Performance of wastewater treatment plants in emission of greenhouse gases.

The present work has estimated greenhouse gas emissions in aerobic and anaerobic Wastewater Treatment Plants in Southern Italy. Greenhouse gases emissions from each treatment unit were calculated based on emission factors related to Chemical Oxygen Demand removal for biogenic CO2 and CH4 assessment and on Nitrogen removal for N2O. N2O, biogenic CO2, and CH4 emissions vary for aerobic and anaerobic-based WWTPs respectively from 73 kgCO2eq/PE*y for anaerobic plants to 91 kgCO2eq/PE*y for aerobic plants. In aerobic and anaerobic digestion systems WWTPs the contributions to CO2eq total emissions from N2O, CH4, biogenic CO2, and fossil CO2 are 30 %-33 %, 20 %-29 %, 22 %-25 %, and 26 %-16 %, respectively. N2O emissions from biological processes were found the most contributing sources of greenhouse gases while in the physical processes higher contribution is indirect carbon dioxide related to energy consumption. Compensatory measures are reported to reduce greenhouse gases emissions.

Influence of climate change on wastewater treatment plants performances and energy costs in Apulia, south Italy.

This paper studies the influence of temperature and of rainfall intensity and the effect of such variations on the treatment efficiencies and on the electrical consumptions in seven medium-large size Wastewater Treatment Plants (WWTPs) in Apulia in South Italy (Bari, Barletta, Brindisi, Lecce, Foggia, Andria and Taranto). It has been observed, in the considered WWTPs, a slight but clear increase of the incoming flow due to the increase in rainfall intensity, which results to an increase of the energy consumption per incoming volume. The impact of the climate change to the incoming flow, during the last five years (2016-2020), has been assessed indicating that an increase in rainfall intensity results to an increase of the WWTPs energy consumptions per wastewater treated volume. More specifically, for a specific WWTP (Lecce) it was found that the electrical consumption increases from 0.36 kw/m3 to 0.51 kw/m3 when the rainfall intensity was increased from 0.8 mm/min to 2.9 mm/min. Some adaption measures have been considered to upgrade the existing WWTP so to mitigate the energy increase and to limit the global effects of climate change.

Evaluation of greenhouse gas emissions from aerobic and anaerobic wastewater treatment plants in Southeast of Italy.

An evaluation of the operative functioning data of 183 Wastewater Treatment Plants (WWTPs) in Apulia (Southeast of Italy) has been carried out aimed to assess their Green House Gases (GHGs) emissions and the level for which the use of anaerobic sludge treatment should be more convenient in terms of electricity consumption and of GHGs emissions. Out of the 183 studies WWTPs, 140 are practicing aerobic digestion of sludge, while the remaining 43 are practicing anaerobic digestion of sludge. WWTPs in Apulia are serving about 4,81 million PE (Population Equivalent), yielding approximately 600,000-ton equivalent CO2 per annum. The production of GHGs emissions has been estimated by evaluating the contribution of CO2 deriving from: a) electric energy consumption (fossil CO2), b) biogenic CO2, c) N2O and d) CH4 emissions. The present study investigates a number of technical measures for upgrading the existing WWTPs, so to reduce GHGs emissions through the amelioration of CH4 production and capture in the anaerobic step, and through reducing the production of biogenic N2O and CO2 emissions in the aerated basin. The methodology employees artificial intelligence-based control for upgrading the aerobic oxidation of the organic carbon and the nitrification-denitrification steps. As a result, GHGs emissions are expected to be reduced by approximately: 71% for CH4, 57% for N2O, 20% for biogenic CO2 and 15% for fossil derived CO2.

Chromium phytoextraction using Phyllostachys pubescens (Moso Bamboo).

In this study, a bamboo species, the Phyllostachys pubescens - Moso Bamboo (MB) -, was selected for its heavy metals accumulation and translocation potential to restore Chromium (Cr)-contaminated soil. In order to evaluate the MB Chromium growth, tolerance and the potential for phytoremediation using MB to restore Cr-contaminated soil, pot experiments were carried out in simulated Mediterranean conditions in a laboratory, in a controlled environment, at a temperature of 20 °C. The results showed that MB growth rate was 4.28 cm/week on average, with an irrigation flow of 1.644 mm/d. MB tolerance was tested over a 12-week irrigation period with the addition of Cr-contaminated water. Cr removal from soil was 43% starting from a Cr content of approx. 200 mg/kg dry weight (dw) and the quantity of Cr per gram of root and rhizome was equal to 1.31 mg/g dw, while the quantity of Cr per gram of stem and leaves was equal to 0.86 mg/g dw, after 12 weeks. Pot experiments confirm that phytoremediation using plants such as MB provides an alternative approach for handling Cr-contaminated soil.

Moso Bamboo has shown a great adaptability of growing in Mediterranean semi-arid conditionsMoso Bamboo tolerance to contaminated water has been registered up to 125 g/cm³ of chromium. Cr Phytoextraction from soil was found to be significant −43%-and Cr is accumulated mostly in the roots.

Phytoextraction by Moso Bamboo under high level chromium stress in mediterranean conditions.

