Methane production and microbial adaptation in high-load vacuum-enhanced anaerobic digestion: Addressing ammonia and propionate toxicity
Bibliographic record
Abstract
• IntensiCarb technology processed 6 times the OLR of conventional AD. • Methane yield decreased linearly with increasing propionate concentrations over 2.20 g/L. • Side-stream vacuum increased ammonia toxicity resilience by a factor of 3. • Population of propionate degraders in IC was different from conventional AD. • Methanosaeta dominated conventional AD, while Methanosarcinaceae dominated IC reactors. Ex-situ vacuum-enhanced anaerobic digestion (IntensiCarb-AD) of primary and thickened waste activated sludge (PS/TWAS) was tested at an organic loading rate (OLR) of 11.0–11.3 kg COD/m 3 -d. IC-AD reactors with similar solids retention times (SRT = 20 d) and OLR, were operated at hydraulic retention times (HRT) of 5 days (IF defined as SRT/HRT of 4) and 3.33 days (IF6). IF4 had a higher steady-state methane yield of 0.214 ± 0.009 L-CH 4 /gCOD fed compared to 0.148 ± 0.029 L-CH 4 /gCOD fed in IF6. COD removals of 53.5 %±2.25 % were obtained with IF4 but fluctuated with IF6 (37.0 %±7.25 %). Both IF4 and IF6 processed 6 times the OLR of a conventional AD with comparable volatile solids reduction efficiency. The relative instability in IF6 was linked to a greater reduction in microbial activity due to longer vacuum application and higher propionate concentrations (>2.20 g/L), which affected the performance of hydrogenotrophic methanogens. Methanosarcinaceae and Methanobacteriaceae populations were 10.8 % and 35.2 % more abundant in IF4 than in IF6, respectively, corroborating the significantly higher methane yields observed in IF4 compared with IF6. Ammonia recovery efficiencies of 52.0 % and 49.1 % were observed in IF4 and IF6 respectively. Batch ammonia toxicity tests indicated a higher inhibitory constant (K i ) for IC-AD (5.60–5.70 gN/L) compared to conventional AD (1.90 gN/L). Acetate degradation was effective even with ammonia and propionate concentrations as high as 2,000 mg/L and 4,000 mg/L, respectively.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".