Water Treatment and
Nanotechnology
Prakhar Shukla
Karan Singla
Ravi

INTRODUCTION
Water is the most essential and critical for all human
activities
Sources of clean water are very limited While
Requirement is increasing
Sources is often contaminated by many causes
eg; microbes, harmful chemicals, bacteria, minerals, and
pharmaceuticals
The amount of water to be treated should also be
assessed
Malaria, Cholera, Typhoid, Viral hepatitis, Skin diseases
are caused by contaminated water

Conventionally Used Methods For Water
Treatment
 Five types of contaminants are found in water
Methods that are in use to remove these elements have
wider Range (from simple and inexpensive to elaborate and
costly)
Around Twenty-five conventional methods used to purify
water are divided into four categories:
1) Separation
2) Filtration
3) Chemicals
4) Oxidation.

Conventionally Used Methods For Water
Treatment
Separation:
Sedimentation, Boiling, Distillation, UV light
Filtration:
Sand,
Diatomaceous earth,
Porous stone/Ceramic,
Paper/Cloth,
Charcoal/Carbon Block,
Reverse Osmosis,
Enzymes & Bacteria,
Plants.

Conventionally Used Methods
For Water Treatment
Chemicals:
Halogens(Cl, Br, I)
Hydrogen Peroxide (H2O2),
Silver (Ag),
Nontoxic organic acids,
Lime & mild alkaline agents,
Coagulation-flocculation,
Ion exchange
Oxidation: Ozonization, Electronic Purification &
Dissolved Oxygen Generation

Drawbacks in present water treatment
process
Most of the methods available have impact either on our health or on
the environment.
Time consuming,
Fails to remove the heavy metal,
Not able to remove micro organisms,
Chemical pollutants and heavy metals,
Application of UV lightning require longer radiation time
Removes the useful minerals and Nutrients

A combination selected from the
following process
 Pre-chlorination for algae control and arresting
biological growth
 Slow-Sand filtration
 Coagulant aids, also known as polyelectrolytes – to
improve coagulation and for more robust floc
formation.
 Sedimentation for solids separation- removal of
suspended solids trapped in the floc.
 Disinfection for killing bacteria viruses and other
pathogens

Solution
•The highly efficient, modular, and multifunctional processes enabled by
nanotechnology are envisaged to provide high performance, affordable
water and wastewater treatment solutions that less rely on large
infrastructures.
•Nanotechnology is the design, characterization, production and
applications of structures, devices and systems by controlling shape and
size at nanometer scale.
• Nano Structured Materials are applicable as adsorbents or catalysts in
order to remove toxic and harmful substances from wastewater.

What is nanotechnology ?
We all are familiar:
• Greek word for dwarf
• Nanotechnology is science, engineering, and
technology conducted at the nano-scale, which is about 1
to 100 nano-meters
• One nm is a billionth of a meter, or 10-9 of a meter

The key features that make nano-particles attractive for water
treatment……….
 More surface area and small volume
The higher the SA:V - the stronger, more stable and durable
Materials may change optical, electrical, physical, chemical, or
biological properties at the nanoscale level
Makes biological and chemical reactions easier
Can attach various reactor groups to increase the chemical affinity
to words the target

Adsorption : Polymeric Based nano-adsorbents and Metal based nano-adsorbent
 Efficiency of current conventional adsorbents is usually limited by the
surface area or active sites, the lack of selectivity, and the adsorption
kinetics.
 Nano-adsorbents offer significant improvement with their extremely
 High specific surface area
 Associated sorption sites,
 Short intraparticle diffusion distance
 Tunable pore size
 Enhanced Surface chemistry.
Current and potential applications of
Nanotechnology in Water treatment:
- Adsorption
- Membrane Nanotechnology
- Photo-catalysis
- Disinfection and Microbial Control
- Sensing and Monitoring

Metal Based
Nano-Adsorbents:
 Multifunctional Magnetic nanoparticles are used as the core material in a core–shell
nanoparticle structure where the shell provides the desired function while the
magnetic core realizes magnetic separation.
 Silica coating helps functionalization due to the rich silica chemistry.
 It is a two-step process: These magnetic nanoparticles can be either used directly
as adsorbents or as the core material in a core–shell nanoparticle structure where
the shell provides the desired function while the magnetic core realizes magnetic
separation
 Metal based nanomaterials have been explored to remove a variety of heavy metals
such as arsenic, lead, mercury, copper, cadmium, chromium, nickel

