The effects of iron and cobalt on methanogenesis from dairy cattle manure were studied. Four-liter digestors with 3-liter working volumes were charged daily with dairy manure (4.5% W/V volatile solids) to achieve a 3-day retention time. Digestors were incubated at 37°C and pH 7.0 on a rotary shaker. Duplicate digestors were maintained under the following parameters: controls (no ions added), Co++ at 4.958 mg/liter, Fe++ at 20.64 mg/liter and Fe++ and Co++ at above stated final digestor concentrations. Significantly higher production of biogas and methane occurred with the addition of iron (p = .05). Iron-amended digestors produced 3.88 ± 0.26 liters/liter/day of biogas and 2.03 ± 0.14 liters/liter/day of methane. Control digestors produced 3.59 ± 0.27 liters/liter/day of biogas and 1.85 ± 0.14. Cobalt did not stimulate methanogenesis and may have nullified the stimulating effects of iron. Neither the cobalt nor the iron/cobalt-amended digestors demonstrated increases in biogas or methane production. Iron or cobalt did not affect efficiency of fermentation (liters of methane per gm of volatile solids destroyed) or volatile fatty acid conversion. The total counts of methanogens grown in roll tubes were unaffected by addition of the metals. Methanobrevibacter smithii was isolated from all digestors, however, Methanobacterium formicicum was isolated only from digestors amended with iron.

The research work is directed towards the investigation, optimization and application of some plant-based waste materials for the removal of some toxic trace metals (Cd, Pb and Mn) as well as selected oxyhalides (CIO3-,IO3- and BrO3-) in aqueous system. Waste materials from three plants; Athrixia philicoide, an indigenous bush tea; the outer covering peels of butternut Squash (Cucurbita Moschata) and pineapple (Ananas comosus) were evaluated for their sorption efficiency of the selected metals. batch and continuous experimental processes as well as conditions that might influence the sorption of the metals were investigated. These conditions include effects of pH sorption time, amount of adsorbent, volume of the aqueous medium, amount of metals etc. Qualitative and quantitative analysis of metal ions in solution was carried out using the ion chromatograph (IC) while the functional group identification present in waste materials was established using the Fourier Transform infr-red spectroscopy (FTIR), Quantitative biosorption equilibrium of 98.99% was reached within 6h at pH 6 and 100 ppm concentration of Pb metal with Athrixiaphilicoide under 30 min contact time. Applicability of the sorption process was tested on wastewater. Results revealed that > 99.93 %; 84.5 % and 64.3 % sorption efficiency was obtained for Mn, Cd and Pb respectively at pH 7 using Ananas Comosus adsorbent. For Athrixia philicoide, sorption efficiency from spiked wastewater ranged from 99.98 % for Cd; 99.96 % for Mn and 82.5 % adsorption for Pb at pH 7. For Juglans Cinerea, wastewater sorption efficiency varied between 78.76 %, 94.50 % and 96.50 % for Cd, Mn and Pb respectively at pH6. Results from the optimized method revealed the applicability of the method to environmental water samples. Possible large scale and industrial/commercial application of developed materials and methods would be explored. ) in aqueous system. Waste materials from three plants; Athrixia philicoide, an indigenous bush tea; the outer covering peels of butternut Squash (Cucurbita Moschata) and pineapple (Ananas comosus) were evaluated for their sorption efficiency of the selected metals. Batch and continuous experimental processes as well as conditions that might influence the sorption of the metals were investigated. These conditions include effects of pH, sorption time, amount of adsorbent, volume of the aqueous medium, amount of metals etc. Qualitative and quantitative analysis of metal ions in solution was carried out using the ion chromatograph (IC) while the functional group identification present in waste materials was established using the Fourier Transform infra-red spectroscopy (FTIR). Quantitative biosorption equilibrium of 96.99 % was reached within 6h at pH 6 and 100 ppm concentration of Pb metal with Athrixia philicoide under 30 min contact time. Cd and Mn adsorption by the same adsorbent under similar condition were less than 50 % for individual metal evaluation experiment. However, > 99 % adsorption was achieved with Cd in a mixture of the three (3) evaluated metals. Highest adsorption of 93 % of Pb was achieved with the Butternut Squash peel (Cucurbita moschata) at the optimal sorption pH of 6 followed by quantitative sorption of 99.2 % of Mn while Cd recorded a sorption level of 45 % all at 6 pH. The sorption efficiency of Pb, Cd and Mn using pineapple peels (Ananas comosus) also at the optimal sorption conditions of (pH 6, 30 min contact time and 100 ppm metal concentration) ranged from 98.7 %, 100 % and 99.90 % respectively. / Enviromental Science / M.Sc (Enviromental Science)

