Quantitative microbial rsk assessment and water quality modelling : on drinking water sources, recreational and recycled waters

Despite various efforts to improve water quality in all pathways, waterborne diseases are still a major public health concern in both developing and developed countries. To address the threat of waterborne diseases through different measures, understanding the level of risk is very important. In this regard, quantitative microbial risk assessment (QMRA) is an emerging modelling approach, used to estimate the risk of infection and illness from an exposure to disease causing microorganisms, and is currently promoted by the World Health Organization (WHO) to be used for setting water safety criteria and regulations. While QMRA has been useful in estimating health risk levels, and therefore highlighting risk based management options, there are various challenges to apply this method under different conditions. One of the major challenges is the shortage of quantitative data on the concentration of microbial pathogens and inconsistency in water-related pathways. Therefore, monitoring of microbial pathogens is the preferred form of information for QMRA. Currently, the potential for the integration and use of microbial water quality monitoring and modelling as an input for the QMRA framework is an important issue. This study will enrich the QMRA approach through microbial water quality modelling. The trend, extreme microbial loads, transport, and spreading of microbial pollutants in the identified pathways of interest (drinking water source and recreational coastal water) were investigated using statistically (Paper I), and deterministically (Paper II) based water quality modelling techniques, and then coupled with the QMRA framework (Paper III). There is also a microbial decay rate study in seawater, which could be an input for microbial fate and transport modelling (Paper IV). Furthermore, this study addressed the health risk issues associated with treated greywater reuse (Paper V), and microbial pollutant and nutrient removal efficiency of treated greywater disposal systems (Paper VI). Unsaturated and saturated flow studies provided valuable insights about the removal of microbial pathogens by on-site wastewater treatment systems that could be relevant in some QMRA settings