FILTER SAND PRODUCTS AND MEDIA
PRODUCT AVAILABLE IN 25L AND 1m³ BAGS
14/25 Filter Sand (0.6-1.2mm)
7/14 Filter Sand (1.2-2mm)
Pea Metal 6-10mm (Nominal)
14/25 Silicon Sponge 0.6-1.2mm
7/14 Silicon Sponge 1.2-2mm
2/4 Gravel-Support Media
Drainage Gravel – 8-20mm
WATER FILTRATION PRODUCTS
We process a wide range of products for water filtration and waste water needs.
Our specially designed sand and pumice dryers allows us to sterilize our product so it’s free of germs and seeds. Once our sand and pumice has been thermally treated, it is transferred for size grading and quality checks then packed for end use.
Our system allows us to modify our product and packaging on request to suit individual needs.
For more detailed information on these and other products, or if you wish to discuss your filtering requirements, please contact us and our friendly staff will be happy to help.
MODIFIED PUMICE FOR WATER FILTRATION
The demand for treated water is ever increasing both in terms of volumes required and water quality. Apart from domestic and municipal uses, large amounts of treated water are needed for agriculture, food processing and specialized industrial uses.
Of the various Water Treatment processes involved in converting natural water into the everyday commodity that many take for granted, filtration is one of the most critical. Efficient filtration is essential to produce water of high clarity and low suspended solids. Filtration and microfiltration are valuable defences against water borne organisms such as Giardia and Cryptosporidium, providing a means of removing these organisms without recourse to chemicals. With an appropriate choice of media, filtration can also guard against carry over of water treatment chemicals such as the alum and polyelectrolyte used in flocculation. Residual aluminium is of particular concern if present at elevated levels in drinking water or water intended for food processing. Any residual dissolved or suspended mineral or organic constituent will also place an added burden on subsequent processing such as adsorption treatment and demineralisation. Pumice, graded and thermally modified to increase its’ specific gravity, is a material that is finding important applications and filtration technology to assist in filtration and to minimise residual aluminium.
Pumice is a natural vesicular aluminium silicate glass formed as a result of volcanic activity. It is extremely porous and as a consequence has a surface area of approximately 5 M2 to g^1. The surface charge of pumice arises from two types of surface site. 70% of pumice consists of silica with silicon atoms joined by bridges through oxygen atoms. At the surface, silicon atoms may not be fully coordinated and tend to react with water to form surface hydroxyl groups. These groups function as protionic acids. Dissociation of protons from such groups results in the surface becoming negatively charged and acquiring cation exchange properties. In addition, further cation exchange sites are possible through the introduction of negative charge by the replacement of tetrahedral silicon atoms by aluminium. The negative charge and large surface area make pumice particularly useful for the removal of positively charged flocs, for example those carried over from alum flocculation.
AN ALTERNATIVE TO ANTHRACITE
While anthracite generally performs satisfactorily in dual media filters it has some drawbacks. It’s specific gravity is less than ideal and being soft is significantly abraded during back-flushing. Pumice, graded and thermally modified to produce material commercially available as Silicon Sponge, has all the properties necessary to replace anthracite. It has surface characteristics that make it superior to anthracite in some applications.
Modified pumice is an indigenous New Zealand material that can be used to replace anthracite in Dual Media Filtration and has been shown to be particularly effective when used in conjunction with PCDM Filtration technology. Modified pumice has the useful advantages of being cheaper, more resistant to abrasion and more active in removing residual aluminium. Modified pumice has been installed in a number of filters throughout New Zealand. These filters have performed well, particularly with respect to flow characteristics, turbidity of the filtered water and residual aluminium.