Water Clarification and Media Filtration

PROVEN AND COST-EFFECTIVE TREATMENT METHODS FOR TYPICAL WATER POLLUTANTS: TURBIDITY, IRON, MANGANESE, ARSENIC, PESTICIDES, ETC..

Media filtration is a conventional and cost-effective separation process for the removal of suspended matter by passing the water through a porous bed of granular materials.

This filtration method is widely used for applications such as turbidity removal, metals and toxic elements removal (Iron (Fe), Manganese (Mn), Aluminium (Al),  Arsenic (As)) or pesticides and odours removal.  It is also used commonly used for remineralization purposes after reverse osmosis treatments.

Media filtration is also often used as a pre-treatment to more complex solutions like reverse osmosis or ultrafiltration as RO and UF membranes are very sensitive to turbidity or metals.

  • Turbidity
  • Iron / Manganese
  • Arsenic
  • Dechlorination / organics / Pesticides
  • Remineralization

Turbidity reduction with anthracite, sand and garnet media filters

Data Sheet Media Filters for Turbidity Reduction
Feed Flow
5 - 200 m3/h
Raw Water Turbidity
< 10 NTU
If turbidity > 10 NTU floculation + sedimentation is recommended
Filtration Media
Anthracite (1.5mm ES)
Sand (0.8mm ES)
Garnet (0.3mm ES)
Filtration Rate
8 - 12 m/h (m3/h per m2)
Working Pressure
2 bar - 8 bar
Filter Diameter
0.3 - 3 m
Filter Height
1.1 - 3 m
Vessel Materials
FRP filament winding
Backwash options
Manual
Automatic (Timer)
Automatic (diff Pressure)

Turbidity along with Iron and Manganese are the most common quality issues found in water supplies. The recommended limit of 1 NTU for turbidity is the approximate value above which disinfection is not effective.

Conventional media filtration with anthracite, sand and garnet is the most common filtration system for turbidity reduction. Typically used with any surface or bore water, this filtration method responds well to changes in the source water quality.

When turbidity > 10 NTU (up to 100 NTU),  flocculation and sedimentation or a two-stage filtration is recommended.

Contact us for a custom made design.

Iron and Manganese reduction

Data Sheet Fe & Mn reduction by media filtration
Feed Flow
5 - 200 m3/h
Raw Water Turbidity
< 1 NTU
If turbidity > 1 NTU it is recommended to use a pre-filtration
Filtration Media
GAC + Sand
DMI-65
Greensand
Filtration Rate
8 - 12 m/h (m3/h per m2)
Working Pressure
2 bar - 8 bar
Filter Diameter
0.3 - 3 m
Filter Height
1.1 - 3 m
Vessel Materials
FRP filament winding
Backwash options
Manual
Automatic (Timer)
Automatic (diff Pressure)

Iron and Manganese along with turbidity are the most common quality issues in water supplies. The recommended limits of 0.3 mg/l for Fe and 0.05 mg/l for Mn are the approximate concentrations above which iron and Manganese cause problems like taste/odour, laundry stains, and blockages.

Iron can be found in water as dissolved Fe2+ (ferrous) or as precipitate Fe3+ (ferric).  In the same way, Manganese can be found dissolved as Mn2+ or insoluble as Mn3+ or Mn4+.

Dissolved Iron and Manganese cannot be filtered easily and the common practice is to oxidise all Fe2+ and Mn2+ to Fe3+ and Mn3+ and then remove the precipitate flocks by filtration.

Fe and Mn can be oxidised using aeration, chlorine dosing or any other oxidation agent but reaction times are, in general, high (5 to 30 min). These reaction times can be accelerated by means of a catalytic media like Greensand or DMI-65, with which Fe and Mn are oxidised and precipitated by contact with the catalytic media.

Based on the water analysis, lay-out and other factors we recommend the next two alternatives:

Pre-oxitation and standard media filtration

Iron and Manganese are oxidised for a minimum of 30 min and then solids are removed on a non specialised filter, typically in dual-media with 500 mm of 1.1 mm GAC and 500 mm of 0.6 mm filter sand.  Filtration rate shall be a maximum of 12m/h.

