Assessment of Silt Density Index (SDI) as Fouling Propensity Parameter in Reverse Osmosis Desalination

摘要

Reverse osmosis operations are facing persistent fouling phenomenon that has challengedthe integrity of these processes. Prediction of fouling potential by measuring a fouling indextoward feed water is essential to ensure robust operation. Moreover, employing a reliablefouling index with good reproducibility and precision is necessary. Silt density index (SDI)is considered insufficient in terms of reliability and empirical theory, among otherlimitations. Nevertheless due its simplicity, SDI measurement is utilized extensively in ROdesalination systems. The aim of this research is to assess the reliability of SDI. Methodsinclude the investigation of different SDI membranes and study of the nature of the SDIfiltration. Results demonstrate the existence of the membrane properties' variation withinmanufacturers, which then causes a lack of accuracy in fouling risk estimation. The natureof particles during SDI filtration provides information that particle concentration and sizeplay a significant role on SDI quantification with substantial representation given by particleswith size close to membrane nominal pore size. Moreover, turbidity assisted SDImeasurements along with determination of UF pretreated and clean water fouling potential,establishes the indication of non-fouling related phenomena involved on SDI measurementsuch as a natural organic matter adsorption and hydrodynamic condition that alters duringfiltration. Additionally, it was found that the latter affects the sensitivity of SDI by beingrepresented by some portions of SDI value.Keywords: Reverse Osmosis, Fouling index, Particulate Fouling, Silt Density Index (SDI),and Assessment of SDI.