Power Ultrasound, the field devoted to the use of ultrasonic energy to produce permanent changes in the treated medium, is considered an emerging, environment friendly and energy saving technology. Presently there is a growing interest for the application of power ultrasound in a large variety of operations. It can be attributed to the special characteristics of ultrasonic energy to provide a sustainable and versatile technological alternative for the development of enhanced energy efficient processes. In fact, ultrasonic waves offer a clean mechanical non-ionizing radiation that due to its effectiveness, low instrumental needs compared with other techniques and reduced process time, make their application to be considered a green and sustainable technology.

Until recently, most of the ultrasonic processes have dealt with the treatment of solid and liquid media. To be mentioned plastic and metal welding, machining, metal forming in solids and cleaning, atomisation, emulsification and dispersion, degassing and sonochemical reactions in liquids as the current more representative conventional applications of power ultrasound. However, there are other important media, including gases and multiphase media (gas with particles, bubbles or drops in suspension and liquids with gas content or porous solids with liquid inside), to which the application of ultrasonic energy has been notoriously discarded for long time. The reason of such a situation lies in the difficulty to efficiently generate and propagate ultrasound through low density and inhomogeneous media.

The creation and development by Prof.Gallego-Juárez of a novel family of power ultrasonic generators with extensive radiating surfaces of stepped profile has significantly contributed to address this challenge by allowing the implementation, at laboratory, semi-industrial and even industrial scale, of a number of new ultrasound assisted technologies for environmental, food, and manufacturing sectors. The development of these technologies, generally based on the exploitation of the nonlinear effects created by high intensity waves, has been carried out through theoretical and experimental studies in the field of power ultrasound whose results have been collected in a large number of scientific publications. Such results have been used to determine the mechanisms activated by ultrasonic energy in the new processes treated in low density and multiphase media. 

One of the present requirements in sewage treatment is the dewatering of sludge. To that purpose, conventional filtration techniques are not satisfactory because the phenomenon of fouling or blocking the pores is frequently produced resulting in slow processing rates or in flux decline. As a consequence the residual moisture in the filter cake always remains high, and it is very difficult to remove. Power ultrasonics has shown to be effective in the release of the residual moisture. Ultrasonic energy directly coupled to the sludge by using the new plate generators causes the alternating stresses an effective deliquoring by creating channels for moisture migration. By the application of ultrasonic energy, dewatering higher than 80% can be obtained with a short treatment time (2 seconds) and a relatively low intensity applied (about 0.25W/cm2). 

Foam is generally an unwanted by-product in industrial processes because it causes difficulties in process control and in equipment operation. A typical example is in the fermentation industry where foam represents one of the biggest problems. The most efficient conventional method for defoaming is the use of chemical anti-foaming agents but they contaminate the product. High-intensity ultrasonic waves represent a clean and efficient procedure to break foam bubbles. A new ultrasonic defoamer based on the use of the stepped-plate power generator has been developed. Such system has been successfully tested for the control of excess foam produced in fermenting vessels and in other reactors of great dimensions as well as on high-speed canning and bottling lines during the filling operation. 

The use of supercritical fluids as extracting agents has been attracting wide interest for years and, in particular, supercritical carbon dioxide is considered nowadays as a very useful solvent in the extraction process because it is non-toxic, recyclable, cheap, relatively inert, and non-flammable. Nevertheless, the process has a slow dynamics. 

The use of power ultrasound represents an efficient way for enhancing mass transfer processes by radiation pressure, microstreamings and agitation. This new technique has been successfully tested on vegetable oils extraction in a semi-industrial plant constituted by four high-pressure extraction vessels. The results obtained have shown that the kinetics and the extraction yield are enhanced in a range of 30% to 90%depending of the product 

Fabric processing in textile manufacturing is a wet processing to improve the appearance and serviceability of the fabric. It includes several operations that usually require washing the fabric. The use of ultrasonic energy in such operations speeds up the process and improves the quality of the final product. In this way a new ultrasonic washing machine has been developed and patented in which the textiles are exposed to the ultrasonic field in flat format and within a thin layer of liquid by applying specific plate transducers. Both process and device have been implemented at semi-industrial stage. 

Pigment dispersion in paint manufacture 

 Pigment dispersion is a critical factor in the manufacture of paint because it is a complicated and cost-intensive operation. Most of the paint properties are enhanced when the pigment particles are the smallest possible. The degree of pigment dispersion determines most of the essential properties of a paint. The application to this processing problem of a new technology based on power ultrasound offers a potential of innovation which is required in the paint industry .By using t rectangular-plate power ultrasonic generators, an ultrasound reactor to enhance pigment dispersion in paints, pastes and inks at industrial scale has been developed Trials performed with the prototype of ultrasound machine, sonicating with applied powers to the transducers in the range of 400W-600W and treating paint flows of 50 to 100 kg/h, proved  the pigment disagglomeration effect and that  better pigment dispersion can be obtained than with classical grinding machines.(Unpublished work)