High-pressure jet-induced hydrodynamic cavitation as a pre-treatment step for avoiding cyanobacterial contamination during water purification

• Published in: Journal of environmental management Vol. 255; p. 109862
• Main Authors: Zezulka, Štěpán, Maršálková, Eliška, Pochylý, František, Rudolf, Pavel, Hudec, Martin, Maršálek, Blahoslav
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-02-2020
• Subjects: Advanced oxidation processes; Biotic contamination removal; Continuous treatment technology; Cyanobacteria; High-pressure water jet; Hydrodynamic cavitation; Hydrodynamics; Hydrogen Peroxide; Organic Chemicals; Water Purification; Water treatment; Hydrodynamic cavitation; Advanced oxidation processes; Water treatment; Biotic contamination removal; High-pressure water jet; Continuous treatment technology
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2019.109862

Due to specific physical properties, hydrodynamic cavitation (HC) is assigned to the powerful technologies for treating the biotic contamination in water including cyanobacteria. Contaminated water stream (CWS) can be cavitated directly by passing through some HC device, or indirectly when high-pressure jet stream (HPJS) is directed against its flow. Relatively small HPJS stream can thus treat a big volume of CWS in a short time or even work in continuous mode. Cyanobacteria floating in the CWS are forced to flow through the mixing cavitation zone. Within 2 h after single HC treatment, cyanobacterial cell suspensions showed disintegration of larger colonies and enhanced biomass sedimentation. Additional pre-treatment of CWS with low amounts of hydrogen peroxide (H2O2; 33, 66 and 99 μmol/L) enhanced the effect of HC and led to further inhibition of cyanobacterial photosynthesis (maximum quantum yield of photosystem II decreased by up to 60%). The number of cyanobacterial cells in the treated CWS decreased continuously over 48 and 72 h, though some cells remained alive and were able to recover photosynthetic activity. The technique proposed (direction of a HPJS against a CWS and pre-treatment with low H2O2 concentrations) provides (i) effective removal of cells from the water column, and (ii) reduced contamination by organic compounds released from the cells (especially cyanotoxins) as the cell membranes are not destroyed and the cells remain alive. This process shows potential as an effective pre-treatment step in water purification processes related to cyanobacterial contamination.
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•High pressure jet submerged into water causes hydrodynamic cavitation.•Cyanobacteria are sensitive to HC conditions showing enhanced sedimentation.•HC itself or combined with H2O2 pre-treatment limits photosynthesis temporarily.•Already one run of HC is able to evoke effects without damage to cells.•HPJS as pre-treatment step could improve water purification process.