Environmental Engineering Reference
In-Depth Information
systems because of natural causes and human intervention. Large decreases in groundwa-
ter level and decline in water quality have become common problems in many countries
worldwide. The scenario is worse in developing countries of Asia, including India and
Pakistan.
Various contaminants such as luoride [3,4]; nitrate [5,6]; pesticides [7,8]; arsenic [9,10];
heavy metals such as lead, chromium, and mercury [11,12]; endocrine-disrupting com-
pounds [13]; nanoparticles (NPs) [14,15]; and pathogenic organisms have been found in
many groundwater sources worldwide. Both geogenic and anthropogenic reasons are held
responsible for the elevated concentrations of these contaminants in aquatic environments.
Abuse of chemicals and drugs; improper sewerage and septic systems; indiscriminate use
of pesticides [8], fertilizers, and agrochemicals [16]; urbanization [17]; and associated land
use alteration with shortsighted economic beneits, storage of waste materials in excava-
tions, such as pits or mines, acid mine drainage [18], and direct disposal of untreated or
partially treated wastewater into aquatic environments [19] have caused the contamina-
tion of water systems, both surface and subsurface. Saltwater intrusion in coastal cities,
overexploitation of groundwater for agricultural and drinking purposes, has also resulted
in decline in groundwater quality and storage [20]. Hence, the protection of existing water
resources against potential chemical and biological contamination should be carried out for
a sustainable environment and economy. It is also important to remediate already polluted
resources for meeting the current demands of public water supply as an interim measure.
19.2 Search for Affordable Treatment Options
The availability of safe and clean water in suficient quantities at the point of use is a fun-
damental human right. We are currently facing formidable challenges in meeting rising
demands of potable water. In addition to the decline in the quality of water due to pollu-
tion, erratic monsoon, unpredictable weather, draught, or lood further exerts pressure on
the limited and dwindling freshwater reserves. According to estimates, 1.2 billion people
worldwide do not have access to clean water [21]. Every year, more people die from the
consequences of unsafe water than all forms of violence, including war and terrorism.
Unfortunately, most of the affected populations are from the poorer parts of the world [22],
especially rural areas where high levels of poverty prevail. Urban areas are typically better
developed compared with rural areas in terms of water infrastructure. In rural areas of
poor and developing countries, infrastructures are either poorly developed or nonexistent.
Because of the lack of infrastructure in place, the water needs of the rural population are
largely met by subsurface water. It has been established beyond doubt that water derived
from the subsurface is heavily contaminated and not suitable for drinking purposes, in
many locations. Fluoride is one such contaminant widely present in the groundwater
sources, which needs a quick solution.
Over the years, many technologies have been developed to tackle the issue of dissolved
luoride in groundwater. However, most of the technologies did not produce the desired
results in the ield owing to poor eficiency or higher pricing. There is clear and urgent
need for an eficient and affordable alternate treatment system for the removal of luo-
ride in aqueous medium. In recent years, with the advancement made in nanotechnol-
ogy, nanomaterials have emerged as potential candidates for water puriication. They are
attractive because of their unusual properties compared with their bulk counterparts,
