LINX - Model 600 - Electrical Water Purification Systems
The LINX 600 System is our first Industrial product. It can treat up to 170 tons of feed water per day. For larger volumes, multiple LINX 600 systems are configured in parallel and series. This product is comprised of six LINX cells, four operating in deionization (a coarse cell pair and a polish cell pair), and the third cell pair in regeneration. Cell pairs change roles after a short pre-determined time to provide continuous water treatment at up to 120 L/minute. Our water purification systems use electricity to uniquely remove contaminants from solution to purify valuable products, reuse waste water, meet discharge standards, produce softened or safe drinking water, and provide process water.
The LINX 600 system is fully automated – it will shut itself off if conditions warrant it and deliver warnings when conditions may be approaching a problem level. Furthermore, a one hour cleaning process using strong mineral acid is initiated either automatically, or manually as scheduled, to return LINX cells to their original performance if scale or COD has accumulated. The LINX 600 system can also be operated intermittently to fill a large tank, such as to provide safe drinking water for small communities. Our next generation product, now in development, is the LINX 1000 platform – a custom designed system comprised of up to 150 LINX cells for very large production volumes.
ERIX Solutions invented our Electrically Regenerated Ion Exchange technology (our tradename is LINX® technology) to create the first commercial devices that provide water purification chemical free, using electricity rather than chemicals to practice the ion exchange process.
Figure 1 illustrates a cross-sectional view of a simple LINX cell. Feed water enters the inlet at the top of the figure, flows between the water-splitting membranes, and exits via the outlet at the bottom of the figure. There is one contiguous water channel in the cell, rather than the two present in electrodialysis cells.
As seen in Figure 1, water-splitting membranes are comprised of two layers: a cation exchange material (e.g. P-SO3H or P-COOH) which is secured to an anion exchange material (e.g. P-NR3OH or P-NR2). Water-splitting membranes and apparatus were well known before the invention of LINX systems, and are used for the production of acid and base chemicals from simple salts in electrodialysis cells. ERIX Solutions has invented and manufactures for captive use water-splitting membranes optimized for use in LINX devices.
As an example, the deionization step for removing sodium chloride from solution is shown in Figure 2. This is the classic ion exchange process in which the cation and anion exchange materials are in the acid (H+) and base (OH–) forms, respectively, at the outset of deionization.
In the LINX chemical free water treatment process, however, a voltage is applied during the deionization step to accelerate ion extraction (ions move faster in the electric field). The negatively charged chloride (Cl–) ions migrate toward the anode (positive electrode) to replace OH- ions, and the positively charged sodium (Na+) ions migrate toward the cathode (negative electrode) to replace the H+ ions. OH– and H+ combine to form water, H2O, so the net result is the deionization of water.
When the absorbtion capacity for sodium and chloride ions of the two ion exchange materials is significantly reduced, the regeneration process in Figure 3 is initiated. The polarity of the two electrodes is reversed so that the water-splitting reaction at the boundary between the anion and cation exchange layers produces acid (H+) and base (OH–) which migrate through the cation and anion exchange materials, respectively. They reject the absorbed sodium and chloride ions into a concentrate between membrane layers and return the cation and anion layers to the acid (H+) and base (OH–) forms. When regeneration is complete, another deionization step is initiated.
- Reduction of N, P, heavy metals, COD
- Enable waste water reuse, zero emissions
- 10-fold concentration of waste
- Resistant to fouling by oils, COD, particles
- Compact equipment for Municipal facility nitrate reduction
- Selective removal of nitrates, metals, COD
- Electrical operation – chemical free water purification
- Best (90%) water recovery
- Good cold weather performance
- Original performance after strong acid clean
- One-step, low cost salt removal from slurries
- Eliminate the slow diafiltration process
- Self-disinfecting (log 6 bacterial reduction)
- Clean-in-place (CIP) with strong acid
- Electrical operation
* Compared to reverse osmosis (RO)
and ion exchange (IX) – See Appendix
The core advantage of LINX technology lies in the unique characteristics of LINX water-splitting membranes. The figure below illustrates the cross-sectional view of the company’s patented, textured membrane. Both surfaces have numerous ~100 µm diameter grooves – a total of 480,000 grooves in each industrial-sized LINX cell.
These grooves provide two benefits:
- Eliminate the need for spacer when winding membrane, thereby increasing ion exchange membrane packing density in LINX TDS cartridges, and
- Increase the membrane surface area approximately two-fold to provide faster ion exchange rates.
