Field use of ultrasound for management of algal blooms: evaluation of sound pressure and water quality

Ultrasound is an emerging technology to manage cyanobacteria harmful algal blooms (cHABs). It involves ultrasonic transducers placed in reservoirs that emit ultrasound throughout the cHAB season. Various mechanisms have been proposed, including targeting gas vesicles that regulate algal buoyancy, potentially collapsing them or inducing cavitation. Despite laboratory findings, field operation effects remain unclear. This study characterized ultrasound signals and water quality in lakes and reservoirs with ultrasound deployed to understand field operation. Field data from five sites were analyzed. The ultrasound signal attenuated with distance with attenuation coefficients about ten times greater than pure water. Attenuation was consistent across sites and minimal variation with environmental factors were observed. Spatially, no significant water quality differences were observed in reservoirs with ultrasound, but variations across connected reservoirs indicated the potential influence of detention time. Field evaluation suggested that known mechanisms such as cavitation and gas vesicle collapse are unlikely to affect cHABs at measured sound pressures and frequencies. Water quality paired with ultrasound did not show significant differences compared to control reservoirs.

Primary Presenter: Linda Weavers, The Ohio State University (weavers.1@osu.edu)

Authors:

Linda Weavers, Ohio State University  (weavers.1@osu.edu)

Mark Tischer, The Ohio State University  (tischer.14@osu.edu)

Christopher Weaver, City of Columbus  (CRWeaver@columbus.gov)

Elisabeth Crafton, Hazen and Sawyer  (ECrafton@hazenandsawyer.com)

Kaiden Murphy, The Ohio State University  (murphy.2399@osu.edu)

Ricky Vehar, The Ohio State University  (vehar.5@osu.edu)

Chin-Min Cheng, The Ohio State University  (cheng.160@osu.edu)