The reverse osmosis method is one of the most widely used methods of seawater desalination at present. Hydrophilic and desalting membranes in reverse osmosis systems are highly susceptible to the input pollutants. Various contaminants, including suspended organic and inorganic matter, result in membrane fouling and membrane degradation. Fundamental parameters such as the turbidity, the amount of chlorine injection, and silt density index (SDI) are the most predominant parameters of fouling control in the membranes. In this study, the operation system included a water intake unit, a pretreatment system, and an RO system. The pretreatment system encompassed a clarifier, a gravity sand filter, pressurized sand filters, and a cartridge filter. The correlation between the amount of chlorine injection in terms of the oxidation-reduction potential (ORP) and the SDI value of the input water was investigated at a specified site next to the Persian Gulf. The results showed that, at certain intervals of inlet turbidity, injection of a certain amount of chlorine into the raw water has a distinct effect on the decrease of SDI. ? 2019 Hohai University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).