Luca Pucci

A pilot-scale moving-bed biofilm reactor (MBBR), operated under alternating intermittent aeration (IA) and non-aeration phases, was used for single-stage carbon (C) and nitrogen (N) removal from high-fluctuating municipal wastewater via simultaneous nitrification–denitrification. The reactor was operated under highly variable chemical oxygen demand to total nitrogen (COD/TN) ratios, low dissolved oxygen (DO) conditions, and progressively extended non-aerated periods to evaluate process robustness under real operational conditions. An active denitrifying biofilm developed on the carriers after 23 days of the anoxic start-up, as confirmed by batch activity tests. Under the most carbon-limited condition tested (COD/TN = 5.5), the application of 16 h·d⁻¹ of non-aerated phases at DO levels of 0–1.0 mg·L⁻¹ enabled simultaneous COD, N–NH₄⁺ and TN removal efficiencies of 70, 95 and 84%, respectively. These results confirm that transient IA is an effective strategy for simultaneous C and N removal at very low COD/TN ratios and real fluctuating influent concentrations. Energy assessment showed that extended non-aeration phases reduced blower energy demand by 67% and total plant energy consumption by 34%, improving the environmental sustainability of the single-stage process. The main novelty of this study lies in the pilot-scale validation of an IA-MBBR for SND using real municipal wastewater under naturally fluctuating C and N loadings, thereby bridging previous laboratory-scale evidence with realistic operating conditions.

The need to ensure adequate levels of both human and environmental health protection calls for the identification of efficient wastewater treatment processes that target the removal of conventional pollutants as well as emerging contaminants, including synthetic dyes. This study explores the potential of ozone for use in the decolorization of both pretreated tannery wastewater and urban wastewater effluents. Different ozone contact times (15, 30, and 45 min) were applied to such wastewater samples at an uncontrolled (7.5–8.2) pH as well as at a pH adjusted to 10. The highest color removal efficiencies (REs) (>90%) were obtained with urban wastewater after a 45 min contact time and at pH 10. Under the same conditions, a COD RE from 31 to 51% was achieved. Even without pH adjustment, color and COD REs ranging from 81 to 92% and 39 to 41%, respectively, were obtained. A preliminary evaluation of the costs associated with the implementation of an ozonation stage within the wastewater treatment plant (WWTP) generating the urban wastewater used here was carried out. The energy cost of the ozone treatment would account for a 69% increase in the total energy cost of the WWTP, suggesting the need to identify proper strategies to enhance the cost-competitiveness of this technology.

Conventional fertilization practices in agroecosystems concern the supply of bioavailable nutrients, such as mineral fertilizers. A consolidated alternative to restoring the long-term fertility of agricultural soils is their amendment with organic fertilizers. Soil amendment with biowaste compost or sewage sludge represents a sustainable strategy to avoid the landfilling of organic matter derived from urban waste and sewage sludge. This study aims at validating the use of quality biowaste compost and sewage sludge from secondary sedimentation (alone or in combination with mineral fertilizers) in a Mediterranean agroecosystem and their effects on soil chemical and biological quality, with a view to verifying the maintenance of soil fertility and functionality. In particular, the dynamics of soil organic matter, pH, potentially toxic elements and microbial community functionality were assessed, in experimental mesocosms, during 6 months of incubation. The research showed that, while soil amendment with biowaste compost induces positive effects on soil organic matter and phosphorous concentrations, as well as on microbial community functionality, the amendment with the selected sewage sludge does not determine any benefit to the microbial community or any danger in relation to soil potentially toxic element concentrations and toxicity. The quantity of sewage sludge employed, chosen according to regional directives, was thus not enough to stimulate the edaphic microflora activity.