Impulse response tests in completely mixed tanks and reactors. Key assumptions and steps in mathematical developments.

Stimulus-response technique is a method to obtain the Residence Time Distribution (RTD) for the elements of a fluid passing through a vessel. Generally speaking, in reactor science unsteady-state tests may often appear preferable to steady-state since they are made up of a chain of intermediate ones; but without any theoretical necessity holding. In RTD studies, however, non-steady state tests are the only conceivable ones if conservative tracers are employed, because once a transition is over there is no way to reconstruct it and assess the hydraulic behaviour of the tank. Only a series of tests with non-conservative tracers of known disappearance rate would achieve the task, but at the pr…

Rifiuti sanitari: i “coefficienti di produzione unitaria” in due casi di studio

Entalpia dei fumi prodotti dalla combustione dei rifiuti solidi

Assessment of the embodied energy for manufacturing and laying a submarine outfall pipeline

The Life Cycle Assessment (LCA) methodology was applied to a submarine outfall pipeline intended for the disposal of treated MWW in the South Tyrrhenian Sea, on Western Coast of Sicily. The pipe serves 115 thousands inhabitants; it is 3,1 km long with an outer diameter of 800 mm and is allocated in a submarine trench down to 18 m bsl. The pipe ends with a multiport diffuser with outer diameter 500 mm. The whole pipeline is made in HDPE and is statically stabilized by cast iron rings and concrete anchor blocks. From the detailed constructive project of the pipeline the most relevant items involved were drawn and the most important ones were selected, both as materials employed and as laying …

Disoleatori statici per il trattamento delle acque di piccole e medie utenze

Per rimuovere gli olii dalle acque reflue di piccole e medie utenze si utilizzano molto i disoleatori prefabbricati. Le verifiche di tre disoleatori commerciali di tipo statico hanno suggerito il limite inferiore per il tempo di detenzione idraulica, e quello superiore per il carico superficiale. Le vasche bi-stadio non hanno dimostrato vantaggi sulle mono-stadio.

PRODUZIONE DI RIFIUTI A RISCHIO INFETTIVO E INDICI DI COMPLESSITÀ IN UN “CENTRO TRAPIANTI”

Questo studio analizza la produzione di rifiuti a rischio infettivo in una grande struttura ospedaliera specializzata per le attività di trapianto: Ismett (Istituto Mediterraneo per i Trapianti e Terapie ad Alta Specializzazione), che si trova a Palermo. Sono state determinate le relazioni fra la quantità e la composizione dei rifiuti, da una parte; la complessità della struttura e la natura delle cure erogate, dall’altra. In letteratura si trovano regolarmente i risultati di ricerche sulla produzione di rifiuti a rischio infettivo nei più diversi Paesi del mondo; i dati pubblicati provengono quasi esclusivamente da Ospedali Generali, anche complessi e di Alta Specializzazione. Tali dati po…

BIOLOGICAL STABILITY ANALYSIS OF THE OFMSW MATRIX TREATED IN A COMPOSTING PLANT

Composting, mechanical-biological treatment (MBT), biodrying and biostabilization processes of pre-selected organic fraction from municipal solid wastes (OFMSW) have recently become important in municipal solid waste management. Through these treatment processes the potential impacts of the produced wastes and the volume to treat in the landfill are strongly reduced. However, the residual organic matter contained in the treated fraction may provide negative effects when e.g. the treated OFMSW is used as compost. The biological stability degree of the treated matrix provides usefull informations for the final use of it. Indeed, knowing the degree of biological stability of the compost makes …

A LAB-SCALE MICROWAVE SYSTEM FOR EXPERIMENTS OF HIGH TEMPERATURE WASTE PYROLYSIS

The reactor designed and assembled at Università degli Studi di Palermo - presented here - was conceived to explore high unit power input, high temperature reductive processes. Its main field of use therefore is likely to be the destruction of liquid waste fed as an aerosol; or of VOCs; or of granular waste making a fluidized bed. If required, a 3 - phase system including a solid catalyst could also be set up. These waste should be free of low - melting or boiling metals. Incidentally, a literature review shows that the compounds taken as benchmark in thermal VOC destruction are trichloroethylene, benzene and toluene. At lower unit power rates this MW - based system lends itself also to rec…

Healthcare Waste Treatment by Microwave: Critical Parameters and Future Perspectives

Drawing the Materials Balance for an MBT cycle from Routine Process Measures in a Plant located in Venice

An observation term was carried on in an MBT plant owned and run by a public Company to treat MSW left by separate collection. All observations and measurements were made without interfering with the ordinary operation rules, in order to assess the efficiency of one process cycle for a given batch of waste. Analytical data came from both a) process instruments and b) physical analysis of a batch of waste entering / exiting from a selected bio-cell. From the process mass losses (about 37% – including moisture evaporation – in that single process cycle) the theoretical amounts of water and carbon dioxide produced by biodegradation were calculated. A verification of the results was tried throu…

Incenerimento di rifiuti ospedalieri con processo pirolitico statico: un caso di studio

ABSTRACT: The Health Care Agency 6 (ASL 6) of Regione Sicilia, Italy, owns and operates a “pyrolytic static oven” for the infectious waste produced by all health care services of the District. Operation records kept by ASL were used by the authors to establish the mass and energy balances. Among the results it was found that the plant requires primary energy as oil or gas at the rate of up to two-thirds of the energy yielded by the input waste. The energy obtained (about 1,2 thermal MW) is recovered uniquely as heat: a plain technical choice that actually exposes the operator to seasonal drops in customers’ demand. It appears worth recommending to upgrade the plant, at least fitting it with…

STERILIZZAZIONE CON MICROONDE DI RIFIUTI SANITARI: DETERMINAZIONE DIRETTA DELL’EFFICACIA DEL PROCESSO

In the sterilization of those Health Care Waste that are marked as possibly infectious, microwaves (MW) have long been proposed as an alternative means to steam. The effectiveness of the operation is assessed determining the fraction that has survived to the sterilizing agent of a known starting population of micro-organisms. Customarily, this population is introduced into the waste mass in the form of one or more sealed vials. These make up an artificial environment which is completely under control; but onto it the sterilizing agent could a priori behave with higher or lower effectiveness, compared with the loose mass which is directly exposed to it. As far as the traditional steam steril…

Health Care Waste production: measures and estimates in “V. Cervello” Hospital, Palermo, Italy.