Many other important advantages are provided by our membrane and system designs:
- Low Pressure Drop: Textured LINX membranes allow high flow rates and/or low pumping energy costs, particularly when treating more viscous liquids. Conventional IX employs packed beds of 0.5 mm diameter beads, and ED and RO systems require spacer between the flat membranes. All three of these competitive water treatment technologies exhibit substantial pressure drops at high flow rates and thus high pumping energy costs. They are not practical for treating viscous liquids, such as many food and beverage slurries and oil/water mixtures encountered in petroleum recovery applications.
- Resistance to Plugging or Fouling: LINX membrane texture channels (~100 micron across) tolerate relatively large suspended particles (up to 20 microns) to enable the direct treatment of many viscous solutions or slurries found in food and beverage industries, petroleum recovery, oil refining, mining, and wastewater treatment applications. The competitive technologies described above will plug up in the presence of substantial suspended solids. LINX membranes and cell materials are mechanically strong and chemically resistant to fouling by most dissolved chemicals, including wastewater contaminants, oil and molasses.
- Clean-in-Place (CIP) with Strong Acids (or Bases): LINX TDS cartridge and module materials are resistant to strong acids and bases (pH=0 and 14, resp.), enabling the efficient and thorough periodic cleaning and disinfection of LINX water systems. RO systems require pre-treatment to avoid fouling. When they do require cleaning, dilute acids or other chemicals must be used (pH>2) to avoid degradation of their membranes. This results in long cleaning cycles and incomplete cleaning, causing a continual decline in performance over time. With periodic cleaning cycles, LINX membranes show no decline in performance, allowing consistent high water or product recoveries (>80%).
- Selective: LINX membranes are selective for nitrates and heavy metals, which are a widespread health hazard in many countries. This high selectivity ensures that in drinking water purification or industrial water discharge implementations, these health contaminants are reliably removed.
- Bacteriostatic and Disinfecting: Biofilms do not form on LINX cells or membranes, in contrast to RO and ED systems. Biofilms cause substantial reductions of production rates. In addition, LINX membranes have shown at least 2-6 log disinfection which will reduce the growth of microbes downstream.
- Chemical-Free Regeneration: LINX systems are electrically regenerated ion exchange systems which greatly simplifies disposal of the waste stream. Wastewater treatment from the operation of conventional ion exchange using hazardous acids and bases is expensive, creating a major barrier to entry for IX in many large applications.
- Uncontaminated Recovered Species: LINX water systems can be utilized for the recovery of valuable solutes by first concentrating the solute on the LINX membrane, and then releasing the bound solute during regeneration. The regenerant solution contains only the recovered solute in high purity. This is in sharp contrast to IX in which concentrated acid or base is used during regeneration, thereby contaminating the recovered solute of interest with chemicals and greatly increasing the cost of recovery.
- Low Capital Cost: The only required pre-treatment equipment is 20 micron sediment filtration. LINX membranes and cartridges are resistant to many foulants (chlorine, organics, and small particles) which interfere with IX and RO system performance. Power supplies, LINX cells, and software are custom designed for LINX systems to minimize capital and operating costs.
- Quick servicing: LINX systems, cells and power supplies are designed for efficient repair, replacement and maintenance.
The traditional technologies for TDS reduction are summarized below. Electrodeionization (EDI) is not included here because its applications are limited to production of ultrapure water using very low TDS feed water produced by other TDS reduction technologies. LINX technology is effective for product processing below 5000 ppm TDS (eg. Food processing water treatment), and for wastewater and supply water applications below 2000 ppm TDS (as for conventional ion exchange).
- Conventional Ion Exchange (IX): Large cation and anion exchange columns are used sequentially coupled with pH adjustments of feed stream in between for complete demineralization in a batch process. Regeneration takes up to 2 hours using large volumes of concentrated strong acid and base such as hydrochloric acid (HCl) and sodium hydroxide (NaOH). This process is particularly effective for low TDS feed solutions ( Must use hazardous chemicals for operation, susceptible to plugging.
- Electrodialysis (ED): Less selective ion removal is governed by mass transport rates across stacks of alternating cation and anion exchange membranes rather than by chemical equilibria as in ion exchange. ED is effective for intermediate salt concentrations, in particular for brackish water (5,000-15,000 ppm). A drawback is membrane fouling due to inorganic and biofilm formation which decreases deionization rates and increases power consumption. Susceptible to fouling.
- Reverse Osmosis (RO): This water treatment technology relies on a high pressure difference across the membrane to obtain product liquid flow across the membrane, while the dissolved solids remain on the feed side of the membrane. RO is particularly effective for high TDS feed solutions (>15,000 ppm) where ion exchange is impractical due to the need for frequent regeneration and ED power consumption is excessive. Susceptible to fouling and unable to be thoroughly cleaned.