مجله آب و فاضلاب
پیاپی 148 (آذر و دی 1402)

The rise in population growth and subsequently,the spread of various diseases have led to increased production of medicines, including antibiotics. Discharging wastewater and dispersing pollutants such as drug waste in the water cycle is a very important issue that has received considerable attention in recent years. In this study, the thermodynamics of Amoxicillin and Cefixime adsorption by chitosan-polyacrylamide coated by ZIF-8 has been investigated. SEM analysis indicated that ZIF-8 is well placed in the structure of the adsorbent and no separation phases were seen. The results obtained from the temperature data in the conditions of 15 mg of adsorbent, pH 4 and adsorbent concentration of 50 ppm showed that the removal percentage decreases with increasing temperature, so it can be found that the adsorption process was exothermic. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were also calculated. As the temperature rose, Gibbs free energy also increased, indicating  that at higher temperatures, the rate of spontaneous progress of adsorption has decreased. The negative values of enthalpy and entropy in both adsorbates confirms that the reaction is exothermic and spontaneous, respectively.

Urban wastewater combines black and gray wastewater, which can be thought of as a way to separate and optimize its treatment. In this research, the separation and recycling of gray water treated by photoelectrocatalytic method, to be used in irrigation of plants, etc., has been investigated. First, the gray wastewater of a 10-unit residential building was sampled. BOD and COD concentrations were measured by respirometry and closed reflux calorimetry, respectively. Then, the removal efficiency of photoelectrocatalytic treatment by direct current with titanium and graphite electrodes, at two current densities of 10 and 20 mA/cm2 and at three electrode distances of 6, 12 and 15 cm, and the feasibility of using this method from the point of view of energy consumption, was studied. Based on the results, the optimal conditions for pollutant removal have been obtained at a current density of 20 mA/cm2 and a distance of 12 cm between the electrodes in a period of 60 minutes. With an increase in current density, the removal efficiency increases and as the distance between the electrodes increases, the removal efficiency experiences an increase with partial changes, but, it causes an elevation in voltage, resulting in an augmented consumption of electrical energy. The initial pH decreased with increasing voltage and further decreased with decreasing electrode distance. The amount of electrical energy consumed in the photoelectrocatalytic reactor is estimated to be about 2 kWh/m3 and 11.43 kilowatts per kilogram of COD removal. The results indicate a 64% reduction in water consumption at the site of operation, a reduction in energy consumption in the water and wastewater distribution and treatment system, and as a result, a reduction in CO2 production. Although the possibility of using the photoelectrocatalytic system on a large scale requires more studies, other suitable methods can be used.

To remove pollutants, many methods have been used so far, including ion exchange, coagulation and reverse osmosis. Most of these methods have many disadvantages and among them, the adsorption method is considered as a useful method. The purpose of this study is to synthesize adsorbents in the form of nanocomposites based on graphene oxide and modify the surface of graphene oxide by using iminodiacetic acid ligand to remove chromium ion by adsorption method. To determine the chemical structure and characterization of functionalized magnetic graphene oxide, we used XRD, BET, FTIR and SEM analysis. After that, the factors affecting the removal rate such as adsorbent amount, time of reaction, pH and initial concentration of chromium ion were investigated. The optimal conditions for removal of chromium ion were obtained as pH of solution 2, initial adsorbent weight 30 mg, initial chromium ion concentration 15 mg/L, absorption process time of 15 minutes and removal efficiency was 92.00%. The experimental results and the results of the response surface design were in good agreement (98.8%). Reviewing kinetic and isotherm studies showed that the adsorption process follows the pseudo second-order kinetics and Langmuir isotherm. Magnetic graphene oxide functionalized with iminodiacetic acid has the highest adsorption rate and was considered as the optimal adsorbent for successful metal removal.

