The demand for clean drinking water is increasing each year, while freshwater supplies are diminishing. The use of treated wastewater for irrigation is the most prevalent reuse option but comes with significant challenges due to wastewater being a primary source of contaminants of emerging concern. It is crucial to improve the removal of these pollutants from wastewater and, consequently, prevent or at least reduce their entry into the environment. Bisphenols are a notable example of such pollutants. According to the legislative resolution of the Urban Wastewater Treatment Directive, quaternary wastewater treatment should remove ≥ 80% of contaminants of emerging concern and other micropollutants. Advanced oxidation processes, and particularly their combinations, show great potential in this regard.
In this master's thesis, we monitored the removal of pollutants of concern, specifically bisphenol A and four of its substitutes (bisphenol AF, bisphenol F, tetramethylbisphenolF, and bisphenol S), using a combination of two advanced oxidation processes – photocatalysis and hydrodynamic cavitation. We conducted seven different types of tests for the removal of the selected bisphenols from drinking water (200 ng/L) and wastewater (1000 ng/L): (a) adsorption of bisphenols onto a photocatalyst (TiO2) in the dark, (b) photocatalysis, (c) hydrodynamic cavitation, (d) simultaneous photocatalysis and hydrodynamic cavitation, (e) hydrodynamic cavitation followed by photocatalysis, (f) hydrodynamic cavitation followed by photocatalysis with the addition of H2O2, and (g) UV radiation. To determine the effectiveness of removing selected compounds during various cleaning processes, we developed, optimized, and validated analytical methods for detecting specific bisphenols in drinking and wastewater. These methods are based on solid-phase extraction and analysis using gas chromatography coupled with mass spectrometry.
In testing with drinking water, we found that the removal rate of bisphenols in experiments with a combination of photocatalysis and hydrodynamic cavitation was higher compared to either photocatalysis or hydrodynamic cavitation alone. The most effective treatment was found to be 15 min of hydrodynamic cavitation followed by 15 min of photocatalysis, though only tetramethyl bisphenol F achieved the desired removal of ≥ 80%. In wastewater, we found that none of the tests achieved ≥ 80% removal. This confirmed that wastewater is a more complex matrix than drinking water, indicating the need for further development of advanced oxidation process combinations for bisphenol removal from wastewater.
|
