Effect of hydraulic retention time and attachment media on sulfide production by sulfate reducing bacteria
Bibliographic record
Abstract
The effects of hydraulic retention time (HRT) and attachment media on the rate of microbial sulfate reduction with lactate as a carbon and energy source were investigated for sulfate reducing bacteria (SRB). Laboratory experiments were conducted in semi-continuous and continuous modes by using synthetic feed in three parallel 10-L PlexiglasTM upflow anaerobic reactors. The lactate:sulfate was maintained below 2 for proper SRB activity. Results indicated that 70% of the lactate fed was bio-oxidized and 30% was biosynthesized, which showed that the energy production reaction dominated over the synthesis reaction in non-packed reactors. Continuous mode operation of three upflow anaerobic suspended growth reactors yielded effluent sulfide concentrations as high as 190 mg/L at the optimum conditions of 20 h of HRT, 1.5 m/d of upflow velocity, and an organic loading rate (OLR) of 6 kg d–1 m–3, regardless of the presence of attachment media in the reactor. The critical HRT was 10 h. Lower retention times showed a significant decrease in the effluent sulfide concentration and washout of biomass. When the OLR was doubled, the rate of sulfide production increased proportionately. Key words: sulfate reducing bacteria (SRB), hydraulic retention time (HRT), support media, sulfide production.
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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) | 0.001 | 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 | 0.001 |
| 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".