Household Water Treatment and Safe Storage Factsheet: Source ...
Household Water Treatment and Safe Storage Factsheet: Source ...
Household Water Treatment and Safe Storage Factsheet: Source ...
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<strong>Household</strong> <strong>Water</strong> <strong>Treatment</strong> for Arsenic Removal<br />
Fact Sheet: Coagulation-Flocculation<br />
Bucket <strong>Treatment</strong> Unit (BTU)<br />
Potential <strong>Treatment</strong> Capacity<br />
Very Effective For: Somewhat Effective For: Not Effective For:<br />
Most pathogens<br />
Turbidity<br />
Taste, odour, colour<br />
Arsenic<br />
Chemicals<br />
What Is Bucket <strong>Treatment</strong> Unit (BTU)?<br />
The Bucket <strong>Treatment</strong> Unit is a two bucket filter<br />
developed within the DPHE-Danida project in<br />
Bangladesh. It uses oxidation,<br />
coagulation/flocculation <strong>and</strong> filtration to remove<br />
arsenic. The BTU can be constructed from locally<br />
available materials.<br />
How Does It Remove Arsenic?<br />
Arsenic is removed by:<br />
The mixture is then allowed to settle for 1 to 4 hours<br />
or longer (see manufacturer’s recommendation).<br />
Then the upper tap is turned on so that the water<br />
can pass through a cloth filter <strong>and</strong> a s<strong>and</strong> filter in<br />
the lower bucket.<br />
The effectiveness of the DPHE-Danida Bucket<br />
<strong>Treatment</strong> Unit decreases if inlet water arsenic<br />
concentrations are above 0.12 mg/L (Sutherl<strong>and</strong> et<br />
al., 2001).<br />
<br />
<br />
<br />
<br />
<br />
<br />
Oxidation (loss of electrons) of the arsenic to<br />
change its form from As(III) to As(V), by<br />
applying an oxidizing agent (e.g. potassium<br />
permanganate*)<br />
Coagulation <strong>and</strong> flocculation using alum or<br />
aluminum sulphate, forming flocs (large<br />
combined particles)<br />
Adsorption (sticking) of arsenic onto flocs<br />
Sedimentation<br />
Straining through a cloth<br />
S<strong>and</strong> filtration<br />
*Coagulation/flocculation can also be achieved by using<br />
iron chloride or iron sulfate.<br />
Operation<br />
The upper bucket is filled with inlet water, with the<br />
tap closed. The required chemicals are added <strong>and</strong><br />
the water is stirred with a wooden spoon (provided<br />
with the unit).<br />
Recommended chemical doses are (Tanhura et al.,<br />
no date):<br />
<br />
<br />
200 mg/L aluminum sulphate<br />
2 mg/L of potassium permanganate<br />
Key Information<br />
<strong>Treatment</strong><br />
Efficiency<br />
~ 60% arsenic<br />
removal<br />
Bucket <strong>Treatment</strong> Unit<br />
(Credit: T. Ngai)<br />
Output<br />
20 litres/hour<br />
Cost<br />
$10 capital cost<br />
$15-25 chemical<br />
cost/year