Abstract
For effective ultrasonic algae removal, several studies have considered the ultrasound equipment linked factors, such as power and frequency. However, studies on the response of mixed algal cultures and associated water quality parameters to ultrasound are limited. In this lab-scale sonication, the removal of cyanobacteria at a pre-set frequency of 200 kHz on mixed algae suspensions collected from a eutrophic lake was investigated. The caution (17.5 µg/L) and outbreak (1450 µg/L) alert levels in terms of chlorophyll-a (Chl-a) concentrations of the initial samples were each sonicated for 10, 15, and 20 min, and then kept in an incubator. Fifteen minutes of sonication resulted in best removal efficiency of 0.94 and 0.77, at an ultrasonic dose of 30 kWh/m3 at the outbreak and caution level concentrations, respectively. Immediately after 15 min sonication, and after standing in the incubator for a day, chlorophyll-a removal efficiencies of 0.28 and 0.90 were achieved in the outbreak level, respectively, and the matching removal efficiencies for the caution level were 0.23 and 0.64. Even though the removal was substantial in both cases, the final 147 µg/L chlorophyll-a concentration of the outbreak, which is itself still in the outbreak level range, shows that ultrasonication is not effective to satisfactorily remove algae from a concentrated suspension. Total dissolved nitrogen and chemical oxygen demand were reduced, overall, due to sonication. However, total dissolved phosphorus of the concentrated level was increased during the treatment. Although sonication needs further replicated experimental testing in whole-lake systems, our results show that 200 kHz sonication was able to reduce chlorophyll-a concentrations in small-scale laboratory tests.
Highlights
Eutrophication is perhaps the greatest threat to water quality globally [1,2]
Sonication needs further replicated experimental testing in whole-lake systems, our results show that 200 kHz sonication was able to reduce chlorophyll-a concentrations in small-scale laboratory tests
Chlorophyll-a was determined in the lab using the standard methods, in which the phytoplankton containing Chl-a in a measured volume of sample was concentrated by filtration through a glass-fiber filter [49]
Summary
Eutrophication is perhaps the greatest threat to water quality globally [1,2]. the gradual enrichment of surface water with plant nutrients, mainly nitrogen and phosphorus, has resulted in shifts from systems dominated by rooted aquatic plants to systems that are dominated by algae suspended in the water column [3,4]. Long water residence times, due to operational procedures applied to reservoirs, encourage internal nutrient release and, cause regulated river waters to suffer from eutrophication [5,6]. This has already worried ecologists in South Korea, where reservoirs and regulated rivers are the major sources of freshwater. The control of eutrophication involves nutrient source reduction measures, such as wastewater treatment, as well as interception of non-point sources, and in-water methods, such as chemical treatment, bio-manipulation, artificial circulation, aeration, and dredging [7,8,9,10,11,12].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
