LINX TDS Reduction
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.
Other TDS Reduction Technologies
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 (<1000 ppm) which do not require frequent regeneration. 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.
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