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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.

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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.

A waste stabilization pond (WSP) is a hole in which household wastewater and other types of sewage are stored for long periods so that organic materials existing in them are deposited, decomposed and stabilized through exposure to light, heat, growth of algae and microorganisms. In this study, wastewater samples collected and treated by the treatment plant of a slaughterhouse in Ahvaz region of Iran and compared the relevant measured parameters with the standards, which set by the Environmental Protection Organization of Iran in order to determine the efficiency of WSPs in treating wastewater and making them usable for irrigation purposes. The results indicate that Turbidity, BOD5, PH, COD, TDS, and TSS values for the treated wastewater stood at >1000 NTU, 912 mg/l, 8.78, 1520 mg/l, 1052 mg/l, and 2180 mg/l respectively. A comparison of these values with the standard values set by the Environmental Protection Organization of Iran revealed a significant difference. This finding shows that the wastewater treatment plant under study had a poor productivity and performance. The wastewater treated by that facility should not be used for irrigation or discharge into surface water. Key Words: Environmental standards, Wastewater reuse, Waste stabilization pondİran'ın Ahvaz Bölgesinde Mezbahane Stabilizasyon Havuzu Arıtma Veriminin Araştırılması ÖZ: Atık stabilizasyon havuzu (ASH), evsel atık su ve diğer kanalizasyon türlerinin uzun süre bekletildiği, içinde bulunan organik materyallerin ışığa, ısınmaya, alg ve mikroorganizmaların büyümesine ortam hazırlayarak çökelmesine, parçalanmasına ve stabilize edilmesini sağlayan bir kuyudur. Bu çalışmada; İran'ın Ahvaz bölgesinde bulunan bir mezbahane toplanan ve arıtma tesisinde arıtılmış atık sulardan numune alınarak ASH ile atık suyun arıtımındaki verimin saptanması ve sulama amaçlı kullanılabilmesi için İran Çevre Koruma Örgütü tarafından belirlenen standartlarla ilgili ölçülen parametrelerin karşılaştırılması yapılmıştır. Çalışma sonucunda, arıtılmış atık suyun Türbiditesi, BOİ5, pH, KOİ, TÇKM ve TAKM değerleri sırasıyla > 1000 NTU, 912 mg/L, 8.78, 1520 mg/L, 1052 mg/L ve 2180 mg/L olarak elde edilmiştir. Bu değerlerin İran Çevre Koruma Örgütü tarafından belirlenen standart değerlerle karşılaştırılması sonucunda anlamlı bir farklılık gözlemlenmektedir. Bulgular sonucunda çalışmakta olan atık su arıtma tesisinin verimlilik ve performans açısından zayıf olduğu görülmektedir. Tesis tarafından arıtılan atık su, sulama için kullanılmamalı ve yüzeysel suya deşarj edilmemelidir.

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