en تخصصي Special مقاله اصیل Original Article <div style="text-align: justify;"><span class="fontstyle0">Background: </span><span class="fontstyle2">Membrane clogging is one of the most important problem for desalination plant operators in Iran, therefore, this study was conducted to investigate the main causes of this problem using field analysis.</span><br> <span class="fontstyle0" style="color:rgb(25,100,40);">Methods: </span><span class="fontstyle2">In this study, six continuous membranes in a reverse osmosis (RO) pressure vessel under the 33-month service period (April 2017 to November 2019) were selected. The membranes were analyzed through visual evaluation of the outer and inner membrane surface, analyzing the damages and physical harms, oxidative stress tests, iron spot test, fouling chemical analysis using loss on ignition (LOI) tests, X-ray fluorescence (XRF), and Fourier transform infrared (FTIR) spectroscopy.</span><br> <span class="fontstyle0" style="color:rgb(25,100,40);">Results: </span><span class="fontstyle2">Particle size distribution in raw seawater (EC = 55 000 &micro;s/cm, turbidity = 11 NTU) was 66.4% smaller than 1 &micro; and 28.3% between 1 to 1.9 &micro;m. Physical damages were not seen on the membranes but telescopic damages were observed which was due to membrane fouling. Removal efficiencies of turbidity and silt density index (SDI) were 84% and 18%, respectively. Membrane oxidation was also seen. Most of the sediments compositions on the membranes were SiO</span><span class="fontstyle2" style="font-size:5pt;">2</span><span class="fontstyle2">, Al</span><span class="fontstyle2" style="font-size:5pt;">2</span><span class="fontstyle2">O</span><span class="fontstyle2" style="font-size:5pt;">3</span><span class="fontstyle2">, MgO, and Fe</span><span class="fontstyle2" style="font-size:5pt;">2</span><span class="fontstyle2">O</span><span class="fontstyle2" style="font-size:5pt;">3</span><span class="fontstyle2">. Biological fouling was detected on the membranes surface.</span><br> <span class="fontstyle0" style="color:rgb(25,100,40);">Conclusion: </span><span class="fontstyle2">Inaccurate use of chlorine neutralizer caused the residual chlorine to be present in the membrane entering water, which damaged the membrane. Accumulation of clogging agents on membrane surface showed malfunction of pretreatment function, therefore, revision of design and operation of units is necessary. Biological fouling is due to non-effective pre-chlorination of drinking water. Metallic compounds sedimentation on the membrane is due to improper use of anti-fouling chemicals. High SDI in the influent shows the need to change the cartridge filters.</span><br style=" font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " > &nbsp;</div> Seawater, Drinking, Chlorides, Particle size, Spectroscopy, Fourier transform infrared, Iran 119 126 http://ehemj.com/browse.php?a_code=A-10-1-172&slc_lang=en&sid=1 Leila Rezaei rezaeil2000@gmail.com 10031947532846008194 10031947532846008194 No Department of Environmental Sciences, Islamic Azad University, Qeshm International Branch, Qeshm, Iran Mohsen Dehghani dehghani933@gmail.com 10031947532846008195 10031947532846008195 No Department of Natural Resources and Environmental Sciences, Islamic Azad University, Bandar Abbas Branch ,Bandar Abbas, Iran Amir Hesam Hassani ahh1346@gmail.com 10031947532846008196 10031947532846008196 No Department of Environmental Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran Vali Alipour v_alip@yahoo.com 10031947532846008197 10031947532846008197 Yes Corresponding author:Department of Environmental Health Engineering, School of Health, Hormozgan University of Medical Sciences, Iran