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The cake layer deposited on the membrane modules of membrane bioreactors (MBRs), especially under a submerged configuration, represents a relevant and fundamental mechanism deeply influencing the development of membrane fouling. It negatively affects the total resistance to filtration, while exerting a positive effect as a “pre-filter” promoting the “dynamic membrane” that protects the physical membrane from internal fouling. These two opposite phenomena should be properly managed, where the submerged membranes are usually subjected to a periodical cake layer removal through ordinary (permeate backwashing and air scouring) and/or irregular cleaning actions (manual physical cleaning). In this context, the physical removal of the cake layer is needed to maintain the design filtration characteristics. Nevertheless, the proper evaluation of the effect of physical cleaning operations is still contradictory and under discussion, referring in particular to the correct evaluation of fouling mechanisms. The aim of the present work was to summarize the different aspects that influence the fouling investigations, based on simple models for the evaluation of the resistance to filtration due to the cake layer, through physical cleaning operations.

This study aims to assess the ecological and human health risks associated with four heavy metals (Cd, Cr, Cu, and Zn) in the soil of a dumpsite in Targuist city, Morocco. In total, 16 surface soil samples were collected from the dumpsite and its nearby areas following leaching drain flows. The pollution load index (PLI), geo-accumulation index (Igeo), and potential ecological risk index (RI) were subsequently determined. In addition, hazard quotient (HQ) and health index (HI) were used to assess the non-carcinogenic and carcinogenic risks associated with the soil heavy metal contents. The PLI indicated significant contamination by the studied heavy metals. On the other hand, the Igeo values suggested no Cr contamination, moderate contamination by Cu and Zn, and severe contamination by Cd. The RI indicated a dominant contribution from Cd, with minor contributions from Cu, Zn, and Cr accounting for 92.47, 5.44, 1.11, and 0.96%, respectively, to the potential ecological risk in the study area. The non-carcinogenic health risks associated with exposure of the nearby population to the soil heavy metals at the dumpsite and burned solid waste-derived air pollution were below the threshold value of 1 for both children and adults. Although carcinogenic risks were observed in the study area, they were acceptable for both children and adults according to the United States Environmental Protection Agency (USEPA). However, carcinogenic risks associated with Cr were unacceptable according to the Italian Legislation. Finally, strategies to mitigate the risks posed by the dumpsite were also discussed in this study.

Over the last decade new technologies are emerging even more for wastewater treatment. Among the new technologies, a recent possible solution regards Moving Bed Biofilm Reactors (MBBRs) that represent an effective alternative to conventional processes. More specifically such systems consist in the introduction of plastic elements inside the aerobic reactor as carrier material for the growth of attached biomass. Recently, one of the mostly used alternatives is to couple the Moving Bed Biofilm Reactor (MBBR) process with the conventional activated sludge process, and the resulting process is usually called HMBBR (Hybrid MBBR). In the MBBR process the biofilm grows attached on small plastic elements that are kept in constant motion throughout the entire volume of the reactor. Indeed, in such a system, a competition between the two biomasses, suspended and attached, can arise for the availability of the substrates, leading, as a consequence, to a modification in the biokinetic parameters of the two biomasses, compared to that of a pure suspended or attached biomass process. This paper presents the first results of a study aimed at estimating the kinetic heterotrophic constants in a HMBBR pilot plant using respirometric techniques. The pilot plant was built at the Acqua dei Corsari (Palermo) wastewater treatment plant and consisted of two parallel lines realized in a pre-anoxic scheme, in one of which the carrier material was added to the aerobic reactor with a filling ratio of 30%.

Wastewater treatment plants (WWTPs) require an urgent transition from a linear to a circular economy operation/design concept with a consequent resource recovery and more sustainable waste management. Natural resources have to be preserved, and wastes have to become an opportunity for recovering resources and materials (water reuse, energy, sludge reuse). However, the transition toward a circular economy is a complex and long process due to the existence of technical, economic, social and regulatory barriers. These existing barriers are critical challenges for a modern and sustainable WWTP concept. The recovery of resources must be considered a strategic target from the earliest process-design phase. In this context, the European Union’s Horizon 2020 project “Achieving wider uptake of water-smart solutions—WIDER UPTAKE” aims to overcome the existing barriers (technological, regulatory, organizational, social and economic) toward the transition from a linear to a circular economy model for WWTPs. This study is aimed at increasing the awareness of the existing barriers to a circular economy and summarizes the key contributions of the WIDER UPTAKE project in terms of water reuse, sludge reuse and nutrient recovery.

The wastewater sector paradigm is shifting from wastewater treatment to resource recovery. In addition, concerns regarding sustainability during the operation have increased. In this sense, there is a need to break barriers (i.e., social, economic, technological, legal, etc.) for moving forward towards water resource recovery facilities and demonstration case studies can be very effective and insightful. This paper presents a new water resource recovery case study which is part of the Horizon 2020 EU Project “Achieving wider uptake of water-smart solutions—Wider Uptake”. The final aim is to demonstrate the importance of a resource recovery system based on the circular economy concept. The recovery facilities at Palermo University (Italy) are first presented. Afterwards, the resource recovery pilot plants are described. Preliminary results have underlined the great potential of the wastewater treatment plant in terms of resources recovery and the central role of the University in fostering the transition towards circular economy. The fermentation batch test highlighted a volatile fatty acids (VFAs) accumulation suitable for polyhydroxyalkanoates (PHAs) production. The results of static adsorption and desorption tests showed that the highest amount of adsorbed NH4+ was recorded for untreated and HCl-Na treated clinoptilolite.

