Thesis (MSc)--Stellenbosch University, 1998. / One copy microfiche. / ENGLISH ABSTRACT: The biologically catalysed oxidation of pyrite in the outer layers of coal waste dumps leads to the
formation of acid mine drainage. The oxidation of pyrite to ferric iron and sulphate is a complex
process involving various abiotic and biologically catalysed reactions. Pyrite is abiotically
oxidized by ferric iron, with the formation of thiosulphate and ferrous iron. Thiosulphate
decomposes to form various inorganic sulphur compounds. Bacterial catalysis of pyrite oxidation
is achieved by iron-oxidizing bacteria oxidizing ferrous iron to ferric iron. Bacteria that oxidize
sulphur compounds assist the catalysis by oxidizing thiosulphate and its decomposition products.
Heterotrophic organisms may play a role by consuming organic substances inhibitory to the
lithotrophic bacteria.
Abiotic ecological factors, acid formation and populations of iron-oxidizing bacterial groups were
studied in 10 differently constructed pilot scale coal waste dumps, as the second phase of a study
which started in September 1993. Gas samples were withdrawn weekly from coal waste through
permanently buried stainless steel probes, for analysis in the field using a portable oxygen/carbon
dioxide meter. Samples of coal waste were extracted by auger for analysis of moisture, pH and
microbial populations. The analyses of oxygen and pH can be recommended for the routine
monitoring of rehabilitated waste dumps.
Covers of Avalon soil 0.3 or 0.5 m thick, were not adequate to prevent acidification. Coal waste
covered with 0.7 m compacted beneath 0.3 m uncompacted Avalon soil, showed a slow pH decline,
but reached approximately pH 3 in 1997. Covers of compacted Estcourt soil beneath tmcompacted
Avalon soil to a cover depth of 1 m were effective in preventing acidification and generally kept the
coal waste anaerobic. However, all covers developed cracks during drought conditions in 1995,
allowing aeration. Low pH of some samples from these dumps during 1995/1996 may have
indicated the start of acidification.
Bacteria oxidizing high concentrations of ferrous iron and considered to be Thiobacillus
ferrooxidans, were monitored routinely, but may not have been the dominant iron-oxidizer, as
population counts using media with a lower ferrous iron concentration were higher. The majority of
the latter organisms could also not oxidize sulphur, hence were not T. ferrooxidans. The populations of the high ferrous iron-oxidizing bacteria were affected by pH, tending to be high in
acidified and low in non-acidified coal waste.
Investigations of microbial populations forming iron-oxidizing consortia in enrichment cultures
from coal waste and acid drainage samples showed the presence of T. ferrooxidans, the
heterotrophic bacterial genus Acidiphilium, fungi of the genus Penicillium, unidentified filamentous
fungi, including Cladophialophora-like morphological types, and a yeast of the genus Dipodascus.
In interaction studies, the Penicillium isolate had an inhibitory effect on T. ferrooxidans (subjected
to organic compound stress), but the Cladophialophora-like fungi reduced inhibition by organics.
Fungi have not previously been studied in detail as components of iron-oxidizing consortia, but the
bacterial isolations agree with those elsewhere, indicating that appropriate conclusions from acid
mine drainage research in other parts of the world can be applied in KwaZulu-Natal. / AFRIKAANSE OPSOMMING: Die biologies gekataliseerde oksidasie van piriet in die buitenste lae van steenkoolafvalhope lei tot
die vorming van suur mynafloopwater. Die oksidasie van piriet tot ferri-yster en sulfaat is 'n
komplekse proses wat abiotiese en biologies gekataliseerde reaksies insluit. Piriet word abioties
deur ferri-yster geoksideer, met die vrystelling van tiosulfaat en ferro-yster. Tiosulfaat verval om
verskeie anorganiese swawelverbindings te vorm. Bakteriese katalise van pirietoksidasie word deur
ysteroksiderende bakteriee wat ferro-yster na ferri-yster oksideer, bewerkstellig. Bakteriee wat
swawelverbindings oksideer maak 'n bydrae tot die katalise deur tiosulfaat en vervalprodukte
daarvan te oksideer. Heterotrofe organismes mag ook 'n rol speel deur organiese verbindings wat
die litotrofe bakteriee mag inhibeer, te verbruik.
