Corrosion control strategies for the Halifax regional distribution system
Bibliographic record
Abstract
Corrosion in drinking water distribution systems is an important issue for many water utilities because it can lead to water losses, increased headloss, and deterioration in water quality. The objective of this investigation was to evaluate the effectiveness of different corrosion control strategies for maintaining water quality in the Halifax regional distribution system. The corrosion control methods investigated at the pilot scale were lime addition, polyphosphate addition, and pH adjustment with NaOH. The strategies were evaluated with both pilot- and full-scale distribution systems. The pilot-scale system used in the investigation consisted of four 1.5-m sections of 100-year-old cast-iron pipe. Water flowed continuously through the pipe section for the first phase of the pilot-scale investigation. For the second phase of the pilot study, water was allowed to stand in the pipe for 1, 3, 6, and 12 h, which was intended to represent a no-flow or dead zone in the distribution system. Eight sampling points were used in the full-scale portion of the investigation. The hydraulic retention times of the sampling point ranged from 1.5 to 55 h. Both the lime and polyphosphate treatments provided similar performance during the pilot-scale continuous flow and standing periods. However, lime addition significantly increased post-filtered turbidity levels, which resulted in excessive deposition of insoluble material during the standing periods. At full scale, polyphosphates provided better corrosion protection than pH adjustment with NaOH. Based on both pilot- and full-scale data collection, polyphosphate was considered as the preferred corrosion control strategy for the Halifax regional distribution system.Key words: corrosion, water distribution system, corrosion control, polyphosphates, cast iron.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".