Tesis sobre el tema "Refuse and refuse disposal Recycled products"

The Second-Hand Society tells the stories of people in Portland, Oregon who redefine waste by making use of objects others discard. The author spends time in repair shops watching craftsmen hammer and polish broken typewriters, vacuum cleaners and shoes back to life. She follows book scouts, clothes pickers and liquidators as they gather merchandise to resell and spends hours at nonprofits that collect and redistribute unwanted electronics and building supplies. She watches junk artists and fashion designers assemble found objects into display pieces, accompanies Dumpster divers and "freegans" along their regular collection routes and visits the homeless encampment by the airport to see how an entire community of people survives on nothing but reclaimed materials. The members of the second-hand society challenge the traditional conception of things as "broken" or "unwanted" and assert that forward movement and new-new-new is not always optimal. By examining the motivations and practices of the people who make use of our discards and looking at the contradictions they run up against, this thesis develops a more complete understanding of the reality that's possible if we think differently about our waste.

Thesis (Doctor of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2017.
The search for alternatives to fossil fuel is necessary with a view to reducing the negative environmental impact of fossil fuel and most importantly, to exploit an affordable and secured fuel source. This study investigated the viability of municipal solid waste gasification for a fuel cell system. Potential solid fuels obtained from the study in the form of refuse-derived fuel (RDF) had high heating value (HHV) between 18.17 MJ/Kg - 28.91 MJ/Kg with energy density increased from 4142.07 MJ/m3 to 10735.80 MJ/m3. The molecular formulas of RDF derived from Ladies Smith drop-off site, Woodstock drop-off site and an average molecular formula of all thirteen municipal solid waste (MSW) disposal facilities were CH1.43O1.02, CH1.49O1.19, and CH1.50O0.86 respectively. The comparative ratios of C/H were in the range of 7.11 to 8.90. The Thermo Gravimetric Analysis showed that the dehydration, thermal decompositions, char combustions were involved in the production of gaseous products but flaming pyrolysis stage was when most tar was converted to syngas mixture. The simulation of RDF gasification allowed a prediction of the RDF gasification behaviour under various operating parameters in an air-blown downdraft gasifier. Optimum SFR (steam flowrate) values for RDF1, RDF2 and RDF3 were determined to be within these values 2.80, 2.50 and 3.50 and Optimum ER values for RDF1, RDF2 and RDF3 were also determined to be within these values 0.15, 0.04 and 0.08. These conditions produced the desired high molar ratio of H2/CO yield in the syngas mixture in the product stream. The molar ratios of H2/CO yield in the syngas mixture in the product stream for all the RDFs were between 18.81 and 20.16. The values of H2/CO satisfy the requirement for fuel cell application. The highest concentration of heavy metal was observed for Al, Fe, Zn and Cr, namely 16627.77 mg/Kg at Coastal Park (CP), 17232.37 mg/Kg at Killarney (KL), 235.01 mg/Kg at Tygerdal (TG), and 564.87 mg/Kg at Kraaifontein (KF) respectively. The results of quantitative economic evaluation measurements were a net return (NR) of $0.20 million, a rate of return on investment (ROI) of 27.88 %, payback time (PBP) of 2.30 years, a net present value (NPV) of $1.11 million and a discounted cash flow rate of return (DCFROR) of 24.80 % and 28.20 % respectively. The results of the economic evaluations revealed that some findings of the economic benefits of this system would be viable if costs of handling MSW were further quantified into the costs analysis. The viability of the costs could depend on government responsibility to accept costs of handling MSW.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016.
The generation of municipal solid waste has increased significantly due to the exponential population growth and it has become a global issue. Gasification technology, an alternative method for waste treatment is a thermochemical process where carbon-based material are exposed to an environment deprived in oxygen, was used for this project. The aim of this thesis is to study the gasification of plastic waste which is a potential alternative energy source using infrared heaters. To achieve this goal, fundamental studies have been numerically and experimentally conducted for an infrared gasifier and subsequently establishing the temperature profile for gasification using a small scale reactor. A detailed study on low density polyethylene was conducted using Infrared Spectrometry and thermal decomposition techniques such as Thermogravimetry and Differential Scanning Calorimetry were performed to establish the temperature at which plastic pellets sample used for this research gasify. The gasification behaviour of pelletized low density polyethylene (plastic pellets) was tested and three case studies were done to evaluate the most suitable temperature profile for the reactor to gasify the low density polyethylene at high temperature for less amount of time. Subsequently, the reactor model was simulated and results validate the use of reactor at an optimum temperature of 800 °C for a gasification process with less residue content. The reactor designed for this research is fully functional and validates the temperature behaviour predicted during simulation. The experimental results show infrared heaters are suitable for gas production using this gasification process.

