Turbidex™ Filter Media: How It Works, Benefits and Applications

Turbidex™ is a natural mineral filtration media used to reduce suspended solids, sediment and turbidity in water. It is particularly useful in backwashing filtration systems where fine particle removal and relatively high service flow rates are required.

Compared with conventional filtration sand, Turbidex has a highly porous structure that enables it to retain smaller suspended particles throughout the filter bed.

It is widely used in private water supplies, commercial water treatment and industrial filtration applications.

What Is Turbidex Filter Media?

Turbidex is a naturally occurring mineral known as clinoptilolite, a type of aluminosilicate zeolite.

Unlike conventional filtration sand, which has relatively smooth granules, Turbidex has an angular, irregular surface containing numerous microscopic pores.

These physical characteristics provide a large surface area and allow suspended particles to be retained through a combination of:

• Mechanical straining: Particles become trapped between the media granules.

• Particle adhesion: Suspended material adheres to the irregular mineral surfaces.

• Deep-bed filtration: Particles are captured throughout the depth of the media rather than accumulating solely at the surface.

This deep-bed filtration capability helps Turbidex retain suspended solids while maintaining relatively low resistance to water flow.

How Fine Does Turbidex Filter?

One of the principal advantages of Turbidex is its ability to remove fine suspended particles.

Supplier literature commonly quotes filtration performance in the region of 3–5 microns, with some technical data describing typical particle reduction to approximately 5 microns or less under suitable operating conditions.

However, this should not be confused with the micron rating of a cartridge filter.

A 5-micron cartridge may have a specified nominal or absolute filtration efficiency, whereas Turbidex is a granular filter media whose performance depends on several factors:

• Filter bed depth

• Water flow rate through the vessel

• Particle size and characteristics

• Suspended solids loading

• Condition of the filter bed

• Backwashing frequency and effectiveness

For this reason, Turbidex should not be regarded as an absolute 3-micron or 5-micron barrier.

Where a specific particle-removal efficiency is essential, additional cartridge filtration or another appropriately rated filtration technology may be required.

Advantages of Turbidex Over Conventional Sand Filtration

1. Improved Fine Sediment Removal

Conventional filtration sand is widely used for removing larger suspended particles.

The porous structure of Turbidex allows it to retain finer material under suitable conditions, making it particularly useful where improved water clarity is required.

Applications include reducing:

• Fine sediment and silt

• Suspended mineral particles

• Particulate iron following suitable oxidation

• General turbidity caused by suspended solids

The actual removal efficiency will depend on the nature of the contamination and the filtration system design.

2. Higher Potential Service Flow Rates

Turbidex can operate at relatively high filtration velocities compared with many conventional sand filtration arrangements.

Its porous structure allows particles to penetrate further into the media bed, helping reduce rapid surface blockage and excessive pressure loss.

However, higher flow rates are not automatically better.

Operating at the maximum permitted flow may reduce the effectiveness of fine particle removal, particularly where incoming turbidity or suspended solids concentrations are high.

For applications requiring very low turbidity, a lower filtration velocity may be preferable.

3. Longer Filter Runs

Because suspended material can be retained throughout the filter bed, Turbidex may accommodate greater sediment loading before the pressure drop becomes excessive.

This can potentially provide longer periods between backwash cycles compared with some conventional filtration media.

The benefits depend on the incoming water quality and the amount of suspended material being removed.

4. Protection for Downstream Equipment

Effective sediment removal can help protect equipment installed further along the treatment system.

Examples include:

• Fine sediment cartridge filters

• Activated carbon filters

• Water softeners

• Reverse osmosis membranes

• UV disinfection systems

Reducing the suspended solids load may extend cartridge life and reduce the frequency of maintenance.

However, additional filtration stages may still be necessary, depending on the required water quality.

Turbidex Service Flow Rates and Backwashing

Correct flow rate selection is essential when designing a Turbidex filtration system.

The filtration vessel must be large enough to provide the required service flow without compromising treatment performance.

It must also receive sufficient water during backwashing to expand and clean the media bed.

Typical Operating Parameters

The following figures are examples from published supplier specifications:

Parameter	Typical guidance
Filtration performance	Approximately 3–5 microns under suitable conditions
Service filtration velocity	Approximately 28 m/hour in one published supplier specification
Backwash velocity	Approximately 36 m/hour in the same specification
Media bed depth	Typically around 600–900 mm, depending on system design
Freeboard	Approximately 50% of media bed depth
Support gravel	Required for systems designed around the relevant technical specification

These are indicative values, not universal operating limits. Published specifications vary, so the selected media, vessel and valve manufacturer's requirements should always be followed.

Why Backwash Flow Is Important

During normal filtration, water travels down through the media bed and suspended particles become trapped.

During backwashing, water flows upwards through the bed, expanding the media and carrying accumulated sediment to drain.

