Dynamics of nitrate degradation along an alternative latrine improved by a sawdust permeable reactive barrier (PRB) installed in an irregular settlement in the municipality of São Paulo (Brazil)
Bibliographic record
Abstract
Nutrients, like nitrate and phosphate, and pathogens are the primary contaminants released into groundwater by on-site sanitation systems, which are an effluent disposal outcome for regions not covered by sanitation infrastructure, as periurban communities in developing countries. As appropriate setback distances between pit latrines and supply wells often cannot be met to avoid groundwater contamination, especially in a densely-populated situation, efficient, low-cost and accessible technologies are extremely necessary to protect water resources and surpass critical and persistent public health problems. This paper presents 1-year field-testing of an alternative latrine (AL) that incorporates two waste materials as permeable reactive barriers (PRB) in an irregular settlement at the municipality of São Paulo (Brazil). Basic oxygen furnace (BOF) slag in contact with wastewater effluent increases its pH level, which causes pathogens inactivation and phosphate adsorption. Sawdust under water saturation creates reducing conditions that encourage the growth of denitrifying bacteria that remove nitrate. A control latrine (CL) was constructed 90 m apart from AL with similar hydraulic characteristics and nonreactive materials for hydrochemical comparison. It was evident for AL the formation of well-defined nitrification and denitrification reaction zones, whereas CL overall presented nitrogen in its ammoniacal form, with incipient nitrate production at CL bottom, indicating that nitrification is probably boosted below that. BOF slag had attenuated microorganisms and phosphate almost completely, but nitrate removal average efficiency was 42%. The high pH effluent generated in BOF media may have also affected in the short-term the denitrifying bacteria in sawdust barrier 1 m below. The inverted position of the reactive barriers, i.e., sawdust PRB overlying BOF slag PRB, should be a more suitable design to achieve nitrate and pathogens removal. This kind of sanitation solution employing cheap and accessible waste materials have never been applied in the design proposed in this paper and also was a novelty for Brazilian context, proving to be a suitable technology to meet local needs.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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 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".