Groundwater has been believed to be free of microbial contamination because of long vertical transport for microbes to reach aquifers (Krauss, 2011). However, leakage from sanitation systems, disposal systems, underground storage tanks and accidental waste water discharge are potential sources of pathogenic entry to groundwater (Krauss, 2011; Selvam et al., 2014). Common pathogens contaminated from various sources with groundwater includes bacteria such as Escherichia coli, Salmonella species, Shigella species, Vibrio Cholerae and Legionella species, viruses such as Piconaviridae, Caliciviridae, Reoviridae, Adenoviridae and Coronaviridae and protozoans such as Crptospiridium pavum, Giardia lambia, Taxoplasma gondii and Entamoeba histolytica (Close et al, 2008; Krauss, 2011).
A number of factors such as number of pathogens released to the environment, the persistence of the pathogens in the environment, filtration of pathogens through the soil and the hydrological conditions influence the pathogenic contamination of groundwater (Close et al., 2008). Groundwater with greater depth and fine grained soil can filter more pathogens.
Various factors influence the transport and survival of microorganisms in groundwater. The processes such as advection, dispersion, diffusion, size exclusion, retention and release from solid-water or air-water interfaces has effects on the transport and survival of micro-organisms (Bradford et al., 2014 ). Higher concentration of microorganisms can be found in the capillary fringe, the region of the subsurface above the groundwater table (Horn et al., 2014). Further, microbial transport and survival in groundwater is affected by physio-chemical, biological and hydrodynamic factors (Bradford et al., 2014). Bacterial transport through a porous medium has been found to be affected by cell shape, the ratio of cell width to cell length (Newby et al., 2014).
Bradford, S.A., Wang, Y., Kim, H., Torkzoban, S. and Simunek, J. (2014) Modeling Microorganism Transport and Survival in the Subsurface. Journal of Environmental Quality, Vol 43, pp. 421-440.
Close, M., Dann, R., Ball, A., Pirie, R., Savill, M. and Smith, Z. (2008) Microbial Groundwater Quality and its Health Implications for a Border-Strip Irrigated Dairy from Catchment, South Island, New Zealand. Journal of Water and Health, Vol 6(1), pp. 83-98.
Horn, P., Jost, D., Bastian, P. and Ippisch, O. (2014) Microbial Growth and Transport in Saturated and Unsaturated Porous Media [Online] Available at http://www.meetingorganizer.copernicus.org [Accessed on 16 August 2014].
Krauss, S. and Griebler, C. (2011) Pathogenic microorganisms and viruses in Groundwater [Online] Available at http://www.acatech.de [Accessed on 15 August 2014].
Newby, D.T., Pepper, I.L. and Maier, R. M. (n.d.) Microbial Transport [Online] Available at http://www.scholar.enu.kz [Accessed on 16 August 2014].
Selvam, S., Antony Ravindaran, A., Rajamanickam, M. and Sridharan, M. (2014) Microbial Contamination in the Sediments and Groundwater of Tuticorin Corporation, South India using GIS. International Journal of Pharmacy and Pharmaceutical Sciences, Vol 6(4), pp. 337-340.