The scale of the problem is staggering. Pharmaceuticals and personal care products, steroid hormones, UV filters from sunscreens, pesticides, industrial chemicals, per- and polyfluoroalkyl substances, microplastics, and artificial sweeteners all slip more or less continuously through conventional wastewater treatment plants, which were simply never designed to catch them. Studies cited in the review document pharmaceutical residues in the Ganges River Basin, contaminants of emerging concern across Kenya’s River Athi Basin, steroid hormones in wastewater streams worldwide, and pesticide residues detected in maternal and umbilical cord blood. The common thread is that these compounds are biologically active at vanishingly small concentrations, are released continuously rather than in discrete spills, and persist long enough to travel far from their sources.

The health and ecological consequences are equally sobering. Endocrine-disrupting chemicals interfere with hormonal signaling and have been linked to reproductive health effects in humans and feminization of fish populations. Antibiotic residues in freshwater ecosystems drive the evolution of antimicrobial resistance, one of the most serious public health threats of the century. Polycyclic aromatic hydrocarbons accumulate in sediments and biota, with documented effects on wildlife and mammalian ovarian function. UV filters such as avobenzone become more toxic in combination with microplastics, as demonstrated in studies on the water flea Daphnia magna. Even mixtures of pharmaceuticals at low individual concentrations can impair the early life stages of fish, a reminder that the risk lies in the cocktail, not just the individual ingredient.

Perhaps the most provocative conclusion of the review is that the world’s failure to remove these contaminants is not a failure of technology per se. Effective removal methods exist. The real problem, the authors argue, is a fundamental mismatch between the properties of the contaminants and the mechanisms of the treatments deployed against them. Adsorption onto activated carbon and membrane filtration can strip contaminants from water with high efficiency, but they do not destroy anything; they merely concentrate the pollutants into spent sorbents and brines, creating secondary waste streams that must themselves be managed. Separation, in other words, is not destruction.

Biological treatment, the backbone of municipal wastewater engineering, fares no better against this class of pollutants. Activated sludge communities and constructed wetlands are remarkably good at degrading ordinary organic matter, but microbial metabolism is selective and slow when confronted with synthetic molecules engineered to resist breakdown, such as certain antibiotics, pesticides, and pharmaceuticals. Degradation kinetics are too sluggish for the hydraulic residence times of real plants, and some compounds pass through essentially untouched. The review notes that even advanced biological strategies, including microalgae-bacteria symbioses and bioaugmentation, remain constrained by this selectivity problem and by the sensitivity of microbial communities to toxic shocks and seasonal variation.

Advanced oxidation processes represent the current state of the art in destructive treatment, generating hydroxyl radicals and sulfate radicals that attack organic molecules with ferocious speed. Ozone-based systems, UV/hydrogen peroxide, UV/persulfate, photocatalysis with titanium dioxide, and electro-Fenton chemistry can all degrade pharmaceuticals, endocrine disruptors, and pesticides within minutes to hours. Yet the review is candid about their limits: high energy demand, incomplete mineralization that leaves behind partially oxidized transformation products sometimes more toxic than the parent compound, sensitivity to the complex matrix of real wastewater, and operational complexity that complicates full-scale deployment. Hybrid systems that couple, for example, ozonation with nanofiltration or photocatalysis with biological polishing can push performance further, but at the price of added cost and engineering intricacy.

Into this landscape the authors introduce cold plasma technology, and here the physics is genuinely distinctive. A cold plasma is a partially ionized gas in which electrons, accelerated by strong electric fields, reach temperatures of tens of thousands of kelvin while the bulk gas remains near ambient temperature. When such a discharge is created in air or oxygen above or within water, energetic electrons collide with gas molecules and dissociate them, generating a rich cocktail of reactive oxygen and nitrogen species: hydroxyl radicals, atomic oxygen, ozone, hydrogen peroxide, nitrate, nitrite, and peroxynitrite, alongside ultraviolet photons and shock waves. Crucially, these oxidants are generated in situ, on demand, without the storage, dosing, and transport of hazardous chemicals. When plasma contacts water directly, through dielectric barrier discharges, pulsed corona discharges, plasma jets, or bubble and falling-film reactor geometries, the reactive species diffuse into the liquid and attack contaminant molecules through oxidation, nitration, and bond cleavage.

The evidence base for plasma water treatment has grown rapidly. Studies compiled in the review report successful plasma degradation of antibiotics including sulfonamides, tetracyclines, fluoroquinolones, and penicillins; pharmaceuticals such as carbamazepine, ibuprofen, diclofenac, paracetamol, and fluoxetine; pesticides including atrazine, chlorpyrifos, endosulfan, and imidacloprid; endocrine disruptors such as bisphenol A; dyes; and UV filters. Reactor engineering matters enormously: water-film and bubble configurations maximize the plasma-liquid interface where chemistry happens, and hybrid plasma-catalytic systems, pairing discharges with titanium dioxide, tungsten oxide, zinc oxide, graphene composites, or activated carbon, exploit plasma-generated species and photons to accelerate photocatalysis and adsorption synergistically. The authors’ own recent work includes a dual-function dielectric barrier discharge bubble system that decouples nitrogen fixation from contaminant degradation, hinting at reactors that could clean water while recovering a nutrient value.

Still, the review refuses to oversell the technology. Energy efficiency remains the central hurdle: plasma systems must compete on energy per order of pollutant removal with ozone and UV-based oxidation, and comparisons published in the literature show plasma-based advanced oxidation can be competitive but is not yet uniformly superior. Reactor scalability from laboratory milliliters to treatment-plant cubic meters per hour is unproven at municipal scale. The field lacks standardized performance metrics, making cross-study comparison difficult, and most demonstrations use ultrapure water spiked with a single contaminant rather than real wastewater, whose organic matter, salts, and suspended solids quench radicals and shield targets. Residual toxicity assessment after treatment, though increasingly reported, needs to become routine. The authors frame these not as disqualifiers but as the research agenda: mechanistic frameworks linking plasma chemistry, reactor design, and plasma-liquid interaction to predictable degradation outcomes.

The bigger picture the review paints is one of process intensification, the engineering philosophy of doing more chemistry in smaller, smarter reactors. Cold plasma’s appeal lies in its versatility: one electrical input yields a spectrum of oxidants capable of broad-spectrum attack on chemically diverse pollutants, tunable by gas composition, power modulation, and reactor geometry, and combinable with catalysis, adsorption, and biological polishing in hybrid trains. As regulatory scrutiny of pharmaceuticals, PFAS, and endocrine disruptors tightens worldwide, and as water reuse becomes a necessity rather than an option, the gap between what conventional plants deliver and what modern chemistry demands will only widen. Whether cold plasma fills that gap will depend on the coming decade of scaling studies, but this assessment makes a compelling case that the fourth state of matter deserves a seat at the table of water treatment’s future.

Subject of Research: Assessment of emerging contaminants in water and the potential of cold plasma technology for their degradation

Article Title: Emerging contaminants in water pathways: sources, impacts, conventional, and cold-plasma-based cleaner technology assessment

Article References: Abdulsalam, M., Kimani, B. G., Ahlawat, K., & Machala, Z. (2026). Emerging contaminants in water pathways: sources, impacts, conventional, and cold-plasma-based cleaner technology assessment. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-026-38258-x

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38258-x

Keywords: emerging contaminants, cold plasma, water treatment, wastewater, advanced oxidation processes, pharmaceuticals, endocrine disruptors, pesticides, reactive oxygen species, plasma-liquid interaction, process intensification, antimicrobial resistance