Dissertation (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Constructed wetlands have been widely used in the treatment of industrial
and domestic wastewater to reduce biological and chemical oxygen demand
(BOD and COD), to remove nitrate and enteric viruses as well as to generally
improve water quality. Distillery wastewater has a complex character due to high
concentrations of sugars, lignins, hemicellulose, dextrins, resins, polyphenols
and organic acids, leading to a high COD that may exceed 100 000 mg/L. The
potential application for the treatment of distillery wastewater by means of
constructed wetlands is relatively unexplored.
In 1999 a study was initiated at Distell Goudini distillery, Western Cape,
South Africa, to explore the possibility of using constructed wetlands to treat
distillery wastewater. It was found that constructed wetlands do have the ability to
treat distillery wastewater providing that the influent COD does not exceed 15
000 mg/L for extended periods and the correct substrate material is used. The
present study expanded on the above-mentioned study and specifically aimed to
provide information on the microbiological controls in wetland systems in an
applied sense that may contribute to improved treatment efficiency. Furthermore,
this project aimed to contribute to our fundamental understanding of the microbial
ecology of constructed wetlands used for the treatment of distillery wastewater.
This study revealed that a highly dynamic microbial composition exists within
wetlands. Furthermore it was found that wetlands can efficiently remove COD
even though a low degree of similarity exists between microbial communities in
various zones of the same wetland and those between different wetlands, as well
as low similarity between communities sampled from the same zone over time.
This demonstrates that it will be difficult to define the ‘ideal’ degradative
community in terms of microbiological criteria and serves as a reminder that
various indicators should be considered for monitoring system health.
Furthermore the shifts in microbial community composition illustrate the ability of microbial communities to adapt to changes in the environment without
compromising their functional efficacy. When studying the attached microbial
communities within wetland systems it was found that different morphotypes are
detected at certain stages of biofilm development while some organisms are
present at most phases of biofilm formation.
Measurement of CO2 production and dissolved organic carbon (DOC) removal in
laboratory scale columns showed that grazing protists had a notable effect on
overall microbial activity and that organic loading influenced these predator-prey
interactions. Interestingly, increased clogging of pores occurred in the presence
of protists, resulting in reduced flow through the porous matrix. Terminalrestriction
fragment length polymorphism (T-RFLP) analysis of biofilms on gravel
in experimental wetlands indicated that the presence of protists and algae had an
effect on the microbial community composition. Scanning electron microscopy
(SEM) showed that the presence of algae also had an influence on biofilm
structure suggesting that the algae provided labile nutrients that were utilized by
the bacterial and yeast members of the community. Finally, augmentation with a
commercial mixture or microbial populations isolated from distillery effluent
demonstrated that the concentration at which supplements are applied influence
degradative efficiency. / AFRIKAANSE OPSOMMING: Kunsmatige vleilande word wêreldwyd gebruik in die behandeling van
indusriële en huishoudelike afvalwater om biologiese en chemiese suurstof
aanvraag (BSA en CSA) te verminder, om nitrate en ingewandsvirusse te
verwyder asook om waterkwaliteit in die algemeen te verbeter.
Distilleerafvalwater het komplekse eienskappe as gevolg van hoë konsentrasies
suiker, lignien, hemisellulose, dekstrien, harpuis, polifenole en organiese sure,
wat lei tot ‘n hoë CSA wat 100 000 mg/L kan oorskry. Daar is tot op hede relatief
min studies gedoen oor die potensiële gebruik van kunsmatige vleilande vir die
behandeling van distilleerafvalwater.
In 1999 is ‘n studie by Distell Goudini distilleeraanleg in die Wes Kaap van
Suid Afrika onderneem om die moontlikheid van kunsmatige vleilande vir die
behandeling van distilleerafvalwater te bestudeer. Daar was bevind dat
kunsmatige vleilande die vermoë het om distilleerafvalwater te behandel gegewe
dat die invloeiende CSA nie 15 000 mg/L oorskry nie en dat die regte substraat
materiaal gebruik word. Die huidige studie het by die bogenoemde studie
aangesluit met die doel om informasie oor die mikrobiologiese kontroles in
vleilandsisteme op ‘n toegepaste wyse te voorsien, wat tot verbeterde
behandeling doeltreffendheid kan lei. Hierdie studie het verder beoog om by te
dra tot ons fundementele kennis van die mikrobiese ekologie van kunsmatige
vleilande wat gebruik word vir die behandeling van distilleerafvalwater.
Dié studie het bevind dat daar ‘n hoogs dinamiese mikrobiese samestelling
binne vleilande bestaan. Daar was verder bevind dat CSA steeds effektief deur
vleilande verwyder kan word alhoewel daar ‘n lae graad van ooreenstemming is
tussen mikrobiese gemeenskappe in verskeie sones van dieselfde vleiland en
verskillende vleilande, asook ‘n lae graad van ooreenstemming tussen
gemeenskappe wat in dieselfde sone oor tyd gemonster is. Dit demonstreer dat
dit moeilik sal wees om die ‘ideale’ degraderende gemeenskap te vind in terme van mikrobiologiese kriteria en dien as ‘n herinnering dat verkeie indikatore in ag
geneem moet word om die welstand van ‘n ekologiese sisteem te monitor. Die
verskuiwings in mikrobiese gemeenskapsamestelling illustreer verder die vermoë
van natuurlike sisteme om aan te pas by veranderinge in die omgewing sonder
om funksionele doeltreffendheid te verminder. Die studie van aangehegte
mikobiese gemeenskappe het aangedui dat veskillende morfotipes bespeur kan
word tydens sekere fases van biofilm formasie terwyl sekere organismes tydens
meeste van die fases teenwoordig is.
Die bepaling van CO2 produksie en die verwydering van opgeloste organiese
koolstof in laboratoriumskaal kolomme het geïlustreer dat voedende protiste ‘n
waarneembare effek gehad op die algehele mikrobiese aktiwiteit en dat die
organiese lading hierdie predator-prooi interaksie beïnvloed het. Dit was
interessant om te vind dat die teenwoordigheid van protiste die verstopping van
porieë aangehelp het en dus tot verlaagde vloei deur die poreuse matriks gelei
het. Terminale-restriksie fragment lengte polimorfisme (T-RFLP) analiese van
biolfilm op klipgruis in eksperimentele vleilande het aangedui dat die
teenwoordigheid van protiste en alge ‘n effek gehad het op die mikrobiese
gemeenskapsamestelling. Skandeerelektronmikroskopie (SEM) het bewys dat
die teenwoordigheid van alge ook ‘n invloed op biofilm struktuur gehad het wat
daarop dui dat alge maklik afbreekbare voedingstowwe aan die bakterieë en
giste van die mikrobiese gemeenskap beskikbaar gestel het. Laastens was
bewys dat die konsentrasie van toevoeging van ‘n kommersiële mikrobiese
mengsel of mikrobiese populasies wat uit afvoer geïsoleer was, die effektiwiteit
van degradering kan beïnvloed.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17322 |
| Date | 04 1900 |
| Creators | Du Plessis, Keith R. (Keith Roland) |
| Contributors | Wolfaardt, G.M., Botha, A., University of Stellenbosch. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiv, 139 leaves : ill. |
| Rights | University of Stellenbosch |
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