Cavitation triggers multiple effects in salt water; among these it should be noted that first of all it makes the physical bonds of the saline molecules less strong with those of the water: therefore in the subsequent reverse osmosis the saline molecules «detach» more easily from those of the water and will be able to pass the membranes easily.
Therefore much less energy is used than comparable systems.
The Empowering Device combines the effects of cavitation with osmotic membranes and filters that can remove the precipitate or floated substances, obtaining a complete purification of the treated water while removing also oils, pathogens and pollutants.
The use of cavitation ultrasound will also help in cleaning the membrane surface through mechanisms such as acoustic streaming, microstreaming, microstreamer, microjet and shock waves.
The acoustic streaming mechanism improves membrane cleanliness by transmitting acoustic energy through the feed solution to produce a flow of liquid that is obstructed, causing unidirectional waves of liquid flow with a flow velocity reaching up to 10 m / s parallel to the surface of the deposits, which can be of great help in removing dirt.
The cavitation bubbles are attracted to the antinodes of the standing wave and structured in a certain path in which the size of the bubble increases as it travels towards the antinodes located on the surface of the membrane. Once the antinodes reach the surface of the dirty membrane, bubbles are formed which cause a entrainment and detachment effect on the particles deposited on the surface of the membrane.
The shrinking effect of the cavitation bubbles moves the liquid molecules away from the surface of the membrane, while the expansion effect pushes the molecules onto the surface of the membrane, causing shear and drag forces necessary for the removal of fouling from the membrane surface.
When the cavitation bubble reaches its minimum size, at the end of the compression cycle, the cavitation bubbles reach a sudden stop causing the liquid molecules, moved towards the bubbles, to reflect with high pressure towards the surface of the membrane.
The increase in high flow when switching from a low to a high CFV (cross flow rate) with the ultrasound facing the support layer confirms that the use of ultrasound in the support layer induces mixing and turbulence zones and thus, it reduces the impact of the ICP and improves the flow of water.
The advantages of this cleaning technique are the absence of use of chemicals, the shutdown of the system and the need to remove the membrane from the system for ex situ cleaning, in order to minimize possible contact of the membrane with the ‘air.
Ultrasound affects membrane filtration through three ways: by detaching deposited contaminants and moving particles and molecules away from the membrane interface (i.e. reducing concentration polarization) (cleaning effects), improving water transport across the membrane (effects mass transfer) and increasing the heat transfer of water for thermally operated membrane processes.
Furthermore, by applying cavitation it is possible to collect the precipitated salts by passing the post-shock wave samples through a special filter, the precipitate is crystalline in nature, comprising spherical particles that are larger when derived from groundwater.
The particles contain various elements - such as chlorine, potassium and magnesium - which are consistent with the dissolved content of the original water.
The approach to desalination that we have chosen for the EMPOWERING DEVICE is by no means the one that has been tested for a long time in the Russian / Chinese context and considered, at least for a few years, rightly or wrongly, the way forward to apply cavitation to the removal of salt from the sea water.
These exploited the chemical and thermal conditions of cavitation to obtain an intensive evaporation of a solution in the purification phase: the superheated water after an electromagnetic treatment, in the presence of fixed obstacles placed according to a peculiar geometry, went into cavitation.
For us, however, cavitation must be understood as a process that prepares the water for osmotic desalination, also providing for its purification. Then the membranes are inserted inside the EMPOWERING DEVICE device becoming an integral part of it.
With both cavitation systems, the EMPOWERING DEVICE and the Russian / Chinese system, no chemicals are added to the water but the EMPOWERING DEVICE, the SOFRON16 which represents the largest model, can desalinate over 23,000 m3 / d with a consumption of approximately 0.05 kW per m3 while the other system produced up to 1,200 m3 / d with a consumption of 3 kW per m3.
Furthermore, the EMPOWERING DEVICE is modular and therefore allows the installation of multiple systems side by side or overlapping.