Thesis (MScEng)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Can salts present in an aqueous industrial effluent be retained by the [me ash that is produced as a by-product of gasification or by power stations utilising coal as the raw material? In order to answer this question, the actual chemistry that occurs during the mixing and settling process, needs to be understood. At the Sasol Secunda petrochemical plants in South Africa, ash is produced as a byproduct from the gasification of coal, and by the coal-fired power stations (steam plants). The [me portion of the ash (± 50J.lm in diameter) is disposed of through the use of a closed loop wet ash disposal system. The ash is transported as a slurry to the disposal sites (ash darns). The industrial effluent used to transport the ash consists mainly of the recycled ash effluent, known as clear ash effluent (CAE), as well as a variety of process waste streams containing high concentrations of salts. This mixture of ash and water is pumped to ash dams, where the ash is allowed to settle and is therefore separated from the effluent. From the ash darns the effluent flows into evaporation dams, and finally into CAE dams before being returned to the ash plant in Sasol 2 and 3 to be mixed once again with the ash. During this contact time of the ash with the water certain chemical reactions may occur. If one understands what chemical reactions occur during this process, and under what conditions they occur, then it will be possible to utilise the ash disposal system to its full potential, possibly enhancing the salt retention ability. An investigation was thus conducted into what processes actually occurs during the entire ash water contact period. The overall aim of the project was to obtain an understanding of the functioning of the [me ash disposal system so that its efficiency can be improved upon, and furthermore, so that the ash darns can be utilised more effectively in retaining salts. This investigation focussed on the chemical reactions that occur when an industrial effluent is mixed with fine ash, and consisted of four main aspects: • A literature survey on related issues. • An analysis and evaluation of the changes that occur in the actual disposal system. • Laboratory column experiments to investigate, in more detail, the different chemical reactions, which occur during the different stages of the disposal process. • The drilling of boreholes into the ash dams to obtain core material at a variety of depths and locations for analysis purposes. From this investigation it was concluded that salts are retained in the ash dams; based on the results obtained from the laboratory column experiments and the production rate of the fine ash from Sasol 2 and Sasol 3, the potential amount of salts that can be removed from the system (either due to precipitation or water retention in the ash dams) is approximately 95 tons/day. The salts that were found to be most pertinent to the wet ash disposal system utilised at Sasol, Secunda, are Ca, S04, Na, and Cl. Of these, Ca, S04 and Na were identified in literature to be the components most commonly associated with fly ash leachate. The Ca chemistry, which occurs in the ash disposal system, was explored extensively. Is was found that Ca, which is initially present in the fresh fine ash as lime, is leached from the ash into the effluent, where it reacts with carbon dioxide in the atmosphere, and is therefore removed from the system due to the precipitation of calcite. Sodium, S04, and Cl were all found to be retained in the ash; the S04 appears to be retained in a stable form within the ash, not merely due to hydraulic retention, which suggests that the ash system has the potential to act as a salt sink for S04 ions. The mechanism of salt retention in the ash darns was found to be predominantly by means of hydraulic retention, and therefore the salts have the potential to be flushed out of the ash dams into the underlying soil material. However, results from the core drilling exercise revealed that there doesn't appear to be a significant seepage of elements from the ash fill material into the underlying vertisol material. Some components (AI, Fe, Na, K, Mg, Cr, P, Ti and V) from the older, and inactive ash dam, do appear to have percolated into the underlying material. However, a significant amount of water, and therefore salts, are still retained in the ash dam. In terms of the mineralogical composition of the ash dams, a significant difference was observed between the mineral phases present in the ash fill material of an active and an inactive ash dam. Ettringite was detected throughout the borehole drilled into the inactive ash darn, and was not evident at all in the core material from the two boreholes drilled into the active dam, which suggests that this mineral is formed in the ash darns over a long time period. The minerals quartz and mullite were found in the fresh [me ash as well as in most of the core material obtained from the drilling exercise. The mineralogical composition of the ash fill samples, from the boreholes drilled into the centre of the active and inactive ash darns, was found to be very consistent with depth. This finding, combined with the fact that the chemical composition of the core samples varied more significantly in the borehole located near the edge of the active fine ash darn, indicated that the lateral position of the ash in the ash dam influences the chemical reactions that occur. Overall, from this investigation it was concluded that although the chemistry, involved in the mixing of an industrial effluent with fine ash, is extremely complex and site-specific, it is possible to determine the most significant changes which occur within a wet ash disposal system. Besides providing one with a better understanding of the working of the Secunda ash disposal system, the results of this investigation have also provided the framework for future research on this topic and related issues, i.e. the construction of a pilot scale ash darn set-up; further column experiments to investigate the extent to which S04 ions can be removed from the system; the influence of the addition of CO2 to the system; and more extensive core drilling in the vicinity of the ash darns.
AFRIKAANSE OPSOMMING: Kan soute teenwoordig in 'n industriële uitvloeisel teruggehou word in fynas geproduseer as neweproduk van steenkoolkragsentrales? Om 'n antwoord op hierdie vraag te kry, moet die chemiese reaksies wat gebeur tydens die meng en wegdoening van die as en aswater verstaan word. By die Sasol petrochemiese aanlegte in Secunda, Suid Afrika, word fynas geproduseer as 'n neweproduk in die vergassing en die stoomopwekkingprosesse. Die fynas (50)lm diameter) word weggedoen deur 'n geslote nat asstelsel. Die industriële uitvloeisel wat gebruik word vir die vervoer van die as bestaan hoofsaaklik uit hergebruikte aswater (genoem CAE - clear ash effluent), asook 'n verskeidenheid ander prosesafvalstrome wat hoë konsentrasies soute bevat. Die mengsel van as en aswater word in 'n asflodder gepomp na die asdamme, waar die as besink en sodoende geskei word van die waterfase (aswater). Vanaf die asdamme vloei die aswater na verdampingsdamme, en daarna na die CAE damme, vanwaar die CAE weer na die Sasol aanleg teruggepomp word om weer met as gemeng te word. Gedurende die kontak tussen die CAE en as gebeur sekere chemiese reaksies. Indien hierdie reaksies verstaan word, en onder watter toestande dit plaasvind, kan die asdamstelsel tot volle kapasiteit benut word deur moontlik die soutretensie binne die asdam te verhoog. 'n Ondersoek is gedoen om te bepaal watter prosesse plaasvind gedurende kontak tussen die as en water. Die doel van die ondersoek was om 'n beter begrip te kry oor die funksionering van die fynas-wegdoeningstelsel en om te bepaal of die asdamme meer effektiefbedryfkan word om moontlik meer soute te akkommodeer. Die ondersoek het uit vier hoofaspekte bestaan: • Literatuuroorsig, • 'n Analise en evaluering van die veranderinge wat plaasvind oor die asdamstelsel, • Laboratoriumskaal kolomeksperimente om in meer besonderhede die chemiese reaksies wat 'n rol in die aswaterstelsel speel, te bepaal, en • Die boor van toetsgate op die bestaande asdamme om boorkerne te ontleed by bepaalde dieptes en liggings. Uit die ondersoek is bevind dat soute wel in die asdamme behou word. As die kolomtoetse as basis gebruik word, en die produksietempo van fynas vanaf Sasol 2 en 3, dan kan daar 'n potensiële 95 ton soute per dag deur die asstelsel verwyder word (deur hoofsaaklik waterretensie en presipitasie van soute). Die mees prominente soute wat in die Sasol asstelsel voorkom is Ca, S04, Na, en Cl. Vanhierdie soute, is Ca, S04, en Na deur die literatuur geïdentifiseer as komponente wat met vliegas loog geassosieer word. Die Ca chemie, wat in die asstelsel plaasvind, is in besonderhede ontleed. Dit is bevind dat Ca, teenwoordig in die vars fynas as kalk, vanuit die as in die aswater geloog word, waar dit dan met atmosferiese CO2 reageer en dan vanuit die stelselverwyder word deur die presipitasie van kalsiet. Natrium, S04 en Cl word in die as teruggehou. Dit wil voorkom asof die S04 in 'n stabiele vorm in die as teruugehou word, nie net deur die hidrouliese retensie nie en dat die asstelsel dalk as 'n potensiële sink vir S04 kan optree. Die meganisme van soutretensie in die asdamme is hoofsaaklik deur hidrouliese retensie, met die gevolg dat die soute potensieel in die onderliggende grond uitgewas kan word. Die resultate van die boorkernondersoek wys egter dat daar nie beduidende uitwassing van hierdie soute in die grond is nie. Dit wil voorkom of sekere komponente (Al, Fe, Na, K, Mg, Cr, P, Ti en V) van die ou en onaktiewe asdam in die grond geloog is. 'n Beduidende verskil was gevind tussen die minerale fases in die asmateriaal van die aktiewe en onaktiewe asdamme. Ettringiet was teenwoordig deur die hele diepte van die boorkern van die onaktiewe dam, maar was nie teenwoordig in beide boorkerns van die gate op die aktiewe asdam nie. Dit impliseer dat hierdie mineraaloor 'n langer tyd gevorm word. Kwarts en mulliet was deurentyd in al die boorkerne teenwoordig. Die mineralogie van die boorkern van die middel van die aktiewe asdam was baie konstant met diepte (in teenstelling met dié van die boorkern op die kant van die asdam) wat daarop dui dat die laterale posisie van die as in die asdam die chemiese reaksies wat mag plaasvind kan beïnvloed. Die ondersoek bevestig dat alhoewel die chemiese reaksies betrokke in die aswaterstelsel baie kompleks en liggingspesifiek is, die mees beduidende veranderinge wat in die asstelsel plaasvind, wel bepaal kan word. Die ondersoek het benewens 'n beter begrip van hoe die asdamme reageer, ook 'n raamwerk gegee vir verdere navorsing in hierdie veld, bv. die bou van 'n loodsskaal-asdam, verdere kolomtoetse om die vermoë van die asstelsel om S04 ione te verwyder te bepaal en die invloed van gemanipuleerde kalsiet presipitasie deur die byvoeging van CO2.

