a flow chamber is provided through which is flowed a mixture of a fluid and a particulate . the flow chamber comprises at least one multi - phase water inlet through which multi - phase water enters the flow chamber , a water outlet through which water exits the flow chamber , a solids outlet through which particles having a density at or above a pre - defined threshold exit the flow chamber , and a low density outlet through which particles having a density below the pre - defined threshold exit the flow chamber . also provided are one or more ultrasonic transducers and one or more reflectors corresponding to each transducer to acoustically filter the fluid and cause particles / fluid to be selectively diverted to one of the outlets . related apparatus , systems , techniques and articles are also described .