From Canal to Tap: The Hidden Chemical Tide Moving Through Vietnam’s Urban Water
In the canal networks that drain Hanoi’s densest districts, researchers have measured individual antibiotics at concentrations approaching 50,000 nanograms per liter, levels at which certain compounds approach or exceed screening benchmarks for antimicrobial-resistance selection in the environment. That figure marks the sharpest edge of a much larger picture. A new mini-review synthesizing more than a decade of Vietnamese monitoring studies, published in Case Studies in Chemical and Environmental Engineering, traces how contaminants of emerging concern—pharmaceuticals, antibiotics, pesticides, per- and polyfluoroalkyl substances known as PFAS, plasticizers, and the by-products formed when water is disinfected—move through the country’s urban water systems, from storm drains and hospital outfalls to drinking-water plants, distribution pipes, and the household tap. Led by Hoang-Phuong Nguyen and colleagues at Ho Chi Minh City University of Technology, with support from the Saigon Water Supply Company and the city’s Department of Science and Technology, the review argues that Vietnam’s water-quality problem is not a single pollutant but a system: wherever intense chemical use meets incomplete sanitation, mixtures concentrate, persist, and travel.
Contaminants of emerging concern, or CECs, are synthetic or naturally occurring chemicals increasingly detected at trace levels in aquatic systems for which monitoring, risk assessment, and regulation habitually lag behind patterns of use and release. The prominent classes include pharmaceuticals and personal care products such as caffeine, metformin, and carbamazepine; antibiotics; pesticides tied to rice cultivation and peri-urban farming; and industrial additives ranging from PFAS and phthalate esters to alkylphenols, bisphenols, and cyclic volatile methylsiloxanes. A second generation of concern involves transformation products created during treatment itself, most notably the regulated and emerging disinfection by-products generated when chlorine reacts with organic matter. What unites these chemically disparate groups is behavior: persistence, mobility, and biological activity at extraordinarily low concentrations, typically nanograms to micrograms per liter. Documented hazards span aquatic ecotoxicity, endocrine disruption, and the amplification of antimicrobial resistance, alongside chronic low-dose human exposure through drinking water and food. Critically, conventional infrastructure was never designed to strip out dissolved, low-molecular-weight organic molecules, so many of these compounds pass through wastewater works and drinking-water plants with only partial attenuation.
Vietnam concentrates these risks with unusual efficiency, and the review identifies the structural reasons why. Urbanization has outpaced sanitation: centralized sewerage and wastewater treatment reach only a small fraction of the urban population, leaving untreated or partially treated domestic wastewater as the dominant source of chemical inputs to city waters. Urban canals double as drainage corridors, so Hanoi’s Kim Nguu and To Lich canals and the canal outlets feeding Ho Chi Minh City’s Saigon River collect essentially everything a megacity sheds. Hospitals act as point-source micro-hotspots for antibiotics and specialty pharmaceuticals, particularly where on-site treatment is conventional or poorly optimized. Industrial parks and craft villages contribute their own signatures—the Phong Khe paper-making village is a documented PFAS source—while intensive rice cultivation, coastal aquaculture, and delta farming release pesticides and veterinary antibiotics through shared drainage networks. Monsoonal hydrology then modulates everything: dry-season low flows concentrate residues, wet-season first flushes mobilize contaminants from sediments and pipes, and increasing saline intrusion in the Mekong Delta heightens hydrological connectivity among farms, canals, and household water sources. The Red River system, the Saigon–Dong Nai continuum, and the Mekong Delta therefore warrant differentiated monitoring and control.
The occurrence data are striking in their breadth. Broad screening studies have detected more than 100 organic micropollutants across Vietnamese aquatic environments—one survey of the national aquatic environment targeted 1,153 compounds—with urban waters routinely flagged by sewage markers such as caffeine, metformin, fecal sterols, and phthalates. The underlying synthesis drew on Scopus, Web of Science, and Google Scholar records published through December 2025, harmonizing concentrations to nanograms or micrograms per liter and treating cross-study comparisons as indicative, because analytical methods, detection limits, sampling frequencies, and target lists differ markedly. In Ho Chi Minh City, summed micropollutant concentrations near canal-influenced zones have reached the microgram-per-liter to tens-of-micrograms-per-liter scale, while main river channels run lower thanks to dilution and transport. Hanoi’s canals and lakes carry multi-class antibiotic mixtures—fluoroquinolones, macrolides, sulfonamides, and beta-lactams—of which selected compounds exceed predicted-no-effect-concentration benchmarks for antimicrobial resistance selection or aquatic toxicity. Groundwater generally fares better, but screening in Hanoi, Ho Chi Minh City, and northern Vietnam shows trace organic mixtures in urban and agricultural wells, especially where shallow aquifers are vulnerable to septic leakage or river–aquifer exchange. PFAS detections in groundwater and sediment near industrial and craft-village settings confirm that persistent, mobile compounds demand attention well beyond surface water, and hospital and municipal wastewater studies add persistent pharmaceuticals and resistance-related signals at the emission points themselves.
