Environmental Engineering Reference
In-Depth Information
Reports from Sri Lanka have inferred that with 300 g charcoal (mainly to remove color and
odor) and 1 kg bone char, an ICOH ilter can treat on an average 450 L of water containing
5 mg/L luoride at a low rate of 4 L/h. Regeneration of spent bone char is not recom-
mended for these household units. Instead, it should be replaced with fresh material com-
mercially available in local shops.
17.7.8.4.3 Domestic Deluoridation Units Developed by IIT (Indian
Institute of Technology) Kanpur (Iyenger, 2005)
Extensive studies are reported from IIT Kanpur on AA-based and other adsorbents for
deluoridation of water. The unit consisted of two chambers made of suitable materials
such as stainless steel (SS), copolymer plastic, etc. The upper chamber was itted with a
microilter. This has an oriice at the bottom to give a controlled low rate of about 12 L/h
for domestic application. This chamber was charged with 3 kg of AA and the depth was
about 17 cm. A perforated plate made of SS was placed on the top of the AA bed to facili-
tate uniform distribution of raw water onto the adsorption bed. A lower chamber was
provided as a treated water storage with a tap to withdraw the treated water. If desired, a
lower chamber can be replaced with an earthen pot in rural areas, which not only lowers
the initial cost but also keeps water cold in summer months. The ilter was found to be
quite user-friendly even considering the rural population. Fluoride-containing raw water
is illed in the upper chamber. Water percolates through the AA adsorption bed, where
luoride is adsorbed onto the adsorbent. Treated water, collected in the lower chamber, can
be withdrawn as needed.
17.7.8.4.4 Development of Hand-Pump Attached Deluoridation Units (Iyenger, 2005)
A cylindrical deluoridation unit was designed and fabricated by using mild steel sheet.
The unit was designed to operate in the uplow water movement to achieve better contact.
AA of grade G-87 (IPCL), with a particle size range of 0.3-0.9 mm, was illed in the unit
with an approximate bed depth of 55 cm. This unit was ield tested at Makkur village,
Unnao district of Uttar Pradesh in India.
Experimental trials have been performed using a shallow type India Mark II hand pump
(≈35 ft depth). The deluoridation unit installation was executed in 1993. The hand pump
discharge level was raised with an addition to its normal pedestal and by constructing
an elevated platform. Users had to go up a few steps to operate the hand pump for water
discharge. A bypass was also provided to draw the water directly from the hand pump for
washing and bathing to make the water source suitable for this dual purpose. Raw water
luoride concentration studied was in the range of 6-7 mg/L. Regeneration of exhausted
AA was done
in situ
,
i.e., within the device column with a regeneration treatment time of
8-10 h. The average yield of safe water output (<1.5 mg/L luoride) per cycle was around
25,000 L. Seventeen deluoridation cycles were reported to be required in a span of 4 years.
There were no major maintenance issues observed during this period, while there was
no complaint from the users regarding the operational dificulties or the palatability of
treated water. However, community support during regeneration was minimal. No details
about handling of spent regenerant and its disposal are available.
17.7.8.5 Green Chemical Approach
Yadav et al. (2012) explored a green chemical approach by preparation of tradition soil
pots using aluminum oxalate as adsorbent for luoride removal. The adsorbent dose was
optimized in the range of 2-8 g/500 g soil, while other parameters like pH, TDS, hardness,
