Lenntech Water treatment & purification Lenntech Water treatment & purification

Precipitation and Filtration - Plant principle

Material Ceramic
Color Taupe, Brown/Gray
Surface Characteristics Highly Textured
NSF 61 Approved Yes
Shape Spherical
Diameter 0.17 - 1.4 mm
Mesh Size 80 - 14 Mesh
Coefficient of Uniformity 1.1 - 1.5
Bulk Density 28 - 75 (lbs/ft²)
Specific Gravity 0.6 - 2.7
Moisture Absorption < 0.5% by weight
Acid Solubillity (%) 0.7 - 2.7
Surface Area (m²/g) 0.592 - 1.08
Krumblen Sphericity 0.9
Krumblen Roundness 0.9

The easiest and most effective way of removing Arsenic is by adding ferric chloride (FeCl3) to the water. The Iron (III) precipitates with the Arsenate under the form of FeAsO4. This compound forms particles of 50-60 µm diameter size, which can easily be filtered out. Furthermore, the Cl- added oxidize the arsenite to arsenate, which allow precipitation of arsenite to arsenate.

This way arsenic can be removed nearly totally from the water. Filtration media is macrolite, a ceramic filtering media with strong affinity to arsenic. From experience, Arsenic concentration drops below 2 µg/L, far below the WHO guideline. In some cases, air is also added with the ferric chloride to enhance oxidation of Arsenite.

Low energy consumption, low maintenance

    Figure 2 : Macrolite filtration module, with mechanical controlled backwash valve

Compared to other methods, such as reverse osmosis, this method is rather low in energy consumption. No need for high pressure pump, only a dosing pump is required and, if needed, a circulation pump. The backwash of the filter media is completely automatic and mechanical: no energy, no control cabinet needed.

Maintenance is easy: refilling the dosing tank with FeCl3. Valves should be cleaned twice a year with some citric acid. Chemical required are not harmful nor expensive and available all around the world.

 Figure 3: Scheme of the arsenic removal plant

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