Managing risks in advanced wastewater treatment plants

Owing to stronger requirements for wastewater management solutions, stemming from physical, regulatory or reputational necessities, the next generation design of wastewater treatment plants (WWTP) will need to take account of water reclamation, energy conversion and material recycling as integral parts. These integrated solutions are more complex than those for conventional WWTPs. Owing to the integration of different technologies, the level and variety of risks will increase as well. Operators face new challenges. Therefore, proper risk management is required to guarantee smooth, robust, long-term and sustainable operation. Understanding the underlying risks and being able to implement a risk management framework are critical to effective and efficient wastewater management. Risk management helps organizations reduce risks related to operational, health, environmental and finance. Furthermore, it also helps in decision-making, when related to opportunity-risk relationships and sustainability (Li 2007). To move toward a more strategic, forward-looking, approach for utility management, a risk-based approach, from source to tap and throughout the whole system life cycle, needs to be considered whenever adopting new, integrated solutions.

The risk management work flow process incorporates multiple steps. In general, it includes risk identification, analysis, evaluation and control measures (IEC 1995; AZ/NZS 2004; International Organisation for Standardization 2009a ). The key components of a risk management process are stakeholder involvement, scientific knowledge, data analysis, technology management and performance goal definition (Carroll et al. 2006 ).

Further, it is understood that risk management is an iterative process. Therefore, the work should be continuously reviewed and updated (International Organisation for Standardization 2009a). There are no strict boundaries between the different steps. Successful risk management also requires careful communication of risks and related aspects to decision makers, scientists and other stakeholders. This paper presents a risk management framework to identify, quantify and ultimately manage the implied risks in complex WWTP.

To develop a sound and cohesive integrated risk management framework, the following domains must be considered:

The strategy needs to set integrated solutions in position as the foundation for new and innovative products and services, since strategic decisions, whether made at corporate or operational level, have a long-term impact on the future success of an organization (Foss 1997). Furthermore, management systems and internal governance have to be established to foster risk-resilience throughout the organization and strengthen its ability to respond to interoperability, reliability, health, safety, and security issues.

The adoption of advanced treatment technologies brings new requirements on the organization's structure. This leads to changes both to processes and the skill sets required. Hence, organizations and ultimately the public must adapt their communications, culture, structure, training and education, and knowledge management, in order to ensure the success of the transformation from a segmented approach to an integrated solution. However, changing the structure is a ‘dynamic process of adjusting to environmental change and uncertainty – of maintaining an effective alignment with the environment while managing internal interdependencies – [and] is enormously complex, encompassing myriad decisions and behaviors at several organization levels.’ (Miles et al. 1978). It is, therefore, critical to follow a structured and transparent process, which includes all of these factors.

Suitable technology is the basis of successful integrated solutions. Major objectives are to develop a technology strategy and establish comprehensive technology management, including business processes, for the evaluation, acquisition, integration, and testing of new, innovative, and proven technologies. Against this background, environmental technology verification has been assigned an important role in evaluating the performance of innovative technologies (Hartzell & Waits 2004).

All stakeholders – e.g., end-users, technology vendors, investors and operators – need to be involved and engaged, in order to realize the successful initiation, implementation and operation of such integrated, complex solutions. For instance, operators need to be aware of the specific consequences of potential wrong operation, such as quality degradation of recycled water. Component suppliers should be involved in the overall plant design so that they can optimize their component for the overall plant safety and performance. End-users may be informed about the specific risks of recycled water to create acceptance to use the water. The importance of stakeholder involvement was shown, for instance, during the implementation of Singaporés NEWater program. The full involvement of the end-user was a critical success factor for the project (Ong 2010).

The outline of the generic risk management process is shown in Figure 1 (Rosén et al. 2007). It covers the analysis, evaluation and control of risk. The arrows show how the results and other information are transferred between the steps. The results of risk analysis are used as input for risk evaluation, to determine whether the risk is acceptable or not. If it is unacceptable, possible risk reduction measures must be identified and implemented.

Risk estimation can be carried out at various levels of detail. In general, evaluation is based on the likelihood (probability) and consequence of each risk event (International Organization for Standardization 2009b ). It is commonly performed using a 5 × 5 risk matrix. A typical risk matrix is shown in Table 1. Red shaded events are most critical and require continuous monitoring even after implementing suitable control measures.

