Degradação de 2-metilisoborneol e geosmina de água de abastecimento público utilizando processos oxidativos avançados.

Abstract

Eutrophication is an environmental problem related to the increase of phosphorus and nitrogen in aquatic environments, occurs with greater intensity in periods of high temperatures and higher solar incidence. The microorganisms involved produce several metabolites, including geosmin (GSM) and 2-methylisoborneol (MIB), associated with taste and odor of soil and mold, and that even in very low concentrations can be perceived by humans (4 to 20 ng L-1), and are not removed by conventional water treatment processes. The objective of the present work was to evaluate the oxidative processes using UV radiation (254 nm), O3 and O3 / UV in the degradation of these two metabolites in synthetic samples with different rates of O3 application by Gas Chromatography with Mass Spectrometry (GC/MS) using the solid phase microextraction technique (SPME), the tests were monitored for 45 minutes with samplings every 15 minutes of reaction. Lake Dorado was also monitored, the same was developed between January, February and March 2017, and December 2017 and January 2018. The results obtained showed a great variation among the collected collections, arriving at the values of 707.04 ng L-1 of GSM in January/2017 and 41.78 ng L-1 of MIB in March/2017, the presence of both substances in the months of December/2017 and January/2018 was detected in lower concentrations, being at most of the monitoring points below the limit of quantification. The degradation tests showed that the application of UV radiation alone was not efficient for the degradation of these two compounds. The best results were obtained with the use of O3/UV with the application of the highest ozone rates (15.84 mg L-1) after 45 minutes of reaction, in which the final concentrations of GSM were below the limit of quantification and for MIB was obtained degradation of 95.05% of the initial concentration, when the same ozone rate was applied without the use of UV radiation obtained 62.99% degradation of the initial concentration of MIB and 65.71% for GSM . Tests with different ozone rates also showed that the decrease in reaction time due to the use of higher concentrations of O3 in the reaction medium are related to better degradation efficiency. However, a better understanding and determination of reactional conditions for the application of the studied techniques is of fundamental importance the application of the oxidizing agents in real sample in algae blooms episode.