Environmental Engineering Reference
In-Depth Information
With the presence of luoride being a major issue of drinking water quality, extensive
efforts have been made toward luorosis mitigation, mainly focusing on deluoridation
of drinking water. A large number of approaches and technological options have been
reported for luoride removal from water. However, despite intensive efforts and huge
investment in the water supply sector, the objective of providing adequate potable drink-
ing water is falling short, as at any point of time, there is considerable gap between assets
created and service available, especially to the rural population in less developed coun-
tries. With exponential increase in water demand and water quality problems, as well as
treatment options being region- and water input quality-sensitive, scientiic efforts are still
being put in for the development of improved technological options for luoride removal.
There are also challenges concerning the relatively poor translation of laboratory develop-
ments to successful technology development and its implementation in the ield.
Reducing the luorosis disease burden in a cost-effective way is the primary objective
of any luoride removal effort and, further improvements are still required to develop
techno-economically feasible water puriication technologies for rural applications in less
developed countries. Considering the serious issues related to regeneration of adsorbents
on a sustainable basis, materials with high luoride uptake capacity are being explored.
Nanomaterials, including nanocomposites, show potential properties in this regard with
their high irst cycle capacity. Improved water quality monitoring in the recent past has
resulted not only in identiication of new contaminated locations but brought out the pres-
ence of more than one pollutant in many areas. Multipollutant treatment processes with
increasing number of multipollutant contaminations are, therefore, getting more attention.
In general, there has been limited work to address the minimization of waste, handling
and safe disposal as well as treatment of the sludge/used materials, and management of
liquid wastes generated during the regeneration and treatment processes. The concept
of integrated luorosis mitigation (IFM) and estimation of disease burden prove useful
in assessing the various technological options for effective luorosis mitigation through
water treatment and other options.
The various options to tackle the high luoride problem discussed in previous sections
are preferred; however, in most of the luoride-affected areas, alternate sources are either
not available or implementation is restricted owing to techno-economic and social fac-
tors. In such cases, removal of excess luoride to make the water potable is the only rem-
edy. Deluoridation techniques can be implemented at a household level or community
level depending on site-speciic factors. The central or community-level deluoridation
schemes are more suitable for urban areas where availability of skilled manpower and
other resources are not limited. Such community-level deluoridation schemes can be cou-
pled with other general treatment schemes normally available in most of the urban areas.
On the other hand, household or decentralized deluoridation options are more suitable
for rural areas, where population is highly scattered and other water supply infrastructure
is not available. Furthermore, decentralized deluoridation can also be limited to treat the
water used for drinking and cooking purposes, which results in signiicant cost reduc-
tion and less chemical handling and sludge generation. Several techniques are presently
in practice to reduce the luoride levels below prescribed limits, which can be categorized
into four main categories, namely coagulation-precipitation, membrane processes, ion
exchange, and adsorption onto various adsorbents. Brief details of these techniques along
with their merits and demerits are provided in the following sections and summarized in
F i g u r e 1 7.1.
