ABSRACT

Egypt has considered desalination as a strategic option for coastal areas development. Sharm El-sheikh mainly depends on it for touristic development. The capacity of its desalination plants has increased from 25.000 m3 /day in the year 2001 to 150 000 m3 /day in year 2018. This has entailed daily discharge of large amounts of desalination reject (brine) into the surrounding environment. There are two different types of feeding water intake (beach wells and open seawater).The disposal of brine discharge can be either through the injection wells or by diffuse into open sea. This study aims to evaluate the potentiality of beach filtration technology for low cost reverse osmoses (RO) desalination and environment protection. The main aquifer in the study area is hydraulically connected with the sea water at Gulf of Aqaba. It has mean hydraulic conductivity of 35 m/day and thickness exceeds 50 meters. The reference water quality has total dissolved solids (TDS) range from 34000 to 35000 mg/l. The simulation model has shown that after 20 years of operation the drawdown will reach only 3- meters at the middle of the feeding wells field and the water salinity as TDS will increase to 45000 mg/l due to brine injection in the aquifer. Beach wells water has silt density index (SDI) value less than one while it reaches 4.4 for open seawater. High SDI values shorten the life of the membranes and increase the chemicals dose required for the removal of deposits on the membrane surface. The removal efficiency of both total organic carbon (UVA245) and dissolved organic carbon (DOC) in beach wells is 35% and 50% respectively. Also, the total coliform and algae are not detected at beach wells. Beach well filtration prevents clogging of desalination membranes and prolongs its life and reduces the chemicals used compared to direct seawater intakes. The natural filtration action of the subsoil reduces the cost of purchasing chemicals for membranes regeneration and the frequency of backwashing. The chemicals consumption rate per month that is used for beach well intake is much lower than that for open seawater intake desalination plant. Moreover, Beach filtration is environmentally friendly technique that helps to preserve the surrounding environment for sustainable tourism activities.