Rapid population and economic growth have increased the demand for depleting resources. Nitrogen (N) and phosphorus (P) are mineral elements that perform important functions in plants, but their extraction is not sustainable. In addition, these elements contribute significantly to the eutrophication of water bodies. The recovery of these nutrients from wastewater by adsorption techniques offers a promising solution. Previous studies have demonstrated the adsorption capabilities of materials such as zeolite for ammonium (NH4+) and biochar for P. In addition, these materials can serve as a source of N and P for plants in a circular economy context. In this regard, this study aims to evaluate the recovery of N and P by the adsorption capacities of zeolite and biochar through a column test with treated wastewater. Two columns positioned in series, one filled with 2.7 kg of zeolite and the other with 397 g of biochar, were placed at the outlet of the full-scale sewage treatment plant of Marineo (Italy). The zeolite adsorbed 3.6 g of NH4+ accumulated during the test with a rate of adsorption of 44% and adsorption of 1.33 mg g−1 of NH4+. The biochar adsorbed about 11 g of P accumulated during the test, with an adsorption percentage of 13% and an adsorption of 26.75 mg g−1 of P. Despite some problems related to the effluent used during the test, the tested materials showed good adsorption properties.

The direct measurement of volatile compounds is becoming increasingly important in assessing site contamination, particularly in relation to human health risk assessment and the design of remediation procedures. This study assesses the influence of direct measurements on the human health risk assessment conducted at a petroleum-contaminated site. Specifically, it provides contaminated-site risk managers with a quantitative comparison of the assessed risks by using measured and modeled data. A total of 16 monitoring campaigns were conducted at a Site of National Interest (SNI) located in Sicily (Italy), during which the hydrocarbon vapor concentrations in the subsurface soil porosity were measured using nested soil gas probes, while the related emitted fluxes were quantified with dynamic flux chambers. Measured data were compared with those obtained with a non-reactive diffusive model using the concentrations measured in the soil. The results highlighted significant overestimations of the expected outdoor concentrations obtained using non-reactive diffusive models by up to four orders of magnitude. These findings underscore the intrinsic limitation of non-reactive diffusive models, which provide overly conservative and unrealistic risk scenarios. Therefore, direct measurements might represent a cost-effective option to account for natural attenuation phenomena occurring in the subsurface, leading to a more realistic human health risk assessment (HHRA).

The current exploitation of freshwater, as well as the significant increase in sewage sludge production from wastewater treatment plants (WWTPs), represent nowadays a critical issue for the implementation of sustainable development consistent with the circular economy concept. There is an urgent need to rethink the concept of WWTPs from the conventional approach consisting in pollutant removal plants to water resource recovery facilities (WRRFs). The aim of this paper is to provide an overview of the demonstration case studies at the Marineo and Corleone WRRFs in Sicily (IT), with the final aim showing the effectiveness of the resources recovery systems, as well as the importance of plant optimization to reduce greenhouse gas (GHG) emissions from WRRFs. This study is part of the H2020 European Project “Achieving wider uptake of water-smart solutions—Wider-Uptake”, which final aim is to demonstrate the water-smart solution feasibility in the wastewater sector. The main project goal is to overcome the existing barriers that hamper the transition to circularity through the implementation of a governance analysis tool. The preliminary actions in the two demonstration cases are first presented, while, subsequently, the water-smart solutions to be implemented are thoroughly described, highlighting their roles in the transition process. The achieved preliminary results underlined the significant potential of WRRF application, a great chance to demonstrate the feasibility of innovative solutions in the wastewater sector to overcome the existing social, administrative and technical barriers.

A hybrid activated sludge/biofilm process was investigated for wastewater treatment in a cold climate region. This process, which contains both suspended biomass and biofilm, usually referred as IFAS process, is created by introducing plastic elements as biofilm carrier media into a conventional activated sludge reactor. In the present study, a hybrid process, composed of an activated sludge and a moving bed biofilm reactor was used. The aim of this paper has been to investigate the performances of a hybrid process, and in particular to gain insight the nitrification process, when operated at relatively low MLSS SRT and low temperatures. The results of a pilot-scale study carried out at the Department of Hydraulic and Environmental Engineering at the Norwegian University of Science and Technology in Trondheim are presented. The experimental campaign was divided into two periods. The pilot plant was first operated with a constant HRT of 4.5 hours, while in the second period the influent flow was increased so that HRT was 3.5 hours. The average temperature was near 11.5°C in the overall experimental campaign. The average mixed liquor SRT was 5.7 days. Batch tests on both carriers and suspended biomass were performed in order to evaluate the nitrification rate of the two different biomasses. The results demonstrated that this kind of reactor can efficiently be used for the upgrading of conventional activated sludge plant for achieving year-round nitrification, also in presence of low temperatures, and without the need of additional volumes.

The paper presents the comparison between the traditional activated sludge system (AS) and a hybrid moving bed biofilm reactor (HMBBR). In particular, an experimental campaign has been carried out at the WWTP in Palermo (Italy), on a pilot plant consisting of two pre-anoxic schemes. The aerated tank of the HMBBR line was filled with suspended carriers (AnoxKaldnes™ K1), with a 30% filling ratio. The hydraulic load of the HMBBR line was increased up to two times the AS one. Further, in order to distinguish the additional contribution of the attached biomass for the HMBBR system, in the two lines the Mixed Liquor Suspended Solids (MLSS) was maintained as equal as possible. The monitoring period lasted three months during which several parameters were monitored. The obtained results showed a good treatment ability of the HMBBR system, referring to the organic matter removal as well as to the ammonium removal. In particular, in spite of the increase of the hydraulic load for the HMBBR line, the two systems showed a similar performance in terms of both organic and nitrogen removal. The results demonstrate the higher treatment capacity of the HMBBR addressing such system as an effective technology for the upgrading of overloaded wastewater treatment plants.