Re-assessment Estimation of the Wastewater Treatment Plants’ Seismic Vulnerability

Many empirical studies use questionnaires for the vulnerability estimation of technical structures. Wastewater Treatment Plants (WWTPs) are critical infrastructure whose the seismic impacts may affect the environment and the society. Interesting results are revealed from the comparison of seismic vulnerability questionnaires granted between different periods. In this study a Questionnaire “A” (Que-A) of 44 questions was distributed to the responsible operators of a representative sample of 116 Greek WWTPs during 7 months in 2021. After six months, a similar Questionnaire “B” (Que-B) of 14 questions was distributed to another representative sample of responsible operators of 40 WWTPs which lasted 3 months in 2022. Both surveys were used Likert Scale and were checked for their internal reliability and validity. The results revealed that the recipients were graduated operators of the WWTPs occupying positions of high responsibility for both “A” and “B” Questionnaires, and their experience didn’t differ each other. A limit correlation between vulnerability and seismic vulnerability was noticed in Que-B. No difference was observed between the frequencies for seismic vulnerability of Que-A and vulnerability of Que- “B”. The same was occurred comparing the seismic vulnerability of both the Questionnaires. The same results for both the Questionnaires were extracted comparing the seismic vulnerability due to structural vulnerability, non-structural vulnerability or operational vulnerability. Finally, the soil-water pollution in the post seismic period (immediate and after 24 hours) presents the same percentages for both the Questionnaires. Concluding, the study supports the claim that these two Questionnaires produce similar results while Que-A has reliability, and can be used for WWTPs’ vulnerability estimations.