ECONANO

The significance of the wastewater treatment, management, and its disposal is gradually increasing in the modern times and it has become a major concern for public health scientific interest. Nanotechnology holds great potential in advancing water and wastewater treatment to improve treatment efficiency as well as augment water supply through safe use of unconventional water sources.
The highly efficient, modular, and multifunctional processes enabled by nanotechnology are envisaged to provide high performance, affordable water, and wastewater treatment solutions that have less reliance on large infrastructures. Nanotechnology-enabled water and wastewater treatment promises to not only overcome major challenges faced by existing treatment technologies but also to provide new treatment capabilities that could allow economic utilization of unconventional water sources to expand the water supply. Nanomaterials were suggested as efficient cost-effective and environmental friendly alternative to existing treatment materials, from the standpoints of both resource conservation and environmental remediation.

Here some applications are listed:

* Adsorption
                                                                                                                         
Adsorption is commonly employed as a polishing step to remove organic and inorganic contaminants in water and wastewater treatment. Efficiency of 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 and associated sorption sites, short intraparticle diffusion distance, and tunable pore size and surface chemistry.

* Membranes and membrane processes
                                                                                                                     
The basic goal of water treatment is to remove undesired constituents from water. Membranes provide a physical barrier for such constituents based on their size, allowing use of unconventional water sources. As the key component of water treatment and reuse, they provide high level of automation, require less land and chemical use, and the modular configuration allows flexible design. A major challenge of the membrane technology is the inherent tradeoff between membrane selectivity and permeability. The high energy consumption is an important barrier to the wide application of pressure driven membrane processes. Membrane fouling adds to the energy consumption and the complexity of the process design and operation. Furthermore, it reduces the lifetime of membranes and membrane modules. 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.



* Photocatalysis
                                                                                                                   
Photocatalytic oxidation is an advanced oxidation process for removal of trace contaminants and microbial pathogens. It is a useful pretreatment for hazardous and non-biodegradable contaminants to enhance their biodegradability. Photocatalysis can also be used as a polishing step to treat recalcitrant organic compounds. The major barrier for its wide application is the slow kinetics due to limited light fluence and photocatalytic activity. Current research focuses on increasing photocatalytic reaction kinetics and photoactivity range.

* Disinfection and microbial control
                                                                                                                 
The dilemma between effective disinfection and formation of toxic disinfection by-products (DBPs) poses a great challenge for the water industry. It is now well recognized that conventional disinfectants, such as chlorine disinfectants and ozone can form toxic DBPs (e.g., halogenated disinfection byproducts, carcinogenic nitrosamines, bromate, etc.). UV disinfection emerged as an alternative for oxidative disinfection as it produces minimal DBPs, while it requires high dosage for certain viruses (e.g., adenoviruses). These limitations urge the development of alternative methods that can enhance the robustness of disinfection while avoiding DBP formation. Many nanomaterials, including nano-Ag, nano-ZnO, nano-TiO2, nano-Ce2O4, CNTs, and fullerenes, exhibit antimicrobial properties without strong oxidation, and hence have lower tendency to form DBPs. The antimicrobial mechanisms of these nanomaterials, their merits, limitations, and applicability for water treatment, and the critical research needs are thoroughly discussed in that review paper. Thus only a brief update mainly regarding nano-Ag and carbon based nanomaterials will be provided here.

* Sensing and monitoring
                                                                                                                  
A major challenge for water/wastewater treatment is water quality monitoring due to the extremely low concentration of certain contaminants, the lack of fast pathogen detection, as well as the high complexity of the water/wastewater matrices. Innovative sensors with high sensitivity and selectivity, and fast response are in great need.