نشریه علوم و مهندسی آب و فاضلاب
سال هشتم شماره 4 (زمستان 1402)

In this study, the quantity and quality of Grey Water (GW) were surveyed in the dormitories of Isfahan University by the aim of its reuse. For this purpose, the non-potable water consumption (bathing and washing clothes) was monitored in both boys and girls dormitories, where its variations were evaluated daily in the academic semesters (October-November and May-June) alongside its quality. Results showed that the average daily GW production of students is 111 liters per capita per day, in which by considering 4400 residents in the dormitories, this wastewater can supply at least 10% of the water required for the irrigation of campus green areas. It was also indicated that the daily average grey water production of girls' dormitories per capita was significantly higher about 20% than boys’. In addition, the daily grey water production per capita of students on weekends was significantly higher than the other days about 16%. Based on these data, the daily and hourly peak coefficients of grey water production were about 1.16 and 1.25, respectively. The quality analysis of discharged grey water showed that the average concentrations of BOD, COD and TSS were 65, 142 and 52 mg/L, respectively, which has a relatively low biodegradability and suspended solids.

Due to continuous changes in the quantitative and qualitative characteristics of wastewater influent in wastewater treatment plants (WWTPs), it is necessary to evaluate the performance of WWTPs under different conditions and adopt appropriate control strategies. The first step in evaluating and improving the performance of a WWTP is to model it. In recent years, there has been an increase in the application of simulation software and mathematical models for this purpose. Calibration is considered the most important step in modeling because improper calibration can lead to unrealistic results with a large error. The main objective of this research is to redevelop the BSM11 model and provide different calibration scenarios to model the carousel oxidation system on a real scale. The high-accuracy model can then be used for various purposes, such as implementing different control strategies and improving the performance of the WWTP under different operating conditions. The developed model was implemented on modules 5 and 6 of the WWTP located in the south of Tehran. After determining the suitable process models for different units of the wastewater treatment plant, model calibration based on the GMP2 protocol was performed under two scenarios: 1) simultaneous calibration of parameters, and 2) step-by-step calibration of parameters. In each scenario, two objective functions were considered to evaluate the effect of main variables, including COD, TSS, and TN, and secondary variables, including X (MLSS3 of the aeration tank) and Xr (MLSS of the return sludge). The genetic algorithm was used to optimize the objective functions during the calibration process. The results showed that in the static calibration, the average error of all variables, as well as the variables considered in the objective function in scenario 2, were significantly reduced compared to scenario 1. The values in scenario 2 for objective function 1 were 2.7%, 7.8%, 8.2%, and 4.3% for the variables mentioned. Additionally, by considering more variables in the objective function, the cumulative error of all variables was reduced. In dynamic calibration, the average error rates of the model for TSS, COD, and TN were 29.8%, 19.8%, and 10.3%, respectively.

The presence of various pollutants, especially pesticides in water sources is one of the important wastewater issues in the field of environment. The main purpose of this study is to remove and evaluate the optimal conditions and adsorption process of Deltamethrin pesticide by AC/Fe3O4 composite from aqueous solutions. For this purpose, adsorbents were first synthesized and then characterized and investigated using FT-IR, SEM, XRD, and VSM methods, which generally showed that the adsorbent was synthesized correctly. Then the optimal conditions (pH, contact time, initial concentration of Deltamethrin, and adsorbent dose) for removal of Deltamethrin by this adsorbent were evaluated according to the response surface methodology. The results showed that the maximum adsorption capacity of the adsorbent in the studied conditions for Deltamethrin is equal to 99.179 mg/g. The best models expressing the process of uptake of Deltamethrin by adsorbents are pseudo-second-order kinetic models, double exponential mechanism and sips isotherm. In addition, the adsorption process of Deltamethrin by AC/Fe3O4 composite is exothermic and with an enthalpy value equal to 54.79 KJ/mol. The results of this study showed that AC/Fe3O4 adsorbents have the ability to be used in the adsorption and desorption process of Deltamethrin with an adsorption percentage of more than 95%.

Population increment, industries growth and development in order to satisfy the increasing needs of human societies, on the one hand, and the risk of the destruction of non-renewable resources such as water, on the other hand, are irreparable results of disregarding the correlation between industry and the environment. In this research, the performance of the physical assets of water and sewage companies is monitored and the appropriate strategy for sustainable maintenance and repairs in these companies is selected. Also, maintenance and repairs and sustainable development data is gathered. Then by using Fuzzy Hierarchy method (Fuzzy AHP), among the strategies that have the most compatibility with sustainable maintenance and repair, the ranking is done. Finally, according to the results, the reactive strategy is determined as the most effective approach in sustainable maintenance and repairs of the physical assets of Tehran Province Water and Sewerage Company.