers a proposal for operationalizing and making more practical the methods of urban planning, which, if used in the future, can solve the problems of urban planning in the country. Sensibly reduce and eliminate.