The rise of emerging contaminants in waters challenges the scientific community and water treatment stakeholders to design remediation techniques that are simple, practical, inexpensive, effective, and environmentally friendly. Emerging contaminants include antibiotics, hormones, illicit drugs, endocrine disruptors, cosmetics, personal care products, pesticides, surfactants, industrial products, microplastics, nanoparticles, and nanomaterials. Removing those contaminants is not easy because classical wastewater treatment systems are not designed to handle emerging contaminants, and contaminants often occur as traces in complex organo-mineral mixtures. Here, we review advanced treatments for the removal of emerging contaminants in wastewater, with focus on adsorption-oriented processes using non-conventional adsorbents such as cyclo-dextrin polymers, metal-organic frameworks, molecularly imprinted polymers, chitosan, and nanocellulose. We describe biological-based technologies for the degradation and removal of emerging contaminants. Then, we present advanced oxida-tion processes as the most promising strategies because of their simplicity and efficiency.

Water contamination by emerging contaminants is increasing in the context of rising urbanization, industrialization, and agriculture production. Emerging contaminants refers to contaminants for which there is currently no regulation requiring monitoring or public reporting of their presence in our water supply or wastewaters. There are many emerging contaminants such as pesticides, pharmaceuticals, drugs, cosmetics, personal care products, surfactants, cleaning products, industrial for-mulations and chemicals, food additives, food packaging, metalloids, rare earth elements, nanomaterials, microplastics, and pathogens. The main sources of emerging contaminants are domestic discharges, hospital effluents, industrial wastewaters, runoff from agriculture, livestock and aquaculture, and landfill leachates. In particular, effluents from municipal wastewater treatment plants are major contributors to the presence of emerging contaminants in waters. Although many chemicals have been recently regulated as priority hazardous substances, conventional plants for wastewater and drinking water treat-ment were not designed to remove most emerging contaminants. Here, we review key examples of contamination in China, Portugal, Mexico, Colombia, and Brazil. Examples include persistent organic pollutants such as polychlorinated biphenyls, dibenzofurans, and polybrominated diphenyl ethers, in lake and ocean ecosystems in China; emerging contaminants such as alkylphenols, natural and synthetic estrogens, antibiotics, and antidepressants in Portuguese rivers; and pharmaceuticals, hormones, cosmetics, personal care products, and pesticides in Mexican, Brazilian, and Colombian waters. All continents are affected by these contaminants. Wastewater treatment plants should therefore be upgraded, e.g., by addition of tertiary treatment systems, to limit environmental pollution.

Coagulation/flocculation is a major phenomenon occurring during industrial and municipal water treatment to remove suspended particles. Common coagulants are metal salts, whereas flocculants are synthetic organic polymers. Those materials are appreciated for their high performance, low cost, ease of use, availability and efficiency. Nonetheless, their use has induced environmental health issues such as water pollution by metals and production of large amounts of sludges. As a consequence, alternative coagulants and flocculants, named biocoagulants and bioflocculants due to their biological origin and biodegradability, have been recently developed for water and wastewater treatment. In particular, chitosan and chitosan-based products have found applications as bioflocculants for the removal of particulate and dissolved pollutants by direct bioflocculation. Direct flocculation is done with water-soluble, ionic organic polymers without classical metalbased coagulants, thus limiting water pollution. Chitosan is a partially deacetylated polysaccharide obtained from chitin, a biopolymer extracted from shellfish sources. This polysaccharide exhibits a variety of physicochemical and functional properties resulting in numerous practical applications. Key findings show that chitosan removed more than 90% of solids and more than 95% of residual oil from palm oil mill effluents. Chitosan reduced efficiently the turbidity of agricultural wastewater and of seawater, below 0.4 NTU for the latter. 99% turbidity removal and 97% phosphate removal were observed over a wide pH range using 3-chloro-2-hydroxypropyl trimethylammonium chloride grafted onto carboxymethyl chitosan. Chitosan also removed 99% Microcystis aeruginosa cells and more than 50% of microcystins. Here, we review advantages and drawbacks of chitosan as bioflocculant. Then, we present examples in water and wastewater treatment, sludge dewatering and post-treatment of sanitary landfill leachate.

Sensitive nanohydrogels were prepared via surfactant free emulsion copolymerization of N‐vinylcaprolactam and poly(ethylene glycol) methyl ether methacrylate, and either N‐vinylpyrrolidone (VP) or 2‐methacryloyloxybenzoic acid (2MBA) to adjust the transition temperature (Ttr). The crosslinker ethylene glycol dimethacrylate was used for the polymer network construction. The resulting nanohydrogel sizes are between 120 and 300 nm. ρ‐Parameter, obtained from light scattering studies, suggests that core‐sell nanogels of flexible chains were obtained. Ttr increases with increasing comonomer content (VP or 2MBA) and decreases with decreasing pH for 2MBA containing nanohydrogels. Nanohydrogels containing 15.5% of 2MBA exhibit Ttr close to 38 °C. Nanogels are able to control the release of the loaded antineoplastic drug 5‐fluorouracil. For the prepared T/pH‐sensitive nanogels, the release is slower at pH 7.4 and 37 °C than at tumor conditions: pH 6 and 40 °C. Mathematical models were applied to evaluate the kinetics of drug release; Peppas model fitted best indicating a Fickian diffusion trough a sphere. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2662–2672

Reversible addition-fragmentation chain transfer (RAFT) polymerization is used to prepare temperature-and pH-sensitive statistical copolymers with lower critical solution temperature (LCST) close to 38 ° C at pH 7.4 based on N -isopropylacrylamide and methacrylic acid derivative comonomers with a p K a close to 6. Statistical copolymers are re-activated to prepare amphiphilic block copolymers and star polymers with cross-linked core. The LCST is maintained by varying the architecture; however, the LCST originated behaviour changes due to self-aggregation. Statistical copolymers and short block copolymers show complex aggregation, whereas midsize block copolymers and star polymers show shrinkage of aggregate dimensions. The pH of the medium has a profound impact on the self-assembling behaviour of the different polymer architectures.