نشریه علوم و مهندسی آب و فاضلاب
سال هفتم شماره 3 (پاییز 1401)

One of the important issues along with water shortage and demand in cities is the issue of wastewater disposal and treatment. When it comes to wastewater and its treatment, the first thing that comes to mind is the discussion of the environment and its protection from pollution because wastewater is always a major polluting parameter in human and natural environment The construction of a wastewater treatment plant is a civil-environmental activity whose main purpose is the proper and hygienic disposal of wastewater, which, if neglected, will have irreparable consequences. The first effective step for the construction of these facilities is to identify their suitable location, which is done by considering various factors and criteria. For this purpose, multi-criteria decision making (MCDM) methods have been used. Here, according to the existing conditions, hierarchical decision making (AHP) and Delphi (delphi) decision methods have been selected to solve the problem. In this research, Farooj city, which is one of the cities of North Khorasan province, was studied for the construction of a wastewater treatment plant.

Nowadays with regard to the climate change issue and also the scarcity of available and usable water, the conjunctive use of surface and groundwater resources is regarded as one of the critical approaches in water resources management. In this respect, the surface water-groundwater interaction is one of the prominent and fundamental components in conducting appropriate analysis of water resources balance and finally their management. In this paper, the Lenjanat sub-basin considered as a study area that is located in the Ghavkhouni Basin in Iran. The weighting method of GCM models under the fifth report of the Intergovernmental Panel on Climate Change (IPCC) was employed to investigate the precipitation and temperature changes due to climate change and the LARS-WG model was hired to provide the microscale output of GCM models. Investigating the surface water-groundwater interaction was carried out through the connection of WEAP and MODFLOW models. Thereafter, through the usage of climate results from the climate change scenarios of RCP2.6, RCP4.5 and RCP8.5 and also implementing the management policies in the form of management scenarios in the future, along with the reduction of 20% and 40% in the area under cultivation, the system performance is assessed for the near future. The findings reveal increasing in temperature and precipitation in the future. The rate of surface water-groundwater interaction will be increased in the future under disparate management and climate change scenarios. Moreover, the maximum rate of the surface water-groundwater interaction is observed for the scenario following the current trend and also the scenario of climate change RCP4.5. Based on the outcomes, the higher the river flow and the groundwater abstraction, the more the aquifer drains the river and consequently increases the interaction of surface and groundwater. Therefore, the results indicated that the recharge effect of the river on the aquifer in the study area and on the other hand uncontrolled pumping of groundwater resources, conjunctive management of water resources can reduce the negative effects of groundwater scarcity, but it is necessary to reduce of cultivated areas and cultivation pattern prevented uncontrolled abstraction of groundwater in this sub-basin.

One of the major problems with urban water supply networks is the large volume of water wastage due to various incidents that cause damage. These damages are mainly irreversible and costly; thus, it is increasingly important to understand the causes of such incidents to prevent and reduce water wastage. This research aims to estimate the failure rate of main urban water supply pipes. In terms of nature, this research is applied, while in terms of administration, it is a combination of descriptive-analytical methods based on library sources. In addition to interviewing experts in the study area, the research uses findings of other research and data provided by Tehran’s Water and Wastewater Organization, which pertain to District 1. The research identifies major criteria affecting failure rates of main pipes of various types. Then, it uses Gene Expression Programming (GEP) software to perform computations and provide the model. Findings conclude that as the working pressure, age, and length of the pipe and the number of service lines increase, the number of incidents increases also. On the other hand, with the increase in the diameter of the pipes and the depth at which they are installed, their failure rates decrease. The type of soil also buried directly impacts the gradual loss of the pipes. Because the proposed models in this research have no limited input parameters and take into account all the effective components, they are highly useful and reliable tools to predict failure rates of the main urban water supply pipes.

The presence of algae in the water treatment process is problematic. The best way to control algae is to remove the algae cell intact without rupturing the cell, as most common methods cause disinfection by-products, which are often very dangerous. The aim of this study was to evaluate the efficiency of microstrainer and ozonation systems in combined removal of algae from raw water. For this purpose, Box-Behnken Design was used in the Response Surface Methodology by Design Expert software. Experimental variables included input turbidity (50-150 NTU), microstrainer surface load (10.8-18 m/h) and injectable ozone dose (1-3 mg/L). Based on the experimental conditions, the algae removal efficiency in the integrated microstrainer and ozonation system was 39.64-88.76%. The parameters of inlet water turbidity, injected ozone dose and micro-strainer surface load with effect coefficients of 15.37, 8.98 and 4.01, respectively, had the greatest effect on system efficiency in algae removal. Increasing the turbidity and surface load of the microstrainer decreased the algal removal efficiency and increased the injection ozone dose increased the efficiency. The final model based on the desired parameters was obtained as a quadratic equation with correlation coefficient, modified correlation coefficient and predicted correlation coefficient equal to 0.948, 0.928 and 0.868, respectively.

Water scarcity is one of the main challenges and constraints in the development of the country. On the other hand, wastewater treatment methods were initially developed as a response to concern about public health and the conditions caused by wastewater disposal in the environment, but now with the expansion of cities and urban life, keeping the environment clean and protecting it is essential for social life. Therefore, the aim of the research is to minimize the cost, optimize and simulate the primary sedimentation tanks in wastewater treatment plants using Flow3D software. In addition to evaluating the accuracy of the model in the simulation, parameters affecting the ratio of inlet through the overflow to the inlet under the valve were determined. The results showed that The Les model had better result in simulating the setting cavitiy in circular-shaped treatment plant tanks in comparison to the other turbulence models. Comparing the effect of settling characteristic parameters on the maximum settling depth, it was concluded that the drag coefficient and static angle parameters had a great effect on the it. According to several simulations performed with Flow3D software, it was found that this software has good accuracy in simulating the flow pattern passing through the circular overflow-valve treatment plant in both solid bed and mobile bed modes. Also, by comparing the effect of deposition characteristic parameters on the maximum deposition depth, it can be seen that the parameters of drag coefficient and static angle have a great effect on the amount of deposition. Also, among different turbulence models, LES model has more acceptable results in simulation. The settling of the refinery tanks indicates a circular Spillway-valve shape.

This study aimed to investigate the efficiency of submerged membrane bioreactors (SMBR) in textile and municipal wastewater treatment. First, membrane bioreactors were designed and fabricated using hollow fiber polypropylene membranes with pores of 0.2 μm on a pilot scale with a volume of 100 liters. Then, for 20 days, activated sludge was formed and municipal wastewater was treated. For 28 days, incremental percentages of 20%, 40% 60%, and 80% of textile wastewater were gradually added to municipal wastewater. Finally, for 10 days, the sewage of the textile wool factory was examined. Pilot performance for municipal wastewater at the maximum concentration of MLSS mg/L 2310, percentages of removal of biological parameters COD, BOD, TSS, VSS equal to 94.65%, 96.03%, 96.72%, 95.58%, for mixed wastewater, respectively Urban and textile in MLSS equal to 2920 mg/L, 94.1%, 95.2%, 97%, 95.9% have been reported, respectively. Finally, for textile wastewater with the hydraulic retention time of 25 hours, the sludge retention time of 25 days with MLSS equal to 1370 mg/L, the studied parameters along with color and turbidity were 95.1%, 95.8%, 96.6%, 95%, 93%, 99.8%, respectively. This study showed that SMBR can be used as an efficient method for textile and municipal wastewater treatment.