Nanotechnology and Biotechnology for Water Treatment: A Comparative Study
In 2012, the World Health Organization estimated that about 11% of the world’s population does not have access to clean water and about 1.6 million deaths are caused by contaminated water annually. Even though there are several drinking water treatment technologies available today, they are not widely distributed or suitable for all types of water contamination because they have different treatment efficiencies and costs. For instance, chemical precipitation for heavy metal removal is effective only when the metal concentration is low; while other methods require long contact times, are ineffective at low metal concentrations between 1-100 mg/L, and are, in most cases, expensive because they require energy or chemical product consumption. Biological treatment methods, such as thermal, ozonation, and UV are expensive methods and therefore are not suitable for developing countries. The traditional disinfectants are cheaper, however, they produce carcinogenic disinfectant byproducts (DBPs). Thus, alternative economical and efficient methods for the removal of heavy metals and biological water contaminants are urgently needed. In the present study we compared the application of nanotechnology and biotechnology for water treatment. The nanotechnology investigation involved the following carbon based nanomaterials: graphene oxide (GO), graphene oxide functionalized with Ethylenediaminetetraacetic acid (GO-EDTA), and the nanocomposite GO-poly(N-vinyl carbazole) (GO-PVK). The results showed different anti-microbial properties for these nanomaterials in the following order PVK-GO>GO-EDTA>GO. In the case of heavy metal removal, GO-EDTA was more efficient than GO. Additionally, none of these nanomaterials presented human toxicity against the human corneal epithelial cell line hTCEpi. The lack of toxicity to human cells makes these materials promising for water treatment. The application of biotechnology for water treatment was investigated using an environmental consortium obtained from the metal-contaminated Tietê River sediment in São Paulo, Brazil. This investigation focused on heavy metal removal since several prior studies have demonstrated the application of microorganisms in filtration systems for pathogen removal from water, but little is known about their ability to remove heavy metals. The consortium, in the present study, was characterized by 16S rRNA metagenomics to determine its structure and diversity and evaluated for its copper and zinc removal functions. The combination of biodiversity analysis with metal removal function demonstrated that it is possible to use microorganisms from heavily contaminated environments as metal biosorbents to enhance current low-cost treatment methods. Additionally, this work demonstrated that biotechnology can potentially be more efficient than nanotechnology in certain heavy metal water treatment applications.