{"id":10970,"date":"2023-09-27T09:00:00","date_gmt":"2023-09-27T09:00:00","guid":{"rendered":"https:\/\/keikengroup.com\/?p=10970"},"modified":"2026-10-21T18:26:32","modified_gmt":"2026-10-21T18:26:32","slug":"pumice-filter-medium-desalination","status":"publish","type":"post","link":"https:\/\/keikengroup.com\/en\/news\/pumice-filter-medium-desalination\/","title":{"rendered":"How pumice is used as a filter medium in water desalination"},"content":{"rendered":"

Many types of granular filter media are used to treat water ahead of reverse osmosis (RO) and seawater reverse osmosis (SWRO), including anthracite, sand and pumice for water filtration<\/a>. Anthracite used to be the usual choice, but pumice filter media offer many advantages today, and several large-scale plants have adopted it.<\/p>\n

Pumice filtration is used in the pretreatment of saline water before desalination, removing coarse particles ahead of the next treatment stage, usually reverse osmosis.<\/p>\n

RO and SWRO produce drinking water by forcing pretreated seawater against a semi-permeable membrane, producing pure water on one side and concentrated brine on the other. The brine is returned to the sea, while the drinking water is distributed for human use.<\/p>\n

Pumice for water filtration<\/h2>\n

Pumice<\/a> performs well because of its porous internal structure. It removes particles effectively, has low bed expansion requirements and relatively low maintenance and replacement costs. Being non-toxic, it does not affect the taste of the liquid it filters.<\/p>\n

It is also effective at removing biological and odorous compounds such as mercaptans, hydrogen sulphide and other volatile organics from wastewater. The quality of the pumice, along with how it is produced, processed and transported, has a significant influence on the quality of the final filter, and the material should be washed thoroughly before use.<\/p>\n

Mixed into soil, pumice improves its natural filtration capacity, a method used in low-impact green infrastructure projects to stop runoff from reaching and contaminating streams, lakes or groundwater.<\/p>\n

Advantages of pumice filter media<\/h2>\n

These are the advantages of pumice over conventional granular filter media:<\/p>\n

Lower pressure loss through the filter<\/h3>\n

The nature of pumice allows greater solids-holding capacity and higher particle loading, so filter runs are longer without affecting filtrate quality.<\/p>\n

Lower head loss<\/h3>\n

Depth filtration avoids the build-up of particles at the top of the filter bed and reduces head loss across the filter.<\/p>\n

Lower backwash rates<\/h3>\n

Because pumice is light (around 400 kg\/m\u00b3), lower backwash rates are needed to fully expand the filter bed. This reduces the operating costs of the filtration<\/a> plant, with backwash consumption around 30% lower than with traditional media.<\/p>\n

Greater bed expansion<\/h3>\n

The lightness of pumice gives greater bed expansion, again saving water and energy, reducing pumping requirements and allowing a smaller filtration plant.<\/p>\n

Wide temperature range<\/h3>\n

Pumice can be used at temperatures between 0 and 40 \u00b0C.<\/p>\n

Suitable for fresh and saline water<\/h3>\n

Pumice performs well in both saline and freshwater conditions.<\/p>\n

High filtrate quality<\/h3>\n

Pumice filtration can remove suspended solids down to 10 microns, giving very high-quality filtrate.<\/p>\n

Applications of pumice filter media<\/h2>\n

1. Desalination<\/h3>\n

Pumice is used to pretreat saline water before desalination, removing coarse particles ahead of the next stage, usually membrane filtration.<\/p>\n

2. Seawater reverse osmosis<\/h3>\n

SWRO and RO are desalination processes that produce drinking water by forcing pretreated seawater against a semi-permeable membrane.<\/p>\n

3. Drinking water filtration<\/h3>\n

Pumice is generally used in multimedia filters to produce safe, clean water for human consumption.<\/p>\n

Performance factors<\/h2>\n

Its porous, vesicular form supports filtration and gives a high particle-holding capacity:<\/p>\n