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Household Water Treatment and Safe Storage Factsheet: Source ...

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<strong>Household</strong> <strong>Water</strong> <strong>Treatment</strong> <strong>and</strong> <strong>Safe</strong> <strong>Storage</strong><br />

<strong>Factsheet</strong>: Nalgonda Technique<br />

Operation<br />

The Nalgonda Technique is a bucket system<br />

designed to be used on a household scale. It<br />

consists of a 40 litre plastic bucket with a tap<br />

located 5 cm above the bottom of the bucket.<br />

The process involves adding aluminum sulfate,<br />

lime <strong>and</strong> bleaching powder (optional) to the<br />

water in the bucket, followed by rapid mixing<br />

for 10 minutes. The water is then left to st<strong>and</strong><br />

for 1 hour. After coagulation/flocculation <strong>and</strong><br />

settling are complete, the treated water is<br />

poured out through the tap, <strong>and</strong> stored for the<br />

day's drinking in a clean bucket or safe storage<br />

container.<br />

The dose of alum to be added depends on the<br />

fluoride concentration <strong>and</strong> the alkalinity of the<br />

raw water (see table below from Lyengar,<br />

2002). The dose of lime to be added is 5% of<br />

the amount of alum (Lyengar, 2002).<br />

Lime is added to maintain the neutral pH in the<br />

treated water. Excess lime is used to help<br />

sludge settling as it helps form denser<br />

(heavier) flocs, which speeds up settling.<br />

This technique produces large quantities of<br />

sludge. The environmental impact of the<br />

hazardous sludge disposal should be<br />

considered.<br />

Moreover, care has to be taken to avoid the<br />

presence of aluminum in the treated water, as<br />

this may have adverse health effects. With this<br />

technique, the free residual aluminum content<br />

in the treated water can be as high as 2.01 to<br />

6.86 mg/L (Kailash et al., 1999). The maximum<br />

limit is 0.2 mg/L aluminum.<br />

Alum <strong>and</strong> Lime Dosage for the Nalgonda Technique<br />

(Credit: Lyengar, 2002)

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