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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]

Waste management planning is a complex task involving a variety factors and professional skills. In order to avoid oversimplification leading to the risk of adopting inappropriate solution the relevant decision problems should be tackled with: (a) a comprehensive decision model (including technical, environmental, economic, social, etc. factors) and (b) a suitable decision supporting tool. In this work as far as (a) is concerned we propose a model based on more than 30 parameters for the evaluation of sewage sludge management strategies. As to (b) we implemented this model by employing both a worksheet (“ home made ” option) and a DSS commercially available (“ buy ” option). As a case study, we considered the selection of the sewage sludge management strategy in a 500,000 inhabitants area comparing the following alternatives: Agricultural use, Incineration, Wet Oxidation and recovery in Cement Kiln. The assessment of the four alternatives led to the following preference order: Agricultural use ≫ Incineration > Cement Kiln ≅ Wet Oxidation. Finally, a discussion on the make-or-buy dilemma and on pros and cons of decision support methods is reported. As a result, a paradigm shift defined make-and-buy approach is proposed. [ABSTRACT FROM AUTHOR]

In order to meet the environmental legislative framework in force in Europe and reduce sludge processing and disposal costs, several sludge treatment technologies and management strategies have been proposed in the last two decades. The evaluation of their technical and economic suitability, case by case, may be a challenge, since many aspects are involved, so that a robust decision support system should be used. Within the ROUTES project (founded within the EU Seventh Framework Programme), the authors have developed an assessment procedure which allows rating several technical factors (such as system reliability, complexity, safety aspects, modularity, etc.) and estimating capital and operating costs, in case a plant is being upgraded. The comparison between the original (reference) plant and the modified configuration informs about technical hot spots (which are expressed by a traffic light-type colour code) and cost gaps resulting from the implementation of the new solution. [ABSTRACT FROM AUTHOR]

Today, several technologies and management strategies are proposed and applied in wastewater treatment plants (WWTPs) to minimise sludge production and contamination. In order to avoid a shifting of burdens between different areas, their techno-economic and environmental performance has to be carefully evaluated. Wet oxidation (WO) is an alternative solution to incineration for recovering energy in sewage sludge while converting it to mostly inorganic residues. This paper deals with an experimentation carried out within the EU project '. A mass balance was made for a WWTP (500,000 person equivalents) in which a WO stage for sludge minimisation was considered to be installed. Both bench- and full-scale test results were used. Design of treatment units and estimation of capital and operational costs were then performed. Subsequently, technical and economic aspects were evaluated by means of a detailed methodology which was developed within the ROUTES project. Finally, an assessment of environmental impacts from a life cycle perspective was performed. The integrated assessment showed that for the specific upgrade considered in this study, WO technology, although requiring a certain increase of technical complexity at the WWTP, may contribute to environmental and economic advantages. The paper provides guidance in terms of which aspects need a more thorough evaluation in relation to the specific case in which an upgrade with WO is considered. [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]