Ozonation of kraft pulp mill effluents: process dynamics
Bibliographic record
Abstract
Pulp mill wastewater discharged from an aerated stabilization basin (ASB) of a kraft pulp mill was ozonated in an extra-coarse-bubble diffuser contactor. The ozonation process is dynamic. Therefore, modeling the reduction efficiencies of contaminants present in the pulp mill effluent and the ozone gas absorption process became more complex than the pure water situation. The ozonation-process-mitigated reduction of colour, absorbable organic halides (AOX), chemical oxygen demand (COD), and total organic carbon (TOC) were examined. Ozone was more effective in reducing the colour and AOX than in reducing the COD and TOC. At an ozone dose (ΔΔO3) of 230 mg L1, the maximum reduction efficiencies of colour, AOX, COD, and TOC were 86, 44, 22, and 15%, respectively. Ozonation was also very effective in increasing the biochemical oxygen demand (BOD5) of the pulp mill effluent. The biochemical oxygen demand increased by about 320% at ΔΔO3 of 230 mg L1. Ozone gas absorption dynamics were investigated by continuous monitoring of the feed-gas and off-gas ozone concentrations and flowrates. Owing to the occurrence of rapid reactions between ozone and some contaminants in the liquid phase, the mass transfer process was enhanced by an enhancement factor, E. The application of the well-known two-film theory and the assumption that the ozone reactions followed pseudo-first-order irreversible kinetics, the overall mass transfer coefficient, kLa, and the enhancement factor, E, were determined as functions of ΔΔO3. The induced reductions of pulp mill effluent contaminants and ozone gas absorption dynamics were compared to those obtained in other ozonation systems to investigate the effects of contactor design, configuration, operating conditions, and scale on the performance of the ozonation process. Key words: absorbable organic halides, chemical oxygen demand, colour, enhancement factor, mass transfer, ozonation process dynamics, total organic carbon.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".