Improving the management of water resources on a global scale is critical at this time. The risks that water bodies are currently exposed to, whether due to climate change or human conditions, affect the availability and quality of water in watersheds around the world. However, water management has emerged as a complex problem. In this light, one of the most promising methods is the construction of dynamic simulation models that may include the largest possible number of variables, not just hydrological. This paper presents a decision support system for the integrated management of water distribution and wastewater collection networks. The proposed method uses system dynamics (simulation with Vensim software) to integrate water and sewage networks with financial and socio-political sectors, which allows the rate adjustment and planning of integrated operational and capital infrastructure of water and sewage in three provinces of the Tabriz region during their life cycle (50 years). The results show that the integrated framework enables the company to accelerate financing for capital and operational works and improve the level of integrated services due to the integration of financial resources of water and sewage. In practice, the proposed integrated framework empowers water and wastewater utilities to manage and plan their assets in an integrated approach to improve the infrastructural, financial, and socio-political performance of their water and wastewater assets compared to separate management. Physical asset management is the only way for water and sewage companies to solve financial, social and infrastructural problems. The sewerage network studied here needs a little more capital work to meet the deficit policy lever of very damaged pipes compared to the water distribution network, which is in a relatively better condition. Implementing a borrowing management strategy for the sewer network to accelerate capital work, a proactive management strategy for the water distribution network should be implemented with the necessary cash reserves for any future setbacks.

The understanding of the mechanisms underlying the diffusion, advection, and mixing of pollutants constitutes a crucial aspect in monitoring water resources quality, particularly in the context of river systems. The longitudinal dispersion coefficient holds significant importance in predicting and illustration of pollutants in river systems. The current study investigated the advection and dispersion of pollution in meandering rivers experimentally. A series of experiments were undertaken to quantify the tracer concentration within a laboratory flume. The meandering flume with 8 bends was used to consider variation of tracer concentration for different discharges and solid and sedimentary beds. Utilizing the collected experimental data and employing the routing process, the longitudinal dispersion coefficient was determined across various segments of meandering rivers. Comparison of results for both solid and sedimentary bed indicates that as the flow discharge increases, the tracer's transfer speed increases while the transfer time decreases. Consequently, the difference between the peak concentration of tracer on the hydrographs (Cr) of input and output sections in the range of 21 to 100 percent decreases. Furthermore, by changing the bed from solid to sedimentary, Cr and the longitudinal mixing coefficient (DL) increased noticeably. In the mentioned conditions, the lowest values of Cr and DL parameters were obtained with 100 and 85% increase in value, respectively. Additionally, the results revealed a positive correlation between the mixing parameters and the length of the traversed tracer along the bends. The analysis of the data indicated that as the Reynolds number increased, the longitudinal mixing coefficient increased in both solid and sedimentary bed.

Bioleaching is a non-invasive, relatively affordable and environmentally friendly method through which toxic compounds are decomposed with the help of microorganisms and with the help of enzymatic reactions. This study was conducted in order to use biological leaching to rehabilitate contaminated soil and resistant to biological decomposition by heavy metal lead and phenanthrene around the south Tehran oil refinery. The design of the experiment was done with the response surface method. In the bioleaching method, the purified strain (Pseudomonas aeruginosa) was isolated from the soil of the refinery. Environmental pH (3, 5, 7, 9, 11), pollutant to biomass ratio (7.50, 15, 22.50, 30, 37.5 mg/g) and retention time (1, 2, 3, 4, 5 hours) were considered as main variables. pH was the most important parameter influencing the removal of lead and phenanthrene from soil. The highest percentage of lead removal with 96.79% pH is equal to 8, pollutant ratio to Live current is equal to 30 W/W and time of  2 hours was obtained. In the case of phenanthrene, the highest percentage of phenanthrene removal (97.4%) in pH was equal to 7, the pollutant to living organism ratio was equal to 22.5 W/W and the time was measured for 1 hour. The results of this study showed that the use of bacteria increased the efficiency of the removal process compared to the cleaning process without bacteria (42% for phenanthrene and 67% for lead).