Insitu vs Other filtration techniques

Comparison of Main Arsenic Removal Technologies
Technology	Advantage	Disadvantage
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

In-situ treatment Vs Filtration Techniques
In-situ Technique	Point of Difference	Filter techniques
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.	Efficiency	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.	Longivity	They require frequent sludge removal & recharge every 4-5 month.
1 to 2 months after starting of the plant.	Start-up time	Instant startup.
$ 5 per month for 3000lt/day plant	Maintenance Cost	100$ for 4 months limited use.
Village plumbers & electricians can maintain it.	Expertise to maintain	Specially trained technicians & particular chemicals are required for maintenance.
Any person with basic training.	Operation	A caretaker may be needed.
Highly sustainable process. Source treatment.	Sustainability	No sustainability issue. Point Treatment.
The aquifer is being restored to its previous arsenic free condition.	Natural resource restoration	Only the pumped up ground water is treated.
Minimum iron-arsenic precipitate generation for 3 months. After that, waste generation is nil.	Waste generation	A cosiderable quantity of iron & arsenic sludge is produced every day. The waste management becomes a problem.