Continuous Fermentative Hydrogen Production Using a Two-Phase Reactor System with Recycle
Bibliographic record
Abstract
The effects of effluent recycle were examined in a two-phase anaerobic system where the first phase was operated for fermentative hydrogen production and the second for methanogenesis. The hydrogen reactor was operated as a chemostat at 35 degrees C and pH 5.5 with a 10 h hydraulic retention time, and the methane reactor was operated as an up-flow reactor at 28 degrees C and pH between 6.9 and 7.2. Two recycle ratios were examined: 0 and 0.98. Effluent recycle reduced the required alkalinity for pH control by approximately 40%. The H2 productivity metric, with a basis in electrons and incorporating both gaseous and dissolved H2, was developed as a more fundamental reporting method than the molar H2 yield. Without recycle, the H2 productivity was 0.115 g of H2 COD/g of feed COD, but decreased to 0.015 q of H2 COD/g of feed COD with recycle (COD = chemical oxygen demand). Mass balances indicated the lower H2 productivity during recycle was due to electrons being partitioned to methane and less-oxidized soluble constituents such as propionic acid, ethanol, and butanol. The results indicated that achieving high H2 productivity with nonsterile wastewaters will be challenging and membrane filtration of the recycle liquid may be required to exclude the return of hydrogen-consuming organisms.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".