The optimization of a two-phase thermophilic anaerobic process treating biowaste for hydrogen and methane production was carried out at pilot scale using two stirred reactors (CSTRs) and without any physical/chemical pre-treatment of inoculum. During the experiment the hydrogen production at low hydraulic retention time (3d) was tested, both with and without reject water recirculation and at two organic loading rate (16 and 21 kgTVS/m3 d). The better yields were obtained with recirculation where the pH reached an optimal value (5.5) thanks to the buffering capacity of the recycle stream. The specific gas production of the first reactor was 51 l/kgVS(fed) and H2 content in biogas 37%. The mixture of gas obtained from the two reactors met the standards for the biohythane mix only when lower loading rate were applied to the first reactor, with a composition of 6.7% H2, 40.1% CO2 and 52.3% CH4 the overall SGP being 0.78 m3/kgVS(fed).

After investigating the application of the mesophilic and thermophilic processes in completely stirred, batch, and plug-flow reactors, in this study the authors consider the anaerobic fermentation of source-sorted organic municipal solid wastes in psychrophilic conditions (14-22 °C) without pH control. The pilot-scale reactor was operated in a batch mode, with a hydraulic retention time of 4-4.5 d. The production of soluble COD from the particulate matter was (on average) 0.27 gCOD per gram of total volatile solids fed to the reactor when operating with a total solids content of 20-35 g/L. The volatile fatty acids (VFA) were 15% of the soluble COD produced after 4 d of reaction. These values are far lower than those found in mesophilic and thermophilic conditions, where the production of soluble COD ranged from 0.5 up to 0.9 gCOD/ gTVS fed and volatile fatty acids could reach 90% of soluble COD. Further, the first-order reaction constant for the hydrolysis process, K h , for the psychrophilic conditions was found equal to 0.11 d -1 at 20 °C, while it was in the range 0.2-0.4 d -1 when operating in mesophilic or thermophilic conditions. Conclusively, the study of the psychrophilic fermentation process allowed for completing the scenario of different options of anaerobic solid-state fermentation of organic waste. Though mesophilic and thermophilic processes resulted in being more effective in dissolution of particulate matter, psychrophilic processes can be of some interest because they are simpler and energy saving. In particular, psychrophilic processes can be useful for the production of rough soluble COD to be used, e.g., for sustaining the biological nutrients removal processes in wastewater treatment.

The experience of P removal by auto-nucleation and crystal growth of struvite (MAP) in a demonstrative plant is proposed. The demonstrative plant is located in a municipal wastewater treatment plant in northern Italy. The trials are a consequence of previous experimentation carried out using silica sand as seed material. Working in metastable conditions the auto-nucleation process is performed, and allows the control of the precipitation and the growth of MAP inside the FBR reactor. No scaling problems are observed in the collecting pipes. After the treatment of 650m3 of anaerobic supernatants, 0.28 tons of granulated crystalline MAP are produced. The chemical analysis shows its possible use in agriculture as fertilizer. Operative costs analysis confirms the SCP as a cheap way to remove and recover P from anaerobic supernatants.

The occurrence, fate and removal of microplastics (MPs) in a wastewater treatment plant (WWTP) in Central Italy were investigated together with their potential adverse effects on anaerobic processes. In the influent of the WWTP, 3.6 MPs . L -1 were detected that mostly comprised polyester fibers and particles in the shape of films, ranging 0.1-0.5 mm and made of polyethylene and polypropylene (PP). The full-scale conventional activated sludge scheme removed 86% of MPs, with the main reduction in the primary and secondary settling. MPs particles bigger than 1 mm were not detected in the final effluent and some loss of polymers types were observed. In comparison, the pilot-scale upflow granular anaerobic sludge blanket (UASB) + anaerobic membrane bioreactor (AnMBR) configuration achieved 94% MPs removal with the abatement of 87% of fibers and 100% of particles. The results highlighted an accumulation phenomenon of MPs in the sludge and suggested the need to further investigate the effects of MPs on anaerobic processes. Accordingly, PP-MPs at concentrations from 5 PP-MPs . gTS -1 to 50 PP-MPs . gTS -1 were spiked in the pilot-scale UASB reactor that was fed with real municipal wastewater, where up to 58% decrease in methanogenic activity was observed at the exposure of 50 PP-MPs . gTS -1 . To the best of our knowledge, the presented results will be the first to report of PP-MPs inhibition on anaerobic processes.

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Reuse of treated wastewater for irrigation purposes is a measure to reduce water stress and overexploitation of freshwater resources. This study aims to investigate the environmental and economic impacts of a current conventional wastewater treatment plant (WWTP) in Peschiera Borromeo (Milan, Italy), and compare possible scenarios to enable reclaimed water reuse for agriculture purposes. Accordingly, we propose alternative disinfection methods (i.e. enhanced UV, peracetic acid) and replace conventional activated sludge (CAS) with upflow anaerobic sludge blanket (UASB) for biological treatment and use anaerobic membrane bioreactor (AnMBR) as the tertiary treatment. Life cycle assessment (LCA) and life cycle costing (LCC) were implemented on the existing full-scale wastewater treatment line and the hypothetical scenarios. In most cases, the impact categories are primarily influenced by fertilizer application and direct emissions to water (i.e. nutrients and heavy metals). The baseline scenario appears to have the largest environmental impact, except for freshwater eutrophication, human ecotoxicity and terrestrial ecotoxicity. As expected, water depletion is the most apparent impact category between the baseline and proposed scenarios. The UASB + AnMBR scenario gives relatively higher environmental benefits than other proposed scenarios in climate change (-28%), fossil fuel depletion (-31%), mineral resource depletion (-52%), and terrestrial ecotoxicity compared to the baseline. On the other hand, the highest impact on freshwater eutrophication is also obtained by this scenario since the effluent from the anaerobic processes is rich in nutrients. Moreover, investment and operational costs varied remarkably between the scenarios, and the highest overall costs are obtained for the UASB + AnMBR line mostly due to the replacement of membrane modules (24% of the total cost). The results highlighted the importance of the life cycle approach to support decision making when considering possible upgrading scenarios in WWTPs for water reuse.