The Water Research Center News “ Qwaterly ” 10 th Issue August 2020 For more details, visit us at Iohexol removal and degradation-product formation via biodegradation by the microalga Chlorella vulgaris Patricia K. Akao, Hadas Mamane, Aviv Kaplan, Igal Gozlan, Yaron Yehoshua, Yael Kinel-Tahan, Dror Avisar. Published in Algal Research https://en-wrc.tau.ac.il/ “ Qwaterly” drop: As we adjust to the new reality of the COVID-19 pandemic, we continue to study and research water issues. In this “Qwaterly”, a summary of research on microalgal applications for wastewater treatment is presented. ENJOY! Microalgal applications are becoming more and more diverse, from wastewater treatment to biofuel and plastics production. Another promising and sustainable application is the removal of organic compounds from drinking water and wastewater sources. This study focused on the removal of the iodinated contrast medium iohexol (IOX) by the microalga Chlorella vulgaris. IOX concentration was measured at time 0, and after 14 and 27 days of exposure to the microalgae by HPLC-UV. After 14 days, 34%, 37%, 42% and 36% of IOX was removed from the growth media in experiments M2, M5, M10 and M100 (representing progressively higher starting concentrations of IOX), respectively. After 27 days, 42%, 45%, 47% and 42% of IOX was removed, respectively. From days 14 to 27, the removal percentages for M10 and M100 showed no significant difference (P>0.05), whereas for M2 and M5, the differences (7–8%) were significant (P<0.05). These results demonstrate that 14 days of incubation with C. vulgaris was sufficient to achieve ~42% removal for high IOX concentrations (M10 and M100), and for small concentrations (M2 and M5), longer incubation times provided slightly better removal. Incubation time is an important and costly factor in wastewater and water treatment [42], and it should taken into consideration when deciding on the best removal approach. Fig. 1. Iohexol (IOX) removal from the growth media in the positive controls and experiments. PC2, PC5, PC10, PC100: positive controls with 2, 5, 10 and 100 mg L-1 IOX, respectively; M2, M5, M10, M100: 2, 5, 10 and 100 mg L-1 IOX, respectively, in the growth media with C. vulgaris. Error bars represent standard deviation of three independent experiments (n = 3). Fig. 2. Mass balance for 2, 5, 10 and 100 mg L-1 iohexol (IOX). Error bars represent standard deviation of three independent experiments (n = 3). Conclusion: IOX lowered the growth rate of the microalgae and increased their overall cell size, indicating its toxicity to C. vulgaris. The removal pathway was predominantly biodegradation, and the two main degradation pathways were oxidation and hydrolysis. C. degradation pathways were oxidation and hydrolysis. C. vulgaris can biodegrade IOX in water and wastewater. Ozonation was used to oxidize the IOX, and IDPs (degradation products) found during incubation with Chlorella were also found after ozonation, confirming the main degradation pathway. Most of these degradation products' structures were confirmed by accurate masses, empirical formulas and their exchangeable hydrogen atoms utilizing deuterated mobile- phase solutions during HPLC-MS analysis. Things are on the move: Tzalul - an interview with Dror Avisar https ://www.facebook.com/ZalulIsrael/videos/349790169754473/ Webinar with Australia – Dror Avisar https ://www.youtube.com/watch?v=FrUzpVcbgZM&feature=youtu.be