Removal of taste and odor from drinking water: performance evaluation and upgrade options for the treatment plants in Istanbul

Istanbul, one of the most crowded cities in the world with approximately 15 million population, has various surface water sources. The city is recently having taste and odor problem originating from 2-MIB and Geosmin due to algal blooms occurring in these water sources. The aim of this study is not only to evaluate the removal of taste and odor compounds in water treatment plants, but also to improve the efficiency of existing removal processes along with suggesting new processes that are effective for the removal of these compounds. In this context; measurements were evaluated along with performing the experiments for the alternative chemicals and a detailed cost analysis were made for the proposed new processes. In 5 main water treatment plants of ISKI, removal efficiencies with ozonation were 2-14% for TOC, 35-62% for 2-MIB and 34-52% for Geosmin, between the years 2013-2016. According to the experimental results, applying 10 mg/L powdered activated carbon with alum provided the highest removal efficiency for 2-MIB (50%) and Geosmin (66%) while TOC removal was higher with FeCl3 (38%). UV254 removal was within the range of 60-70% for all three coagulants. Turbidity removal was quite higher with FeCl3 compared to PACl. Finally, the applicability of peroxone process to the existing plants were evaluated. According to the calculations, unit cost for a water treatment plant with a 100,000 m(3)/day capacity was found as 0.027 $/m(3) (0.14 TL/m(3)) for the peroxone system. This cost is 20% higher than a sole ozonation system.