Municipal solid waste incineration (MSWI) is the most widely used solution in those countries where landfilling areas are limited. Incineration allows reducing the total volume of waste (up to 90%) and generating energy resulting from combustion. The main by-product generated in waste-to-energy plants is known as incineration bottom ash (IBA), which is a heterogeneous mixture of ferrous and non-ferrous metals, ceramics, and glass. IBA is classified as a non- hazardous material due to its composition rich in calcium oxide, silica, and iron. IBA composition and morphology are very similar to natural siliceous aggregates after an ageing treatment where the weathered bottom ash (WBA) is obtained. This maturation process makes feasible the WBA valorisation as a secondary aggregate in the field of construction and civil engineering. Moreover, the high percentage of glass and aluminium found in the WBA would allow its valorisation as a precursor in the alkali-activated binders (AABs) formulation. The main goal of this PhD thesis was the scientific and technological development of new AABs based on the alkali activation of WBA (AA-WBA binders), to reduce the use of ordinary Portland cement (OPC) in building and civil engineering fields. In this sense, this aim is related to the use of more sustainable cement-based materials, which promote the circular economy and zero-waste principle through the valorisation of WBA. The potential of WBA as a precursor in the AA-WBA binders’ formulation was evaluated along with the PhD thesis through different studies that can be classified into four blocks. The first block was based on the evaluation of the WBA potential as a precursor in AABs based on its particle size. This study demonstrated the variability in the reactive SiO2 and Al2O3 availability as a function of the particle size. The potential of the entire fraction (EF) and the 8-30-mm fraction highlighted the possible use of them as precursors in the AABs formulation. The second block of this thesis was focused on the study of AA-WBA binders using the WBA as a sole precursor. Mixtures of sodium silicate (WG) and NaOH (2M, 4M, 6M, and 8M) were used as alkaline activator solutions to assess the effect of the NaOH concentration on the final properties. It was demonstrated the possibility of developing AA-WBA. The influence of alkaline activator solution concentration on the final properties of the AA-WBA was evidenced, obtaining better mechanical performance with the use of the WG/NaOH 6M solution. The results revealed the enhancement in the mechanical properties when the 8-30-mm fraction was used. However, the environmental results revealed arsenic and antimony leaching values that require further research to validate the environmental feasibility of AA-WBA. In the third block, the 8-30-mm fraction was mixed with other precursors with greater availability of Al2O3 (metakaolin and PAVAL®). The main purpose was to improve the mechanical properties and the heavy metal stabilisation effect of the AA- WBA obtained in the second block. In both cases, mechanical performance was improved due to the inclusion of Al2O3. However, the environmental properties continued to show leaching values that did not ensure the environmental viability of the AA-WBA binders. Finally, the fourth block of the thesis was focused on carrying out an environmental and ecotoxicological assessment to validate the use of AA-WBA binders as construction material. The results showed a medium-low level of ecotoxicity in the AA-WBA formulated with the 8-30-mm fraction, similar to the binders activated with MK (AA-MK).
El principal subproducte generat durant la incineració de residus sòlids urbans es coneix com a cendra de fons. La seva composició és molt similars als agregats silícics naturals després d’un tractament d’envelliment on s’obté la cendra de fons madurada (weathered bottom ash; WBA segons les sigles angleses). El seu alt contingut en vidre i alumini el converteixen en un potencial candidat com a precursor en la fabricació d’aglutinants activats alcalinament (alkali-activated binders, AABs segons les sigles angleses). L’objectiu principal d’aquesta tesi doctoral va consistir en el desenvolupament de AABs mitjançant l’activació alcalina de WBA (aglutinants AA-WBA). El potencial de la WBA i els aglutinants AA-WBA es va avaluar mitjançant diferents estudis que es poden classificar en quatre blocs. Al primer bloc es va avaluar el potencial de WBA com a precursor en funció de la seva mida de partícula. Aquest estudi va demostrar el potencial de la fracció sencera i de la fracció 8-30 mm. El segon bloc es va centrar en l’estudi d’aglutinants AA-WBA que utilitzaven el WBA com a únic precursor. Es va evidenciar la influència de la concentració de la solució activadora alcalina en les propietats finals dels aglutinants AA-WBA. Els resultats van revelar la millora de les propietats mecàniques quan es va utilitzar la fracció 8-30 mm. No obstant, els resultats ambientals van revelar valors de lixiviació d'arsènic i antimoni que requerien la validació a nivell ambiental dels aglutinants. Al tercer bloc, la fracció 8-30 mm es va barrejar amb altres precursors rics en d’Al2O3 (metakaolin i PAVAL®) per millorar les propietats mecàniques i l’estabilització de metalls pesants dels aglutinants obtinguts al segon bloc. En ambdós casos, es va millorar el rendiment mecànic, tot i que les propietats ambientals van continuar mostrant valors de lixiviació que no asseguraven la viabilitat ambiental dels aglutinants AA-WBA. Finalment, al quart bloc es va realitzar una avaluació ambiental i ecotoxicològica per validar l’ús d’aglutinants AA-WBA com a material de construcció. Els resultats van mostrar un nivell mitjà-baix d’ecotoxicitat a l’AA-WBA formulat amb la fracció de 8 a 30 mm, similar als aglutinants activats amb MK (AA-MK).

