Presentation on theme: "Marelize Botes 15 March 2010. Contaminated drinking water - main cause of diseases in development countries. 1.1 billion people do not have access to."— Presentation transcript:
Contaminated drinking water - main cause of diseases in development countries. 1.1 billion people do not have access to safe water (WHO, 2004). The importance of water disinfection and microbial control cannot be overstated.
Chemical disinfectants and membrane- based water filtration systems control microbial pathogens. Harmful DBP’s and ↑resistant pathogens 2 significant obstacles in filtration are Biofouling and virus penetration
The accumulation of microorganisms such as bacteria, fungi and algae on the membrane surfaces, with the subsequent formation of harmful biofilms and operational problems. Membrane permeability and membrane lifetime are reduced and energy costs are increased. High cost involved in controlling membrane biofouling and subsequently buying new membranes.
Water loss and quality deterioration associated with aging distribution networks and the increasing cost to transport water. Increasing need for alternative water sources and wastewater reuse for water shortage problems. Urgent need for decentralized/point- of-use water treatment and reuse systems.
Potential solution = nanofibrous filter media High surface to volume Low basis weight High permeability Small pore size → Remove unwanted particles smaller than 0.3 µm Styrene dimethyl aminopropyl maleimide
The first patent was published in the USA. Filters of Petryanov was kept top secret in Russia. Were used after the Second World War to protect the environment from nuclear-active aerosol release. Production gained momentum in 1980 in America and only started in the 1990s in Europe. Currently more than 20 enterprises worldwide.
S.N.EnterprisesCountry 1Donaldson Company Inc.USA 2Espin Technologies Inc.USA 3KX IndustriesUSA 4Ahlstrom CorporationFinland 5Hollingsworth Co. Ltd.USA 6US Global NanospaceUSA 7Finetex TechnologyS. Korea 8Helsa-automotiveGermany 9Nanotechnics Co. Ltd.S. Korea 10Teijin Fibers Ltd.Japan 11TorayJapan S.N.EnterprisesCountry 12 Japan Vilene Company Ltd. Japan 13 Nanoval GmbH & Co. KG Germany 14Hills Inc.USA 15 Nonwoven Technologies Inc. USA 16 Emergency Filtration products, Inc. USA 17Elmarco Czech Republic 18 Hohns Manville Sales GmbH Germany 19 Nanofiber Future Technologies Corp Canada 20Esfil Tehno Republic of Estonia
Small pore sizes, high specific surface areas and high porosity ↓ 3 uses in water treatment Separate solid impurities from the liquid phase ↓ Filtration Selective absorption/ Adsorption ↓ Affinity membranes Neutralise or decompose impurities ↓ Reactive membranes
Functionalization by spinning blends of specific polymers Coating of fibers Inclusion of functional components such as antimicrobial nanoparticles
nanobiocides Metal and metal oxides e.g. nAg, ZnO, CuO, TiO 2 Engineered/syn- thesized nanoparticles such as fullerenes e.g. nanomagnetite (nC 60 ) and carbon nanotubes Natural antimicrobial substances e.g. antimicrobial peptides and chitosan
Silver nanoparticles is considered to be the most toxic element to microorganisms: Ag >Hg >Cu >Cd >Cr >Pb >Co >Au >Zn >Fe >Mn >Mo >Sn considered an alternative to antibiotics. Antimicrobial filters, wound dressing material, water disinfection, sensors, air filtration
PAN fibers with 5 wt% AgNO 3 forming silver nanoparticles on fiber surface with lysed S.aureus Neat PAN fibers with in tact S.aureus
IVIS imaging of PAN fibers with or without 5%wt AgNO 3 Pseudomonas aeruginosa Escherichia coli Staphylococcus aureus
Zinc oxide (ZnO) nanoparticles have strong antimicrobial activity. Penetrate the bacterial cell envelope and disorganize the cell membrane. Applicated in pharmaceutical products and in surface coatings to prevent biofilm. Applications in water treatment is questioned as it is highly soluble in water increasing sensitivity of aquatic organisms towards ZnO. Copper oxide nanoparticles
Titanium dioxide kills bacteria and viruses. Produce hydroxyl free radicals and peroxide formed under UV-A irradiation via oxidative and reductive pathways, respectively. TiO 2 is stable in water and cost effective and can therefore be successfully incorporated in thin films or membrane filters for water filtration.
Fullerenes (C 60 ) Carbon nanotubes should be immobilized on a reactor surface or polymer matrix. Applicated in the prevention of biofilm formation in water filtration membranes. High cost involved and potential toxicity may hamper the use of carbon nanotubes in water filtration. NanoCeram ® cartridges
Natural antimicrobial substances – antimicrobial peptides and chitosan Chitosan nanoparticles show potential in drinking water disinfection applications such as antimicrobial agents in membranes, sponges and surface coatings
Two significant challenges in the long term are apparent. 1) the loss of antimicrobial or antiviral activity The cost involved and the impact on human health and environment. safety of escaped nanobiocides is not proved yet. Nanobiocides can also be turned into harmful chemicals when exposed to chlorine and UV. 2) Bacteria may become resistant towards the nanobiocides.
Solutions → Improve fixation techniques by concentrating the nanobiocides closer to the surface of the membrane. → Encapsulation in a polymer matrix to decrease the release rate. → Modify the polymeric surfaces
Nanofibers show potential in water treatment processes. Reactive membranes may be the solution for high-performance, small-scale/point-of-use systems. →Increase robustness of water supply networks and water systems not connected to a central network. →Emergency response following catastrophic events.