Table 1: Comparison of conventional processes for as removal [12, 13].

TechnologiesAdvantagesDisadvantages% Removal

Oxidation/precipitation

Air oxidationRelatively simple, low-cost but slow processMainly removes arsenic (V) and accelerate the oxidation process80%
In situ arsenic removal
Also oxidizes other inorganic and organic constituents in water
Chemical oxidationRelatively simple and fast processEfficient control of the pH and oxidation step is needed90%
Oxidizes other impurities and kills microbes
Minimum residual mass

Coagulation/coprecipitation

Alum coagulationRelatively low capital cost and simple in operationProduces toxic sludges90%
Durable powder chemicals are availableLow removal of arsenic
Effective over a wider range of pHPreoxidation may be required
Iron coagulationCommon chemicals are availableMedium removal of As (III)94.5%
More efficient than alum coagulation on weigh basisSedimentation and filtration needed
Lime softeningMost common, chemicals are available commerciallyReadjustment of pH is required91%

Sorption techniques

Activated aluminaRelatively well known and commercially availableNeeds replacement after 4 to 5 regeneration88%
Iron-coated sandExpected to be cheapYet to be standardized93%
No regeneration is requiredProduces toxic solid waste
Remove both As (III) and As (V)
Ion exchange resinWell-defined medium and capacityHigh cost87%
The process is less dependent on pH of waterRequires high tech operation and maintenance
Exclusive ion specific resin to remove arsenicRegeneration creates a sludge disposal problem
As (III) is difficult to remove
Life of resins

Membrane techniques

NanofiltrationWell-defined and high removal efficiencyVery high capital cost95%
Preconditioning
High water rejection
Reverse osmosisNo toxic solid waste is producedHigh tech operation and maintenance96%
ElectrodialysisCapable of removing other contaminantsToxic wastewater produced95%