Harold Van Den Berg

Unsafe drinking water and sanitation are major causes of the spread of waterborne diseases in a community. Drinking water supply and sanitation services face threats, such as aging infrastructure, urbanization and climate changes, which may affect the transmission of microbial hazards. Drinking water suppliers and sanitation providers need to know and understand these hazards and the associated risks these hazards pose to the drinking water supply and sanitation system and manage these risks well. To this extent, risk management is crucial for the identification and management of risks in a structured and continuous way. Risk management here includes risk assessment and water quality monitoring. In risk assessment, microbial hazards can be identified and risks can be estimated. Risk assessment can be used to develop control measures to reduces the risks. This may result in prevention of diseases, thereby contributing to public health protection. Monitoring the quality of drinking water and wastewater are key elements to ensure drinking water and sanitation safety by providing (early) signals of hazards for remediate actions.

This thesis will focus on risk management for drinking water supply and sanitation systems to prevent waterborne infectious diseases in different countries and resource settings (see Figure S.2). The main objective of this thesis is to better integrate water quality monitoring and risk assessment into risk management approaches. Another objective is to integrate risk management approaches for drinking water supply and/or sanitation services in order to reduce waterborne infectious diseases. The final objective is to investigate to which extent risk management methods create resilience to future changes, such as climate change and urbanization.

Figure S.2. Overview of the countries (chapters) in which risk assessment and water quality monitoring as part of risk management were addressed for drinking water supply (white circles) and sanitation services (black circles).

Water quality monitoring is an important tool to identify possible risks and validate the effectiveness of control measures. In Mozambique, water quality monitoring was carried out in a small drinking water supply (chapter 2 and chapter 3). The impact of changes in operational strategies, namely increased chlorine dosage, increased supply duration and first-flush, on the microbial water quality was investigated in chapter 2. Based on the results of water quality monitoring, the best strategy could be determined. Increasing chlorine dosage ensured good microbiological drinking water quality but changing the number of supply cycles had no such effect. The detection of E. coli contamination in drinking water at household level could point at recontamination in the distribution or unsafe hygienic practices.
The microbiological quality of drinking water supplied was assessed by analyzing different water samples for the presence of fecal indicators (E. coli) and pathogens (Vibrio cholerae, Salmonella spp. and Campylobacter spp.) and an antibiotic resistance determinant (cefotaxime resistant E. coli) (chapter 3). No E. coli could be detected in 79% of the samples after treatment. Besides E. coli, the pathogens Campylobacter (10%) and Vibrio cholerae (11%) were detected in the treated water. In the distribution system, the number of positive samples increased, presumably due to recontamination. The presence of fecal contamination and pathogens in the drinking water system indicates a health risk.

There are many different risk assessment and risk management approaches. Before implementing a new approach it is essential to start by identifying existing approaches, investigating how information can be shared and if it would be beneficial to implement a new one. Instead of implementing a water safety plan (WSP) as a new approach for drinking water utilities in the Netherlands, existing risk assessment and risk management approaches were identified (chapter 4). The results showed that the six legally required risk assessment and risk management approaches cover the eleven elements of the WHO WSP approach. These legal requirements are complemented by additional activities at sector and water company level such as codes of practice and standard operating procedures. The outcomes of all approaches and activities combined provide information from source to tap. Nevertheless, when using multiple risk assessment and risk management approaches it is crucial to share and combine information derived from the different activities.

An inventory of all communal and industrial wastewater treatment plants (WWTPs) with their characteristics was carried out in the Netherlands (chapter 5). In this study, a risk matrix was drafted to assess wastewater treatment plants at risk for Legionella growth and emission based on the risk criteria type of treatment, temperature of process water, aeration and type of industry. The risk matrix was applied to assess the risk of the identified wastewater treatment plants. Analyzing wastewater collected at WWTPs with moderate to high risk for Legionella growth and emission showed that 18% of the sampled WWTPs were positive for Legionella spp. If Legionella was detected in the wastewater, the responsible authority directly contacted the owner to reduce emission, for example by covering aeration tanks, and protect human health. The work also contributed to the development of guidance to support owners of wastewater treatment plants to identify, interpret, and control risk for Legionella growth and emission. Furthermore, the Dutch Ministry of Infrastructure and Water Management is developing legislation for Legionella prevention from WWTPs.

