**3. Nanotechnology: an approach to improve water quality through nanoparticles**

We need fresh water; it is a big task to have abundant fresh water for agriculture and industrial applications [30, 31]. More than one billion people in the world are facing challenges to have fresh water and in near future situation can be worst. It is estimated that the average supply of water to per person will drop by a factor of 1/3rd, which will result in premature death of millions of

people. Non-contaminated water is also not in reach to meet proper agricultural practices [32]. The need of great amount of fresh water is leading towards the contamination of ground water through the use of pesticides, fertilizers and other chemicals.

Novel, sustainable and cost-effective approach is needed to tackle these problems. Nanotechnological researches have enabled us to find the solution for remediation and purification of waste water. Water resources within reach are usually contaminated with pathogens, salts, metals(Cu, Pb, As, etc.), pesticides, herbicides, pharmaceuticals and personal care products (PPCPs) and radioactive elements due to natural occurrences or anthropological activities [33–35].

Although the conventional methods are effective in many ways, still this method are quite outdated and not much cost effective and requires more man power and specificity and also, conventional methods are not applied to lower concentrations of pollutants (**Table 1**).


#### **Table 1.**

*Physical and chemical methods used for remediation.*

The conventional methods which are used in removing pollutants and particulate matters are broadly categorized into three categories:


The most promising methods can be said to be the biological treatment methods which includes bioremediation through different organisms, biofiltration, biosorption, etc. These are basically useful for in-situ treatment but these are slow processes and take much time but cheap and cost-effective. Biological treatment methods are quite effective but in current scenario these cannot fulfill the human requirements as pollution is many folds so a quick and highly efficient method is needed which can be fulfilled by use of nanoparticles which are quite fascinating in present days.