Carbon Based Nano-
Adsorbents:
 Carbon absorption is a widely used method of home water filter treatment
because of its ability to improve water by removing disagreeable tastes and
odors, including objectionable chlorine and can be effective against
microorganisms. However, generally it will not affect total dissolved solids.
 Carbon Based Nano-Adsorbents(CNTs) have have shown higher efficiency
than activated carbon on adsorption of various organic chemicals due to the
large specific surface area and the diverse contaminante CNT interactions

Membrane Nanotechnology Process
 The basic goal of water treatment is to remove undesired constituents
from water thus membranes provide a physical barrier for such
constituents based on their size, allowing use of unconventional water
sources.
 A major challenge of the membrane technology is the inherent tradeoff
between membrane selectivity and permeability
 The performance of membrane systems is largely decided by the
membrane material. Incorporation of functional nanomaterials into
membranes offers a great opportunity to improve the membrane
permeability, fouling resistance, mechanical and thermal stability, as
well as to render new functions for contaminant degradation and self-
cleaning.

Nanofiber Membranes
 Electrospinning is a simple, efficient and inexpensive way to make ultra-fine fibers
using various materials. The resulting nanofibers have high specific surface area
and porosity and form nanofiber mats with complex pore structures.
 The diameter, morphology, composition, secondary structure, and spatial
alignment of electrospun nanofibers can be easily manipulated for specific
applications.
 Functional nanomaterials can be easily doped into the spinning solutions to
fabricate nanoparticle impregnated nanofibers such as nano-zeolites, nano-Ag,
nano-TiO2, and CNTs TiO2 to remove heavy metals and organic pollutants during
filtration.
 Biologically inspired membranes
 Antimicrobial nanomaterials such as nano-Ag and CNTs can reduce membrane
biofouling from by organisms such as algae.

Photo-catalysis:
 TiO2 is the most widely used semiconductor photo-catalyst while
fullerene derivatives are second most used in Photocatalytic reactors,
and solar disinfection systems.
 TiO2 has low toxicity, chemical stability, low cost, and abundance as raw
material.
 TiO2 generates an electron/hole (e−/h+) pair upon absorbing a UV
photon, which later either migrate to the surface and form reactive
oxygen species (ROS) or undergo undesired recombination.
 The photo-activity of nano-TiO2 can be improved by optimizing particle
size and shape, reducing e−/h+ recombination by noble metal doping,
maximizing reactive facets, and surface treatment.
 The size of TiO2 plays an important role in its solid-phase
transformation, sorption, and e−/h+ dynamics.

Disinfection and Microbial Control:
 Nano-Ag, nano-ZnO, nano-TiO2, nano-Ce2O4, CNTs, and
fullerenes are used.
 These nanomaterials inactivate microorganisms by releasing
toxic metal ions, compromising cell membrane integrity upon
direct contact or generating reactive oxygen species with fewer
tendencies to form DBPs.
 Nano-Ag is a common choice for point-of-use (POU) water
treatment devices because of its strong and wide-spectrum
antimicrobial activity and low toxicity to humans.
 The fibrous structure, antibacterial activity, and conductivity
of CNTs enable their use in antimicrobial filters.

Nanomaterial antimicrobial mechanisms.
Nanomaterials Antimicrobial mechanisms
Nano-Ag Release of silver ions, protein damage, suppression of
DNA replication,
Nano-TiO2 Production of ROS
Nano-ZnO Release of zinc ions, production of H2O2, membrane
damage
Nano-MgO Membrane damage
Nano-Ce2O4 Membrane damage
Fullerol and
aminofullerene
Production of ROS
Carbon nanotubes Membrane damage, oxidative stress
Graphene-based
nanomaterials
Membrane damage, oxidative stress
Nanomaterial antimicrobial mechanisms.

Sensing and monitoring
Quality monitoring Is a bigger Challenge.
Sensors with high sensitivity and fast response are needed.
Nanomaterials can improve sensor sensitivity and speed.
Magnetic nanoparticles and CNTs are explored for sample
concentration and purification
 QDs, nanoparticles, noble metal and CNTs are widely used
in nanosensor

 Availability and cost,
 Toxicity of nano-material,
 Social acceptability must be addressed.
 Potential health and environmental risks,
 CNT may be cause of lung damage.

CONCLUSION
 Toxicity to cells in nano particles may be modified or reduced by coating
the nano particles.
 Already showing promising results.
 Once certain impending hurdles are overcome, will solve the global water
shortages.
 Opportunities to develop next-generation water supply systems.