Nanotechnology for sustainable wastewater treatment

ByRohit ThakurBhagyesh Gaud

Content

Introduction

What is Nanotechnology?

Microfiltration

Ultrafiltration

Nanofiltration

Reverse Osmosis

Conclusion

Reference

Introduction

Water is the most essential substance for all life on Earth and precious resource for human civilization. An adequate supply of safe water drinking is one of the major prerequisites for a healthy life, but

waterborne diseases is still a major cause of death in many parts of the world. This makes the ability to remove the toxic contaminants from aquatic environment rapidly, efficiently and within reasonable costs an important technology challenge.

For this better water treatment processes Nanotechnology is preferred which play an important role in this. Nanotechnology is the field of science, focused on the design, synthesis, characterization and application of materials which holds great promise in desalination, purification and water treatment.

What is Nanotechnology?

Nanotechnology is the study of manipulating matter at atomic and molecular scale. Nanotechnology deals with structures sized between 1nm to 100nm and involves developing materials or devices

with this size. Substances or materials generated having nanoscale dimensions are referred to as ‘nanomaterials’. In terms of wastewater treatment, Nanotechnology is applicable in detection and removal of various pollutants.

Heavy metal pollution poses as a serious threat to environment because it is toxic to living organisms, including humans and not biodegradable

They are having a large surface area, very reactive and exhibit different properties compared to the bulk material of the same substance. They exhibit very interesting mechanical, magnetic, optical, chemical and other properties.

Types of Nanotechnology for wastewater treatment

MicrofiltrationUltrafiltrationNanofiltrationReverse Osmosis

Microfiltration

Microfiltration is defined as the filtration of the suspension with colloidal or other fine particles having linear dimensions of 0.02 micron to 10 micron. Typical operating pressure for filtration is relatively low, lying between 0.02 MPa to 0.5 MPa.

Membranes with a pore size of 0.1 – 10 µm perform microfiltration. It is a pressure driven process in which membrane is applied to separate particles from an aqueous solution. Microorganisms are removed but viruses remain in water.

Micro filtration can be implemented in many different water treatment processes when particles with a diameter

greater than 0.1 mm need to be removed from a liquid.

Applications of Microfiltration

It is used fat or microbial removal. Used in separation of oil-water emulsion. Used for wastewater treatment in industries. Used in beverages sterilization. Used separation of bacteria from water (biological wastewater treatment).

Ultrafiltration

Ultrafiltration (UF) is a variety of membrane filtration in which forces like pressure or concentration gradients lead

to a separation through a semipermeable membrane.

Suspended solids and solutes of high molecular weight are retained in the so-called retentate, while water and low

molecular weight solutes pass through the membrane in the filtrate.

Ultrafiltration membrane have pore size between 1nm to 100nm and can remove the particles of size 0.001-0.1

micron.

For complete removal of viruses, Ultrafiltration is required.

Ultrafiltration can be also be applied for pre-treatment of water for nanofiltration and reverse osmosis.

Applications of Ultrafiltration

It is used for enzyme recovery.

It is used cheese manufacture.

It is used in removal of pathogens from milk.

It is used for filtration of effluent from paper pulp mill.

Nanofiltration

Nanofiltration is a relatively recent membrane filtration process used most often with low total dissolved solid water such as surface water and fresh groundwater, with the purpose of softening and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter

Nanofiltration is a membrane filtration-based method that uses nanometers sized cylindrical through-pores that pass through the membrane at 90°. Nanofiltration membranes have pore sizes from 1-10 nanometers, smaller than that used in microfiltration and ultrafiltration, but just larger than that in reverse osmosis.

 Membranes used are predominantly created from polymer thin films. Materials that are commonly use include polyethylene terephthalate or metals such as aluminium Pore dimensions are controlled by pH, temperature and time during development with pore densities ranging from 1 to 106 pores per cm2. Membranes made from polyethylene terephthalate and other similar materials.

CONTAMINANTS

Nanofiltration

Contaminated water

Pure water

Benefits of Nanofiltration

It requires lower operating cost. Reduction of heavy metals and removal of colour. It softens hard water. Lower energy cost is required. It reduces the total dissolved solids contain of highly brackish water.

Reverse Osmosis(RO)

Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water.

When two of unequal concentrations are separated by a Semipermeable membrane, then the membrane allows solvent particles flow from lower concentrations to the higher concentrations. This phenomenon can be reversed by applying hydrostatic pressure on the concentrated side and thus the process is called Reverse Osmosis.

Semipermeable membrane is membrane which selectively doesn’t permit the dissolved solute particles. Reverse osmosis filters have a pore sized around 0.1nm. After passes through the reverse osmosis filter, it is essentially pure water. It removes all organic molecules, viruses, most minerals that are present in water Reverse osmosis removes monovalent ions,which means that it desalinates the water.

Reverse osmosis is the best method for purification of water

It improves the taste, odour and appearance of water more than any other filtration methods. It is highly effective purification process among all the purification methods. It consumes no energy. It is very convenient. It removes all the pollutants. It doesn't collects any of them. Low cost production. High reliability.

Conclusion

Microfiltration removes these microorganism and suspended particles from water.

Ultrafiltration removes bacteria, protozoa and some viruses from the water.

In Nanofiltration, it removes all organic matter and some natural minerals, especially

divalent ions which cause hard water soften.

Reverse osmosis removes turbidity, including microbes and virtually all dissolved

substance.

Reverse osmosis removes many harmful minerals, such as salt and lead, it also removes

some healthy minerals, such as calcium and magnesium.

Reference

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Xiaolei Qu, P.J.J. and Alvarez, Q.n Li, Applications of nanotechnology in water and wastewater treatment, water research, 47, 3931-3946 (2013)

Nora Savage and Mamadou S. Diallo, (2005), Nano materials and water purification: Opportunities and challenges. Journal of Nanoparticle Research.

Sayan Bhattacharya, Indranil Saha, Dhrubajyoti Chattopadhyay, Uday Chand Ghosh and Debashis Chatterjee, Role of nanotechnology in water treatment and purification: Potential applications and implications, International Journal of Chemical Science and Technology 2013;,3(3): 59-64, ISSN 2249-8532.

Pankaj K. Tyagi, Ravikant Singh, Smriti Vats, Dharmendra Kumar and Shruti Tyagi, Nanomaterials Use in Wastewater Treatment, International Conference on Nanotechnology and Chemical Engineering (ICNCS'2012) December 21-22, 2012 Bangkok (Thailand),65.