Sand filter vs. membrane filter

Sand filters are a technology developed almost 200 years ago. Still, it is heavily applied within pool filtration. There are several categories of sand filters. Generally, sand filters are operated with downward flowing fluids, and they are either driven by pressure or gravity.

A sand filter is a large tank produced of fiberglass, metal, or concrete. There is a thick bed of special-grade sand in this tank with sharp edges. The dirty water from the swimming pool is pumped into the sand filter through an inlet pipe during water filtration. Pressure or gravity will lead the water down through the sand, while the sand particles retain dirt, debris, and particles down to 10-50 microns. As this is a relatively large pore size structure, sand filters may depend on flocculant chemicals, chlorine, and chemical treatment to provide adequate disinfection to remove bacteria and various pathogenic organisms. As a sand filter operates, dirt, debris, and particles accumulate in the sand and eventually slow down the water flow. To restore the water flow, the filter is backwashed. A sand filter is a solution that is both relatively effective and cheap. But although heavily applied in the industry, it has its drawbacks. Let us go through five important aspects of a pool filtration system.

Filtration – Sand filters can filter down to 10-20 microns. This means that various bacteria, pathogens, and viruses are not removed during filtration.

Cleaning – As a filtration unit operates, it gets fouled, ultimately calling for effective cleaning. Cleaning sand filters requires a large volume of water, making it less energy efficient.  

Chemicals – Sand filters may require flocculant chemicals to work effectively due to the larger pore size structure.

Footprint – As a sand filter is large, it requires a large footprint.

Lifetime – As a sand filter operates, the rough edges of the sand are worn off due to erosion. The more water that passes through the filter, the higher the erosion. This will make the sand perform less effectively than intended. Therefore, sand should be changed every 3-5 years.

Ceramic membrane filters are modern technology, gaining traction within all aspects of water filtration as it is a durable, robust, and cost-effective solution. A membrane pool filtration solution consists of several housings, which contain ceramic membranes made of inorganic materials, such as silicon carbide. Click here to learn more about what a ceramic membrane is. As ceramic membranes are made of some of the hardest materials in the world, they are highly durable and long-lasting. The dirty water from the swimming pool is pumped into the ceramic membrane filters through a feedwater inlet during water filtration. Pressure will lead the water through the porous membrane structure, while the membrane retains dirt, debris, and particles down to 3 microns. As this is a much denser pore size structure than that offered by a sand filter, fewer chemicals are needed to provide effective disinfection to remove bacteria and various pathogenic organisms. As membranes operate, dirt, debris, and particles will also accumulate on their surfaces, which will slow down the water flow. To restore the water flow, a backwash is performed. Yet, water consumption for backwash is reduced significantly. Let us go through the same five aspects as above.

Filtration – Ceramic membrane filters can filter down to 3 microns. Thus, ceramic membranes deliver a much more thorough filtration process and remove bacteria, pathogens, as well as viruses. This ultimately provides cleaner water and a safer pool and spa environment.

Cleaning – Ceramic membranes also require cleaning. Yet, they need 70 % less water for backwash than a sand filter.

Chemicals – Ceramic membranes also require chemicals. Still, they require a reduced amount. In total, chemical consumption can be reduced by 30 %, and combined chlorine can be reduced by 40 %. This is both healthier, but it also secures low OPEX.

Footprint – As ceramic membranes are extremely compact, they require a reduced footprint. In fact, ceramic membranes only take up ¼ of the footprint than a sand filter. This means that you can either upgrade your capacity or you may even avoid a building extension once you need a new water filtration solution. The LiqTech pool solution fits through a standard doorway.

Lifetime – Ceramic membranes are produced of silicon carbide (SiC), the second hardest material globally, only beaten by diamonds. Click here to learn more about SiC. This means that ceramic membranes can go on and on, and you do not need to worry about changing or upgrading the solution.

Thus, ceramic membranes provide superior water quality, a healthier environment, and a low cost of ownership.