Effects of foam fractionation and chemical disinfection on the removal of different microalgae cultures

• Published in: Aquaculture research Vol. 51; no. 8; pp. 3274 - 3283
• Main Authors: Figueiras Guilherme, Mafalda, Jesus Gregersen, Kim João, Pedersen, Lars‐Flemming
• Format: Journal Article
• Language: English
• Published: Oxford Hindawi Limited 01.08.2020
• Subjects: Additives; Algae; Aquaculture; Aquaculture development; Aquaculture systems; Aquatic microorganisms; Blooms; Cultures; Dinoflagellates; Disinfection; Dosage; Fish; Foam separation; Fractionation; Hydrogen peroxide; Individual rearing; microalgae; Microalgae culture; Microparticles; Oxidants; Oxidizing agents; Ozonation; Ozone; Ozonization; Phytoplankton; protein skimmer; Proteins; recirculation aquaculture systems; Removal; Tanks; Ultraviolet radiation
• ISSN: 1355-557X; 1365-2109
• DOI: 10.1111/are.14663

The recent development of recirculation aquaculture systems (RAS) potentially allows more sustainable and controlled rearing conditions. However, control of suspended microparticles and microalgae in RAS is challenging, as uncontrolled blooms of toxic algae or heterotrophic dinoflagellates can have catastrophic impacts on the production of fish. In this study, we tested the potential of protein skimmers to remove microalgae. In 100 L batch tests, protein skimmers were tested separately and in combination with ozone (O3), ultraviolet (UV) or hydrogen peroxide (H2O2). Three different and distinct microalgae cultures were tested with densities from 30,000 to 120,000 algae cells/ml in a triplicated experimental setup. Trial 1 included twelve 24‐hr replicated tests where protein skimmers with air or with two levels of ozone (low and high O3 exposure) were compared. The protein skimmer with air alone had a limited effect on the removal of microalgae compared to the untreated control algae tanks. When ozone and protein skimmers were combined, a clear additive effect was found, and all added microalgae were removed. Low O3 dosage and protein skimmers completely removed the algae cultures within 12 hr, while more than 95% of the algae were removed within 7 hr when a higher ozone dose was used. The second trial compared the removal capacity of protein skimmers in combination with UV, H2O2 and O3. These experiments showed no to limited additive effect of UV combined with protein skimming, but significantly increased removal efficiency (270% and 1,300%, respectively) was found when H2O2 and ozone were combined with a protein skimmer. The study showed an algae species‐specific response to a protein skimmer with ozonation and provided information on the transition from reactivity and consumption to accumulation of ozone‐produced oxidants.