EFFECT OF TITANIUM DIOXIDE NANOPARTICLE ON MICROBIAL BIOMETHANE POTENTIAL
Much attention has been given to nanotechnology and nanoscience over the last decade. These studies involve a wide spectrum of research areas and industrial activities from fundamental sciences (that is physics, chemistry and biology) to applied science (that is electronics and materials) on the nanoscale (1nm=10-9m) (Liu, 2006).One of the major developments in nanotechnology and nanoscience is the production and application of nanoparticles. In general, nanoparticles are chemicals smaller than 100nanometers, contain 20-15000 of atoms, and exist in a realm that straddles the quantum and Newton scales (Shan et al., 2005). Nanoparticles can be produced from different materials in different shapes such as spheres, rods, wires and tubes (Chang et al., 2005), they occur naturally in aquatic and terrestrial environments in finer fractions of colloidal clays, mineral precipitates and dissolved organic matter (Batley et al., 2006). The uses of nanoparticles are widely reported in a wide variety of areas including advanced materials, electronics, magnetics and optoelectronics, biomedicine, pharmaceuticals, cosmetics, energy, and catalytic and environmental detection and monitoring. The use of nanoparticles over the last decade has been more frequent in applications of industrial nature and in consumer and medical products (Batley et al., 2011), the use of nanosized materials offers exciting and new options in these fields and the applications of nanoparticles will likely continue to increase (Frohlich, 2011).
Due to its wide applicability, nanoparticles are easily released into the environment when the goods in which they are contained in are disposed. Nanoparticles can be added to soils directly through fertilizers or plant protection products or indirectly through application to land or wastewater treatment products such as sludges or biosolids (Franklin et al., 2007). Nanoparticles may enter aquatic systems directly through industrial discharges or from disposal of wastewater effluents or indirectly through surface runoff from soils. However, researchers found that once released into the environment, nanoparticles might pose as potential risks to human health, microorganisms and other life forms (Zhenget al., 2011). In addition to physiochemical parameters such as contamination with toxic elements, fibrous structure and high surface charge, the formation of radical species was identified as key mechanism for the cytotoxic action of nanoparticles. Toxic effects of nanoparticles dubbed as “nanotoxicity” are increasingly evidenced, the extent of nanotoxicity depends on the charge, size and nature of the nanoparticle.
In the environment, nanoparticles can undergo a number of potential transformations that depend on the properties of both the nanoparticle and the receiving medium (Rogers et al., 2010). These transformations largely involve chemical and physical processes which may change the fate of the nanoparticle in the environment. Risk assessment for nanoparticle releases into the environment is still in their infancy, and reliable measurements of nanoparticles at environmental concentrations remain challenging. Predicted environmental concentrations based on current usage are low but are expected to increase as use increases.
1.2 Aims and Objectives
- Understand the influence of TiO₂ on microbial activity during anaerobic digestion of food waste
- Assess the effect of TiO₂ on the volatile fatty acid production and biomethane potential
- Determine TiO₂ effect on the diversity and population changes in the methanogenic microbial community.