A novel monitoring scheme to detect iron oxide particle deposits on the internal surface of PVC drinking water pipes

Abstract

PVC pipe wall samples were acquired from a full-scale drinking water distribution laboratory using 3D printed coupons. Brightfield microscopy and imaging processing were used to investigate iron oxide particles deposited on samples surface.

The interplay of suspended sediment concentration, particle size and fluid velocity on the rapid deposition of suspended iron oxide particles in PVC drinking water pipes

“…The fact that material deposits on the pipe wall were formed by the larger particle fractions of the initial SSC and that the PST increased with fluid velocity suggests that the gravitational settling mechanism might be driving the particle deposition process. This hypothesis is also supported by the fact that no noticeable quantity of particles was observed to accumulate and adhere to the pipe obvert in previous experiments ( Braga and Filion, 2021 ). In this context, it is possible that current methods used to forecast the settling of suspended particles might not be appropriate for drinking water pipes due to fundamental differences of particle attachment mechanisms that are still poorly understood.…”

“…1 and 6 ), a consistent number of iron oxide particle deposits were observed at the pipe invert. Pipe coupon samples from the obvert location were not analyzed in this study since previous research provided strong evidence that only negligeable quantities of particles accumulate at the pipe obvert ( Braga and Filion, 2021 ). Fig.…”

“…A pipe wall coupon sampling system described in Braga and Filion (2021) was also used in the experiments to characterize the accumulation of material deposits at the pipe wall. The system allows for the collection of representative pipe wall coupon samples from a coupon section located at 55% of the pipe loop length ( Fig.…”

“…One hundred (100) field of views (FOV) of each coupon sample were captured using the Nikon Eclipse Ni-E automated upright microscope in brightfield mode at a final magnification of 400X. A previously developed MATLAB image-processing script was used to calculate the percent coverage sediment (%) and particle size analysis (PSA) of material deposits detected on the pipe coupons ( Braga and Filion 2021 ).…”

“…Furthermore, while cohesion is widely assumed to be related to biofilms, it is unclear which forces contribute to holding inorganic particles on the wall in the absence of biofilms. Previous experiments completed in a full-scale PVC pipe loop facility by Braga and Filion (2021) showed that fine iron oxide particle deposits were accumulated only on the pipe invert and that only a small fraction of particles were still held in suspension after a 30-day period where fluid velocity was held constant. Their results suggest that adhesion forces did not develop between particles and the pipe wall to hold them to the obvert or the springline positions of the pipe, and that particles as small as 1 µm were able to settle onto the pipe invert and resist the WSS of common operational velocities in DWDSs.…”