Micropollutant Mass Transfer Zones in Granular Activated Carbon Contactors
Bibliographic record
Abstract
A “minicolumn” test approach was recently developed to estimate the performance of preloaded granular activated carbon (GAC) in water treatment plants for micropollutant removal. One of the requirements of this test is that the GAC bed must have a broad mass transfer zone (MTZ) for the contaminant of interest, but this has never been verified. In this study, GAC of different ages harvested from three different bed depths was subjected to lab-scale minicolumn and isotherm tests to measure adsorption kinetics and thermodynamic properties, respectively. The GAC was challenged with micropollutants with a range of adsorption characteristics. The GAC was found to exhibit approximately uniform removal efficiencies for all of the selected micropollutants across the depth, indicating a broad MTZ. Additionally, the MTZ for 2-methylisoborneol and geosmin in a newly installed GAC filter was observed to broaden to beyond the depth of the filter within 7 weeks of installation. This work helps to verify the minicolumn test protocol and supports a novel approach by eliminating the dependence of GAC performance on bed location. With such an approach, utilities may more easily conduct the minicolumn test to establish an accurate GAC replacement schedule and to optimize GAC operation for maximum contaminant removal.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 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 | 0.000 |
| 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".