In this study a bamboo species, Moso Bamboo (MB) - Phyllostachys pubescens - has been selected for its heavy metal accumulation capacity and translocation potential to restore Cr-contaminated soil. Experiments have been conducted so to evaluate the capability of MB to remove Cr from soil, growing under Mediterranean conditions, irrigated with water containing 180 mgCr/L, at flow rate of 600 mm/year. The soil has been contaminated by the irrigation water. When the concentration of Cr in soil reached 300 mgCr/kg, Cr phytoextraction by MB from soil at the same irrigation rate of 600 mm/year with uncontaminated water has been evaluated. Cr removal from soil was approx. 42% after 6 weeks and 60.7% after 12 weeks, starting from a Cr content in soil of approximately 300 mg/kg. MB growing in Cr contaminated soil has shown Cr concentration per gram of dry biomass in aerial parts greater than the underground parts of the plants. After 12 weeks of cultivation, the quantity of Cr in roots and rhizome was measured as 1.79 mg/g, while in stems and leaves as 2.49 mg/g. Results shown a bioconcentration factor of 0.77, 0.65, 0.18, 0.08, after 6 weeks and 0.64, 0.98, 0.53, 0.26 after 12 weeks for roots, rhizomes, stems and leaves, respectively and a translocation factor equal to 0.23 and 0.11 after 6 weeks and 0.83 and 0.40 after 12 weeks, for stems and leaves, respectively.

Compact and portable quartz-enhanced photoacoustic spectroscopy sensor for carbon monoxide environmental monitoring in urban areas.

We report on the realization, calibration, and test outdoor of a 19-inches rack 3-units sized Quartz Enhanced Photoacoustic Spectroscopy (QEPAS) trace gas sensor designed for real-time carbon monoxide monitoring in ambient air. Since CO acts as a slow energy relaxer when excited in the mid-infrared spectral region, its QEPAS signal is affected by the presence of relaxation promoters, such as water vapor, or quenchers like molecular oxygen. We analyzed in detail all the CO relaxation processes with typical collisional partners in an ambient air matrix and used this information to evaluate oxygen and humidity-related effects, allowing the real CO concentration to be retrieved. The sensor was tested outdoor in a trafficked urban area for several hours providing results comparable with the daily averages reported by the local air inspection agency, with spikes in CO concentration correlated to the passages of heavy-duty vehicles.

Phytoextraction of Cr(VI)-Contaminated Soil by Phyllostachys pubescens: A Case Study.

This work presents the results of experimental tests to evaluate the effects of prolonged contamination by Cr on Moso Bamboo (MB) (Phyllostachys pubescens) and the adaptability of the MB to the Mediterranean climate. A preliminary test on the MB was developed in the laboratory, simulating irrigation under Mediterranean conditions (600 mm per year) and tropical conditions (1800 mm per year), to evaluate the rate of growth and the MB's capability for Cr phytoextraction from contaminated soil. The tolerance of MB to Cr was also performed showing a good response of the plant to 100 mg Cr/L solution, utilized for irrigation of the pots. The results show that the rate of MB's removal of Cr from soil ranged from 49.2% to 61.7% as a function of the soil degree of contamination, which varied from approx. 100 mg/kg to 300 mg/kg. The distribution of Cr in the various sections of the bamboo revealed that the greater percentage was present in rhizomes: 42%, equal to 114 mg Cr for 600 mm per year, and 50%, equal to 412 mg Cr for 1800 mm per year. A noteworthy diffusion of the metal towards the outermost parts of the plant was shown. The values of Cr retained in the stems and leaves of MB tissues were quite high and varied from 1100 mg/kg to 1700 mg/kg dry weight.

Fiber-Coupled Quartz-Enhanced Photoacoustic Spectroscopy System for Methane and Ethane Monitoring in the Near-Infrared Spectral Range.

We report on a fiber-coupled, quartz-enhanced photoacoustic spectroscopy (QEPAS) near-IR sensor for sequential detection of methane (CH4 or C1) and ethane (C2H6 or C2) in air. With the aim of developing a lightweight, compact, low-power-consumption sensor suitable for unmanned aerial vehicles (UAVs)-empowered environmental monitoring, an all-fiber configuration was designed and realized. Two laser diodes emitting at 1653.7 nm and 1684 nm for CH4 and C2H6 detection, respectively, were fiber-combined and fiber-coupled to the collimator port of the acoustic detection module. No cross talk between methane and ethane QEPAS signal was observed, and the related peak signals were well resolved. The QEPAS sensor was calibrated using gas samples generated from certified concentrations of 1% CH4 in N2 and 1% C2H6 in N2. At a lock-in integration time of 100 ms, minimum detection limits of 0.76 ppm and 34 ppm for methane and ethane were achieved, respectively. The relaxation rate of CH4 in standard air has been investigated considering the effects of H2O, N2 and O2 molecules. No influence on the CH4 QEPAS signal is expected when the water vapor concentration level present in air varies in the range 0.6-3%.

Sampling, characterisation and processing of solid recovered fuel production from municipal solid waste: An Italian plant case study.

This article presents the classification of solid recovered fuel from the Massafra municipal solid waste treatment plant in Southern Italy in compliancy with the EN 15359 standard. In order to ensure the reproducibility of this study, the characterisation methods of waste input and output flow, the mechanical biological treatment line scheme and its main parameters for each stage of the processing chain are presented in details, together with the research results in terms of mass balance and derived fuel properties. Under this study, only 31% of refused municipal solid waste input stream from mechanical biological line was recovered as solid recovered fuel with a net heating value (NC=HV) average of 15.77 MJ kg-1; chlorine content average of 0.06% on a dry basis; median of mercury <0.0064 mg MJ-1 and 80th percentile <0.0068 mg MJ-1. The solid recovered fuel produced meets the European Union standard requirements and can be classified with the class code: Net heating value (3); chlorine (1); mercury (1).