الفهرس 
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Abstract
The aim of this work is to investigate Water Quality Index (WQI) of the Suez Gulf seawater as a part of the Red Sea by monitoring the water characteristics in 14 different regions. To synthesize the Cellulose acetate ultrafiltration membranes via the phase inversion technique and to study the effect of Chitosan on both the characteristics and the performance of these membranes; in order to use the ultrafiltration process as a pretreatment step for the reverse osmosis desalination plants 10 increase quality of feed water.
Egypt and the overall world are rapidly encountering serious water scarcity issue. Therefore, new sources of fresh water must be developed to meet the growth in the demand under the present economic and population growth in addition to the probable environmental challenges. According to the location of Egypt in the middle of two seas, the Mediterranean and the Red Sea; Egypt must take fast steps to implement the desalination processes especially in the Red Sea that suffers totally from this water lack because of its distance from the Nile River. There are many desalination technologies in use; the most widely applied and commercially proven technologies include two types: phase change thermal processes and membrane processes that have no phase change. The reverse osmosis (RO) process is one of the most successful methods used for desalination which can be more efficient by implementing a pretreatment step based on the ultrafiltration (UF) process. ♦
The focus of this study depends on the pretreatment of the seawater from the chromium ions Cr(VI) in order to be used as a higher quality feed seawater for the RO desalination plants.
The work was divided into two parts. The first part included the monitoring of the Suez Gulf as a part of the Red Sea by the analysis of 14 locations within 4 seasons during the year of 2016 to obtain the water quality data by reducing the hydrochemical, nutrients and heavy metals results using SPSS program. The data on water quality indicated that the region of Suez bay in the Suez Gulf represented in the stations (W7, W8, W9, Wi0, Wn, W)3 and Wi4) was a highly polluted area especially with the chromium ions. The study focused on Cr(VI) as a result of its harmful effects on the human body and specially on the skin. The second part described the preparation of Cellulose acetate (CA) UF membranes via the phase inversion technique using different preparation conditions including the solvent used in the membrane solution, the composition ratio, the evaporation time, the coagulation bath and the annealing step to get the optimum procedure in the preparation of the CA UF membrane. In addition, the membranes were modified by using the Chitosan (CS) to adsorb the chromium ions and increase their antibiofouling behavior.
The membranes were characterized by FTIR, SEM, Contact angle and porosity measurements, and the biofouling test. In addition, the performance was evaluated using a cross flow UF unit investegating different pH (2, 3, 6, 7 and 8) and different Cr(VI) ion concentrations (0.05, 0.1, 0.5, 1 and 1.5 mg/L) according to the results of the monitoring of the Suez Gulf region and according to the USEPA, where the concentration of the Cr(VI) ion were in the range of 0.01 to 1 mg/L of contaminated seawater and waste effluents on the marine environment, to determine the water flux and the % rejection as indicators for the separation efficiency. The results proved that the modification of the CA UF membranes using CS generally enhanced the characteristics and the performance of the membranes. The porosity of the modified membranes, either with spongy layer or macrovoids structures, increased. Regarding the antibiofouling behavior by antimicrobial effect for S.aureus and E.coli bacteria, it was found to be more effective for the modified membranes with both the spongy layer and macro voids structures and the S.aureus was more sensitive than E.coli in the two membranes.
The performance of the membranes was generally improved for the modified membranes for both the spongy layer and macrovoids structures compared with the unmodified CA membranes. In the acidic medium (pH 3) and at constant Cr(VI) concentration (1 mg/L) the rejection was 95% with flux 9 L/hr.m2 for M2 and 100% with flux 62 L/hr.m2 for M8 that had macrovoids structure compared with the rejection reaching 97% with flux 199 L/hr.m2 for M4 and 99% with flux 300 L/hr.m2 for M9 that had a spongy layer structure. By changing the concentration of the Cr(VI) ion the rejection was slightly changed for the CA-CS modified membrane with macrovoids structure (M8) and remain constant 100% for the CA-CS modified membrane with the spongy layer structure (M9) with higher flux.