Background Information on Arsenic Contamination of Bangladesh Groundwater and Technology for its Removal

• Technology performance

  Amongst several requirements, the Government of Bangladesh, through BCSIR, has stipulated that to be certified for sale in Bangladesh, an arsenic removal technology needs to be able to remove arsenic to below 50 parts per billion (ppb) (the Government of Bangladesh arsenic limit for drinking water). In addition it must do so without adding new contaminants to the water that are above specified Government limits.

   

• Effect of water quality parameters on technology performance

  In addition to arsenic, groundwater in Bangladesh is also contaminated with iron, phosphate, manganese, silicate, etc, which can adversely affect technology performance. Phosphates present in Bangladesh groundwater can affect the life span of the media used to remove arsenic, as they can competitively bind to an adsorption media. Dissolved iron can oxidize to insoluble iron, precipitate out and occupy empty bed volume or fill the cracks and crevices, and cause channeling. The groundwater quality parameters need to be determined before and after treatment, as part of the process of assessing how these parameters influence technology performance. The water quality parameters of the well water that each technology is tested on are described in the verified performance claim for each technology. The water quality parameters for testing are selected in consultation with technology proponents. These parameters are based on technology performance claims and where warranted, existing test data. BCSIR, the verification authority, sets deployment conditions for an arsenic removal technology if and when the performance of that technology is verified and it is certified for sale in Bangladesh.

   

• Arsenic speciation in Bangladesh groundwater

  Arsenic dissolved in groundwater can exist as arsenite, As (III) and arsenate, As (V). Speciation of arsenic in a groundwater is important because an arsenic removal technology may be able to remove one species preferentially or have higher affinity for one species. A successful treatment technology for Bangladesh tube well (TW) water has to be able to reduce the total dissolved arsenic concentration to below the Bangladesh drinking water standard of 50 ppb arsenic.

  For the ETV-AM and BETV-SAM technology testing programs, the concentrations of both As (III) and As (V) were measured, following standard procedures, in samples of water collected from wells at which technologies were to be tested.

   

• Different types of Tube Wells (TWs) in Bangladesh
  
  
  • Shallow Tube Well (STW): < 150 metres
  • Deep Tube Well (DTW): > 150 metres

   

• Scheduling, testing and analysis:

  Events such as the monsoon season can have a significant effect on the timing of testing, even delaying testing.

  Another challenge consists of mobilizing sufficient numbers of laboratories capable of analyzing, with sufficient accuracy, the large number of influent and treated water samples that are collected during a technology field testing program.

  The ETV-AM Program and the BETV-SAM Project have met the above challenges through effective logistical planning and quality control.