The influence of precursors and treatment process on the formation of Iodo-THMs in Canadian drinking water
Bibliographic record
Abstract
The National Survey of Disinfection By-Products and Selected Emerging Contaminants investigated the formation of various disinfection by-products and contaminants in 65 water treatment systems (WTSs) across Canada. Results for six iodo-trihalomethanes (iodo-THMs) are reported in this paper. The participating water treatment systems included large, medium and small systems using water sources and treatment processes which were representative of Canadian drinking water. Five water samples (source water, treated water and three water samples along the distribution system) were collected from each treatment system, both under winter and summer conditions. Samples were stabilized, shipped cold and analysed for six iodo-THMs (dichloroiodomethane-DCIM; dibromoiodomethane-DBIM; bromochloroiodomethane-BCIM; chlorodiiodomethane-CDIM; bromodiiodomethane-BDIM and triiodomethane or iodoform-TIM), using a SPME-GC-ECD method developed in our laboratory (MDLs from 0.02 μg/L for iodoform to 0.06 μg/L for bromodiiodomethane). Concentrations of relevant precursors like dissolved organic carbon (DOC), bromide, iodide and total iodine, as well as other water quality parameters, were also determined. Detailed information about the treatment process used at each location was recorded using a questionnaire. The survey showed that one or more iodo-THMs were detected at 31 out of 64 water treatment systems (WTSs) under winter conditions and in 46 out of 64 WTSs under summer conditions (analytical results from one site were excluded due to sampling challenges). Total iodo-THM concentrations measured during this survey ranged from 0.02 μg/L to 21.66 μg/L. The highest total iodo-THM concentration was measured in WTS 63 where all six iodo-THMs were detected and iodoform was present in the highest concentration. The highest iodo-THM formation was found to occur in treatment systems where water sources had naturally occurring ammonium as well as high bromide, high iodide and/or total iodine concentrations. In two such water systems the total concentration of iodo-THMs exceeded the concentration of regulated THMs.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".