The research work is directed towards the investigation, optimization and application of some plant-based waste materials for the removal of some toxic trace metals (Cd, Pb and Mn) as well as selected oxyhalides (CIO3-,IO3- and BrO3-) in aqueous system. Waste materials from three plants; Athrixia philicoide, an indigenous bush tea; the outer covering peels of butternut Squash (Cucurbita Moschata) and pineapple (Ananas comosus) were evaluated for their sorption efficiency of the selected metals. batch and continuous experimental processes as well as conditions that might influence the sorption of the metals were investigated. These conditions include effects of pH sorption time, amount of adsorbent, volume of the aqueous medium, amount of metals etc. Qualitative and quantitative analysis of metal ions in solution was carried out using the ion chromatograph (IC) while the functional group identification present in waste materials was established using the Fourier Transform infr-red spectroscopy (FTIR), Quantitative biosorption equilibrium of 98.99% was reached within 6h at pH 6 and 100 ppm concentration of Pb metal with Athrixiaphilicoide under 30 min contact time. Applicability of the sorption process was tested on wastewater. Results revealed that > 99.93 %; 84.5 % and 64.3 % sorption efficiency was obtained for Mn, Cd and Pb respectively at pH 7 using Ananas Comosus adsorbent. For Athrixia philicoide, sorption efficiency from spiked wastewater ranged from 99.98 % for Cd; 99.96 % for Mn and 82.5 % adsorption for Pb at pH 7. For Juglans Cinerea, wastewater sorption efficiency varied between 78.76 %, 94.50 % and 96.50 % for Cd, Mn and Pb respectively at pH6. Results from the optimized method revealed the applicability of the method to environmental water samples. Possible large scale and industrial/commercial application of developed materials and methods would be explored. ) in aqueous system. Waste materials from three plants; Athrixia philicoide, an indigenous bush tea; the outer covering peels of butternut Squash (Cucurbita Moschata) and pineapple (Ananas comosus) were evaluated for their sorption efficiency of the selected metals. Batch and continuous experimental processes as well as conditions that might influence the sorption of the metals were investigated. These conditions include effects of pH, sorption time, amount of adsorbent, volume of the aqueous medium, amount of metals etc. Qualitative and quantitative analysis of metal ions in solution was carried out using the ion chromatograph (IC) while the functional group identification present in waste materials was established using the Fourier Transform infra-red spectroscopy (FTIR). Quantitative biosorption equilibrium of 96.99 % was reached within 6h at pH 6 and 100 ppm concentration of Pb metal with Athrixia philicoide under 30 min contact time. Cd and Mn adsorption by the same adsorbent under similar condition were less than 50 % for individual metal evaluation experiment. However, > 99 % adsorption was achieved with Cd in a mixture of the three (3) evaluated metals. Highest adsorption of 93 % of Pb was achieved with the Butternut Squash peel (Cucurbita moschata) at the optimal sorption pH of 6 followed by quantitative sorption of 99.2 % of Mn while Cd recorded a sorption level of 45 % all at 6 pH. The sorption efficiency of Pb, Cd and Mn using pineapple peels (Ananas comosus) also at the optimal sorption conditions of (pH 6, 30 min contact time and 100 ppm metal concentration) ranged from 98.7 %, 100 % and 99.90 % respectively. / Enviromental Science / M.Sc (Enviromental Science)

Call number: LD2668 .T4 1986 C56 / Master of Science / Biological and Agricultural Engineering