This study was conducted in South Africa. South Africa is the first country within the Southern African Development Community to have regulated plastic shopping bags waste through the imposition of both a standard on thickness and a levy. Given this scenario, the Plastic Bags Regulations present an illustrative case for researching complexity, uncertainty and controversies surrounding a new trend in environmental policy making, namely waste product regulation. The thesis focuses on understanding and investigating tensions, debates and responses emerging from the policy process as actors and actor-networks put not only the Plastic Bags Regulations asfocal actant (token) but also other actants and actant-networks as well. To this end, a research question that addressed environmental policies, tensions, debates and responses that informed the development of South Africa's Plastic Bags Regulations was spelt out. The research objectives included the need to: (I) analyse selected international environmental policy processes surrounding plastic shopping bags litter and waste regulation and how these influenced developments in South Africa; (2) identify actors, actants and actor/actant-networks that shaped and were being transformed by South Africa's Plastic Bags Regulations and explain the tensions, debates and responses arising in the policy processes; (3) identify environmental policy outputs and assess outcomes emerging from the formulation and implementation of South Africa's Plastic Bags Regulations; and (4) establish patterns in environmental policy process reforms around South Africa's Plastic Bags Regulations. The language of actors (human), actants (non-human) and actor/actant-networks brings to the fore the aspects of processes and relationships that exist around them. As such, insights from the actor/actant-network theory (AANT) were drawn upon to inform the research. AANT enquiry framework collapses binaries such as nature/society, art/science, structure/agency and global/local historically associated with a particular type of social theory. AANT also denies that purely technical, scientific or social relations are possible (the notion of quaSi-objects or token). Data sets were generated following' the Plastic Bags Regulations as token actant with time frames ranging from prior to, during and after the formulation of the regulations. Similarly, data analysis drew insights from AANT's four moments of translation namely problematisation, interessement, enrolment and mobilisation, with the intervention theory providing an evaluative perspective that complemented AANT. The findings were that after the promulgation of the first draft of the Plastic Bags Regulations in May 2000, tensions emerged around the nature of regulation (whether command and control - preferred by government or self regulation - preferred by industry and labour). In this regard the latter group raised concerns about jobs, income and equipment loss as well as the need to have a holistic approach to waste management rather than targeting a single product at a time whilst the former maintained that this would not be so. As such, education, awareness and stringent antilitter penalties were proposed by industry and labour as sustainable responses to the problem of plastic shopping bags waste rather than regulation. These debates continued and resulted in minor amendments to the original regulations as finalised by Government in May 2002. However, industry and labour continued lobbying government resulting in the conclusion of the Plastic Bags Agreement in September 2002 and the ultimate repulsion of the May 2002 regulations in May 2003. As revealed by this research, these responses led to broader social responses and further tensions as demand for plastic shopping bags went down by about 80% although an estimated 1000 jobs were lost and a number of companies lost equipment and business (with some closing down) following the implementation of the regulations. During implementation, debates emerged around the need to promote locally made carry facilities with two alternatives in sight namely: the Green Bag and the Biodegradable Plastic Bag. Debates also took place regarding enforcement of the new law resulting in the amendments of various pieces of legislation including the Environmental Conservation Act, Environmental Management Act and the Revenue Laws Act. Overall, a 15-year policy reform cycle and sub-cycles was determined. The research also established that the government considered the regulations a success and was already implementing simi lar initiatives to regulate other waste products, among them, used tyres, used oil and glass, confirming the trend towards waste product regulation in South Africa. From these research findings, a series of conceptual frameworks were drawn up to clarify the nature of tensions, debates and responses surrounding certain lead actors, actants and actorlactant-networks. Some of the conceptual frameworks that emerged around the actors and actor-networks include Organised Government, Organised Industry and Organised Labour. Conceptual frameworks that emerged around key actants and actant-networks include the Integrated Pollution and Waste Management, Plastic Bags Regulations as well as the discourses surrounding the Green bag and biodegradable plastic bags. The thesis concludes by reflecting on how the above and the grand actor/actant-network conceptual frameworks emerging from this research might be adopted with varying degrees of flexibility to research environmental and waste management policy processes in different waste product regulation set-ups.
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D’après les limites d’acceptation pour la mise en décharge des déchets, les REFIOM (Résidus d’Epuration des Fumées d’Incinération d’Ordures Ménagères) sont considérés comme déchets dangereux, car ils libèrent des quantités importantes de chlorures et de métaux lourds lorsqu’ils entrent en contact avec de l’eau. Ces solides doivent par conséquent être traités avant leur mise en décharge. A côté des traitements visant l’acceptabilité des REFIOM en décharge, quelques recherches entrevoient la possibilité de valoriser ces résidus, notamment dans des matériaux cimentaires.

