Oxidation and sedimentation: air oxidation, chemical oxidation

Relatively simple, low cost, but slow process (air)

Relatively simple and rapid process (chemical)

Oxidizes other impurities and kills microbes        

Processes remove only some of the arsenic

Used as pretreatment for other processes

Coagulation and filtration: alum coagulation, iron coagulation

Relatively low capital cost

Relatively simple in operation

Common chemicals available        

Not ideal for anion-rich water treatment (e.g. containing phosphates)

Produces toxic sludge

Low removal of As(III)

Preoxidation is required

Efficiencies may be inadequate to meet strict standards

Sorption techniques: activated alumina, iron-coated sand, ion exchange resin, other sorbents        

Relatively well known and commercially available

Well-defined technique

Many possibilities and scope for development

Not ideal for anion-rich water treatment (e.g. containing phosphates)

Produces arsenic-rich liquid and solid wastes

Replacement/regeneration is required

High-tech operation and maintenance

Relatively high cost

Membrane techniques: nanofiltration, reverse osmosis

Well-defined and high removal efficiency

No toxic solid wastes produced

Capable of removal of other contaminants        

High capital and running costs

High-tech operation and maintenance

Arsenic-rich rejected water is produced

Source: World Bank Technical Report, Volumn II: Arsenic Contamination of ground water in South and East Asian countries

After treating water for 45 days, As & Fe content went well below WHO guidelines. Fe content in the water is a boon to this technique.

The filters get clogged up with iron and needs frequent  recharging/re-activation. Often these filter beds are expensive.

With minimum maintenance, it can run for 10 years. But within that time, huge amount of arsenic will be trapped within the soil particles. Periodic oxidation will keep them trapped for decades.

They require frequent sludge removal & recharge every 4-5 month.

1 to 2 months after starting of the plant.

Instant startup.

$ 5 per month for 3000lt/day plant

100$ for 4 months limited use.

Village plumbers & electricians can maintain it.

Specially trained technicians & particular chemicals are required for maintenance.

Any person with basic training.

A caretaker may be needed.

Highly sustainable process. Source treatment.

No sustainability issue. Point Treatment.

The aquifer is being restored to its previous arsenic free condition.

Only the pumped up ground water is treated.

Minimum iron-arsenic precipitate generation for 3 months. After that, waste generation is nil.        

A cosiderable quantity of iron & arsenic sludge is produced every day. The waste management becomes a problem.