Environmental Engineering Reference
In-Depth Information
17.7.8.5.2 TERI (The Energy and Resources Institute)-Implemented Deluoridation Unit
Using Existing Nalgonda Technology (with Copyright Permission from TERI)
TERI Western Regional Centre, Goa, carried out a study to address this critical problem
through community effort toward cost-effective treatment and management of luoride
contamination. The Nalgonda technique that was implemented during the project con-
sisted of two buckets equipped with taps and a sieve on which a cotton cloth was placed.
Known concentrations of alum and lime were added to the raw water bucket at the same
time, and dissolved by stirring with a wooden ladle. The villagers were trained to stir fast
while counting till 60 (1 min), and then slow down while counting till 300 (5 min). The loc
formed was settled down for about an hour. The water was then passed through a sieve
into another bucket. Both the containers were plastic buckets of 20-L capacity, supplied
with covers and equipped with a tap 5 cm above the bottom to enable trapping of sludge.
The treated water was then stored in the treated water bucket through the cloth, and col-
lected for drinking or cooking.
17.7.8.5.3 Fluoride Removal by Bone Char (Handbook of Drinking Water
Technologies by MDWS and CSIR-NEERI, 2013)
To produce bone char suitable as a ilter material, animal bones are charred in a kiln
at a deined temperature, and the oxygen content in a speciic surface area of bones is
increased, organic constituent are removed, and an inorganic HAp matrix remains. The
charred bones are sieved and crushed to produce granular ilter material. Synthetic HAp
has high surface area and adsorption capacity. As it needs to be imported, it is more expen-
sive than locally available bone char and therefore often not an option for projects in devel-
oping countries.
17.7.8.5.4 Emerging Deluoridation Technologies (Handbook of Drinking
Water Technologies by MDWS and CSIR-NEERI, 2013)
17. 7. 8 . 5 . 4 .1 Cr y s t a l a c t o r
In the Netherlands, a new type of contact precipitator, dubbed
Crystalactor, is reported to have been developed. The major part of the Crystalactor instal-
lation is the so-called pellet reactor, partially illed with a suitable seed material such as
sand or minerals. The wastewater is pumped in an upward direction, maintaining the
pellet bed in a luidized state. To crystallize the target component on the pellet bed, a driv-
ing force is created by a reagent dosage and pH adjustment. By selecting the appropriate
process conditions, cocrystallization of impurities is minimized and high-purity crystals
are obtained. The pellets grow and move toward the reactor bottom. At regular intervals,
a quantity of the largest luidized pellets is discharged from the reactor and fresh seed
material is added. After atmospheric drying, readily handled and virtually water-free
pellets are obtained. A major advantage of the Crystalactor is its ability to produce high-
purity, nearly dry pellets. Owing to their speciic composition, the pellets can normally be
recycled or reused in other plants, resulting in no residual waste for disposal. As reported,
in the rare event that pellets have to be disposed of by other means, the advantage of low-
volume secondary waste production still remains: water-free pellets, rather than bulky
sludge. The four steps found in conventional treatment processes—coagulation, loccula-
tion, separation, and dewatering—are combined into one as claimed in the Crystalactor.
Because of the production of water-free pellets, troublesome sludge dewatering is reported
to be eliminated. Furthermore, the unit is compact owing to the high surface loadings
(40-120 m/h).