Les recherches présentées ici s’inscrivent dans cette tendance nouvelle et visent l’élaboration d’un procédé combinant traitement et valorisation des REFIOM.

Les REFIOM représentent en fait différents types de résidus provenant des installations que rencontrent les fumées issues de l’incinération des déchets. La composition des résidus diffère selon leur origine. Il est dès lors apparu essentiel de considérer chaque type de résidu séparément et de poursuivre l’élaboration d’un traitement sur un seul type de REFIOM. Nous avons choisi de concentrer les recherches sur les Cendres Volantes de Chaudière (CVC), ces résidus se retrouvant dans tout incinérateur.

Le traitement des CVC est basé sur l’extraction de fractions valorisables et la séparation de fractions contaminées, permettant d’obtenir des résidus acceptables en décharge ou, idéalement eux-mêmes valorisables.

Une séparation magnétique permet d’extraire environ 10% en poids des CVC mais ne semble pas exploitable dans le cadre du traitement des CVC car les particules magnétiques contiennent des impuretés (composés non magnétiques) et que le résidu final reste contaminé.

Une étude de la répartition des éléments en fonction de la taille des particules (granulochimie) est effectuée sur les CVC. Il apparaît intéressant de séparer la fraction inférieure à 38 µm obtenue lors d’une séparation granulométrique, effectuée en voie humide en utilisant une solution dense. En effet, cette fraction semble être nettement plus contaminée en Pb (soluble) que le reste des CVC. Une telle séparation constitue dès lors la première étape du traitement des CVC. Elle est suivie par des étapes de lavage des fractions obtenues, visant à extraire les sels solubles (chlorures et métaux). Les lavages sont envisagés à contre-courant afin d’utiliser au mieux l’eau de lavage. Une recirculation interne des solutions est également prévue, de sorte que, théoriquement, le procédé ne génère pas d’effluents liquides. Une étape de précipitation de composés métalliques (PbS dans ce cas-ci) est prévue après le lavage des boues.

