Technology

A proven filtration technology, inspired by nature.

The KLS Filter relies on two complementary technologies: gravel filtration and slow sand filtration. Combined in a compact, prefabricated polyethylene structure, they produce high-quality drinking water without electricity or chemical reagents. This process, one of the oldest and best-documented in the world, has proven its effectiveness in over 30 installations in Switzerland and internationally since 2002.

Process

How does the KLS Filter work?

Five successive, entirely gravity-based steps transform raw water into drinking water meeting Swiss standards — without electricity, without chemistry.

1

Raw water inlet

Raw water is fed into the filter by free flow, without pumping. It is directed to the bottom of the first compartment. The overflow defines the water level throughout the filter and regulates the treatment flow.

Water enters the filter naturally, without energy, without pressure. Gravity does all the work.

2

Upward-flow gravel filtration

Water rises from bottom to top through a gravel bed of different grain sizes. This upward filtration eliminates the vast majority of suspended solids and greatly reduces the turbidity of the raw water. The flow direction promotes uniform load distribution and facilitates periodic backwashing.

First line of protection: the different gravel layers retain particles and clarify the raw water thoroughly.

3

Slow sand filtration with quartz sand

Pre-filtered water overflows into the slow sand compartment, where it flows by gravity from top to bottom through a quartz sand bed. This filter medium progressively develops an active biofilm (schmutzdecke) on the surface, which plays a decisive role in eliminating pathogenic organisms.

Slow sand reproduces the filtration mechanism of groundwater. Simple, natural, remarkably effective.

4

Slow bauxite filtration

Water passes through a section of bauxite, a natural aluminium silicate with high adsorption properties. This filter medium has a surface charge favourable to the retention of pathogenic microorganisms and particles, including from the very first volumes filtered, before the biological maturation of the filter. This bauxite filtration technology has been patented by RWB Groupe SA.

Bauxite is the finishing touch that guarantees drinking water from the moment of commissioning, without a cumbersome run-in period.

5

Treated water — outlet

The outlet valve is manually adjusted to the desired flow. This target flow determines the sizing of each compartment, respecting the optimal filtration speeds for each medium. Treated water can be directly distributed or stored in a drinking water reservoir.

A simple adjustment, compliant water. The filter is sized for your needs, not the other way around.

Performance

Measurable results, documented over 20 years.

< 1 NTU Turbidity

Below 1 NTU at filter outlet, regardless of the target flow. The filter has already been tested on raw water with turbidity above 1000 NTU.

100 % Bacteria

Complete elimination (100%) of pathogenic bacteria under normal operating conditions.

200–120'000 L/j Flow range

From 200 to 120,000 litres per day depending on model and configuration.

OFCO Compliance

Treatment compliant with the requirements of the Ordinance on Foodstuffs and Common Objects for drinking water.

Maintenance

KLS Filter maintenance is very simple, infrequent and achievable without tools or specialised training.

Gravel filter — gravity backwash

By opening the drain valve located under the gravel compartment, water flows rapidly downward. The downward flow velocity is sufficient to rinse the gravel and flush out particles accumulated on the surface and in the mass. No mechanical intervention required. Recommended frequency: 3 to 6 times per year.

Open a valve, wait a few minutes. The filter cleans itself.

Sand and bauxite filter — surface scraping

After several months of operation, the first 2 to 5 centimetres of the filter bed gradually clog. Renewal involves manually removing this surface layer with a shovel or scraper. No complete media replacement is necessary. Recommended frequency: once a year.

A 2 to 5 cm layer to remove once a year. That's all it takes to keep the filter at maximum performance.

Durability

A design built to last.

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No electricity

The system operates entirely by gravity. No electrical connection is required, making it usable in off-grid areas.

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No chemicals

No chemical reagents are used in the treatment process. The filter generates no chemical effluents.

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Durable materials

The cylindrical and modular structures are made of high-density polyethylene (HDPE), a lightweight, durable, recyclable material resistant to alpine weather conditions.

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Longevity

The first installations completed in are still in service, demonstrating a service life of over 20 years without structural replacement.

Ready to discover the right model for your project?

The KLS Filter range covers all needs, from 200 to 120,000 litres per day. Compare models and find the one that fits your context.

Discover the product range →
FAQ

Frequently Asked Questions

How does the KLS Filter slow filtration work?

The KLS Filter uses 3 to 4 gravity-fed filtration stages: ascending gravel filter, slow quartz sand filter (with biological schmutzdecke formation), and optionally a bauxite filter. Water flows through these layers by gravity alone, with no pump or energy required.

Does the KLS Filter require electricity or chemicals?

No. The system operates entirely by gravity, without electricity and without any chemicals. This is one of its main advantages for remote sites, alpine pastures and areas without a power grid.

What water quality results are achieved?

The treatment ensures a resulting turbidity of less than 1 NTU and complete elimination of pathogenic bacteria. The water produced meets Swiss drinking water standards, provided it is not contaminated by chemical agents (micropollutants).

How long does a KLS Filter last?

KLS Filter installations are designed to last several decades. The first installation dates from 2002 and is still in service. Filter media (gravel, sand, bauxite) are replaced periodically without dismantling the tank.

What maintenance is required?

Maintenance is minimal and can be carried out without specialist technicians: periodic cleaning of the sand layers depending on the suspended matter load of the source water.