Abiotiese ekologiese faktore, suurvorming en bevolkings ysteroksiderende bakteriee is in 10
verskillend gekonstrueerde loodsskaal steenkoolafvalhope bestudeer, as die tweede fase van 'n
studie wat in September 1993 begin het. Gas monsters is weekliks uit die steenkoolafval onttrek
deur vlekvrye staal peilers wat permanent daarin begrawe is, en met behulp van 'n draagbare
suurstoflkoolstofdioksiedanaliseerder in die veld ontleed. Monsters van die steenkoolafval is met
behulp van 'n kleiboor vir die analise van vog, pH en mikrobepopulasies geneem. Die analise van
suurstof en pH kan aanbeveel word vir die roetiene monitering van gerehabiliteerde afvalhope.
Bedekkings van 0.3 of 0.5 m Avalongrond was nie voldoende om suurvorming te verhoed nie.
Steenkoolafval wat met 0.7 m gekompakteerde en 0.3 m ongekompakteerde Avalongrond bedek is,
het 'n stadige pH-daling getoon, maar het in 1997 ongeveer pH 3 bereik. Bedekkings van
gekompakteerde Estcourtgrond onder ongekompakteerde A valongrond met 'n totale dikte van 1 m,
was effektief in die voorkoming van suurvorming. Hulle het oor die algemeen die steenkoolafval
anaerobies gehou, maar aile bedekings het tydens die droogte in 1995 krake ontwikkel, wat suurstof
laat binnedring het. 'n Lae pH gedurende 1995/1996 by sommige monsters uit hierdie hope mag
die begin van suurvorming aangedui het.
Bakteriee wat hoe konsentrasies ferro-yster oksideer en wat as Thiobacillus ferrooxidans beskou is,
was moontlik nie die dominante ysteroksideerder nie, aangesien bevolkingstellings waar 'n medium
met 'n laer konsentrasie ferro-yster gebruik is, hoer bevolkings getoon het. Die meerderheid van
laasgenoemde organismes kon ook nie swawel benut nie en dus nie T. ferrooxidans was nie. Die bevolkings van die hoe ferro-ysteroksiderende bakteriee is deur pH beInvloed, met 'n geneigdheid
tot hoe bevolkings in suur en lae bevolkings in minder suur steenkoolafval.
Ondersoeke na die rnilcrobebevollcings wat in ysteroksiderende konsortia in verryldngslculture vanaf
steenkoolafval- en suur mynafloopwatermonsters voorgekom het, het die teenwoordigheid van 7'.
ferrooxidans, die heterotrofe balcteriegenus Acidiphilium, fungi van die genus Penicillium,
ongeIdentifiseerde fungi, insluitend Cladophialophora-agtige tipes en 'n gis van die genus
Dipodascus aangetoon. By interaksiestudies het die Penicillium-isolaat 'n inhiberende effek op T
ferrooxidans (onderworpe aan organiese verbindingstres) gehad, maar die Cladophialophora-agtige
fungi het die inhibisie deur organiese verbindings verminder. Fungi is nog the in detail as
komponente van ysteroksiderende konsortia bestudeer the, maar die isolasies van bakteried stem
saam met die van elders wat aandui dat toepaslike gevolgtreldcings ten opsigte van suur
mynafloopwatemavorsing vanaf ander dele van die wereld ook in KwaZulu-Natal toegepas kan
word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/55926 |
| Date | 03 1900 |
| Creators | Modinger, Heinrich |
| Contributors | Loos, M. A., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 143 p. : ill. |
| Rights | Stellenbosch University |
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