Ozone enhances biological treatment of hydrothermal liquefaction aqueous stream from municipal sludge
Bibliographic record
Abstract
• In 0–0.18 g O 3 /g COD of sludge derived-HTL aqueous, pretreatment removed inhibitors. • 98 % and 89 % more methane from HTL aqueous at 0.14 g O 3 /g COD than control (no O 3 ). • Above 0.14 g O 3 /g COD, improvements declined under mesophilic and thermophilic AD. • 0.18 g O 3 /g COD raised HTL aqueous ultimate aerobic biodegradability from 54 to 95 %. • Ozonated HTL aqueous biodegradability: Aerobic > Mesophilic AD > Thermophilic AD. Hydrothermal liquefaction (HTL) is a promising alternative to anaerobic digestion for municipal sludge valorization due to biocrude oil and nutrient-dense hydrochar production, smaller footprint, enhanced micropollutant degradation, and minimized residual biosolids. However, integrating HTL into wastewater treatment plants necessitates on-site treatment of HTL aqueous, which is 80 % of byproducts by volume. HTL aqueous exhibits inhibition on downstream biological treatment due to high chemical oxygen demand (COD), total phenolics, ketones and nitrogen heterocyclics. This study evaluated the efficacy of ozone (O 3 ) pretreatment on HTL aqueous characteristics and subsequent biodegradability under anaerobic and aerobic conditions. HTL aqueous was obtained from dewatered sludge cake at 350 °C with 15 min retention time. Various dissolved O 3 doses (0.03, 0.12, 0.14, 0.16, 0.18 g O 3 /g COD of HTL aqueous) were investigated, with the maximum dose of 0.18 g O 3 /g COD achieving 43 % COD reduction, 72 % removal of total phenolics, 69 % removals of selected nitrogen heterocyclics, while retaining volatile fatty acids (VFA). The optimal dissolved dose for anaerobic and aerobic treatment were 0.14 and 0.18 g O 3 /g COD, respectively. Under mesophilic (35 °C) and thermophilic (55 °C) conditions, the pretreated HTL aqueous at the optimum dose of 0.14 g O 3 /g COD demonstrated 98 % and 89 % improvements in specific cumulative methane yields, compared to non-pretreated HTL aqueous (control), respectively. The maximum improvement in 5-day biochemical oxygen demand (BOD) was 90 % at 0.18 g O 3 /g COD, compared to the control. The enhanced biodegradations were attributed to the removal of total phenolics and nitrogen heterocyclics, ultimately enhancing carbon recovery from municipal sludge.
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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".