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Wastewater treatment facilities are increasingly being considered as centralized installations where various resources can be recovered from the sewage. Novel technological solutions are already available for achieving this goal. However, their application to upgrade existing plants can be far more challenging than building new dedicated plants. While the scientific literature is generally focused on testing and comparing the recovery options, this work was aimed at giving a holistic evaluation of the actual impacts of upgrading existing facilities. Commercially available systems were considered for retrofitting two plants of different size (50,000 and 500,000 population equivalents) and achieving either energy self-sufficiency or material recovery. Based on mass and energy balances, a detailed evaluation of technical, social, economic, and administrative aspects was carried out. Environmental aspects were also included, adopting a simplified approach. It turned out that energy self-sufficiency (external energy supply reduced down to about 10% of the total need) is not far away to be achieved, with moderate techno-economic implications, especially when the plant is already equipped with primary sedimentation and anaerobic digestion. Integral recovery of treated effluent, sludge and nitrogen can also be pursued in large facilities, while several potential criticalities arise for medium-sized plants. The adopted procedure evidenced critical aspects that are often disregarded in the decision process: this may suggest where to address efforts in evaluating real situations. [ABSTRACT FROM AUTHOR]

In recent years, rapid population growth and industrialization have increased the use of natural resources and the production of waste. To develop a circular economy, it is necessary to study and promote alternative long-term solutions for waste disposal, such as reuse and recovery. Wastewater treatment plants (WWTPs) can be an important part of circular sustainability if re-oriented to function as a water resource recovery facilities (WRRFs). In this context, biological sewage sludge (SS) can be treated in order to produce more stabilized residues: biosolids (BS). This paper aims to review the possible alternatives to reuse the BS in order to increase matter recovery. Around 250 papers, reviews, books and conference proceedings have been examined. Authors explored the application of BS on land, such as soil amendment/fertilizer both in agriculture and for interventions on abandoned mine sites, and on engineering fields, in partial or total substitution of virgin materials. The reuse of BS as adsorbent materials and as a source of phosphorus is also discussed. • Population perceives the reuse of biosolids as dangerous for human and environment. • In agricultural reuse of biosolids, heavy metals effects continue to be studied. • Feasibility of the utilization of biosolids for brick construction. • Conversion into adsorbent material and source of phosphorus is also presented. • Further investigation on emerging organic contaminants would be conducted. [ABSTRACT FROM AUTHOR]

Abstract: A key issue in biological Waste Water Treatment Plants (WWTPs) operation is represented by the sludge management. Mechanical dewatering is a crucial stage for sludge volume reduction; though, being a costly operation, its optimization is required. We developed an original experimental methodology to evaluate the technical (dewatering efficiency) and financial (total treatment costs) performance of dewatering devices, which might be used as a DSS (Decision Support System) for WWTP managers. This tool was then applied to two real case studies for comparing, respectively, three industrial size centrifuges, and two different operation modes of the same machine (fixed installation vs. outsourcing service). In both the cases, the best option was identified, based jointly on economic and (site-specific) technical evaluations. [Copyright &y& Elsevier]