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Due to decreasing rainfall, drought is an environmental problem becoming even more alarming every year. The direct reuse of treated wastewater (WW), in compliance with current legislation, can be one of the applicable solutions to deal with water scarcity. In this study, an analysis of wastewater treatment plants (WWTPs) (>400 population equivalent) in the Lombardy region (Northern Italy) was performed to identify the most critical parameters in their effluents (total and ammonia nitrogen, and phosphorous). Biochar filters, as final adsorption means for WWTP effluents, could improve water quality for direct reuse. Biochar from biological sewage sludge produced by an urban WWTP (130,000 population equivalent) was prepared via pyrolysis (350–650–950 °C) and chemical activation with KOH. In each preparation step, the material was analyzed to follow the physicochemical transformations. The removal efficiency of COD, N-NH4+, N-NO3-, and P from real WW was studied using batch adsorption tests. Pyrolysis at 650 °C + KOH activation guaranteed higher yields for N-NH4+ (32%), P (44%), and N-NO3− (66%) with a contact time in the batch test of 6 h for N-NH4+ and P, and 3 h for N-NO3−. Up to 50% COD removal was achieved in 6 h with 950 °C pyrolyzed + KOH-activated biochar. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) constitute a group of organofluorine chemical synthetic compounds widely used in industries and manufacturing due to their hydrophobic properties. However, PFAS have been found to cause negative human health outcomes. Therefore, a strong interest in the possible removal of these compounds from wastewater (WW) has been shown. This work aims to present a systematic analysis of the scientific literature related to the innovative and alternative adsorbent materials that can be used for treating PFAS-contaminated WW. Moreover, the adsorption processes are considered, focusing the attention on virgin adsorbent materials and biochar as adsorbents. Virgin adsorbent materials comprise conventional adsorbent materials, functional clays, metal–organic frameworks, and functionalized organic polymers. Biochar includes materials obtained from agricultural or food residues and from sewage sludge. The review shows that conventional treatment units using virgin adsorbent materials are characterized by high adsorption capacity, but also high costs. In addition, the refunctionalization of adsorbent materials is difficult to obtain. On the contrary, biochar, which is a residual product of other production processes, appears to be a cost-effective solution. [ABSTRACT FROM AUTHOR]