•The use of 3 different types of waveguide systems for activation of ASFC reagents was investigated.•Ultrasound enables to reactivate the alumosilicic flocculant-coagulant.•In scaled up reactors the choice of the equipment type affects the stability of the achieved effect. Acoustic fields formed during operation of ultrasonic reactors with waveguides of following types: rod-type, cylindrical with rectangular protrusions and tubular were calculated and measured. The influence of distribution of acoustic fields arising from the operation of waveguide systems of three different types on the efficiency of ultrasonic activation of alumosilicic flocculant-coagulant and magnetite intended for water purification was investigated. It was shown that regardless of the equipment used on an industrial scale it is possible to reactivate the alumosilicic flocculant-coagulant even after the shelf life period of it passed, however in case of activation of magnetite the use of a bigger reactor in inefficient. In case of industrial scale processes, the choice of the correct reactor design is of significant importance, since it allows to reduce the required processing time, and, as a result, the energy consumption of the processes. The advantages of tubular waveguide systems include the possibility of processing large volumes of liquid. The high efficiency and uniformity of the excited ultrasonic fields can lead to reduction of operating costs. In case of smaller flows, the waveguide system with rectangular protrusions allowed to obtain better results. Our work illustrates the dependence of the success of a specific method on the choice of the waveguide and the size of the reactor during upscale.