Vorsana

Shear Cavitation for Water Disinfection

 The new Vorsana Radial Counterflow Shear Reactor helps disinfect a continuous flow of water by physical processing, without membranes, filters or chemicals.  It also helps with suspended metals extraction, crystallizing scale and salt, and degassing of volatile compounds.  Because it is a relatively low-tech and low-power device, it is suitable for field water purification.

Disinfection involves the killing of pathogens.  The water supply may contain many pathogens such as Giardia, cryptosporidium, amoebas, bacteria, worms, snails, and viruses.  Some pathogens are in cysts, which are highly resistant to chemical treatment, even chlorine.  The recognized inadequacy of chemicals and membranes has led to increased interest in physical methods for disinfection, particularly cavitation, ultraviolet light, and pulsed electric fields.  The Vorsana Radial Counterflow Shear Reactor can combine all three, as needed.

Cavitation is a well-known force in water which can chip boat propellers and damage spillways.  When water is put under sufficient physical stress, it tears apart at weak points in its structure, forming bubbles which collapse when the tearing force is gone.  Crackling may be heard when tiny cavitation bubbles collapse, creating strong shock waves as well as powerful microjets.  Since depth charges will destroy submarines by the force of the jets and shock waves from cavitation bubble collapse, imagine what occurs on a micro scale when a multitude of cavitation bubbles collapse next to bacteria or Giardia cysts. Because these pathogens constitute interruptions and weak points in the water structure, the cavitation bubbles are likely to form right next to them.

Collapsing cavitation bubbles also emit visible blue light, including UV radiation in the frequency that is most deadly to microbes.  The high-intensity pulses occur right next to the pathogens, so the rapid dissipation that normally happens for UV travelling through water does not apply.  In addition to shock waves and microjets, which rupture nearby cell walls, cavitation also produces reactive species such as OH (hydroxyl) radicals, which at an oxidation potential of 2.80 V are even more powerful oxidants than ozone (2.07 V).  The ultraviolet light from cavitation breaks down hydrogen peroxide (H₂O₂) into more OH radicals.  The high turbulence from cavitation shock wave agitation helps to mix these reactive species into the water for improved sterilization.

In this water sterilization method, an important first step is the upstream extraction of dissolved gases and volatile compounds from the water.  Besides having the benefit of extracting dangerous components such as ammonia, cyanide, acetone, and methane, this degassing is important for high energy cavitation because  any noncondensible gases  in the cavitation bubbles act as a cushion, absorbing energy in compression and thereby impeding a the most rapid and energetic implosion possible to produce shock waves, microjets and UV radiation.

Pulsed electric fields assist in degassing by causing streamers in the water, forming cavitation bubbles where dissolved gases evolve.  Strong electric fields also cause currents through ionized solutions, such as are contained in cells, that rupture the cell walls. 

The Vorsana Radial Counterflow Shear Reactor is designed for treating a large, continuous flow, with the microbes and pathogens simultaneously blasted, irradiated, and electrocuted to oblivion with Vorsana's patent-pending technology.