نشریه مهندسی آب
سال نهم شماره 3 (پاییز 1400)

The present research is the result of laboratory studies related to the comparison of the effect of up- and down-flows in the treatment of artificial biological industrial wastewater (combination of water and molasses of sugar beet factory) using suspended-bed anaerobic reactors. The main purpose of this study is to compare the results of chemical oxygen demand (COD) removal efficiency in different conditions of organic loading in accordance with the type of flow in suspended-bed sequencing reactors containing plastic media, rock materials and activated carbon. For this purpose, three cylindrical pilots with a diameter of 200 mm and a height of 800 mm with a volume of 24 liters on a laboratory scale and made of Unplasticized PolyVinyl Chloride (UPVC) have been used. During the whole period of research, the discharge of sewage entering the reactor varied from 2 to 4 liters per hour and the retention time of the system varied from 18 to 36 hours. After the start-up period was passed and the COD removal efficiency remained constant, the highest efficiency of COD removal percentage in the up-flow with the maximum amount of hydraulic retention time equal to 36 hours and organic load equal to 4.51 kg COD/m3.d equal to 88% was recorded. Also, the highest efficiency of COD removal percentage in the down-flow with hydraulic retention time equal to 24 hours and organic load equal to 3.21 Kg COD/m3 .d equal to 78% was recorded.

Because of its significant toxicological effects on the environment and human health, arsenic (As) is a major global issue. In this study, a zirconium-based metal-organic framework, {[Zn3L3 (BPE) 1.5]•4.5 DMF}n , was synthesized using both solothermal and mechanochemical methods and successfully applied in the arsenic removal reaction. Adsorption efficiency was high in the presence of this MOF and equilibrium was achieved within 20 minutes for As (III) and As (V) at a concentration of 1 mg / l of contaminants. The maximum adsorption efficiencies of As (III) and As (V) at pH 7 were 62 and 81%, respectively. The adsorbent showed high stability in the pH range of 2-12 and the adsorbent can be recovered for at least nine consecutive periods without significant reduction in its efficiency. The adsorption process can be described by a pseudo-second-order kinetic model and the adsorption mechanism was of the electrostatic interaction type.

Estimation of the sediment loads in a stream flow is one of the well-discussed topics in the sediment hydraulics literature. In almost the entire river engineering projects addressing issues such as river morphology, river bed changes, estimation of the annual sediment deposition at the river intakes, banks protection, dredging of the water channels, etc are of prime importance. The amount of sediment transported through a river cross-section may be under a mix of various influences from flow depths and widths, energy slope, temperature and fluid characteristics, flow turbulence and a wide range of their sizes, forms, densities, sediment particle concentrations, and other physical and hydraulic properties. The variety of formulae applied in sediment transport and estimation calculations also the paucity of information and data on the performance of such formulae makes the selection of the suitable ones for different specific conditions an extremely difficult task. Any choice in this regard should incorporate the evaluation and analysis of river hydraulics. In the present paper, several sediment estimation formulae examined for Greater Karun River along Mollasani-Farsiat reach with the purpose of proposing the best sediment transport relation to be applied in later researches. Results showed flow-based energy-based methods are better suited for the Karoon River.

Unsteady currents in pipes can occur in various forms, one of which is the unsteady current of damping, which is called Surge shock.These currents are in the form of pressure waves and if not controlled in some way, can cause irreparable damage to the pipeline. In the present study, the ram phenomenon was introduced and the effects of different parameters, pipe thickness and diameter, different flow velocities on the dynamic loads due to the occurrence of ram impact were investigated.Finally, it was observed that under the same conditions, the effect of pipe material is 25% effective in reducing the maximum impact. The maximum impact increase is about 1% due to a very small increase in pipe thickness. Doubling the moment of inertia reduces the maximum impact pressure by about 42%, which has been investigated using Water Hammer software.

Understanding chemical changes in groundwater and their mapping play a substantical role in optimal management of groundwater in an area. The aim of this study was to investigate hydrogeochemical charactristics of groundwater resources of south Mashkan in 2020.To achieve this goal,10 water samples were taken from the region wells. The hydrogeochemical analysis was carried out in the laboratory through induction plasma method and statistical analysis were performed in ArcGis, AqQA and Excle software environment. Geochemical ion ratios were used to determine the source of ions and combination diagram in the studied aquifer. Geochemical diagram confirmed the activity of water- rock reactions in the studied aquifer and showed the natural ion exchange process in most resources. Based on the results obtained in all wells,the ratio is Cl/Sum anions>0.8, Mg/Mg+Ca<0.5 , Ca/Ca+So4<0.5.In most wells, the ratio is Na/Cl>1, Na/Na+Cl>0.5 ,and So4/Hco3<1. In most wells, is 1<Ca/Mg<3 According to the results of using Kriging method zoning the concentration of ions, the concentration of calcium, magnesium, sulfur and chlorin ions increase in the west and southwest and sodium in the west of the region.

From the point of view of political geography, water is not separate from politics. There are 281 shared catchments between 151 countries and more than 42% of the world's population lives in these areas. Due to the heterogeneous distribution of freshwater on Earth, the management of water resources, especially in shared catchments, is critical to achieving maximum utilization of this limited element. Tigris, Euphrates and Arvand River catchments are one of the most important catchments in Iran and West Asia, which has always faced various challenges in the field of joint exploitation. In this research, an attempt has been made to study the various aspects of the joint watershed between Mesopotamia and Arvandrud, to analyze water diplomacy in this basin, and it should be noted that according to various contracts and agreements in the field of exploitation of these waters, There are many problems and disagreements regarding the common use of these waters.