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.
Combined sewer overflows (CSOs) are of major environmental concern for impacted surface waterbodies. In the last decades, major storm events have become increasingly regular in some areas, and meteorological scenarios predict a further rise in their frequency. Consequently, control and treatment of CSOs with respect to best practice examples, innovative treatment solutions and management of sewer systems is an inevitable necessity. As a result, the number of publications concerning quality, quantity and type of treatments has recently increased. This review therefore aims to provide a critical overview on the effects, control and treatment of CSOs in terms of impact on the environment and public health, strict measures addressed by regulations, and the various treatment alternatives including natural and compact treatments.Drawing together the previous studies, an innovative treatment and control guideline is also proposed for the better management practices.
Long term operation of an anaerobic membrane bioreactor (AnMBR) treating municipal wastewater was investigated in a real seawater intrusion spot in Falconara Marittima (Central Italy) on the Adriatic coastline. Changes in biological conversion and system stability were determined with respect to varying organic loading rate (OLR) and high salinity conditions. At an OLR of 1 kgCOD . m 3-1 d -1 , biogas production was around 0.39 ± 0.2 L . d -1 . The increase of the OLR to 2 kgCOD . m 3-1 d -1 resulted in the increase of biogas production to 2.8 ± 1.5 L . d -1 (with 33.6% ± 10.5% of CH4) with methanol addition and to 4.11 ± 3.1 L . d -1 (with 29.7% ± 11.8% of CH4) with fermented cellulosic sludge addition. COD removal by the AnMBR was 83% ± 1% when the effluent COD concentration was below 100 mg O2 . L -1 . The addition of the fermented sludge affected the membrane operation; significant fouling occurred after long-term filtration, where the trans-membrane pressure (TMP) reached up to 500 mbar. Citric acid solution was applied to remove scalants and the TMP reached the initial value. High saline conditions of 1500 mgCl -. L -1 adversely affected the biogas production without deteriorating the membrane operation. The treated effluent met the EU quality standards of the D.M. 185/2003 and the new European Commission Resolution for reuse in agriculture.
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.
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