Le procédé de traitement des CVC produirait ainsi des boues et des granulats décontaminés, des sels et des précipités métalliques. Seules certaines étapes du procédé ont été investiguées en laboratoire ;des essais supplémentaires sont encore nécessaires pour optimiser chaque étape, comprendre les phénomènes physico-chimiques qui se produisent et assurer des filières de valorisation.

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Municipal Solid Waste Incineration (MSWI) fly ashes and Air Pollution Control (APC) residues are considered as hazardous waste according to the limits for the acceptance of waste at landfills, because high amounts of chlorides and heavy metals leach from the solids when those are in contact with water. These residues have thus to be treated before they can be accepted in landfill. Several treatments aim to limit the leaching of the residues. Beside these treatments, some research works go further the treatment and consider the valorisation of MSWI fly ashes and APC residues, e.a. in cementitious materials.

The present work follows the new trend and aims to build up a process that combines treatment and valorisation of MSWI fly ashes and APC residues.

MSWI fly ashes and APC residues come from the devices encountered by the flue gases from waste incineration. The residues composition differs according to their origin. It seems thus essential to consider each type of residues separately and to develop the treatment only on one sort of residue. Boiler Fly Ashes (BFA) were chosen because they exist in every modern MSWI plant.

The BFA treatment is based on the extraction of valorisable fractions and on the separation of contaminated fractions, which makes the final residues less hazardous; these final residues would then be acceptable in landfill, or, even better, be valorisable.

A magnetic sorting extracts ~10% (wt.) of BFA; however, such a separation would not be useful in a treatment process because the magnetic particles contain some impurities (non magnetic particles) and the final residue is still hazardous.

The repartition of the elements according to the particles size has been studied on BFA. It seems interesting to separate the BFA at 38 µm by a wet sieving process using a dense solution. The lower fraction presents a higher contamination in Pb (soluble) than the larger. Consequently, the first step of the BFA treatment consists of a wet sieving. Washing steps follow the sieving and aim to extract soluble salts (chlorides, heavy metals). These washings work in a counter-current way to optimise the use of water. The solutions are recycled in the process, which implies the absence of liquid effluents. A precipitation step of some metallic compounds (PbS in this case) is foreseen after the washing of the lower fraction.

The BFA treatment process would produce decontaminated sludge and coarse fractions, salts and metallic compounds. Some steps of the process have been investigated at lab-scale; further studies are necessary to optimise each step, to understand the observed reactions and to guarantee valorisation channels.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

O objetivo do trabalho é aplicar um modelo numérico que simule a propagação da pluma de contaminação derivada de chorume, como ferramenta numérica que permita uma análise dos parâmetros envolvidos no sistema, tendo como caso de estudo o lixão de São Pedro da Aldeia, levando em conta: o mecanismo de perda de massa durante o transporte e a variabilidade estatística dos principais parâmetros de entrada (input) no modelo numérico. A perda de massa durante o fluxo pode ocorrer tanto por sorção, como por decaimento microbiológico, será estimada através da interpretação probabilística de dados experimentais obtidos no lixão de São Pedro da Aldeia. Os resultados obtidos pela modelagem numérica serão comparados com os resultados experimentais de concentração do íon cloreto obtidos por medições em campo. Os resultados experimentais foram obtidos considerando distâncias crescentes em relação ao lixão, para oito intervalos de tempo distintos, permitindo, assim, comparar os resultados alcançados pela modelagem numérica com dados experimentais reais, obtidos em função do tempo e da distância ao lixão. Para a modelagem numérica, foi utilizada a equação diferencial do transporte advectivo-dispersivo, levando em conta um termo de perda de massa estimado a partir de interpretações estatísticas dos resultados experimentais obtidos. A solução da equação diferencial do fluxo advectivo dispersivo foi analisada pelo método dos volumes finitos, que se mostra adequado para problemas de avanço de frentes de saturação e/ou de contaminação. Para a modelagem probabilística, foi utilizado o Método de Rosenblueth (ou método das estimativas pontuais), considerando-se, como variáveis aleatórias mais relevantes: a condutividade hidráulica k, a concentração iônica inicial Co e o decaimento da concentração iônica em função da distância (x) ao lixão expresso por um termo bo em (mg/l/m). A interpretação estatística das concentrações medidas experimentalmente mostrou uma faixa de variabilidade muito bem representada pela faixa de variação obtida pela conjugação da solução da equação de transporte de contaminantes (pelo método dos volumes finitos) com análise de variabilidade por formulação FOSM (pelo método das estimativas pontuais de Rosenblueth). Os resultados obtidos indicam que, embora com a contaminação crescente, podemos avaliar com poucos dados a contaminação ao longo do tempo. As simulações indicaram coerência com o resultado obtido experimentalmente, validando assim o modelo utilizado. Entende-se que o trabalho conseguiu demonstrar a aplicabilidade e relativa praticidade no que diz respeito ao estudo do fluxo de contaminantes em meios saturados. Os resultados se mostraram satisfatórios no que tange ao entendimento das questões abordadas.
The objective of this work is to apply a numerical model that simulates the propagation of the contamination plume stemmed from leachate as a numerical tool that allows an analysis of the parameters involved in the system, having the landfill of São Pedro da Aldeia as study case. The model takes into account the loss of contaminant mass mechanism during transport and the statistical variability, in the numerical model, of the main input variables. The loss of mass during the flow, which can occur either in the form of sorption or as a microbiological decay, will be assed by probabilistic interpretation of experimental data. The results obtained by the numerical modeling will be compared to the experimental results of the ionic chloride concentration obtained by field mediations. The experimental results were obtained taking into account the growing distances in relation to the landfill, for eight different time intervals, allowing, this way, the comparison of the results reached by the numerical modeling with the real experimental data results, obtained due to the time and the distance of the landfill. For the numerical modeling, the differential equation of the advective-dispersive transport was used, taking into account a term of loss of mass estimated from statistical interpretations of the experimental results. The differential equation solution of the advective-dispersive flow was obtained by the finite volumes method, which was proved adequate to problems concerning the propagation of contaminating plumes in saturated soils. For the probabilistic modeling, the Rosenblueth Method (or point estimate method) was used, considering, as more relevant aleatory variables, the hydraulic conductivity k, the initial ionic concentration and the rate of concentration decay. The statistical interpretation of the concentrations experimentally measured showed one variability band well represented by the variation band obtained by the conjunction of the contaminant transport equation solution (finite volumes method) with the variability analysis of the FOSM formularization (Rosenblueths point estimate method). The obtained results indicate that even with the increasing contamination it is possible, with little data, to evaluate the contamination throughout time. The simulations indicated coherence with the experimentally obtained results validating, this way, the used model. The work demonstrates the applicability and the relative practicity concerning the study of the contaminant flow in saturated environments. Considering the understanding of the boarded questions, the results seemed satisfactory.

