Separation of bacterial spores from flowing water in macro-scale cavities by ultrasonic standing waves

TL;DR

This study demonstrates the use of ultrasonic standing waves in a macro-scale resonator to effectively separate bacterial spores from flowing water, achieving 15% efficiency at moderate flow rates.

Contribution

It introduces a novel macro-scale ultrasonic resonator setup for bacterial spore separation from water flow, optimizing parameters for improved efficiency.

Findings

Successful separation of B. cereus spores at 40 ml/min flow rate

Achieved 15% separation efficiency in a single pass

Effect of transducer voltage and frequency on separation efficiency

Abstract

The separation of micron-sized bacterial spores (Bacillus cereus) from a steady flow of water through the use of ultrasonic standing waves is demonstrated. An ultrasonic resonator with cross-section of 0.0254 m x 0.0254 m has been designed with a flow inlet and outlet for a water stream that ensures laminar flow conditions into and out of the resonator section of the flow tube. A 0.01905-m diameter PZT-4, nominal 2-MHz transducer is used to generate ultrasonic standing waves in the resonator. The acoustic resonator is 0.0356 m from transducer face to the opposite reflector wall with the acoustic field in a direction orthogonal to the water flow direction. At fixed frequency excitation, spores are concentrated at the stable locations of the acoustic radiation force and trapped in the resonator region. The effect of the transducer voltage and frequency on the efficiency of spore capture in the resonator has been investigated. Successful separation of B. cereus spores from water with typical volume flow rates of 40-250 ml/min has been achieved with 15% efficiency in a single pass at 40 ml/min.