Crucially, the story does not end at the treatment plant. Treated, tap, and bottled waters in Vietnam show far lower contamination than wastewater-impacted canals, yet measurable residues persist. Studies in northern Vietnam have found neonicotinoids, fipronil, chlorpyrifos, carbendazim, chlorotriazines, bentazon, and pesticide transformation products in both surface and drinking water, while Mekong Delta research has detected pesticides across canals, rainwater, groundwater, and bottled water, evidence that household exposure extends well beyond piped municipal systems. In Hanoi, phthalate esters and cyclic volatile methylsiloxanes have been measured in tap and bottled water as well as in wastewater and lake water. The drinking-water side carries its own chemistry: field studies in Ho Chi Minh City document spatial and seasonal variability in trihalomethanes, haloacetic acids, haloacetonitriles, and chloral hydrate across the distribution network, reflecting the combined effects of source-water natural organic matter, chlorination dose, water age, and network hydraulics. The same disinfection step that makes water microbiologically safe can therefore convert organic precursors into a regulated and emerging by-product burden downstream, linking catchment management directly to what consumers drink.
Four Vietnamese case studies anchor the review’s risk analysis. Hanoi’s canal and lake network emerges as the clearest antimicrobial-resistance hotspot, where measured concentrations and screening benchmarks suggest both ecological and resistance-selection pressure in wastewater-impacted waters, a classic One Health setting where chemical and microbial risks overlap. Ho Chi Minh City illustrates the megacity problem: combining targeted chemical analysis with in vitro bioassays in the Saigon River–estuary system revealed strong urban bioactivity signatures near canal outlets, signals that target compound lists alone would have missed. The Mekong Delta demonstrates multi-source domestic exposure, where households relying on canals, harvested rainwater, shallow wells, or bottled water encounter pesticide and antibiotic residues that piped-water monitoring would never capture. Ho Chi Minh City’s drinking-water treatment plants reveal the central dilemma: conventional processes reduce turbidity and part of the organic precursor pool, tracked as dissolved organic carbon and ultraviolet absorbance at 254 nanometers, but residual chlorine demand can still drive by-product formation as water ages in the network. Encouragingly, domestic pilot studies show that integrated ozonation–biofiltration and biologically activated carbon improve removal of both dissolved organic carbon and by-product precursors under local source-water conditions.
The treatment toolbox is assessed with pragmatism. Coagulation, sedimentation, and filtration remain essential for turbidity and bulk organic matter but are generally weak for dissolved, low-molecular-weight compounds and many PFAS. Chlorination can transform some micropollutants yet generates by-products whenever organic matter and bromide precursors coexist, a first-order concern in high-natural-organic-matter tropical waters and saline-intruded deltas. Activated carbon is flagged as the most immediately adaptable barrier: powdered carbon can be dosed during pollution events at minimal capital cost, while granular and biologically activated carbon provide continuous adsorption and, under favorable conditions, biodegradation of selected organics, constrained mainly by operating cost, media regeneration logistics, and competition from natural organic matter that shortens carbon bed life. Ozonation and advanced oxidation processes, spanning ozone–peroxide, UV–peroxide, persulfate, photo-Fenton, and electro-Fenton systems, generate hydroxyl and sulfate radicals capable of degrading persistent organics, but they demand careful management of transformation products, bromate formation in bromide-rich waters, and energy budgets, and should generally be followed by biofiltration. Nanofiltration and reverse osmosis are powerful but energy-hungry, concentrate-producing options best reserved for high-risk sources or reuse schemes. Upstream measures, from membrane bioreactors and wet-weather bypass control to hospital pretreatment, pharmaceutical take-back programs, and pesticide stewardship, together with distribution-side water-age management, flushing, and high-frequency monitoring, complete the portfolio.
