Monitoring the aeration efficiency and carbon footprint of a medium-sized WWTP: experimental results on oxidation tank and aerobic digester.

The efficiency of aeration systems should be monitored to guarantee suitable biological processes. Among the available tools for evaluating the aeration efficiency, the off-gas method is one of the most useful. Increasing interest towards reducing greenhouse gas (GHG) emissions from biological processes has resulted in researchers using this method to quantify N2O and CO2 concentrations in the off-gas. Experimental measurements of direct GHG emissions from aerobic digesters (AeDs) are not available in literature yet. In this study, the floating hood technique was used for the first time to monitor AeDs. The floating hood technique was used to evaluate oxygen transfer rates in an activated sludge (AS) tank of a medium-sized municipal wastewater treatment plant located in Italy. Very low values of oxygen transfer efficiency were found, confirming that small-to-medium-sized plants are often scarcely monitored and wrongly managed. Average CO2 and N2O emissions from the AS tank were 0.14 kgCO2/kgbCOD and 0.007 kgCO2,eq/kgbCOD, respectively. For an AeD, 3 × 10-10 kgCO2/kgbCOD direct CO2 emissions were measured, while CO2,eq emissions from N2O were 4 × 10-9 kgCO2,eq/kgbCOD. The results for the AS tank and the AeD were used to estimate the net carbon and energy footprint of the entire plant.

Molecular and supramolecular structural studies on significant repetitive sequences of resilin.

Resilin is a member of the family of elastomeric proteins and is found in specialised regions of the cuticle of most insects, and provides low stiffness, high strain and efficient energy storage. It is best known for its role in insect flight and the remarkable jumping ability of fleas and spittle bugs. In common with other elastomeric proteins, the recently identified Drosophila melanogaster proresilin shows glycine-rich repetitive sequences; in particular the N- and C-terminal regions of the protein are dominated by 18 repeats of a 15-residue sequence (SDTYGAPGGGNGGRP) and eleven repeats of a 13-residue sequence (GYSGGRPGGQDLG), respectively. We synthesised and analysed the molecular and supramolecular structure of some polypeptides with sequences belonging to the glycine-rich repeated domain of D. melanogaster resilin. The conformational studies performed by CD, FTIR and NMR spectroscopies pointed to the coexistence of two main conformational features, such as folded beta-turns and (quasi)extended structures (e.g., poly-L-proline II conformation) in common with other elastomeric proteins; this suggests an elasticity mechanism for resilin common to other elastomeric proteins. Our data show that also in the case of resilin, repetitive sequences are characterised by autonomous structures almost independent of the remaining parts of the molecule as already extensively found for elastin. From a supramolecular point of view, a great tendency to aggregate in fibrous structures is observed, particularly for the resilin- inspired polypeptide (PGGGN)(10). This is encouraging for the development of resilin-based biomaterials for the production of biocompatible medical devices, as well as high performing elastic materials.