Water Filtration Methods: How do they Stack up?

Understanding the Different Grades of Water Filtration: From Micron Ratings to Log Removal Rates

Water filtration is essential for providing clean and safe drinking water, whether for homes, industries, or emergency water purification systems. However, not all filters are created equal. Different grades of filtration are designed to remove varying levels of contaminants, depending on their micron rating and log removal rate. In this article, we’ll explore the spectrum of filtration, explaining what is removed at each level and how to choose the right filtration for your needs.

The Spectrum of Filtration: Micron Ratings and Log Removal Rates

Filtration is measured primarily by micron ratings, which indicate the size of particles that a filter can remove, and log removal rates, which define how effectively a filter eliminates contaminants in terms of orders of magnitude.

• Micron Rating: The size of particles a filter can block, measured in micrometers (µm). The smaller the micron rating, the finer the filtration.

• Log Removal Value (LRV): A measurement of how much of a specific contaminant is removed. A 1-log reduction removes 90% of contaminants, a 2-log reduction removes 99%, and so on. A 6-log reduction(99.9999%) is often required for microbiologically safe drinking water.

Now, let’s look at the different levels of filtration along the spectrum:

1. 20-Micron Sediment Filtration (Coarse Pre-Filtration)

Removes: Large particles like sand, rust, and sediment.

• Micron Rating: 20 microns.

• Log Reduction: Not rated for microbial removal.

• Common Uses: First stage in LEDI systems to protect finer filters from clogging.

A 20-micron sediment filter serves as a coarse pre-filter, removing large debris that could damage downstream filters or reduce system efficiency.

2. 5-Micron Sediment Filtration (Fine Pre-Filtration)

Removes: Smaller suspended particles such as silt and fine sediment.

• Micron Rating: 5 microns.

• Log Reduction: Not rated for microbial removal.

• Common Uses: Second stage in LEDI systems to further protect RO membranes.

By filtering down to 5 microns, this sediment filter ensures that smaller particulate matter is removed before it reaches more sensitive filtration stages.

3. 5-Micron Carbon Filtration (Chemical and Taste/Odor Removal)

Removes: Chlorine, volatile organic compounds (VOCs), pesticides, and bad taste/odors.

• Micron Rating: 5 microns.

• Log Reduction: 1 to 3-log removal of chlorine, chemicals, and some bacteria.

• Common Uses: Third stage in LEDI systems to improve taste and remove harmful chemicals before RO filtration.

Activated carbon block filters work by adsorption, trapping chemical contaminants within their porous structure. This step is critical for removing chlorine, which can damage reverse osmosis membranes.

4. Ultrafiltration (UF) (0.1-0.01 Microns, Optional for Certain Applications)

Removes: Bacteria, protozoa, and some viruses.

• Micron Rating: 0.1 to 0.01 microns.

• Log Reduction: 3 to 6-log removal of bacteria and protozoa.

• Common Uses: Drinking water purification, pre-treatment before reverse osmosis.

Ultrafiltration uses a membrane with microscopic pores that block bacteria and larger viruses but allow essential minerals to pass through. While not standard in LEDI systems, it is used in some applications where additional bacteria removal is required before RO.

5. Nanofiltration (NF) (0.01-0.001 Microns, Optional for Certain Applications)

Removes: Most bacteria, viruses, heavy metals, and some dissolved salts.

• Micron Rating: 0.01 to 0.001 microns.

• Log Reduction: 4 to 6-log removal of bacteria, viruses, and some dissolved contaminants.

• Common Uses: Water softening, brackish water filtration.

Nanofiltration is used in some advanced water treatment setups but is not a core part of LEDI’s standard systems due to the superior effectiveness of reverse osmosis.

6. Reverse Osmosis (RO) (0.0001 Microns, Core to LEDI Systems)

Removes: Dissolved salts, heavy metals, fluoride, bacteria, and nearly all viruses.

• Micron Rating: 0.0001 microns.

• Log Reduction: 6+ log removal, eliminating 99.9999% of contaminants.

• Common Uses: Desalination, industrial water purification, LEDI emergency water systems.

RO is the backbone of LEDI’s filtration technology, ensuring near-total removal of contaminants. Our systems incorporate pre-filtration (20-5-5 carbon) to protect and enhance RO membrane performance.

7. UV Sterilization (Final Stage for Complete Purification in LEDI Systems)

Removes: Bacteria, viruses, and protozoa by disrupting their DNA.

• Micron Rating: Not applicable (does not use physical filtration).

• Log Reduction: 4 to 6-log removal of bacteria and viruses.

• Common Uses: Final stage in LEDI systems to ensure microbiological safety.

LEDI’s UV treatment stage ensures that any remaining bacteria or viruses that might pass through RO (such as due to membrane wear) are completely inactivated before water is consumed.

Log Removal Rate for LEDI Systems

LEDI’s standard water purification process includes 20-micron sediment filtration, 5-micron sediment filtration, 5-micron carbon filtration, reverse osmosis, and UV sterilisation. The cumulative log removal rate of this system ensures exceptionally high water purity:

This system ensures water is free from pathogens, chemicals, heavy metals, and dissolved salts, making it suitable for disaster relief, emergency response, and remote drinking water applications.

Conclusion: The Smart Choice for Water Purification

By combining multi-stage filtration with reverse osmosis and UV sterilization, LEDI’s water purification systems provide unmatched water safety and reliability. Our process effectively removes sediments, bacteria, viruses, heavy metals, and chemicals, ensuring high-quality, safe drinking water wherever it's needed.

For more details on our advanced water filtration technology, visit LEDI.com.au.

Understanding the spectrum of filtration helps in selecting the right system for any application. Whether filtering out sediments, chemicals, bacteria, or dissolved salts, each stage of filtration plays a crucial role in delivering safe and clean water.