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  • Chapter-5

    Bioreactor System and Nanotechnology for Water Treatment

  • Bioreactor System and Nanotechnology for Water Treatment

    191

    5.1 INTRODUCTION

    Water is one of the essential enablers of life on earth. Beginning with the

    origin of the earliest form of life in seawater, it has been central to the evolution of

    human civilizations. Years of intense research have contributed significant

    breakthroughs in the treatment of polluted water systems. Bioreactor systems and

    application of nanotechnology are recently developed options for the better

    treatment of the contaminated water. Bioreactor offers platform for the laboratory

    evaluation of large scale systems for industrial applications. Once designed, the

    system can be optimised for significant parameters and scale up can be done to

    greater level of precision. Noble metals have been similarly associated with the

    prosperity of human civilizations through their prominent use in jewellery and

    medical applications. The most important reason for the use of noble metals is the

    minimal reactivity at the bulk scale, which can be explained by a number of

    concepts such as electrochemical potential, relativistic contraction, molecular orbital

    theory, etc. Recently, water quality has been associated with the development index

    of society. A number of chemical and biological contaminants have endangered the

    quality of drinking water. The present work includes novel approaches in the area of

    the application of bioreactor systems and noble metal nano particle in the treatment

    of contaminated river water system

    Reactor systems generally offer effective and promising output for online

    applications. Reactor systems can be designed to incorporate multiple stages which

    can be sequentially put into operation according to the requirement. This added

    advantage is a huge benefit in water treatment processes as it requires multiple

    methodologies at various level of treatment.

  • Chapter 5

    192

    The polluting factors of contaminated water belong to various categories and

    specific treatment strategies are required to tackle each polluting factor. The most

    significant polluting aspect of contaminated water system is the presence of high

    amount of suspended particles. These particles may be of dissolved or suspended

    type, The removal of the total suspended matter is mostly effected by physical or

    chemical methods The physical methods are not so cost effective and often result in

    the replacement and frequent service requirement of the tangential screens. However

    subjecting to natural sedimentation is a cost effective process. But this is a very slow

    process and requires more time. Hence additional process aids are required when it

    is a matter of large volume of water and particularly when the suspended solids are

    relatively high.

    The incorporation of additional coagulation and flocculation process to

    facilitate better removal of suspended natter contribute to better performance of

    subsequent treatment strategies.

    Bioreactor may refer to any manufactured or engineered device or system

    that supports a biologically active environment. A bioreactor may also refer to a

    device or system meant to grow cells or tissues in the context of cell culture. These

    devices are being developed for use in tissue engineering or biochemical

    engineering or waste management. On the basis of mode of operation, a bioreactor

    may be classified as batch, fed batch or continuous. The present bioreactor system

    offers multiple treatment strategies contributing to effective removal of suspended

    solids, removal of coliforms and hence facilitating chlorination at low dose. This

    treatment strategy can be applied online effectively and can be easily scaledup.

  • Bioreactor System and Nanotechnology for Water Treatment

    193

    The application of noble metal nanoparticle based chemistry for drinking

    water purification is summarized for three major types of contaminants: halogenated

    organics including pesticides, heavy metals and microorganisms. Realizing the

    molecular nature of contamination in drinking water, significant progress has been

    made to utilize the chemistry of nanomaterials for water purification. Scientist

    working in the field of environmental nanotechnology view that working at the

    nanoscale is not detrimental to the environment. Studies have shown that

    nanotechnologies can be used not only to prevent pollution, but also to clean up

    pollutants once they have made their way in to the environment. Automatically

    precise manufacturing at nanoscale should be able to eliminate chemical pollution

    entirely by giving control of processes at the molecular level

    Today most of the countries are facing drinking water problems and

    conditions are very severe, especially in developing countries. The world is facing

    formidable challenges in meeting rising demands of clean water as the available

    supplies of freshwater are depleting due to (i) extended droughts, (ii) population

    growth, (iii) more stringent health based regulations and (iv) competing demands

    from a variety of users USBRSNL (2003), USEPA (1998b), USEPA (1999).Clean

    water (i.e., water that is free of toxic chemicals and pathogens) is essential to human

    health. In countries such as India, 80% of the diseases are due to bacterial

    contamination of drinking water. The World Health Organization (1996)

    recommended that any water intended for drinking should contain faecal and total

    coliform counts of 0, in any 100 ml sample. When either of these groups of bacteria

    is encountered in a sample, immediate investigative action should be taken. The

    removal or inactivation of pathogenic microorganisms is the last step in the

  • Chapter 5

    194

    treatment of wastewater. USEPA (1998b). The protection of water treatment

    systems against potential chemical and biological acts is also becoming a critical

    issue in water resources planning (USEPA, 1999; USEPA, 1998).

    Despite the modern success of nanotechnology, the potential health and

    environmental risks associated with these applications remain unknown. Prompted

    by the discovery that nanoparticles can enter the human body and accumulate in the

    environment, government agencies have begun to manage research of

    nanotoxicology. In September 2006, the National Nanotechnology Initiative

    reported the intent to research methods to evaluate the toxicity of nanoparticles in

    the environment and the human body. This critical information needed is also the

    primary focus of the USEPA with regard to nanotechnology. Due to the

    overabundance of silver nanoparticles in the consumer market, nanosilver has

    become a specific area of interest among research scientists. The concerns and

    potential consequences related to exposing nanosilver to our water environment

    through consumer products are tremendous. If exposed to the environment, silver

    nanoparticles may induce the death of bacteria that are surrogate environmental

    organisms and vital to all ecosystems. Moreover, in the 1980s, silver ion pollution

    from a processing plant endangered the native population of Macoma balthica clams

    in the South San Francisco Bay. Since nanosilver is a derivative of silver and silver

    ions, the effects of a silver ion pollution in the 1980s may foreshadow a similar and

    possibly even worse consequence with nanosilver pollution. Furthermore, the

    accumulation of nanosilver in the water environment may have an adverse effect on

    the aquatic organisms that inhabit the polluted areas. Current research has shown

    that zebrafish embryos exposed to nanosilver result in delayed development,

  • Bioreactor System and Nanotechnology for Water Treatment

    195

    defective fetal maturation and death. The most detrimental effect of silver

    nanoparticles would be our efforts in recycling water in the wastewater industry.

    Several strains of bacteria are implemented in wastewater treatment to digest the

    organic substances present in the sludge. Later these organisms can be destroyed

    with nanosilver particle. It is clear that the potential consequences of direct or

    indirect exposure of nanosilver to the environment are detrimental. As a result, it is

    necessary to develop a systematic technique to quantify and analyze the bacterial

    toxicity of silver nanoparticles in environmental conditions. In addition, the

    abundance of silver nanoparticles in consumer products increases the possibility of

    environmental exposure; thus, it is necessary to analyze the toxicity of silver

    nanoparticles in such products.

    A water filter with 0.3 nm pores (on left) would clean water down to the

    atomic level with minimal pressure drop due to drag. Silver coated Nanofilters are

    used in many industrial applications for water purification. They are being evaluated

    because of their ability to reduce the coliform content and reduce clogging compared

    to traditional filtration methods

    Nanofilters can help to tackle decontamination of groundwater from

    industrial and natural sources. Semi - permeable membrane can act as a molecular

    sieve allowing water to pass through while rejecting impurities such as viruses,

    spores, bact

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