WITS WATER FILTER, Arsenic Removal Matrix

A Simple, Low Cost, And Effective Arsenic Removal Filter

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Preliminary
(The Useful Bit)

Introduction
(The Technical Bit)

Chemistry and general considerations
(The Science Bit)

Tests and performance
(The Boring Bit)

Operation and maintenance
(The Interesting Bit)

Future outlook
(The Last Bit)

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Operation and maintenance (The Interesting Bit)

The WITS filter only requires maintenance at approximately 12 moth intervals this is when the apparent flow rate decreases. Experiments show that flow rate may decrease 20–30% per year if groundwater has high iron (>5 mg/L) due to formation and deposition of natural HFO in sand layers. The sand layers (about an inch thick) can be removed, washed and reused or replaced with new sand. The presence of soluble iron and formation of HFO precipitate is also a common problem with other filtration technologies.

Water flow disturbance could also occur through accumulation of sand/ HFO deposits into the tap nozzle, which can be removed by detaching and cleaning the tap in a flowing water stream. Pouring 5 L hot water in each bucket every month has shown to kill pathogenic bacteria and eliminate coli form count. This recommended protocol can be followed once a week where coliform counts are high. We have no records of diarrhoea or other water borne diseases from drinking WITS-filtered water. It appears that the WITS filtration system does not foster pathogenic bacteria on its own.

Except for basic training in hygiene, no special skill is required to maintain the filter. The maintenance process requires about 20–30 mins. Because the WITS filter has no breakthrough, the active media does not require any processing (backwashing, regeneration etc). The filter will produce potable water for at least 1 year. The actual filter life span is determined by the water through put. Except for manufacturing defects, mechanical damage due to mishandling, transportation, and natural disasters (flooding), none of the filters showed MCL breakthrough to this date.