Identifying and Analyzing Implicit Interactions in a Wastewater Dechlorination System

Abstract

Critical infrastructures consist of numerous components, and even more interactions, many of which may not be expected or foreseen by the system designers. The existence of these so-called implicit interactions indicates design flaws that, if not mitigated, could result in losses of system stability, safety, and security. In this paper, we apply a formal methods-based approach for identifying and analyzing implicit interactions in a real-world Wastewater Dechlorination System provided by a municipal wastewater treatment facility. A system model is developed using the C\(^2\)KA modeling framework and the analysis is automated using a software prototype. The analysis results include a summary of the identified implicit interactions and a calculation of their severity and exploitability, which helps to inform mitigation efforts at early stages of system design. We validate the results with a questionnaire which shows that the rigorous, practical approaches applied in this case study have the potential to improve overall system security and resilience.