Surface analysis of pilot distribution system pipe autopsies: The relationship of organic and inorganic deposits to input water quality

- 4 different treatment trains fed 4 identical pilot distribution systems (PDS).
- Novel application of ToF-SIMS for assessing autopsied pipe deposits composition.
- Metal deposits were associated with post-coagulation and infrastructure corrosion.
- Low MW organics found at PDS inlet with higher MW biopolymers at PDS outlet.

Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) surface analysis was conducted to characterise deposits in polyethylene pipes used in a novel pilot water distribution system (PDS). The system consisted of four (4) parallel distribution systems receiving water from different treatment processes, ranging from conventional coagulation through to an advanced membrane filtration system. After two years of operation, the distribution system was shut down and samples of pipe were collected for autopsy analysis. Inlet and outlet samples from each PDS were collected for purpose of comparison. ToF-SIMS was used to assess chemical differences in surface biofilm accumulation and particulate deposition, which resulted as a consequence of the treatment method and operational mode of each system. These data supplemented previously collected bacteriological and chemical water quality data. Results from the inorganic analysis of the pipes were consistent with corrosion and contamination events that occurred upstream in the corresponding treatment systems. Principal component analysis of data on organic constituents showed oxygen and nitrogen containing fragments were associated with the treatment inlet and outlet samples. These types of signals can often be ascribed to biofilm polysaccharides and proteins. A trend was observed when comparing samples from the same PDS, showing an association of lower molecular weight (MW) organic fragments with the inlet and higher MW organic fragments with the outlet samples.

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