Water Filtration Media

Techfil are able to supply filtration markets with both the traditional and modern medias. Included in our comprehensive range are: Pumice, Silica Sand, Anthracite, Garnet, Recycled Glass and Support Gravel.

Pumice

Pumice filtration media is a low-density media typically used in multi-media filters to enhance the capacity of the filter and to remove smaller micron particles. Pumice sits as the top layer in a multi-media filter and is widely used for pretreatment in desalination and seawater reverse osmosis plants (SWRO). Further detailed information on Pumice Filtration Media can be found below.

Silica Sand

Sand is an extremely effective filter media because of its ability to hold back coagulum or precipitates containing impurities. Filter sand size, angularity and hardness are the important filter sand characteristics to ensure proper filtering.

Anthracite

Anthracite is commonly used as a component of multi-media filters. Anthracite is a durable media with long life and a wide temperature range. A lower uniformity coefficient has less oversized and undersized particles resulting in a highly uniformed bed.

Garnet

Garnet is well known for its hardness and durability. It has a high specific gravity as well as its chemical and abrasive resistance makes garnet an ideal filter media. Garnet is typically used in multi-media filters as the sub-fill or bottom layers of the filter. Although its density requires high backwash rates combining fine mesh garnet with other media such as sand and anthracite significantly increases the filtration capacity of the filter.

Recycled Glass

Recycled Glass Sand has similar characteristics to natural sand. Glass filtration media generally removes finer particles from water than silica sand of an equivalent grade. Crushed glass filtration media is less likely to block or channel than silica sand.

Support Gravel

Support gravel, the lower strata of a filter bed, acts to support the filter medium. The support gravel must possess the necessary attributes of hardness and be rounded or non-angular. Correct gradation and sizing must be calculated to properly support the filter media.

PUMICE FILTRATION MEDIA – TECHFIL (EUROPE) LTD

Pumice is a granular filter media that  is a suitable alternative solution to sand for the treatment of potable water, sewage and industrial effluents.  The typical use of pumice for each of the various applications is shown in the table below.

Water Treatment and Waste Water Treatment Applications

Applications – Process Descriptions

1. Clarification

When added to the raw water, pumice increases the density of the flocs that result from the coagulation process and accelerates sedimentation.  Coagulation occurs when the raw water, either surface or bore hole, reacts with the chemical primary coagulant and the flocs then attach themselves to the pumice particles giving a ballast effect.  Settlement occurs under gravity and the clarified water is recovered from the upper part of the clarifier with the sludges being removed from the bottom.  This process is suited to potable water, sewage and industrial effluent treatment.

2. Filtration

Pumice is a versatile filtration media used in the treatment of water, sewage and industrial effluents.  It is used in mono, dual and multi media applications in both pressure and rapid gravity installations.

Being of a low bulk density, pumice provides a valid and cost effective alternative to anthracite in dual or multi media media filters.  A dual media filter traditionally consists of an upper layer of pumice above a layer of fine sand.  Pumice traps most of the large floc particles whilst the finer sand in the lower layer removes the remaining impurities with small particle sizes.  The voidage of pumice has an average value of 0.51 which allows for an increased retention of suspended solids in the filter bed and a lower headloss.

Being light in weight, pumice also is able to reduce the operating costs of the filtration plant, be it a rapid gravity or pressure filter installation due to the significantly lower (typically 30% lower) backwash water consumption requirements.

Advantages include:

- Savings in energy and water during filter backwash

- Lower bulk density

- Reduced capital cost

3. Aerobic Treatment

Pumice, in addition to its ability to assist clarification, is an essential addition in the Sequencing Batch Reactor (SBR) process where inadequate time has been allowed for phase separation to take place.  The addition of pumice just prior to the settlement stage enhances the settlement of the sludge allowing the plant to perform as initially designed.

4. Anaerobic Treatment

Where effluents are highly polluted with organic pollutants, the treatment that is finding increasing application is anaerobic treatment or methanisation where the pollutants are treated in the absence of air and methane is generated.  Pumice acts as a biomass support in this process, typically employed in the treatment of wastes from breweries, sugar processing, paper manufacturing, daries etc.  The concentration of biomass is significantly increased, growing in ideal conditions on the porous surface of the pumice and resulting in reduced retention times and higher methane gas generation.

Advantages include: For anaerobic biomass within methanisation reactors, eg. CPB-concentrated proteins from sugar beet, pumice offers:

- Large surface area

- Favourable surface conditions for bacterial growth

- Increased concentration of biomass

- Reduced retention time

- Increased methane generation

5. Sludge Treatment

Sludges derived from the biological treatment of sewage or industrial effluents require further treatment processes to allow their safe disposal.  These processes include de-watering where, by the addition of pumice into the mixer prior to the de-watering stage, a superior filter cake is produced.  This cake does not blind the cloth, allows greater filter runs with improved filtrate quality and produces a cake that can be used for agricultural or horticultural purposes.

Physical Characteristics

Certification

Pumice, as supplied by Techfil (Europe) Limited, is approved by the Drinking Water Inspectorate for potable water applications and complies with BS EN 12906:1999 “Products used for the treatment of water intended for human consumption – Pumice”.

Further Information and Technical Support

For further information and case studies please contact us