This case study was done in KwaZulu–Natal province in South Africa within two municipalities Ethekwini and Umsunduzi Municipality. Three communities participated in this study. The research is motivated by the lack of cooperation between some municipalities and Community Based Organisations (CBOs) in implementing the National Waste Management Strategy (NWMS) at a local level. The primary goal is to explore the availability and development of learning support materials (LSMs) that relates to waste management in collaboration with CBOs and local councillors. The secondary goal is to explore the use of learning support material to promote participation in the implementation of the NWMS. Coresearchers were from the Community Based Organisations as well as local councillors who are located within the communities of these CBOs. Pseudonyms for co-researchers from CBOs and Councillors and the name of their townships have been used to protect co-researchers. A literature review has been conducted to explore research that has been done on the development, usage, accessibility and distribution of the LSMs. Data collection methods included semi-structured interviews; field visits to communities, tape recording of discussions and the keeping of a field journal. Some of the key findings included that LSMs is used by both CBOs and Councillors to try to reduce local environmental problems. It also identified that there are no formal mechanisms between CBOs and Municipalities in dealing with waste management programmes within the identified communities. The other important finding was that the participation of CBOs in the development of LSMs normally excludes the user groups as a result language used is not always understood. Illustrations used in some cases may be misinterpreted if the reader is not English literate as most of material in circulation is written in English. Some recommendations for further research have been made in relation to the findings made in the study. These included recommendations on the development, usage of LSMs, participation of stakeholders in resource development within the context of CBOs and local municipalities.

MPH
Department of Public Health
The sanitary state of an area is largely influenced by waste handling practices of the residents and measures in place for safe waste evacuation and disposal. Despite strategies that the municipality and local communities have put in place; namely, collection of wastes in one central spot in some villages, littering of all types of wastes is still on the increase in many rural areas. The focus of this study was on common refuse generated at Khakhanwa Village, different waste management practices and the knowledge of villagers on the impact of poor refuse management. The study was carried out using the quantitative, descriptive methodology. A total population of 312 households participated. Data was collected using a structured questionnaire and ethical aspects were taken into consideration. Data was analysed descriptively using SPSS version 22.0. It is presented using graphs, tables and pie chart. The findings show that the respondents satisfactorily showed understanding of waste management and the impact of poor waste management. Due to lack of waste services, the majority of the residents resort to storing wastes within their homes, burning it and disposing of it in open dumping sites as major waste management practices. The most familiar wastes in Khakhanwa village are decomposable wastes, napkins and plastics. These findings call for strengthened waste services in rural areas and more waste education amongst all villagers. Policies on waste management need to be put in motion. Communities need to be equipped with the knowledge of reducing, reusing and recycling for the purpose of limiting wastes. Finally school curricula should be adjusted such that they inform learners about waste management from early ages.

