Advanced water purification via contactless ion concentration

Filtration device that concentrates the location of ions within a water stream

Medical & Biotechnology Environmental

The U.S. Army Corps of Engineers has invented a novel water purification technology that is available to qualified businesses who would use it in new products or services.

One example of this charged species concentrating apparatus includes electric circuit 10, negative electrode 12 a, positive electrode 12 b, input water stream 14, ion concentration area 16, reservoirs 18 a and 18 b, electric field 20, ion-concentrated stream 22, ion repellent area 24, main channel 28, negatively charged membrane 30, and ion-depleted stream 34. Reservoirs 18 a and 18 b and the main channel 28 all contain a continuous quantity of conductive liquid that contacts electrode 12 a or electrode 12 b to complete an electric circuit. Membrane 30 separates the liquid contact point of electrode 12 a from the liquid contact point of electrode 12 b. In this example, main channel 28 dimensions are 5 cm in length, 40 μm in height, and 500 μm in width. Increasing the width (e.g. bore) of the main channel can increase the throughput of water and production rate of clean water.

Water purification systems struggle to detect contaminants at high dilution, require substantial energy to operate, and can become fouled too easily. The separation and removal of particles including viruses, bacteria, protozoa, spores, clay, hair, proteins, nucleic acids, peptides, lipids, and humic acids represent an ongoing battle.

The contaminants mentioned above all carry a positive charge and Army scientists have used this commonality to develop a system for separating them out in an energy efficient manner. The system and method resist biofouling by design and is shown in the figure at right. The apparatus is comprised of an electrically charged barrier through which water flows. Positively charged particles are diverted out of the flow and water without ions passes through.

If any neutral (uncharged) organic compounds are present in the liquid to be processed, adding charged sorbents including clay, carbon, or zeolite particles to the incoming liquid stream allows the apparatus to process any neutral organic compounds. The charged sorbents adsorb or bind to neutral organic compounds and then the apparatus can repel the charged sorbent (which is a charged species) while it is attached to the neutral organic compound.

The device is energy efficient with power consumption values of less than 5 Watt-hours per Liter (Wh/L) with maximum water production rates of ˜50-mL/min. Parallel units can reach water production rates in excess of 1 gallon per minute and a scaled-up microfluidic system can reach water outputs of about 1 gallon per minute in water desalination or purification.

A membrane isolates one electrode and has an electrically charged surface (positively or negatively charged) preventing the passage of charged species with a charge sign (polarity) that is the same as the charge on the surface of the membrane.

This design prevents electrically charged species (including bacteria) from physically contacting membrane. This contactless filtration function prevents bacterial biofilm formation on the membrane and clogging or fouling of the membrane, substantially reducing the need for replacing or cleaning, and minimizing overall maintenance requirements.

The invention is protected by a pending patent and a patent license is needed to take advantage of this business opportunity.

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