Precipitation and Filtration - Plant principle
|Surface Characteristics||Highly Textured|
|NSF 61 Approved||Yes|
|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|
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