Thorough and careful risk analysis is essential for making well-versed decisions in order to minimize the public health risk from different infectious waterborne diseases. However, risk analysis methods and procedures are challenged by multiple sources of uncertainty and lack of appropriate information. Water harmonized QMRA framework is a growing multidisciplinary field that combines scientific knowledge about the occurrence of microbial pathogens, their fate and transport in the water systems, the routes of exposure to human being and the different health effects that may result from this exposure, along with the effect of natural and engineered barriers and hygiene measures (WHO 2016). Since QMRA is a young risk analysis approach, the methodology used to examine the occurrence and concentration of the microbial pathogen, and their fate and transport in the water systems are potentially challenging with substantial implications on the magnitude of estimated health risk. While there are a number of QMRA studies in different environment, there is a scant research on the method of assessment about the spatiotemporal spreading of microbial pathogens under different environmental conditions, their trends and probabilistic behaviour of extreme events. This study designed in response to the research need to fuel QMRA approaches with the necessary advance specifically in exposure assessment and risk characterization by addressing such challenges.
Waterborne pathogens are transmitted to human through drinking contaminated water, ingesting contaminated water during bathing, in the preparation of food, or the consumption of food that is infected. Considering the most common pathways, the study was designed to focus on applying a QMRA framework to a drinking water source (Paper I), recreational water (Paper II, III, and IV), and recycled water (Paper V and VI). The QMRA framework encompasses four basic elements as an assessment steps mainly targeted to risk management issues, and with regard to different steps of QMRA framework, the role of individual papers are illustrated in Figure 3.
There are different opportunities for application of QMRA, and the microbial water quality data set collected from the raw water at drinking water treatment plant is one of the potential sources of information readily available to use as an input for QMRA. The application of statistical tools on such data set could potentially provide information about the pollution status of the source water and the behaviour of extreme microbial load events; at the same time, it could be possible to integrate such information with QMRA approaches. The first part of the study focuses on the exploration of valuable information on the microbial water quality data (time series) of drinking water source at DWTP through statistical analysis (Paper I). The statistically based water quality modelling study of the drinking water source from Glomma River provides information about the trend of changes, magnitude and frequency of extreme microbial load; it could be an input for exposure assessment step of QMRA.
The investigation of different processes (rainfall, discharge from boats, and wind directions) on the spreading of microbial contaminants in the recreational beaches using hydrodynamic modelling could also be an input for exposure assessment step in QMRA (Paper II). Considering the importance of hydrodynamic modelling, the study investigates the spreading of microbial pollutant using E. coli as an indicator in order to understand the recreational water quality under
the different condition as well as to make use of the simulated result in QMRA framework. The study that combines discharge-based hydrodynamic modelling with QMRA framework in the context of bathing water quality after rainfall event evaluated the public health risk in order to support beach management decisions (Paper III). This study combined data from the hydrodynamic model simulation, monitored data, and microbial pathogens from secondary data sources. The study fitted with exposure assessment, risk characterization, and risk management steps of QMRA framework. Information about the concentration, growth and decay rates of enteric microorganisms in different wastewater systems and water bodies are crucial for the fate and transport modelling of microbial pathogens and an input for exposure assessment step of QMRA. However, little information is available about the decay rates of faecal bacteria and viruses in the marine environment where many wastewater treatment plants discharge their effluent. To solve such challenges, one of the studies focused on the investigation of the decay rates of FIB and pathogenic viruses in seawater from different depths (Paper IV).
Water reclamation, recycling and reuse is currently a vital component of integrated water resource management, however, associated health risk has been debatable in the different part of the world. With regard to this problem, the third part of the study was designed to assess the efficiency of an integrated greywater treatment system, and evaluate the health risk associated with treated greywater reuse for irrigation (Paper V). The health risk assessment associated with treated greywater reuse for hydroponic lettuce production and consumption considered as exposure assessment, risk characterization, and risk management steps of QMRA framework.
One of the principal objectives of wastewater treatment is to discharge the treated wastewater without causing danger; however, the degree of treatment may not be sufficient and raise concern for the contamination of source water. In order to understand the effectiveness of treated greywater disposal system in removing virus and bacteria and to evaluate removal efficiency of both unsaturated and saturated flow conditions, Paper VI was designed. The assessment of treated greywater disposal system in removing virus and bacteria as a post treatment step was evaluated in both unsaturated and saturated flow conditions and the result could provide information for the decision of safest setback distance between treated wastewater disposal site and drinking water sources.
Overall, the goal of this body of research was to enrich the QMRA approach through the assessment of fate and transport of microbial pathogens in the identified pathways of interest (drinking water source and recreational water) using statistically, and processes-based water quality modelling techniques coupled with the QMRA framework. Moreover, this study addressed the health risk issues associated with water reuse and treated greywater disposal systems. Both studies could give valuable insights about the effect of source separation, greywater treatment, and disposal systems.
Figure 3. Conceptual framework of the study in relation to QMRA framework