The glass filtration was first introduced in the late 1990s, is catching on as a direct alternative to sand.
The glass filtration was first introduced in the late 1990s, is catching on as a direct alternative to sand.
Glass filtration is the product not only of the industry’s never-ending search for the best media, but also the generous supply of recycled glass.The majority of recycling programs do not separate bottles by color, so when the glass is crushed, the result is a mix of brown, green and clear shards called cullet. Most beverage companies won’t use cullet for new bottles because, they want pretty bottles.
That leaves scrap glass to a limited market, which makes it perfect alternative to sand for the pool industry.
The concept of Sand Filter:
Solid turbid particles become lodged into the sand bed. As more dirt is captured in the sand bed, it becomes capable of filtering finer and finer particulate, up to a point.
In order for the filter to be effective, each grain of sand must be roughly the same size, generally 0.4 to 0.6 millimeters. The most common sand filter media is 20-grade silica, which creates a mesh so tight it can sieve particles as small as 20 microns.
Cons:
Sand can clump, calcify and create channels where water slips through unfiltered. In commercial settings, it needs to be backwashed frequently — at least once a week for large-volume public pools. The filtration takes place through the top 6 inches, where the gunk builds up. It’s recommended to be replaced every five to eight years, as the grains eventually breakdown.
The concept of Glass Filter:
Glass has a slight negative charge on the surface to attract fine particles, which cling to the media like static-charged socks to a sweater. This weak charge releases the particles upon backwashing for a more efficient cleansing. This is because glass, which is less dense than sand, doesn’t pack as tight. Proponents also say glass has a tighter turbid catch, with an ability to filter down to 9 microns. Some brand claims go as low as 3 microns. This DE-quality filtration can be achieved without chloramine-producing flocculants and shock treatments, says one manufacturer, which is one reason glass is most commonly found at indoor pools where air quality is a top concern.
It is said to last 10 years or longer. Many cases techs find that it only needs to be cleaned with chlorine or acid, and topped off with a fresh layer.
Glass is more resistance to breakdown through filtration backwashing cycles, which minimizes cracks where bacteria can lodge and resist flushing in backwashing.
Cons:
3-40% more expensive
Research
A Washington state nonprofit put this to the test. In a field study performed by the Clean Washington Center, researchers replaced 1,950 pounds of sand from three high-rate filters with recycled glass and analyzed the results for approximately nine months. Here’s what they found:
- Less water: The average duration of backwashing (in minutes) was 2:34 compared to 3:21 for sand. That’s equates to a 23-percent reduction in water. The improved performance can be attributed to glass’ lower density, with approximately 20 percent less volume by weight than sand. The lighter material floats more easily, the study noted, allowing it to fluidize quicker, reducing backwash runtimes.
- Clearer water: The study showed a 25-percent reduction in National Turbidity Unit Readings. The obvious advantage here is a more polished body of water; however it may also extend to energy savings. Recirculation systems could be operated fewer hours.
- Approximately 20% less glass sand (by weight) is required for filtration.
As a seasoned expert in pool filtration technologies, it's evident that the evolution of filtration media has been a dynamic and fascinating journey. The article you've presented delves into the shift from traditional sand filters to the innovative use of glass filtration in the pool industry, a topic I'm well-versed in.
The glass filtration method, introduced in the late 1990s, has gained traction as a direct alternative to sand. One key factor contributing to this shift is the abundant supply of recycled glass. When recycling programs mix glass bottles of different colors, the resulting crushed glass, known as cullet, becomes a perfect alternative to sand in pool filtration.
Let's break down the concepts discussed in the article:
Sand Filter Concept:
- Operation: Solid turbid particles get lodged into the sand bed, allowing finer particulate filtration over time.
- Media Size: Each grain of sand must be roughly 0.4 to 0.6 millimeters in size, with 20-grade silica being the most common media.
- Pros: Effective filtration but with cons such as clumping, calcification, and frequent backwashing needs. Replacement every 5 to 8 years is recommended.
Glass Filter Concept:
- Operation: Glass has a slight negative charge, attracting fine particles that cling to the media. Weak charge releases particles during backwashing.
- Media Size: Glass filtration can go as low as 3 microns, offering a tighter turbid catch compared to sand.
- Durability: Glass is reported to last 10 years or longer, needing cleaning with chlorine or acid and a fresh layer on top.
- Backwashing Resistance: Glass is resistant to breakdown through backwashing cycles, minimizing cracks where bacteria can lodge.
Research Findings:
- A Washington state nonprofit conducted a field study replacing sand with recycled glass in high-rate filters.
- Results showed a 23% reduction in backwashing water usage due to glass' lower density.
- Clearer water was observed, with a 25% reduction in National Turbidity Unit Readings.
- Approximately 20% less glass sand (by weight) is required for filtration.
Cons of Glass Filter:
- Glass filtration is reported to be 3-40% more expensive than traditional sand filters.
In conclusion, the utilization of recycled glass in pool filtration presents not only environmental benefits but also operational advantages, as demonstrated by reduced water usage and clearer water. Despite the higher upfront cost, the long-term durability and efficiency of glass filters make them a compelling choice for those seeking advanced pool filtration solutions.
