Ciency of the removal processes based on the

  • No School
  • AA 1
  • 121

This preview shows page 90 - 92 out of 121 pages.

ciency of the removal processes based on the available literature in the following section. 8.1 Disinfection Biological contaminants are generally classi fi ed under three categories, namely micro-organisms, natural organic matter (NOM) and biological toxins. Microbial 84 P. Senthil Kumar et al.
Image of page 90
contaminants include human pathogens and free living microbes (Majsterek et al. 2004 ; Berry et al. 2006 ; Dugan and Williams 2006 ; Srinivasan et al. 2008 ; Jain and Pradeep 2005 ). Adsorbents such as activated carbon have reasonably good removal ef fi ciencies and again a number of factors in fl uence the removal process. Groundwater can get easily polluted by bacteria and protozoa. The easiest method for treating micro-organisms is using oxidizing agents such as chlorine and ozone. However, chlorine dioxide is expensive and results in the production of hazardous substances such as chlorite and chlorate in manufacturing process. Ozone, on the other hand, has no residual effects but produces unknown organic reaction products. For UV disinfection, longer exposure time is required for effectiveness and also there is no residual effect. So, advanced disinfection tech- nologies must, at least, eliminate the emerging pathogens, in addition to their suitability for large-scale adoption. There are many different types of nanomaterials such as Ag, titanium and zinc capable of disinfecting waterborne disease-causing microbes present in ef fl uent. Their antibacterial properties arise from their charge. TiO 2 photocatalysts and metallic and metal oxide nanoparticles are a set of promising nanomaterials that exhibit antimicrobial properties. The ability of metal ions to produce the desired results in water disinfection has been highlighted by many researchers (Sondi and Salopek-Sondi 2004 ). The possible nanomaterials that can be utilized as disinfectants are listed. 8.1.1 Silver Nanoparticles Silver has low toxicity and microbial inactivation and hence is the most widely used nanomaterial. Silver nanoparticles can be derived from its salts such as silver nitrate and silver chloride, and their effectiveness as biocides is widely known (Baker et al. 2005 ; Pan á č ek et al. 2006 ; Makhluf et al. 2005 ). Though the antibacterial effect is size dependent, smaller Ag nanoparticles (8 nm) were most effective, while larger particle size (11 23 nm) resulted in lower bactericidal activity (Xiu et al. 2011 ). There are several mechanisms which have been found to explain the bactericidal effects of Ag nanoparticles such as, the damaging of the bacterial membranes due to the formation of free radicals (Xiu et al. 2012 ; Esteban-Cubillo et al. 2006 ) inter- actions with DNA, alteration of membrane properties due to adhesion on cell surface and enzyme damage. Immobilized nanoparticles possess high antimicrobial activity (Balogh et al.
Image of page 91
Image of page 92

You've reached the end of your free preview.

Want to read all 121 pages?

  • Fall '19
  • N. Gokarneshan

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors