Sharif Digital Repository

Aqueous environment with vegetation in coastal areas plays important role in ecologic systems. The plants in aqueous environment caused to vertical and lateral changes of flow velocity profile. When sunlight penetrates the water, it will turns into heat energy. The plants caused to blocking the light path, to make a difference in temperature and thus the density differences on the horizon. This density gradient will lead to the gravity flow. Due to the observations, in coastal wetlands, beside the plants the emerged from the water, there are some completely submerged plants that their root in the soil and shallow layer of fluid covered on them. This study to approaching the conditions, is... 

Discharge of Raw wastewater or effluent of Treatment plants into the natural bodies of water, in the case of high nutrients may cause serious problems such as algae bloom which results in a reduction in concentration of dissolved oxygen. Among the nutrients, phosphorous is known as a limiting factor in growth and intensification (intensifier) of eutrophication. Therefore, elimination of phosphorus from wastewater prior to the discharge point is highly important. Phosphorus can be removed chemically as well as biologically. Chemical methods are known, efficient and reliable but Problems like operational and maintenance costs and chemical sludge production cause tendency to use biological... 

Environmental flows are seldom independent of plants impact. Aquatic canopies are mostly submerged and flexible; this causes a significant impact on Hydrodynamics of flow and mixing structure. Experimental and analytical investigation of vertical mixing in vegetation canopies with flexible submerged vegetation is the aim of this study. Most of the previous studies on flexible submerged vegetation were conducted to study the transverse and longitudinal mixing. In this study, flexible submerged vegetation in the density range of 2.8% to 4.2% was used to study the vertical mixing.The concentration profiles at four separate stations were obtained by image processing. The results for the... 

This thesis presents the results of the performance of a novel technology called submerged membrane electro-bioreactor (SMEBR). The SMEBR treats wastewater by combining membrane filtration, electrokinetic phenomena, and biological processes in one reactor, and improves treatment performance while helping to control membrane fouling. The newly designed SMEBR system was based on applying an intermittent direct current (DC) field between immersed perforated electrodes around a membrane filtration module. The SMEBR system significantly reduced the fouling rate when iron worked as electrodes and an intermittent DC with an operational different mode was applied.
In Phase 1 of this project,... 

In this study, the effect of submerged vanes on the bed erosion pattern at a 90° open-channel junction has been evaluated experimentally. In this study, 41 tests have been conducted in four different steps. In each test, the bed surface level has been measured at the end of 1st, 2nd and 24th hour. In the first step, the preliminary tests have been conducted. In this step, six different formations of submerged vanes have been selected and their performance has been evaluated and the most efficient formation, in the field of maximum scour depth reduction, has been selected. In the second step, six different formations of submerged vanes have been selected and their performance has been... 

In small settling tanks, the sludges can be removed using perforated pipes. In this method the pipe is placed in the depth of a fluid and the lateral inflow through perforations lead to the outlet. Since there are few researches about hydraulic characteristic of perforated pipes, this research will investigate the hyadraulic characteristic of these pipes experimentally. One of the main objectives of these pipes is to use the entire lenghte of the pipe and also provide the uniform distribution of inflow. In the past studies, it was found out that inflow mostly comes through downstream perforations. The objective of this research is to find the distribution of discharge along the perporated... 

In this study, the effect of submerged vanes on the bed scouring and deposition pattern at a 90̊ open-channel junction was investigated. First, the bed formation without submerged vanes were studied under the effect of hydraulic variables like the discharge ratio of tributary to main channel and the ratio of mean approach velocity to the threshold velocity. The results show that scour holes enlarge with time while they move towards the downstream and the outer wall in the main channel. Also, by increasing the ratio of mean approach velocity to the threshold velocity about 0.5, the maximum scour depth occurred at the downstream junction corner with time. In the second stage, the proper vane... 

Resources management is essential duo to sustainable development and marine resources limitations. There are several ways to restore coastal damaged ecosystems, one of the best and most cost effective solution is establishment of artificial reefs. A popular type of artificial reef is named Reef ball, a hollow hemisphere. In some regions these habitats has also been used as submerged breakwater. These structures recover and protect endangered species ecosystem although they provide aesthetic view to a beach. Main application of these structures is to provide a safe environment for marine creature. In this study initially Transmission coefficient variation in two-dimensional model experiments... 

In this study, the effect of submerged vanes on the flow pattern and dimensions of separation zone at a 90˚ open-channel Junction were investigated. The experiments were conducted in three stages. First, for validity of data with the results of webber et al, using ADV, velocities was teken without submerged vanes.in the second stage, experiments with dye injection was performed at confluence for several initial arrangement of vanes. From 54 different arrangements, two arrangements were selected. In three stage, three dimensional velocities was teken in two arrangement selected. Due to the significant reduction the size of separation zone in one of these arrangements, with moving this... 