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: In excess of24 x 106 tons (1997, Eskom) of coal-derived fly ash is produced annually in South Africa for the production of electric power. A large quantity of this ash is disposed of as a solid waste in landfills, thus posing a serious environmental problem. Due to the shortage of landfill sites, new ways of utilising fly ash are needed. Recently several authors have shown that various combustion fly ashes can be converted into zeolites to obtain industrial products with applicability In environmental management. Geopolymerisation has emerged during the last few years as a possible solution to some waste stabilisation and solidification problems. Phenolic compounds have been shown to be toxic to soil microorganisms at the partsper- million level. Indeed several of the organic compounds classified by the U.S. Environmental Protection Agency as priority pollutants, are phenols. Immobilisation of phenols by adsorption on zeolites and encapsulation in a geopolymer appears to be a promising solution to this problem. This thesis reports a technique for the production of a low-silica sodium zeolitic material from fly ash (zeolite NaP1), and its application for the stabilisation of phenols by adsorption and subsequent encapsulation in a geopolymer matrix. A commercial zeolite, clinoptilolite was also utilised as an adsorbent. Due to their uniform pore sizes and large surface areas, zeoli tic materials are suitable for ion exchange and adsorption of certain organic substances. Adsorption data show that the commercial zeolite, clinoptilolite was an effective adsorbent for organics. Adsorption data showed that between 51.2ppm and 74.3ppm of chlorophenol or between 15.4ppm and 32.5ppm of phenol could be adsorbed. Physical encapsulation of the coated zeolite loaded with organic within a geopolyrneric matrix increased the compressive strength of the matrix from 28.80 kN to 40.79 kN. Leaching data for the various geopolymer matrices with encapsulated and loaded zeolites show no organics being leached from the system at a detection level of 2ppm. According to the SABS these would have been acceptable organic concentrations within a waste water stream. In utilising waste materials (fly ash and organic waste) and their reactive properties, it is now possible to create various geopolyrners that are not only strong enough to be used as constructionlbuilding materials, but are also effective immobilisation systems for organic waste containment. / AFRIKAANSE OPSOMMING: Meer as 24 x 106 tons (1997, Eskom) vlieg-as word jaarliks deur die verbranding van steenkool vir die produksie van elektrisiteit geproduseer. Die as, wat tans in groot hoeveelhede as soliede afval in vaste-afval stortingsterreine gestort word, word gesien as 'n groeiende omgewingsprobleem. 'n Tekort aan geskikte stortingsterreine maak die ontwikkeling van nuwe gebruike vir die vlieg-as dringend nodsaaklik. Geopolimerisasie van vlieg-as materiale, 'n proses wat die laaste paar jaar ontwikkel is, blyk 'n potensiele oplossing te wees vir sommige afval stabilisering en solidifikasie toepassings. Daar is bewyse dat fenoliese verbindings, selfs op 'n dele per miljoene (dpm) vlak, toksies is vir grondorganismes. Verskeie van die komponente wat deur die Amerikaanse Omgewingsbeskermingsagentskap (US EPA) as prioritats kontaminants geklassifiseer is, is ondermeer fenole. Die huidige werk ondersoek die adsorbsie van fenol op zeoliet NaPI en clinoptiloliet, gevolg deur fisiese omsluiting deur geopolimerisasie. Verskeie outeurs het onlangs verwys na die omsetting van verskeie verbrandings vlieg-asse na zeoliete om bruikbare industriele produkte (vir gebruik in die omgewingsveld) te vorm. Die tesis rapporteer 'n metode vir die produksie van 'n iae silika natrium zeolitiese material (zeoliet NaP!) uit vlieg-as en die gebruik daarvan in die stabilisering van fenole. 'n Kommersieel beskikbare zeoliet, clinoptiioliet, is ook gebruik as adsorbent. Uniforme porie groottes en hoe oppervlak areas maak zeolitiese materiale geskik vir ioonuitruiling, asook die adsorbsie van verskeie orgamese verbindings. Deur die fisiese omsluiting van die zeolitiese materiaal binne 'n geopolimeer matriks, kan materiale met beduidend hoe druksterktes, geproduseer word. Adsorbsie data het getoon data die kornmersiele zeoliet, klinoptilotiet, 'n effektiewe adsorbent vir organiese stowwe is. Adsorbsie waardes het gewissel tussen 51.2dpm tot 74.3dpm vir chlorofenol en 15.4dpm tot 32.5dpm vir fenol. Fisiese enkalsulering van die bebandelde zeoliet (coated fzeo) binne 'n geopolimeer matriks het die saamdrukbaarheidsterkte van die betrokke matriks verhoog van 28.80 kN to 40.79 kN. Logingsdata verkry vir die onderskeie geopolimeer matrikse het getoon dat geen van die organiese stowwe uit die matrikse vrygestel word nie. Indien die organiese stowwe wel vrygestel sou word, sou die waterfase konsentrasie onder 2 dpm, binne die aanvaarbare spesifikasie vir uitvloeisels volgens die SABS standard, gewees het. Verskeie geopolimere, wat nie slegs sterk genoeg is om as konstruksie materiale te dien nie, maar addisioneel effektief as immobilisasie medium dien, kan dus uit die reaktiewe eienskappe van afval materiale (vlieg-as en organiese afval) vervaardig word.

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.

