Le nostre scuole prima di tutto. Our schools, first and foremost

Realizzare strutture scolastiche temporanee con standard, tempi e costi certi, apre la strada all’applicazione di capacità, procedure e prassi di lavoro utili anche per intervenire sulle scuole tradizional

Pilot scale biofilm reactor for heterotrophic denitrification of groundwater: the Milan city case study

A pilot scale biofilm reactor has been applied to study the efficacy of an heterotrophic denitrification process for the removal of 40 mgNO3/L from Milan city groundwater, characterized by contextual pollution of VOCs and pesticides. The biological submerged filter (Biofor, Degrémont) with expanded clay as biomass support (Biolite, Degrémont) was fed with a constant water inflow of 0.6 m3/h, and the effluent was subjected to an aeration step (3 min HRT) and a GAC filtration (8 min EBCT). Tracer tests using LiCl were performed before and after bacterial colonization, revealing a mean residence time of 22 min and suggesting a PFR with axial dispersion (increasing with the colonizing degree), as the best interpretative model. A continuous dosage of sodium acetate (CH3COONa) and potassium phosphate (KH2PO4) was assured, with a variable organic carbon dosage, obtained fixing the C/DO ratio (0.94 gC/gDO for a concentration of 6.2 ± 0.55 mgDO/L) and varying the C/N ratio. Data observed during 70 days of stationary phase have shown that an applied C/N ratio equal to the stoichiometric value of 1.46 gC/gN led to a stable removal efficiency higher than 88.5%, while lower applied C/N values presented a significant occurrence of nitrite in the effluent. Stoichiometry was used to verify the aerobic and anoxic organic carbon consumption along the biofilter, since a concomitant removal of nitrogen and dissolved oxygen was observed, and suggested that no biomass stratification was present. The observed removal efficiencies did not highlight any inhibition mechanism associated to influent micro-pollutants, and any co-metabolic removal of VOCs or other organic pollutant could be inferred

Which processes are behind the relationship between species abundance and environmental suitability? Monte Albo cave salamander as model species

Species can show a strong variation of local abundance across their ranges. Recent analyses suggested that variation in abundance can be related to environmental suitability, as the highest abundances are often observed in populations living in the most suitable areas. However, there is limited information on the mechanisms through which variation in environmental suitability determines abundance. We analyzed populations of the microendemic Monte Albo cave salamander Hydromantes (Speleomantes) flavus Stefani, 1969 (Plethodontidae), and tested several hypotheses on potential relationships linking environmental suitability to population parameters. For multiple populations across the whole species range, we assessed suitability using species distribution models and measured density, activity level, food intake, and body condition index. In high-suitability sites, the density of salamanders was up to 30 times higher than in the least suitable ones. Variation in activity levels and population performance can explain such variation of abundance. In high-suitability sites, salamanders were active close to the surface and showed a low frequency of empty stomachs. Furthermore, when taking into account seasonal variation, body condition was better in the most suitable sites. Our results show that the strong relationship between environmental suitability and population abundance can be mediated by the variation of parameters strongly linked to individual performance and fitness. Furthermore, we highlighted the potential use of cave animals as model species to answer macroecological questions