Risks can be managed at different levels in an organization depending upon the kind of decision that needs to be made. Pollard (2008) describes risk management as a process based on three different levels: strategic, program and operations. At strategic levels, regulatory, commercial and financial risks are included, while the risks related to assets and technologies are considered at the program level. Risk associated with specific operations, such as the failure of process components, are managed on the operational level.

This approach has been used to manage risks in a WWTP considering four different domains – strategy and management, organizational structure, technology and stakeholder integration. One of Singaporés WWTPs – NEWater Plant – is used as a model for risk analysis and assessment in this study. The generic process flow diagram is shown in Figure 2.

First, it is important to define the scope, to obtain a meaningful result from a risk assessment. It is known that the main objective of the NEWater plant will be to reclaim water economically at the maximum rate without causing any major environmental impacts. In this context, a risk management process should help the organization to manage public health, environmental and finance-related risks during WWTP operation. For instance, incorrect operation of a treatment unit combined with insufficient water quality monitoring can lead to severe consequences for human safety. Thus, used cleaning chemicals may be not compatible with installed membranes, which may affect the integrity of membrane fibers resulting in pathogen leakage.

The first step of the risk management process is to identify hazards and potential threats, and estimate their probability of occurrence. Subsequently, the risks are evaluated to decide on the control measures required, based on the influence of each on WWTP operation. Hazards are identified at both system and component levels. Risk levels are then estimated using probabilities and consequence scenarios, and, subsequently, assessed and controlled. It is recommended strongly that this process begins in the system design phase, as the costs of risk-related adjustments and the implementation of risk mitigation measures increase with system maturity. Stakeholder involvement is the key to successful risk management. The hazards identified in the WWTP are listed in Table 2. Although, the list is not exhaustive, it gives an overview of potential hazards in a WWTP. At present, quantitative estimation of risk levels is incomplete, so the risk management process and its efficiency are explained on the basis of situation analysis.

Figure 3 shows the logic model for implementation of a risk management framework on municipal WWTPs. A situation analysis for a technology-based risk is shown in this paper. The risk level and impact are analyzed using an event tree including all four domains, as mentioned above. To illustrate the process flow in such a model, pathogen leakage into the product water is used as an example. The root cause of such failures can occur anywhere in any of the four domains. Failure can be due, for instance, to poor management [strategy and management], human error [organization structure], wrong system design [technology], or inconsistent supply chain management [stakeholder integration]. Thus, if the pathogen leakage is due to technology failure, the cause could be a sub-optimal RO performance, perhaps from membrane fouling, poor feed water quality, or failure in a feedback system. It is important to consider all these facts as part of the risk management and to develop mitigation measures, in order to minimize such risks in the technology domain.

Following this process, the risk is then categorized as low or high. Low risks are managed by introducing guidelines for best practice. For high-risk events, existing control measures, technologies, and objectives need to be reviewed, and followed up with corresponding mitigation measures. Based on the outcome, retrofitting of the existing system or a new design may be required to manage such high-risk events.

In a risk assessment and management framework, the data requirements for undertaking assessments are crucial and must be correctly addressed. This is mainly a problem of dealing with uncertainties in the data, and how to select appropriate risk evaluation techniques for the specific issue concerned. Among other things, these two factors are driven by the criticality of a system and the effort invested in it. The rule for selection of an appropriate technique is that the accuracy of the method should not override the inherent uncertainty of the data set (Li 2005). This framework allows the assessment and management of risk levels with appropriate mitigation measures. A similar, integrated risk management logic model is reported for an on-site wastewater treatment system (Carroll et al. 2006).

The concept of risk management frameworks has been introduced and applied to WWTPs, in particular the NEWater plant in Singapore. All risks need to be identified and analyzed, in order to develop adequate control measures. Identified high-risk areas are closely monitored and controlled to avoid major breakdown, delay, etc. in large-scale WWTPs. A risk assessment framework, which is sufficiently generic to capture all relevant risks and sufficiently pragmatic to realize economic implementation, enables successful acceptance of innovative WWTPs accounting for long-term business continuity.

The following benefits can be gained by applying the framework with appropriate care and expertise: (1) Identifying and classifying relevant risk enables cost-efficient resource allocation on the basis of the risk level assessed. (2) Knowing all relevant risks and implementing appropriate mitigation measures ensures the reliability of the system and, hence, protects human health, the environment, and the investment. (3) It gives operators the confidence to work with innovative water treatment technologies, which ultimately fosters the realization of more effective and efficient WWTPs.