Pumice Filtration Media

Pumice Filtration Media is used as an alternative to anthracite and sand in the treatment of potable water treatments, seawater reverse osmosis (SWRO), desalination and waste water treatments. Pumice filtration media is increasingly being specified for contracts involving pre-treatment prior to reverse osmosis (RO) and desalination, in both new and refurbished plants particularly in the Middle East, India and the US.

 

The typical use of pumice for each of the various applications is shown in the table below.

 

 

Applications for Pumice in Water and Wastewater Treatments

 

Treatment Process

Type of

water treated

Water Use

Filtration Type

Pumice

Function

Advantages

 

Filtration

 

Pre-treatment

Filtration

 

Surface

 

Ground Water

 

Seawater

(SWRO)

 

Potable

 

Industrial

 

Rapid Gravity

Filtration

 

Pressure Filtration

 

Filtration Media

 

  • Lower energy consumption
  • Lower backwash requirements
  • Improved filtration rates
  • Better bed expansion
  • Low cost filter refurbishment
  • Reduced capex on new plant

 

 

Biological

Aerobic

 

Sewage

 

Industrial

Effluents

 

SAF

 

BAFF

 

Trickling Filter

 

 

Deep Bed

 

Inert Biomass Support Media

 

  • Increased surface area
  • Reduced footprint
  • Rapid biomass growth

 

 

Biological

Anaerobic

 

Breweries

 

Paper Mills

 

 

Anaerobic

Bio-reactors

 

Methanisation

Reactor

 

Biomass Support Media

 

  • Larger surface area
  • Reduced surplus sludges
  • Speeds process

 

 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

 

The use of our pumice filtration media in water filtration applications is increasing worldwide. Pumice filtration media is now recommended in potable water treatments, seawater reverse osmosis (SWRO), desalination and waste water treatments. Pumice filtration media is increasingly being specified for contracts involving pre-treatment prior to SWRO and desalination, in both new and refurbished plants. This is due to its extremely high particulate removal, low density and its versatility; it can be used in mono and multi-media filters in both pressure and rapid gravity filter designs.

 

Pumice Water Filtration

 

 
All our pumice filtration media has British Standard approval (BS EN 12906-1999) – Products used for treatment of water intended for human consumption and UK Drinking Water Inspectorate approval.

 

Additionally our pumice filtration media is NSF-61 approved and meets all the chemical and physical testing requirements for AWWA B-100 and DIN EN 12906.

 

We are currently in the process of seeking full SWCC (Saline Water Conversion Corporation) approval to further expand our Middle East Division.

 

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

Grades No.3 No.5 No.6 No.8
Applications Inert Support Filter Media Filter Media Filter Media
Typical Properties        
Size – mm 0.2 – 0.5 0.8 – 1.3 1.2 – 2.4 1.4 – 3.0
Silica Content – SiO2 % 71.75 71.75 71.75 71.75
Bulk Density – kg/cu.m 460 440 425 410
True Density – kg/cu.m 2400 2400 2400 2400
Moisture Content Dry Dry Dry Dry
Hardness – Mohs 6 6 6 6

 

Certification

 

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

 

Additionally all our pumice filtration media is NSF-61 approved and meets all the chemical and physical testing requirements for AWWA B-100 and DIN EN 12906.

 

Further Information and Technical Support

 

For further information and case studies please contact us at: water@techfil.co.uk

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