On the policy side, the review maps an implementation route that starts from instruments Vietnam already possesses. The national drinking-water standard QCVN 01-1:2024/BYT, the surface-water and groundwater regulations QCVN 08:2023 and QCVN 09:2023, the industrial-effluent rule QCVN 40:2025/BTNMT, and the national environmental monitoring master plan anchored by Decision 224/QD-TTg together provide legal anchors, yet most pharmaceuticals, antibiotics, broader personal-care chemicals, and PFAS remain outside routine compliance monitoring. The proposed fix is a tiered national watch list modeled on the European Union’s water-policy watch list and the United States’ Unregulated Contaminant Monitoring Rule. Tier one would cover hotspot-action compounds, including antibiotics, high-use pesticides, alkylphenols, bisphenol A, and sewage markers, tied to discharge permits and inspections. Tier two would cover intake- and treatment-relevant compounds such as carbamazepine, persistent pharmaceuticals, a priority PFAS suite, and by-product precursors. Tier three would track emerging substitution chemicals, including organophosphate esters and newer bisphenols, through periodic high-resolution mass spectrometry screening. Implementation would roll out in three phases: within two years, a first watch list, harmonized quality-assurance protocols, and sentinel monitoring at urban canals, hospital corridors, intakes, treatment-plant effluents, and distribution endpoints; by years three to five, permit conditions, water safety plans, effect-based screening, and targeted upgrades; and within a decade, open national datasets and formal regulation of validated compounds.
The research agenda that follows is deliberately mixture-aware. Priority studies include paired influent–effluent datasets linking upstream load reduction to downstream by-product formation, operating windows that suppress bromate while maintaining micropollutant oxidation, rapid small-scale column tests that predict PFAS breakthrough in granular activated carbon, and regeneration pathways for spent media. Antimicrobial-resistance surveillance should be coupled to chemical monitoring through quantitative polymerase chain reaction panels for resistance genes and integrons at hospitals, outfalls, and treatment plants, with source apportionment to distinguish hospital from community and industrial inputs. Risk assessment would combine screening-level risk quotients and additive hazard indices grouped by mode of action with effect-based bioassays and effect-directed analysis at sentinel nodes, flagging biologically relevant mixtures even when the chemical space is incompletely mapped. The bottom line is stark but actionable: contaminants of emerging concern occur widely across Vietnamese waters at nanogram-to-microgram levels, hotspots cluster in urban canals, hospital and wastewater corridors, industrial drains, and agro-aquaculture landscapes, and conventional treatment alone cannot break the exposure chain. What the review offers instead is a staged, evidence-building strategy, intercepting hotspots first, monitoring from source to tap, and upgrading treatment where the data justify it, that allows Vietnam to act immediately on its highest-risk nodes while assembling the proof needed to regulate the rest.
Subject of Research: Occurrence, risks, treatment options, and policy priorities for contaminants of emerging concern (CECs)—including pharmaceuticals, antibiotics, pesticides, PFAS, plasticizers, and disinfection by-products—across Vietnam’s urban water cycle, from sources and receiving waters through drinking-water treatment and distribution to consumers.
Subject of Research: Chemistry
Article Title: Occurrence of contaminants of emerging concern (CECs) in water sources and urban water systems in Vietnam: A mini-review
Article References: Nguyen, H.-P., Nguyen, T.-Y.-P., Hoang, M.-N., Huynh Ky, P.-H., Bui, X.-T., Baduel, C., Le, M.-T. T., & Nguyen, P.-D. (2026). Occurrence of contaminants of emerging concern (CECs) in water sources and urban water systems in Vietnam: A mini- review. Case Studies in Chemical and Environmental Engineering, 14, Article 101464. https://doi.org/10.1016/j.cscee.2026.101464
Image Credits: AI Generated
DOI: 10.1016/j.cscee.2026.101464
Keywords: contaminants of emerging concern, Vietnam, antibiotics, antimicrobial resistance, PFAS, disinfection by-products, pharmaceuticals and personal care products, pesticides, drinking water treatment, urban water cycle
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Bethany Barker. (August 30, 2026). Emerging contaminants found in Vietnam’s water sources and urban systems, review shows. Scienmag. https://scienmag.com/emerging-contaminants-found-in-vietnams-water-sources-and-urban-systems-review-shows/
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