Fouling mechanisms in nanofiltration membranes for the treatment of high DOC and varying hardness water
Bibliographic record
Abstract
ABSTRACT This study investigates the behavior of flux decline and change in fouling mechanisms in nanofiltration membranes, for the treatment of high dissolved organic carbon (DOC) water in the presence of divalent cations (Ca 2+ ) at different concentrations. A model synthetic water composed of sodium alginate concentration of 17 mg/L as DOC and calcium chloride of three concentrations: low 50, medium 200, and high 350 mg/L as CaCO 3 , was used for the fouling study. The synthetic water quality was based on the DOC and hardness concentrations reported in three potable water sources in the Province of Manitoba and Ontario, Canada. A thin-film composite (TFC) NF90 membrane (DOW Filmtec., USA) was used for the fouling studies. Resistance-in-series model and other fouling models were used to describe the permeate flux decline and changing fouling mechanisms in NF90 membranes. The fouling study demonstrated that low calcium concentration formed an irreversible fouling layer with a relatively low surface roughness of 15.38 nm. This was attributed to high adhesive forces between the foulant (primarily alginate molecules) and the rough membrane surface. At high calcium concentration, a dense, compact and reversible fouling layer was formed, due to increased cohesive forces between calcium and alginate molecules, resulting in maximum Ca-Alginate complexation and aggregation. The aggregates further linked together to form a cross-linked foulant structure with a surface, roughness of 38.17 nm. However, for medium calcium concentration a complex (nonuniform porosity) matrix of foulants was formed with a very high surface roughness of 67.97 nm, due to the insufficient calcium available to fulfill the binding sites on alginate molecules. The fouling layer so formed resulted in offering highest flux decline and total hydraulic resistance. Results of fouling experiments identified that the reversibility of alginate fouling increased with increasing calcium concentration. However, the flux decline and the total hydraulic resistance were dependent on both alginate and calcium concentrations for maximum complexation and aggregation. In addition to the aforementioned effects of Ca 2+ , results also show that the dominance of gel layer formation fouling mechanism increases with increase in calcium concentrations.
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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".