MENVSC
Department of Ecology and Resource Management
Solid waste management (SWM) has become an issue of increasing worldwide concern as urban populations continue to rise and consumption patterns change. The health and environmental effects associated with SWM are escalating, predominantly in the perspective of developing countries. The rise in rural-urban migration rates in developing countries has left local authorities overwhelmed and failing to cope with the increase in solid waste. This has led to a shift from conventional systems of solid waste management to contemporary systems such as community based solid waste management (CBSWM). Despite the shift, it seems local authorities in developing countries still fail to manage suburban waste effectively. This study investigated the performance of a CBSWM scheme in Nkulumane, a high-density suburb in Bulawayo. Both quantitative and qualitative data were collected, hence a mixed methods approach employed. The study incorporated systematic sampling and purposive sampling in the selection of research participants. Data was collected through qualitative questionnaires, semi structured interviews and field observations. Thematic content analysis and descriptive statistics from SPSS version 25 were used in data analysis. The study revealed that community members from Nkulumane had sound knowledge on what CBSWM entails, however the community members had negative attitude towards CBSWM and traditional notions on SWM had an influence of their perception of CBSWM concepts. The study also revealed that Bulawayo City Council had managed to create employment for the community through a CBSWM scheme. Furthermore, operating expenses of the city council had decreased over the years. The level of environmental awareness had improved in the study area as well. However, Bulawayo City Council has battled with community participation problems, financial constraints and inter-institutional infighting. This study provides a comprehensive report on the performance of the CBSWM scheme in Nkulumane high density suburb, Bulawayo, Zimbabwe.
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MESHWR
Department of Hydrology and Water Resources
This research involves the investigation of the interaction of different sized Nano Gold particles released into municipal drinking water and municipal waste water. Waste water was collected from Malamulele waste water treatment plant and the municipal water was collected at Mintek in Johannesburg, Randburg, South Africa. The waste water was analysed using ICP-MS to detect the metals and anions in it. The results showed the abundance of Sulphur (464 ppm), Calcium (28 ppm), Chloride (27.8 ppm), Iron (20 ppm), Magnesium (8.2 ppm), silicon (6.192 ppm) in descending order and other trace elements, including gold, that were immeasurable (<0.1). The simulated situation was created by adding 20nm gold and 40nm gold nanoparticles into municipal drinking water and waste water and kept at different environmental conditions (light, light and agitation, dark, dark and agitation) under aerobic and anaerobic conditions over a period of two months. Physico-chemical properties (pH and chemical oxygen demand) of the solutions were checked once in a month. The pH fluctuated between the acceptable ranges (5.5 – 9.5) for the two month period. Both municipal water and waste water, with and without gold nanoparticles, under aerobic condition showed an increase in chemical oxygen demand. The gold content in waste water under anaerobic condition showed an increase while under aerobic condition the decline in gold content was evident. The zeta potential of gold nanoparticles in waste water in light and agitation showed (-30 mV) while waste water on other environmental condition (light, dark and dark with agitation) presenting unstable (-18 mV) charge, but the charge shifted positively on the second month rendering them also unstable. Dynamic light scattering and TEM were used to check any possible aggregation or agglomeration of nanoparticles in the waste water. There were some few discrepancies where TEM and DLS contradict, but overall there was no significant probability of any aggregation of gold nanoparticles. The EDX was used to confirm the presence of Au0 in the waste water (with added gold nanoparticles). The research did show that the gold nanoparticles would exist as Au0 in the waste water and thus the discharge of Au-NPs to the sewer system is not recommended, but rather recycle them.

MENVSC
Department of Ecology and Resource Management
The purpose of this study was to evaluate the strategic management of the Thohoyandou Block J landfill site. There are limited documented materials on strategic management of landfill sites in South Africa. As a result, this study sought to close this gap and expose new insights that it deemed to be of great importance in the management and operations of landfill sites. The capacity of a TBJ landfill site in terms of its efficiency in disposing waste, adherence to rules and procedures and the overall management of the site are the key areas of this study. The dominant types and sources of solid waste disposed at the TBJ landfill site, efficiency and effectiveness of operation of TBJ landfill site and operational challenges are the main areas covered in this study. The study adopted the mixed methods approach, involving both qualitative and quantitative research methods. Both primary and secondary data were acquired. Primary data were obtained through a questionnaire, an interview and field observation, using an observation checklist. Secondary data were obtained from ArcGIS Desktop Help 9.2 and documented materials from the Thulamela Local Municipality and the TBJ landfill site, the Integrated Waste Management Plan, Integrated Development Plan, TBJ landfill site’s monthly report, audit report and landfill site’s operating plan. Basically, field observation and a questionnaire completed by the waste manager, landfill operator and supervisor, were used to collect data on the operational challenges of TBJ landfill site and to obtain data on the efficiency and effectiveness at which the TBJ landfill site is operating. Waste pickers were interviewed and field observation was undertaken, to identify the dominant types and sources of waste disposed at the TBJ landfill site. A questionnaire completed by TBJ landfill operator, ArcGIS Desktop Help 9.2 for field measurement, reports of the amount of waste recorded and the municipality’s database, were utilized to elicit data regarding the determination of the capacity of TBJ landfill site. The results obtained revealed that the TBJ landfill site’s remaining capacity is 317 085 m3, which will be exhausted in the next 4 years. Plastics were found to be the dominant waste disposed at the TBJ landfill site, at 40%, followed by card-boxes, which constituted 32%. The dominant sources of solid waste generation in the TBJ landfill site were households, at 51%, followed by commercial, at 31% and industrial, at 11%. The absence of a weighbridge, to weigh loads of waste, frequent break down of equipment, lack of equipment required to operate the TBJ landfill site efficiently and the presence of fire hazards, were some of the
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