The backwash flow must be sufficient to clean the media effectively.

If the flow is too low:

• The media bed may not expand adequately.

• Trapped sediment may remain in the vessel.

• Filtration performance can gradually deteriorate.

• Pressure loss may increase.

Excessive backwash flow can also cause problems, including loss of media to drain.

An important consideration for borehole systems: The available backwash flow may be the limiting factor when selecting a filter vessel.

A borehole pump that provides sufficient water for normal household use will not necessarily deliver the higher flow required to backwash a large Turbidex filter.

The pump capacity, available pressure, vessel diameter, control valve and drain line must therefore be considered together.

Can Turbidex Remove Iron and Manganese?

Turbidex is primarily a sediment filtration media, rather than a dedicated dissolved iron or manganese removal media.

It can be effective at retaining particulate iron, such as ferric iron that has already been oxidised and precipitated from the water.

However, dissolved iron and manganese may pass through the filter without suitable pretreatment.

Where dissolved metals are present, additional processes may be necessary, including oxidation and appropriately designed filtration.

The most suitable treatment arrangement will depend on the water analysis, particularly pH, dissolved oxygen, iron, manganese and other relevant parameters.

Where Is Turbidex Commonly Used?

Turbidex can be suitable for a variety of applications.

Private Borehole and Well Water

Borehole supplies can contain fine sediment, suspended iron particles and turbidity.

A correctly sized Turbidex system can help remove suspended material before the water passes through other treatment equipment.

Surface Water Supplies

Streams, springs and other surface water sources can contain variable amounts of suspended solids.

Turbidex may form part of a multistage treatment system, although additional processes may be required where turbidity is particularly high or contains fine colloidal material.

Commercial and Industrial Filtration

Turbidex can be used where suspended solids reduction is required before further treatment or process use.

Applications may include industrial process water, agricultural supplies and water recycling systems.

Pretreatment for Reverse Osmosis

Reducing suspended solids before reverse osmosis can help protect downstream cartridge filters and membranes.

However, Turbidex alone does not guarantee water quality suitable for RO. Further pretreatment may be required depending on the feedwater analysis and membrane manufacturer's requirements.

What Does Turbidex Not Remove?

Although Turbidex is effective for many sediment filtration applications, it is important to understand its limitations.

It should not be relied upon to remove:

• Dissolved hardness minerals

• Dissolved salts or nitrates

• Dissolved iron and manganese without appropriate treatment

• Bacteria, viruses or other microbiological contamination

• Dissolved organic contaminants

• Arsenic or other dissolved contaminants requiring specialist treatment

Turbidex is not a disinfectant and does not make microbiologically contaminated water safe to drink.

For private drinking water supplies, a suitable water analysis should be used to determine whether additional treatment, such as UV disinfection, is required.

Does Turbidex Need Replacing?

Turbidex is a backwashing filter media and does not require chemical regeneration or salt.

Routine backwashing removes accumulated suspended solids and restores filtration performance.

The media can provide a long service life when correctly installed and maintained, although eventual replacement may be necessary.

Media life depends on operating conditions, including:

• Incoming water quality

• Sediment loading

• Backwash effectiveness

• Chemical fouling

• Physical degradation or media loss

Monitoring pressure loss and treated water quality can help identify when maintenance or media replacement may be necessary.

Is Turbidex Better Than Sand Filtration?

Turbidex can offer advantages over conventional sand where fine sediment removal and higher service flow rates are important.

However, it is not necessarily the best solution for every application.

Sand remains a reliable and economical filtration media for many types of suspended solids removal.

The most appropriate choice depends on the water quality, desired filtration performance, available space, operating flow and backwash capacity.

Existing sand filters should also be assessed before replacing the media with Turbidex, as support gravel, bed depth, freeboard and backwash arrangements may need to be altered.

Choosing the Right Turbidex Filtration System

At GAPS Water Treatment, we supply Turbidex filtration media and complete automatic backwashing filtration systems for domestic, commercial and industrial applications.

Correct sizing is essential, particularly where the system is installed on a private borehole or well supply.

When selecting a Turbidex filter, we recommend considering:

1. Water analysis: Including turbidity, iron, manganese and any other identified contaminants.

2. Required service flow: The normal and peak water demand.

3. Available backwash flow: The flow the pump can actually sustain at the required pressure.

4. Vessel size and media volume: To provide suitable filtration velocity and bed depth.

5. Additional treatment requirements: Such as fine cartridge filtration, iron removal or UV disinfection.

A properly designed Turbidex system can be an effective and economical way to reduce suspended solids and improve water clarity.

Browse our Turbidex Filtration Systems

If you are unsure which system is suitable, email your water analysis and available flow rate details to sales@gapswater.co.uk, and our team will be happy to advise.