Ricerc@Sapienza

The biological denitrification process is extensively discussed in scientific literature. The process requires anoxic conditions, but the influence of residual dissolved oxygen (DO) on the efficiency is not yet adequately documented. The present research aims to fill this gap by highlighting the effects of DO on the specific denitrification rate (SDNR) and consequently on the efficiency of the process. SDNR at a temperature of 20◦C (SDNR20◦C) is the parameter normally used for the sizing of the denitrification reactor in biological-activated sludge processes.

The influence of temperature on the production of enrichment biomass and polyhydroxyalkanoates by activated sludge was evaluated within a practical case study. Two laboratory-scale sequencing batch reactors (SBRs) were operated in parallel over 131 days to treat a wastewater from a potato-starch modification facility, and produce surplus activated sludge biomass with PHA accumulation potential. The SBRs were operated similarly but at different temperatures (15 and 25 °C). Temperature did not influence wastewater treatment performance (average 97% COD removal).

The present study investigated the effects of ozonation pre-treatment at low-ozone dosage (below 100 mgO3/gTS0) with respect to previous studies, on the anaerobic digestion of waste-activated sludge alone and a mixture of activated sludge and primary sludge. Methane production and volatile suspended solids reduction efficiency were determined for different specific ozone dosages and compared with the values obtained in the absence of pre-treatment.

Cycles of dissolved oxygen perturbation can affect emerging contaminants removal. The nitrification process can also be enhanced by oxygen perturbations. Perturbation frequency is a sensitive parameter

Adsorption was the main removal process of PFOS and PFOA in activated sludge reactors at laboratory scale. Some biodegradation of the two tested contaminants was also detected, after adsorption. Respirometric tests showed inhibition of the nitrifying bacteria up to 30% due to the presence of PFOS and PFOA. COD removal was not affected by the presence of PFOS and PFOA.

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most investigated compounds in the class of perfluoroalkyl substances for their persistence and wider diffusion in the environment. However, fate and behaviour of PFOA and PFOS in the Wastewater Treatment Plants (WWTPs) have not been fully understood yet. The aim of the present study was to obtain a better understanding of the processes occurring to PFOS and PFOA in the activated sludge reactor. Several experimental tests were performed in the presence of activated sludge and sterilized sludge.