Fate and Transport of Pathogen in Sub Surface Environment-A Review

Abstract

Micro-organisms are a threat to water quality and human health due to its large-scale distribution in the aquatic environment. The cause of health risk is due to the discharge of untreated / partially treated wastewater from various sources. The wastewaters are also used for irrigation during lean seasons in many parts of the urban environment. It is essential to understand the impact of wastewater usage in agriculture due to lack of investigations on the movement of microorganisms.  Several research gaps exist in the studies related to fate and transport of pathogens in the vadose zone.   Microbial transportation in the unsaturated zone poses many challenges which   comprises the tracing of pathogens in the unsaturated zone because of uneven preferential flow conditions. The estimation of survival rates of microorganisms in the subsurface environment is significant as it directly affects the health risks of living organisms. The hydraulic properties of soil are critical in the movement of pathogens in the vadose zone. The retention predictions of microbes are highly variable due to the presence of colloids, dissolved organic matter, and variable solution chemistry (pH and ionic strength) which changes the surface charge of the media and the microbes. There is a scarcity of field scale data representing different soil layers which is a major constraint in model prediction of preferential flow paths and survival of pathogens in the vadose zone. Review focusses on pathogen transport processes, decay rates. This review is about the process of attachment, detachment, undergoing straining action of pathogens when they are bound with complex organic matter.