Hydrodynamic cavitation in combination with the ozone, hydrogen peroxide and the UV-based advanced oxidation processes for the removal of natural organic matter from drinking water.

Natural organic matter in drinking water is causing concern especially due to the formation of disinfection by-products (DBPs) by chlorine, as these are proven to have adverse health effects on consumers. In this research, humic acid was used as a source of dissolved organic carbon (DOC) in drinking water (up to 3mgL-1). The efficiency of DOC removal was studied by applying O3, H2O2/O3, H2O2/UV and O3/UV advanced oxidation processes (AOPs) alone and combined with hybrid hydrodynamic cavitation (HC), generated by an orifice plate, as this technology recently shows promising potential for the treatment of water, containing recalcitrant organic substances. It was observed that the combined treatment by HC could significantly affect the performance of the applied AOPs, with as little as 3-9 passes through the cavitation generators. For O3 and H2O2 dosages up to 2 and 4mgL-1, respectively, and UV dosage up to 300mJcm-2, HC enhanced DOC removal by 5-15% in all combinations, except for O3/UV AOPs. Overall, the potential benefits of HC for DOC removal were emphasized for low ratio between applied oxidants to DOC and high UV absorbance of the sample. Investigated DBPs formation potentials require special attention for H2O2/UV AOPs and combinations with HC.

The Enhancement of H2O2/UV AOPs for the Removal of Selected Organic Pollutants from Drinking Water with Hydrodynamic Cavitation.

Drinking water contains organic matter that occasionally needs to be treated to assure its sufficient quality and safety for the consumers. H2O2 and UV advanced oxidation processes (H2O2/UV AOPs) were combined with hydrodynamic cavitation (HC) to assess the effects on the removal of selected organic pollutants. Water samples containing humic acid, methylene blue dye and micropollutants (metaldehyde, diatrizoic acid, iohexol) were treated first by H2O2 (dosages from 1 to 12 mg L-1) and UV (dosages from 300 to 2800 mJ cm-2) AOPs alone and later in combination with HC, generated by nozzles and orifice plates (4, 8, 18 orifices). Using HC, the removal of humic acid was enhanced by 5-15%, methylene blue by 5-20% and metaldehyde by approx. 10%. Under favouring conditions, i.e. high UV absorbance of the matrix (more than 0.050 cm-1 at a wavelength of 254 nm) and a high pollutant to oxidants ratio, HC was found to improve the hydrodynamic conditions in the photolytic reactor, to improve the subjection of the H2O2 to the UV fluence rate distribution and to enhance the removal of the tested organic pollutants, thus showing promising potential of further research in this field.