A monitoring work was carried out in May/June 2007 in one large hospital located in Palermo. The monitoring consisted in weighing the infectious waste containers filled in some Departments purposely chosen. As a second stage of the work a comparison was attempted between the results obtained from the waste production monitoring and the Hospital’s purchases recorded in the same time. A restricted list of purchased products out of the general one was extracted. Such list allows one to calculate approximately the mass of medical devices purchased and their composition. To these materials a reasonable change in humidity after use was attributed. It was possible in this deductive way to draw a p…

PLASTICS RECOVERY FROM MUNICIPAL WASTE: MAINSTREAMS AND BY-PRODUCTS IN A CASE STUDY IN NORTHERN ITALY.

In the case study dealt with here, the factory treatments of dry Municipal Solid Waste are aimed primarily at materials recovery; restraining energy recovery to the hardly recyclable by-products. The main input consists of the so-called multipak from MSW source-sorted collection; plus packaging waste, paper and cardboard and other similar waste from curb-side collection. The principal fractions produced by the selection plant, own and operated by the Public Company in charge of MSW management, in the Year 2012 were 27 064 tonnes of plastics, 5 066 of paper, 3 014 of tin coated steel and 4 886 tonnes of extraneous fraction to dispose of. A minor – though valuable – product was aluminium. The…

WASTE PLASTICS MANAGEMENT IN MUNICIPALITIES: LOGISTICS AND PROCESSES IN LOMBARDIA (NORTHERN ITALY)

A partnership of 49 Municipalities lying in Lombardia (Northern Italy) and belonging to the District “Monza and Brianza” has entrusted the management of the Municipal Solid Waste (MSW) to two Public Companies: “C.E.M. Ambiente S.p.A.” - which owns and operates a transfer station and a multi-material centre - and “SERUSO S.p.A.”, whose single facility is set up and equipped for a high performance factory sorting of the dry fraction of the urban waste. The catchment area is populated by 448 000, living in an area of 366 km2. The management system starts with household sorting for multi-bin curbside collection; followed by hauling to selection and physical treatment facilities; and last, trans…

Posa e recupero di cavi sottomarini per telecomunicazioni: energia e materiali in gioco.

Undersea cables for telecommunications are put out after 20 to 25 years of service in order to be replaced by new type ones that can yield a better service. As a rule, decommissioned cables are retrieved for the part stretching from the shoreline to the line (-30 m). This operation is useful from the environmental standpoint, as at the price of an energy expenditure of about 3 MJ/m an amount of materials having embodied energy as high as 72 times of it are recovered. Still, the larger part of an undersea cable lies offshore and is usually left on the site, so the actual energy recovery is small – just about few units per cent – compared with the energy (embodied + used for laying) required …

Experimental Sorting of Municipal-Like Waste in the Hospital “Civico”, Palermo (IT)

An experiment of source sorting - based management of Health Care Waste (HCW) was carried out in 2011 in 4 Departments of the Public Hospital “Civico” (Palermo, IT), where the basic mandatory separation between hazardous and non-hazardous waste was already going on since year 2000.The experiment consisted in weighing every day for 15 days 4 predefined fractions collected in the Infirmaries (namely paper, plastics, glass and unsorted fraction), and the bags with unsorted waste from the patient’s stay room. Furthermore, in 1 of the 4 Departments also the boxes of Infectious Waste (IW) were weighed for a week.As a result a weighted average value of 0.56 kg of Municipal-like Waste (MLW) per bed…

Materie plastiche nei rifiuti. I fabbisogni di energia e di acqua per il recupero: un caso di studio

Physical features of Health Care Waste

A monitoring work was recently carried out in two major Health Care Facilities (HCFs) in Italy, both located in Palermo, to obtain information on waste generation rates. Monitoring consisted in weighing infectious waste containers for 15 days in 4 Departments for each health care facility. From values obtained monthly production, specific weights and Production Indexes were calculated. The main producers of waste appeared Oncological DH and Resuscitation for both HCFs, with more than 4 and 3 kg measured per occupied place and day, respectively. About specific weight, apparent bulk values always below 200 kg/m3 were calculated. From the short observation performed it seems that notable impro…

UNIVERSITA’ DEGLI STUDI DI PALERMO - LABORATORY OF SANITARY ENGINEERING

Health Care Waste production: measures and estimates in Joint Hospitals “Civico e Benfratelli, Ascoli e Di Cristina”, Palermo, Italy.

A monitoring work was carried out in October 2006 in one large health care facility located in Palermo. The monitoring consisted in weighing infectious waste containers filled in some Departments purposely chosen. As a second stage of the work a comparison was attempted between the results obtained from the waste production monitoring and the archive data recorded in the same time. A restricted list of purchased products out of the general one was extracted. Such list allows one to calculate approximately the mass of medical devices purchased and their composition. To these materials a reasonable change in humidity after use was attributed. It was possible in this deductive way to draw a pr…