A study published on 27 October 2026 found some of the highest per- and polyfluoroalkyl substance concentrations ever reported for South America in the Educandos urban stream in Manaus, Brazil’s Amazon region. Total PFAS ranged from 76.5 to 366.9 nanograms per liter, with a median of 189.2 nanograms per liter, according to Bioengineer.org.
Key takeaways
- Total PFAS in the Educandos stream ranged from 76.5 to 366.9 nanograms per liter, with a median of 189.2 nanograms per liter, according to Bioengineer.org.
- Researchers sampled surface water daily at five sites over five consecutive days in May 2025, finding no PFAS at the background spring and the highest values at Point 3 near the Studio 5 bridge, according to Bioengineer.org.
- Only five of 24 targeted PFAS compounds were detected, while the legacy compounds PFOA, PFOS, PFNA, PFHxS and PFDA were not found, according to Bioengineer.org.
- All 18 samples exceeded Canada’s drinking-water objective for the sum of 25 PFAS, and 12 exceeded the European Union drinking-water limit for the sum of 20 PFAS, according to Bioengineer.org.
- The authors concluded that untreated sewage contributes to the pollution but that a localized, possibly industrial source near Point 3 requires confirmation through sampling of outfalls and effluents, according to Bioengineer.org.
Study traces PFAS through Manaus stream
The research team, led by Erickson Oliveira dos Santos, conducted the first assessment of persistent synthetic chemicals in an Amazonian waterway. It sampled surface water daily at four points along the roughly 15-kilometer Educandos stream and a background site at its spring in forested headwaters during five consecutive days in May 2025, at the end of the wet season, according to Bioengineer.org.
The median total PFAS concentration exceeded roughly 84 percent of more than 40,000 PFAS measurements compiled from rivers, lakes and estuaries across 56 countries. That placed a tropical urban stream without known fluorochemical manufacturing or firefighting-foam sites in the same concentration range as heavily industrialized catchments in the Northern Hemisphere, according to Bioengineer.org.
Using a modified version of US EPA Method 1633 with solid-phase extraction and ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry, the researchers quantified 24 target PFAS compounds. Only PFBA, PFPeA, PFHxA, PFHpA and 6:2 FTS were detected, according to Bioengineer.org.
PFPeA and 6:2 FTS together represented about 92 percent of total PFAS, with PFPeA accounting for 48 percent and 6:2 FTS for 44 percent. The authors interpreted this pattern as consistent with fluorotelomer-based products undergoing partial transformation during transport, according to Bioengineer.org.
Spatial results pointed to a concentrated upstream input. No PFAS were detected at the background spring, concentrations increased downstream, and mean 6:2 FTS at Point 3 near the Studio 5 bridge reached 194.1 nanograms per liter, more than double the levels at Points 2 and 4. Statistical testing confirmed the difference between Point 3 and the upstream industrial bridge site, according to Bioengineer.org.
The study reports that the Educandos stream crosses 16 neighborhoods containing about 450,000 people and borders Industrial District 1, Manaus’s primary industrial zone, which has more than 400 companies. The city has about 2.3 million residents; recent estimates indicate that only about 20 percent of its urban population has sewage collection and roughly 12 percent of households are connected to the sewer network, according to Bioengineer.org.
Correlations between individual PFAS and wastewater-related ions such as chloride, sodium and ammonium were mostly not significant, while the mean chloride-to-sodium mass ratio of 1.1 sat slightly above the range typical of domestic sewage. The authors concluded that untreated sewage contributes, but that 6:2 FTS likely has an additional, localized source near Point 3, possibly industrial, which targeted sampling of outfalls and effluents must confirm, according to Bioengineer.org.
PFAS levels exceed selected international benchmarks
Brazil has no PFAS limits in its national drinking-water standard or surface-water classification, but the study compared its results with international rules. Summed perfluorocarboxylic acids exceeded the European Union drinking-water limit of 100 nanograms per liter for the sum of 20 PFAS in 12 of 18 samples, while no sample crossed the 500-nanogram PFAS-total ceiling, according to Bioengineer.org.
| Benchmark | Study result |
|---|---|
| Canada drinking-water objective for the sum of 25 PFAS | 30 nanograms per liter; all 18 samples exceeded it |
| European Union drinking-water limit for the sum of 20 PFAS | 100 nanograms per liter; 12 of 18 samples exceeded it |
| European Union PFAS-total ceiling | 500 nanograms per liter; no sample exceeded it |
| European Union surface-water environmental quality standard, expressed as PFOA-equivalent | 4.4 nanograms per liter; three samples exceeded it |
Using relative potency factors, the researchers calculated PFOA-equivalent concentrations of 1.5 to 5.8 nanograms per liter, with a mean of 3.5, according to Bioengineer.org.
Specification read
The reported scale was a roughly 15-kilometer urban stream serving a corridor of about 450,000 people, but the source did not report treatment-plant flow in megaliters per day, daily cubic meters per day or population-equivalent loading. A plant-equivalent design flow therefore cannot be calculated from the supplied information, according to Bioengineer.org.
For a conventional municipal wastewater train, treatment would progress from screening and grit removal to primary clarification, biological treatment and tertiary or disinfection stages. Depending on discharge objectives and the quality of incoming effluent, DAF, activated carbon, ion exchange or other residuals-management steps may need evaluation; the study itself does not specify a treatment configuration. A synthetic-media biofilm approach such as Air Dust Treatment should not be treated as a substitute for PFAS-specific residuals management, while Chemical application planning must account for the need to confirm the source before selecting a removal train.
The source characterizes the pollution as a combination of untreated domestic sewage and a possible localized industrial contribution near Point 3, with short-chain PFAS and 6:2 FTS dominating the profile. If your plant looks like an urban municipal system with industrial inputs, a flow specified in m³/day, BOD/COD loads specified in mg/L, and tightening PFAS or discharge requirements, this means source tracing and treatment selection should be coordinated: the reported results do not establish that one unit operation will remove the full PFAS mixture, according to Bioengineer.org.
For operators evaluating similar treatment challenges, broader process selection can be compared with the approaches discussed in DAF vs. Clarifier for EV Wastewater in Spartanburg: 2026 Guide and DAF vs Clarifier for Food & Bev Wastewater in Chicago 2026. For municipal planning, the Municipal product hub provides the relevant entry point.
FAQ
What does the study mean for a municipal wastewater plant receiving industrial wastewater?
It means the influent should not be treated as a conventional domestic-sewage profile until the potential industrial source near Point 3 is investigated. The study found that PFAS concentrations rose downstream, while 6:2 FTS was more than twice as high at Point 3 as at Points 2 and 4, and the authors said targeted outfall and effluent sampling is needed to confirm a localized source, according to Bioengineer.org.
What flow and contaminant data are needed to size a treatment plant for this case?
The reported flow in m³/day, BOD and COD in mg/L, PFAS species, daily and peak flows, and applicable discharge limits were not provided, so plant capacity and removal performance cannot be specified. Source tracing should first establish whether untreated sewage or a localized industrial discharge is the controlling input, according to Bioengineer.org.
How much would treatment cost, and what lead time should a buyer allow?
The source reported no capital cost, operating cost, procurement schedule or delivery lead time. Those figures require a defined flow, influent and effluent limits, treatment objectives and site information; without them, selecting a supplier or committing to a delivery date would be premature, according to Bioengineer.org.
Does the study identify the PFAS source conclusively?
No. The authors concluded that untreated sewage contributes, but that 6:2 FTS likely has an additional, localized and possibly industrial source near Point 3. They said targeted sampling of outfalls and effluents must confirm that source, according to Bioengineer.org.
