Microplastics are nowadays considered as ubiquitous pollutants since have been found widespread in all environmental compartments, particularly in the water sources. In the urban water cycle, the drinking water treatment plants and the wastewater treatment plants are the first and last barriers to microplastics pollution, respectively. The present work aims at presenting the information available on microplastic presence in the urban water cycle, reporting and linking what is known at the different stages. Focus is on the water sources and on the role of the water treatment plants as source and control of microplastics pollution. Aspects evaluated are microplastics abundance, characterization in terms of morphology, size and polymer composition, spatial and temporal variations, factors influencing their distribution and abundance, effects of treatments on their removal. Up to now there is no common framework for microplastics collection, sample pre-treatment, identification, quantification and classification. Data comparison is hindered due to the various analytical protocols implemented; hence the conclusions driven are mostly indicative or of very local significance. The available information is not evenly distributed among the urban water cycle components. For the establishment of proper microplastics pollution control strategies, the relative role of wastewater and drinking water treatment plants needs to be better deepened in terms of both quantity and quality effects. All these aspects are afforded in the present review which is based on the more recent data published by the specialized literature.
Carbamazepine (CBZ), one of the most used pharmaceuticals worldwide and a Contaminant of Emerging Concern, represents a potential risk for the environment and human health. Wastewater treatment plants (WWTPs) are a significant source of CBZ to the environment, polluting the whole water cycle. In this review, the CBZ presence and fate in the urban water cycle are addressed, with a focus on adsorption as a possible solution for its removal. Specifically, the scientific literature on CBZ removal by activated carbon and its possible substitute Biochar, is comprehensively scanned and summed up, in view of increasing the circularity in water treatments. CBZ adsorption onto activated carbon and biochar is analyzed considering several aspects, such as physicochemical characteristics of the adsorbents, operational conditions of the adsorption processes and adsorption kinetics and isotherms models. WWTPs usually show almost no removal of CBZ (even negative), whereas removal is witnessed in drinking water treatment plants through advanced treatments (even >90%). Among these, adsorption is considered one of the preferable methods, being economical and easier to operate. Adsorption capacity of CBZ is influenced by the characteristics of the adsorbent precursors, pyrolysis temperature and modification or activation processes. Among operational conditions, pH shows low influence on the process, as CBZ has no charge in most pH ranges. Differently, increasing temperature and rotational speed favor the adsorption of CBZ. The presence of other micro-contaminants and organic matter decreases the CBZ adsorption due to competition effects. These results, however, concern mainly laboratory-scale studies, hence, full-scale investigations are recommended to take into account the complexity of the real conditions.
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