Control of Silt Density Index of Osmosis Membranes Through Chlorine Injection and its Effect on Cartridge Filter Replacement Period

Abstract

Background: Various suspended organic and inorganic contaminants including biological deposits, different types of algae and barnacles and causative factors of water turbidity result in irreparable damages to pretreatment systems and membranes in reverse osmosis systems. Objectives: In this study, the effect of injection of disinfectant materials such as calcium hypochlorite on the reduction of silt density index (SDI) value at the inlet of reverse osmosis system has been investigated. Methods: In this research, correlations between fundamental parameters in pretreatment system such as turbidity, chlorine injection, residual chlorine content and SDI values were thoroughly analyzed and evaluated at one of the desalination plants located in Persian Gulf. Results: The results indicated that there is a close link between the amount of chlorine injection and SDI inlet value. By adjusting the nephelometric turbidity unit values in specific ranges of 35-55, 55-80 and 80-150 and oxidation reduction potential in the ranges of 280-680, 315-680 and 420-680 mV, favorable SDI value of inlet water was obtained. Conclusions: SDI control via chlorine injection increased the lifetime of cartridge filters at reverse osmosis input units and reduced the operation costs significantly.

Seawater reverse osmosis membrane fouling causes in a full scale desalination plant; through the analysis of environmental issues: raw water quality

“…In addition, by analyzing the reasons, it is possible to find a suitable method for chemical cleaning of the membranes (11). Many studies have been done in details regarding the fouling reasons through which one or two reasons have been identified, however, there are less global or comprehensive studies in this regard (12)(13)(14)(15)(16)(17)(18)(19). In a study by Gutiérrez Ruiz et al, which is similar to the recent study, chemical composition and structure of fouling agents on the membrane surface were determined using the energy dispersive X-ray microanalysis and scanning electronic microscopy.…”

“…The results showed that the presence of calcium carbonate and excess colloidal silica intensifies the deposition on the membrane and clogging and decreases the permeate flux (17). In another study by Fayaz et al, the effect of disinfectants injection was evaluated to find the reduction of SDI efficiency, and it was revealed that injection of chlorine in the inlet of RO system can increase the lifetime of cartridge filters, and significantly, reduce the operation costs (19). Given the importance of desalination plants to supply the water needed for communities and industries in southern Iran, it is important to pay attention to the technical and economic aspects of this category.…”