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The fine ash produced at the Sasol Secunda Petrochemical Plant is disposed of through a wet ash disposal system. Other process waste streams with high salt concentrations are co-disposed of in the Sasol Secunda ash disposal system. This has led to a steady rise in the salt concentrations of the recycled clear ash effluent (CAE) over the past 17 years. To combat this increase in salt concentrations, the capability of the Sasol Secunda ash disposal system to act as a salt sink, needs to be enhanced. This investigation focussed on ways to enhance the salt removal/retention capabilities of the Sasol Secunda ash disposal system and consisted of the following: • A literature survey of relevant information. • The mixing of different combinations of fine ash, brine and CAE. • Adding CO2 to the fine ash and CAE mixtures. • Investigation to enhance salt precipitation in the CAE and Evaporation dams. • Salt balances and a residence time calculation over the CAE and Evaporation dams. From these investigations it were concluded that the Sasol Secunda ash disposal system could be used as a salt sink for SO4 ions. Up to 43% of the SO4 is removed from the brines after the initial ash/water contact. It was also found that the tubular reverse osmosis (TRO) brine could be used as a carrier medium for the ash. The large amounts of Ca that is leached into the ash water during the mixing of the CAE and fine ash can be prevented by the addition of CO2 to the mixing point. There is usually an increase of 240% in the Ca concentration and this is reduced to only an 8% increase with the CO2 addition. The most feasible precipitation enhancement for the CAE and Evaporation dams is an increase in evaporation. This enhances CaCO3 precipitation, which is the main mechanism for salt removal in the CAE and Evaporation dams. Ca, Na and Cl are retained in the evaporation and CAE dams. SO4 is leached from solid phases in the dams. There is however an overall decrease in the total dissolved solids (TDS) of the ash water. The salt removal of the CAE and Evaporation dams is approximately 57 tons per day. The capability of the Sasol Secunda ash disposal system to act as a salt sink can be enhanced by the addition of CO2 at the mixing point and by increasing the evaporation rate in the CAE and Evaporation dams. Using the TRO brine as carrier medium may also increase the SO4 precipitation capabilities of the Sasol Secunda ash disposal system. / AFRIKAANSE OPSOMMING: Die fynas wat by die Sasol Secunda Petrochemiese Aanleg geproduseer word, word verwyder deur ‘n geslote nat asstelsel. Ander afvalstrome wat hoë konsentrasies soute bevat word ook in die Sasol Secunda asstelsel gestort. Dit het tot gevolg dat daar oor die afgelope 17 jaar ‘n volgehoue styging in die sout konsentrasies van die hergebruikte aswater (genoem CAE – “clear ash effluent”) was. ‘n Manier om hierdie styging in die sout konsentrasies teen te werk, is om die sout verwyderingsvermoë van die Sasol Secunda asstelsel te verbeter. Hierdie ondersoek het gefokus op maniere om die sout verwyderings- /terughoudingsvermoë van die Sasol Secunda asstelsel te verbeter en het die volgende ingesluit: • ‘n Literatuur oorsig van toepaslike inligting. • Die meng van verskillende kombinasies van fynas, soutstrome en CAE. • Toediening van CO2 by die fynas en CAE mengsels. • ‘n Ondersoek na metodes om die soutverwydering in die CAE en Verdampingsdamme te verbeter. • Soutbalanse en ‘n residensie tyd berekening vir die CAE en Verdampingsdamme. Na hierdie ondersoeke kon die gevolgtrekking gemaak word dat die Sasol Secunda asstelsel ‘n sout sink vir SO4 ione is. Tot 43% van die SO4 word verwyder na die aanvanklike as/water kontak. Daar is ook gevind dat die TRO (“tubular reverse osmosis”) soutstroom gebruik kan word as ‘n draer vir die fynas. Die groot hoeveelhede Ca wat in die aswater in loog, kan voorkom word deur die toediening van CO2 by die mengpunt van die fynas en aswater. Daar is normaalweg ‘n verhoging van 240% in die Ca konsentrasie van die aswater en dit word verminder na ‘n skrale 8% met die toediening van CO2. Die mees praktiese metode om die soutverwydering in die CAE en Verdampingsdamme te verbeter, is met die verhoging van die verdamping. Dit sal die neerslag van CaCO3, wat die meeste soutverwydering tot gevolg het, verhoog. Ca, Na en Cl word teruggehou in die Verdampings en CAE damme. SO4 loog uit soliede fases in die damme. Daar is wel ‘n afname in die algehele opgeloste spesies (“TDS”) van die aswater. Die soutverwydering van die Verdampings en CAE damme is ongeveer 57 ton per dag. Die vermoë van die Sasol Secunda asstelsel om as ‘n sout sink gebruik te word, kan verbeter word deur CO2 by die mengpunt by te voeg en die verdampingstempo in die Verdampings en CAE damme te verhoog. Die gebruik van die TRO pekelstroom as draer van die as kan die SO4 neerslag in die Sasol Secunda asstelsel ook verhoog.

published_or_final_version / abstract / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management