University of Twente Student Theses


Carbon footprint assessment of maintenance and rehabilitation techniques of sewer systems

Sharif, O. (2020) Carbon footprint assessment of maintenance and rehabilitation techniques of sewer systems.

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Abstract:Purpose: The main aim of this thesis was to get a better understanding of the environmental impacts that are associated with the maintenance and rehabilitation of conventional gravity sewer systems. Results obtained in this study should support decision-making processes in sewer system management. Methods: In this study, a carbon footprint assessment was performed according to the ISO14067:2018 standard. Open trench replacement, trenchless renovation, open trench and trenchless repair, inspection, and cleaning of sewer pipes were the object of the assessment. The life cycle stages considered were raw material extraction, manufacturing processes, maintenance/rehabilitation, and transportation. The functional unit was defined as: “To maintain the original function of a gravity sewer section with an average length of 45 meters and a diameter of 200 to 1500 mm during a period of 100 years in the Netherlands”. Widely recognised embodied carbon databases for construction materials were used to calculate the environmental impacts. Finally, a sensitivity analysis was performed in this study to assess how the results vary as a consequence of changes in inputs. Results and discussion: Considering open trench pipe replacement, the reinforced concrete has the worst environmental performance (highest kg CO2-eq emissions) whereas the replacement using concrete pipes was found to be the best performer. The production of pipe materials and asphalt are the main contributors to the CF score of pipe replacement. With regard to trenchless renovation, curedin-place pipe (CIPP) lining with fibreglass material was found to be significantly more environmentally sustainable than CIPP lining using needle felt material. The results also show that fibreglass CIPP lining is much more favourable than open trench replacement (including asphalt rehabilitation). Furthermore, trenchless sewer repair technologies have a slightly better environmental performance than open trench repair. Finally, the results suggest that sewer inspection using the so-called “Manhole-Zoom” camera approach is by far the most environmentally sustainable option. As far as the sensitivity analysis is concerned, the results show that the environmental impact results are most sensitive to changes related to the material properties of components, such as, for instance, the asphalt pavement width, CIPP liner thickness, sewer pipe length, etc. Conclusions: The findings of this study suggest that the main opportunities for reduction in the environmental impacts of pipe replacement lie in the choice of pipe materials and design of asphalt pavement. Furthermore, adopting trenchless technologies can significantly reduce the environmental burdens of sewer pipe rehabilitation. For sewer maintenance, the use of the Manhole-Zoom camera approach for pipe inspections should be encouraged and promoted.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Programme:Civil Engineering BSc (56952)
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