|
Technologies | Advantages | Disadvantages | % Removal |
|
Oxidation/precipitation | | | |
|
Air oxidation | Relatively simple, low-cost but slow process | Mainly removes arsenic (V) and accelerate the oxidation process | 80% |
In situ arsenic removal | |
Also oxidizes other inorganic and organic constituents in water | |
Chemical oxidation | Relatively simple and fast process | Efficient control of the pH and oxidation step is needed | 90% |
Oxidizes other impurities and kills microbes | |
Minimum residual mass | |
|
Coagulation/coprecipitation | | | |
|
Alum coagulation | Relatively low capital cost and simple in operation | Produces toxic sludges | 90% |
Durable powder chemicals are available | Low removal of arsenic |
Effective over a wider range of pH | Preoxidation may be required |
Iron coagulation | Common chemicals are available | Medium removal of As (III) | 94.5% |
More efficient than alum coagulation on weigh basis | Sedimentation and filtration needed |
Lime softening | Most common, chemicals are available commercially | Readjustment of pH is required | 91% |
|
Sorption techniques | | | |
|
Activated alumina | Relatively well known and commercially available | Needs replacement after 4 to 5 regeneration | 88% |
Iron-coated sand | Expected to be cheap | Yet to be standardized | 93% |
No regeneration is required | Produces toxic solid waste |
Remove both As (III) and As (V) | |
Ion exchange resin | Well-defined medium and capacity | High cost | 87% |
The process is less dependent on pH of water | Requires high tech operation and maintenance |
Exclusive ion specific resin to remove arsenic | Regeneration creates a sludge disposal problem |
| As (III) is difficult to remove |
| Life of resins |
|
Membrane techniques | | | |
|
Nanofiltration | Well-defined and high removal efficiency | Very high capital cost | 95% |
| Preconditioning |
| High water rejection |
Reverse osmosis | No toxic solid waste is produced | High tech operation and maintenance | 96% |
Electrodialysis | Capable of removing other contaminants | Toxic wastewater produced | 95% |
|