Climate change puts intense pressure on the availability and quality of water. A climate resilient WSP was implemented in the urban drinking water supplies of Addis Ababa and Adama in Ethiopia (chapter 6). In this study, water quality monitoring was extended at the utilities and at the national level to support the WSP. Based on the risks identified with the WSP, water quality monitoring was optimized by prioritizing parameters. Examples are measuring Cryptosporidium, fluoride and arsenic in raw water to provide information on the severity of the risks. Monitoring E. coli and free chlorine in the distribution network, showed to which extent the risks of recontamination in the distribution network or insufficient chlorination, were controlled. Implementing trend analyses on existing water quality data provided insight on risks over the years, as well as seasonal fluctuations. By continuously linking water quality monitoring and climate resilient WSP, utilization of the collected data was optimized, and both approaches benefit from linking these activities.
Applying risk management approaches for drinking water and sanitation separately might be challenging for small systems or communities with limited human, financial and administrative resources. An integrated water and sanitation safety planning (iWSSP) approach was developed together with guidance and training material for practical application of this novel approach (chapter 7). The integrated approach was piloted in three small systems in rural Serbia. Implementing iWSSP at the pilot sites contributed to a better understanding of both drinking water supply and sanitation system. It also resulted in increased awareness, knowledge and understanding among staff of drinking water supply and sanitation services. The experiences for capacity building on water quality monitoring, risk assessment and risk management in Ethiopia and Serbia are described in chapters 6 and 7. Even though legislation might be in place, better connection to the local context was needed in the form of guidance, capacity building and tools. This was especially the case in small settings.

In chapter 8 the results are discussed and future perspectives are given. The different studies in this thesis contributed to limit exposure of people in different countries to unsafe drinking water or unsafe sanitation practices and therefore support public health protection. In this thesis, we did not investigate to what extent risk management, including risk assessment and water quality monitoring, reduced waterborne infectious diseases. It has become clear that there is still room to improve the implementation and application of risk management in different settings. Firstly, many international and national regulations and risk management guidelines exist to guarantee safe drinking water and sanitation services. To ensure that risk management is applied both urban and rural, as well as in all countries, it is necessary to minimize the gap between legislation and practice. Taking into account local needs and challenges in different areas plays an important role. For the monitoring of water quality, a selection can be made based on resources and local needs. Secondly, water quality monitoring and risk assessment can be better linked, to strengthen both. A risk assessment could form the fundament for the selection of parameters, the frequency of the analyses and the method of analysis. Water quality monitoring contributes to safe drinking water and sanitation, which is reinforced by the use of water quality data to improve risk assessment and risk management.

The main conclusion from this thesis is that both risk assessment and water quality monitoring contribute to risk prevention and therefore should be well embedded in the risk management approach. It is possible and useful to integrate or combine risk management approaches. This can be done for a single water application, such as drinking water or sanitation, but also for multiple water applications. Risk management for drinking water or sanitation services needs not be limited to one approach as other methodologies can be complementary. If multiple approaches are used, sharing data between the different methodologies and reviewing the approaches regularly to be up-to-date is needed to address and manage new challenges. In this way, health risks related to drinking water and sanitation now and in the future are minimized. In this thesis, risk management for drinking water and sanitation services were integrated into one approach (iWSSP). In the future, water scarcity will be an increasing problem on every continent due to climate change and a growing population. To be resilient to these challenges, an integrated and inclusive approach to the management of available water should be adopted. iWSSP can be extended by integrating or combining risk management for other water applications in order to use the water correctly and efficiently (fit-for-purpose), depending on the quality and possible health risks.