 

In-line oxidation and filtration with catalytic media

An oxidising agent is dosed in line and Greensand or DMI-65 are used as catalytic and filtrating media.

 

Arsenic removal

Presence As (3+, 5+)
Colloidal Form
Coagulation (Ferric Hydroxide) + filtration
Organic form
Oxidation + coagulation
GAC absorption
Dissolved
Reverse Osmosis

Arsenic is usually present in natural waters in low concentrations (<0.001 mg/l) , however in groundwater, the concentration can be significantly elevated, specially in drainage from water-filled abandoned mines. The recommended limit of 0.01 mg/l for As is the approximate concentrations above which it is considered to be toxic.

Based on how Arsenic is found in the water, a number of options are available for its removal:

Colloidal form:

  • Coagulation (Ferric Hydroxide precipitation) plus conventional filtration

Organic form:

  • Oxidation of the organic matter and subsequent coagulation.
  • Absorption through GAC

Dissolved:

  • Reverse Osmosis
Contact us for a complete assessment

Dechlorination and organics/pesticides removal by GAC

Data Sheet GAC (granular activated carbon) filtration
Feed Flow
5 - 200 m3/h
Raw Water Turbidity
< 10 NTU
If turbidity > 10 NTU floculation + sedimentation is recommended
EBCT
1- 10 min
Filtration Rate
10 - 20 m/h (m3/h per m2)
Working Pressure
2 bar - 8 bar
Filter Diameter
0.3 - 3 m
Filter Height
1.1 - 3 m
Vessel Materials
FRP filament winding
Backwash options
Manual
Automatic (Timer)
Automatic (diff Pressure)

Granular activated carbon (GAC) has a strong attraction for organic compounds and other non-polar contaminants in water and adsorbs them onto the carbon surface.

Typical uses:

Dechlorination: GAC has the ability to reduce chlorine from an oxidizer (NaOCl) to a salt (NaCl) by taking away the reactive oxygen.

Removal of taste, odour, colour, organics etc: GAC (granular activated carbon) is widely used to reduce undesirable taste, odour and colour and to improve the safety of drinking water by also effectively removing common disinfection byproducts (THMs), organic contaminants like chlorinated solvents and other industrial pollutants, pesticides

Removal of selected heavy metals:  such as lead and mercury.

Radon removal: GAC has been shown to achieve greater than 90% reduction of radon from treated drinking water.  It is recommended though that media be replaced at least once a year.

 

Water remineralisation and PH correction with calcite filtration

Data Sheet Water hardness and PH correction by Calcite filtering
Feed Flow
5 - 200 m3/h
Filtration Media
Calcite (limestone contactor)
Filtration Rate
10 - 15 m/h (m3/h per m2)
Working Pressure
2 bar - 8 bar
Filter Diameter
0.3 - 3 m
Filter Height
1.1 - 3 m
Vessel Materials
FRP filament winding
Backwash options
Manual
Automatic (Timer)
Automatic (diff Pressure)

The optimum water composition from a PH and hardness point of view is that with a PH between 7.5 and 8.5 and hardness between 60 and 200 mg/l as CaCO3. If water is too soft (too low calcium and Magnesium composition) it can be very corrosive and it is recommended to restore some hardness.

Calcite (calcium carbonate media) provides a controlled PH correction to water reaching a non-corrosive equilibrium. It does not overcorrect under normal conditions if overexposed.

As the Calcite’s calcium carbonate neutralizes the water, it will increase the hardness by increasing the dissolved Calcium and Bicarbonate of the water.

Water remineralisation is strongly recommended for reverse osmosis permeate when it is for human use.

 

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*(1) All data for information only and subject to change based on actual water analysis and final design parameters

Media Filtration

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Contact Info

  • sales@alscore.com.au
  • 1300-74-20-10
  • Level 5, 203-233 New South Head Rd, Edgecliff, NSW 2027