Discharge quality from municipal wastewater treatment plants and the Sludge Biotic Index for activated sludge: integrative assessment

Abstract Wastewater treatment plants (WWTPs) are scrutinized by Environmental Authorities particularly regarding the compliance to discharge limit values fixed by national and local regulations. An integrated approach is necessary to achieve the objectives established with Directive 2000/60/EC (WFD) considering the ecological status of the receiving water body and the quality of the discharge. Specifically, documentary, technical, management and analytical controls should be developed. Moreover, integrative information on the behaviour of the activated sludge in the aeration tank can be useful for plant managers as well as for the regulating Authorities. The study presents the experience concerning WWTP regulation considering the analytic assessment of the discharge as well the monitoring of the Sludge Biotic Index (SBI) for activated sludge. Data from monitoring during the period 2008–14 on SBI values and chemical and microbiological data on the discharges of a sample of 35 WWTPs in the province of Venice (north-east Italy, Veneto region) are presented and discussed. Together with chemical and microbiological analysis, the SBI appears to be a highly useful index for the integrative assessment of plant functionality, in particular when monitoring and identifying critical situations that can determine the exceedance of discharge limit values. The SBI method, in an integrated control approach, can be used for small and medium sized WWTPs that only treat domestic wastewaters. In a case by case assessment this may even substitute part of the analytical monitoring carried out in the WWTPs' control process

Troposphere-to-mesosphere microphysics of carbon dioxide ice clouds in a Mars Global Climate Model

We have implemented full CO ice cloud microphysics into the LMD Mars Global Climate Model (MGCM) and we have conducted the first global simulations. The microphysical model implementation follows the modal scheme used for water ice cloud microphysics in the MGCM, but includes specific aspects that need to be accounted for when dealing with CO ice clouds. These include nucleation of CO on water ice crystals and CO condensation theory adapted for the Martian conditions. The model results are compared to available observations globally, and separately for polar regions and equatorial mesosphere. The observed seasonal and latitudinal variability of the CO ice clouds is in general reproduced. The polar regions are covered by CO ice clouds during the winter as observed. Instead of forming only in the lowest 10–15 km of the atmosphere, they extend up to several tens of kilometers above the surface in the model, dictated by the modeled temperature structure. We have also quantified the contribution of the cloud microphysics to the surface CO ice deposits. Snowfall from these clouds contributes up to 10% of the atmosphere–surface ice flux in the polar regions in our simulations, in the range that has been indirectly deduced from observations. In the mesosphere, notable amounts of CO ice clouds form only when water ice crystals are used as condensation nuclei in addition to dust particles, and their spatial distribution is in agreement with observations. The mesospheric temperature structure, dominated by tides, dictates the longitudinal and seasonal distribution of these clouds. The seasonal and local time variations of the clouds are not fully reproduced by the model. There is a long pause in CO ice cloud formation in the model around the aphelion season, but clouds have been observed during this period, although with a lower apparition frequency. Modeled mesospheric clouds form mainly during the night and in the morning, whereas during the daytime, when most of the cloud observations have been made, the model rarely predicts clouds. These discrepancies could be explained by the strong dependence of the cloud formation process on mesospheric temperatures that are themselves challenging to reproduce and sensitive to the MGCM processes and parameters. The rare possibilities for nighttime observations might also bias the observational climatologies towards daytime detections. Future developments of the model consist in the inclusion of a possible exogenous condensation nucleus source in the mesosphere and the radiative effect of CO ice clouds. © 2022 Elsevier Inc. All rights reserved.This paper presents the results of ten years of development that has been supported by funding from several sources. We thank the Agence National de la Recherche for funding (project MECCOM, ANR-18-CE31-0013). We are also grateful for the financial support by the LabEx (Laboratoire d’Excellence) ESEP, by the French space agency CNES and the European Space Agency ESA. We acknowledge the support of the French national planetology programme (PNP) as well. F.G.-G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00, and acknowledges financial support from the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This work was performed using HPC computing resources from GENCI-CINES (Grant 2021-A0100110391), and resources at the ESPRI mesocentre of the IPSL institute .Peer reviewe

In-flight measurement of the absolute energy scale of the Fermi Large Area Telescope

The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron-plus-positron (CRE) spectrum in low earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between ~6 and ~13 GeV with an estimated uncertainty of ~2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.Comment: 11 pages, 7 figures, submitted to Astroparticle Physic

The Second Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars

This catalog summarizes 117 high-confidence 0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars.We compare the gammaray properties with those in the radio, optical, and X-ray bands.We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermiﾒs selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions

Il processo depurativo a letto mobile

I reattori a letto mobile sono una tecnologia depurativa a biomassa adesa sviluppata a partire dagli anni ’90; in questi reattori il biofilm aderisce a supporti in materiale plastico mantenuti in costante movimento all’interno di vasche costruttivamente analoghe a quelle a fanghi attivi. Il principale vantaggio di questa tecnologia è l’elevata attività specifica della biomassa adesa, che permette di realizzare reattori di minore volume rispetto ai fanghi attivi con biomasse specializzate in ciascuno di essi. Inoltre questi reattori non richiedono controlavaggi a differenza dei processi a biomassa adesa fissa. Sono trattati in dettaglio i processi a letto mobile; il primo capitolo è dedicato alle necessarie premesse teoriche sui processi a biofilm, con l’illustrazione delle cinetiche e dei loro fattori controllanti, e cenni alla modellistica. Il secondo capitolo, dopo un’illustrazione sui principali parametri di funzionamento di un reattore a letto mobile, prende in esame i principali tipi di corpi di riempimento sviluppati finora, con esempi di applicazioni e risultati ottenuti in impianti su scala reale. Tra i vari tipi di reattori a letto mobile la maggiore attenzione sarà dedicata ai sistemi con il maggior numero di applicazioni nel mondo (oltre 400 impianti). Il terzo capitolo illustra i risultati di una serie di sperimentazioni su scala di laboratorio e su scala pilota svolte in Italia presso importanti centri di ricerca (Università di Padova, Politecnico di Milano, Università di Trento) e presso aziende. Queste sperimentazioni sono state e sono attualmente il punto di partenza per lo sviluppo e l’applicazione su scala reale dei reattori a letto mobile. Le applicazioni ad impianti su scala reale sono oggetto della trattazione dei capitoli 4 e 5. In particolare nel capitolo 4 vengono riportati i risultati delle principali applicazioni italiane del processo per la depurazione dei reflui civili e industriali: vi sono esempi di filiere a letto mobile realizzate ex-novo, di potenziamento di impianti a fanghi attivi esistenti e di reattori di sgrossatura di acque di scarico concentrate. Nel capitolo 5 sono riportati significativi esempi di impianti MBBR realizzati in Europa e negli Stati Uniti. Il capitolo 6 è dedicato all’analisi biologica e microbiologica del biofilm; anche nei processi a biomassa adesa un’indagine di questo tipo è importante per stabilire lo stato della flora batterica e diagnosticare eventuali disfunzioni. Infine, il capitolo 7 esamina gli aspetti più significativi legati all’avviamento e alla gestione degli impianti che adottano questo processo