Sensing acid permeation conditions of wastewater pipe coatings for long-term quality assurance

Corrosion of concrete wastewater pipes is a major problem for water utilities around the world. Internal pipe coatings for protecting wastewater pipes from corrosion-related structural damage are viewed as a low-cost alternative to the expensive process of replacing pipes. The coatings are, however, susceptible to defects owing to acids produced by microbes that dwell on pipe walls. Therefore, water utilities are keen on assessing the state of acid permeation of internal pipe coatings on a regular basis to ensure the coating's long-term performance. Current standard practice for evaluating acid permeation is to collect core samples from the pipe and analyze them in a lab, which is costly, and labor intensive. In this paper, we propose an improved method for accessing acid permeation conditions of cement-based pipe coatings within hostile wastewater pipes using real-time pH measurements. Field experiments were carried out within a real wastewater pipe owned by Sydney Water in Australia. Sensor measurements of three different coatings were obtained, and the results were compared to the benchmark values. Overall, the proposed sensing method improves the current practice (core sampling) of acid permeation assessments of wastewater pipe coatings.