Membrane bioreactors can replace the activated sludge process and the final clarification step in municipal wastewater treatment. The combination of bioreactor and crossflow microfiltration allows for a high chemical oxygen demand (COD) reduction of synthetic wastewater. In this study, experimental data from a laboratory scale membrane bioreactor are presented. In order to investigate the influence of various operating parameters such as hydraulic retention time (HRT), biomass concentration and organic loading rate on organic pollutant removal, the pilot scale submerged membrane bioreactor (SMBR) with a Polyvinylidene Fluoride (PVDF) hollow fiber membrane module was conducted using synthetic... 

Selective withdrawal from water and settlement reservoirs and tanks is necessary for water and environmental systems. Perforated pipes can be used for selective withdrawal within the length of these reservoirs. In this method, the lateral inflow through perforations leads to the outlet of the pipe that is placed in a depth of fluid. In relation to the hydraulics of perforated pipes, most studies are about drainage pipes and perforated pipes that are used as wellbores in horizontal wells, but application of these pipes have not been investigated in submerged situations. Capacity estimation of perforated pipes based on inside diameter of the pipe, material of the pipe, perforations of the... 

There are different flow regimes in multiphase flows through the pipes, which affect the flow structure and other important fluid parameters. Each of these flow regimes are considered to be suitable or not in different industries. So it is needed to provide the situation of suitable flow regimes formation and to prevent the others from development. One of the main parameters affecting the flow regimes development is considered to be the passing flow’s channel section are or the pipe diameter. This project is defined to investigate the effect of changing pipe diameter on the formation of flow regimes in an air-water upward two-phase flow, experimentally. Therefore, a vertical pipe of 6 meters... 

The effect of alloying elements such as Chrome, Molybdenum and Chrome-Molybdenum on microstructure and mechanical properties of submerged-arc weld of structural St37 and 4135 Chromoly Steel was investigated. Addition of alloying elements was done through flux and slag-weld metal reactions. Bonded flux was used to achieve this purpose. Mechanical properties were studied by means of Longitudinal Tensile, Hardness and Charpy V-notch tests. Microstructure was studied by means of Optical and Scanning Electron Microscope. The results show that chromium increase Ultimate Tensile Strength (UTS) and impairs Impact Toughness (IT), although it increases the percentage of acicular ferrite (AF). In the... 

The X80 high-strength low-alloy microalloyed steel was procured as a hot rolled plate with accelerated cooling. The four-wire tandem submerged arc welding process, with different heat input, was used to generate a welded microstructure. The effects of real and Gleeble simulated double pass thermal cycles on the properties of the heated and reheated coarse grained heat affected zones (CGHAZ) in X80 microalloyed pipeline steel has been investigated. The thermal simulated process for heated region involved heating the X80 steel specimens to the peak temperature of 1400 °C, with different cooling rates. The influence of the second peak temperature during real and simulated welding hass been... 

Submerged Membrane Electro-Bioreactor (SMEBR) was invented to increase the efficiency of Membrane Bioreactor (MBR) systems by reducing the fouling amount. The objective of this study was to understand the physical effects of Electrocoagulation (EC) method on membrane fouling and compares the critical flux number by applying electricity under different conditions and without any electrifying. This paper measured the critical flux, that obtained under different process condition including different MLSS concentrations (8000 ppm, 5000 ppm, 2000 ppm), different current densities and electrodes distance. The best result was obtained during highest CD (30 mA/cm2) and lowest distance of electrodes... 

The dairy industry wastewater has high biological oxygen demand(BOD) and high chemical oxygen demand(COD). In this study, membrane bioreactor(MBR) was used for the treatment dairy industry wastewater. Since two diffuser,submerged membrane modul and intermittent suction method were adpted to system. In this study, the response surface method and experimental design were applied as an alternative to conventional methods for the optimization of the treatment. A central composite design, with 5 replicates at the center point were used to build a model for predicting and optimizing the treatment. Mathematical model equations were derived by computer simulation programming with Design Expert... 

In recent years,because of increasing problems that result from water shortage ,using of wastewater treated by high quality and entering them to water cycle is considered more than past.Large amount of waste waterare produced through cooling towers in industries per a day .Therefore ,cooling tower’s blow down is a most important source for reclamation and reuse of water .The purpose of this project was investigation ofefficiency of submerged aerated filter for treating low organic simulated blowdown water as a feed . The experimental unit consisted of 8/5 L filled with 70 percent of propylene media . After obtaining steady –state condition ,The SAF reactor was tested under... 

One of the most important parts of bacteria growth is specific concentration of nutrients added. Although the trace amount of heavy metals are required for bacteria growth, after a threshold concentration they may cause damage or kill the bacteria. Scientifically speaking, all these trace nutrients should be consider as a profitable source of energy for bacteria growth. There are several studies throughout pondering whether the advantages of using heavy metals, such as Zn, outweigh the drawbacks. It has been proven that heavy metals, especially, zinc salt, can improve microbial growth up to a specific threshold concentration. In this study, two upward submerged aerated reactors, which had 12...