The presence of microplastics (MPs), as an emerging pollutant is a growing concern in different water resources. These particles are recognized as less than 5 mm in size. Most of the studies have been carried out in surface waters and wastewater treatment plants (WWTPs), but there are few studies on MPs in drinking water treatment plants (DWTPs). This study investigates these particles in three different conventional DWTPs in the city of Tehran, Iran and aims to analyze these particles down to the size of 1 µm. A scanning electron microscope (SEM) was utilized in this study to quantitatively analyze MPs. Accordingly, the average abundance of MPs in raw and treated water samples varied from 1996±268 to 2808±80 MPs L -1 and 971±103 to 1401±86 MPs L -1 , respectively. While particles smaller than 10 µm comprised 65-87% of MPs. Moreover, µ-Raman spectroscopy was used to characterize MPs. As the results, polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE) were the most abundant identi ed polymers among MPs comprising more than 53% of particles. Additionally, MPs were categorized as bers, fragments and spheres. This study lls the knowledge gap of MPs presence in Tehran DWTPs which is of high importance since they supply drinking water for more than 8 million people and investigates the performance of conventional DWTPs in removing MPs.
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.
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