Thesis (MSc Food Sc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The start-up period of Upflow Anaerobic Sludge Bed (UASB) reactors can
significantly be reduced by enhancing the time-consuming granulation process
through the batch cultivation of anaerobic granular sludge and thus seeding the
reactor with this cultivated granular sludge, instead of raw anaerobic sludge. The
precise mechanism for granule formation is not well known, but it is believed that
extracellular polymers (ECP) play a critical role in the granulation process.
Information on the precise role of ECP is also limited and no universal
standardised method for ECP extraction is used at present. Therefore,
comparison of results from different researchers has to be made with great
caution.
The objectives of this study were to evaluate an ECP extraction methód so
as to optimise the extraction time, and then to correlate ECP composition of UASB
granules with granule metabolic activity. The impact of changes in the
environmental conditions, such as sludge sources (Paarl and Kraaifontein-sludge),
carbon growth substrates (yeast extract lactate, glucose medium and fruit cocktail
effluent) and batch cultivation techniques (roller-table and shake-waterbath), on
batch cultivation studies was also evaluated in terms of granule activity, ECP
composition and granule formation.
A physical extraction method was used to quantify the ECP content of
UASB granules from six different sources. The optimal extraction time was taken
as the time needed before cell lysis took place, and before intracellular material
started contributing to the ECP content of the granules. It was concluded that the
ECP composition was affected by the wastewater composition fed to the original
UASB reactors, It was also found that the activity test results could be used to
indirectly predict the activity of the different trophic groups present in the UASB
granules. A correlation was found between the activity test results and the total
ECP content, and this showed that the granules with the higher ECP yields
exhibited greater biogas (SB) and methanogenic (SM) activities. However, based
on the activity data and total ECP content, it appeared that a protein:carbohydrate
ratio < 1 affected the activity of the granules,
The sludge source used as inoculum for batch cultivation of anaerobic
granular sludge had a significant effect on granule formation. The use of a pre- granulated raw anaerobic sludge, such as the Paarl-sludge, resulted in a greater
increase in granule numbers at the end of the cultivation period. The acetic acid
activity profiles showed that the acetoclastic methanogens that are involved in
initiation of granulation by nucleus formation, were inactive or absent in the
different batch systems, with the exception of the roller-table glucose cultivated
Kraaifontein-sludge (RKG) batch system.
The addition of glucose as carbon growth substrate for batch cultivation not
only enhanced the activity of the acidogenic population, but also led to the
establishment to a greater variety of granule trophic groups within all the glucose
cultivated batch systems. The addition of fruit cocktail effluent as carbon
substrate enhanced ECP production in the Paarl-sludge cultivated batch systems.
However, the addition of carbon substrates showed no discernible trend on
granule formation itself. The roller-table cultivation technique resulted in the
higher increase in granule numbers, and it was speculated that the more vigorous
shake-waterbath technique probably shortened the contact time between biomass
and substrate.
Large variations in the ECP composition of the different batch systems were
found, and these were ascribed to the composition heterogeneity of different
sludges. For future studies, it is advisable to characterise sludge, both chemically
and microbiologically before using as inoculum. The selection of an appropriate
sludge inoculum should then lead to optimisation of the granulation process. / AFRIKAANSE OPSOMMING: Die aanvangsperiode van "Upflow Anaerobic Sludge Bed" (UASB) bioreaktors kan
noemenswaardig verminder word deur die tydsame granulasie proses te versnel
deur die vooraf lot-kweking van anaërobe granulêre slyk waarmee 'n reaktor dus
geïnokuleer kan word in plaas van rou anaërobe slyk. Die presiese meganisme
van granulevorming is nog nie welbekend nie, maar daar word beweer dat
ekstrasellulêre polimere (ECP) wel 'n kritiese rol speel in die granulasie proses.
Inligting; oor die presiese rol van ECP is ook nog beperk, en tans word daar nog ,
geen universele standaard metode vir ECP-ekstraksie gebruik nie. Gevolglik moet
resultate vanaf verskeie navorsers met groot omsigtigheid vergelyk word.
Die doelwitte van hierdie studie was om 'n ECP ekstraksiemetode te
evalueer deur die ekstraksietyd te optimiseer, en dan te korreleer met die ECP samestelling
en metaboliese aktiwiteit van die UASB granules. Die inwerking van
veranderinge in omgewingskondisies, soos slykbronne (Paarl- en
Kraaifontein-slyk), koolstofbronne (gisekstrak-Iaktaat-, glukose-medium en
vrugtekelkie-uitvloeisel) en lot-kwekingstegnieke (rol-tafel en skud-waterbad) op
lot-kweking studies in terme van granule aktiwiteit, ECP-samestelling en
granulevorming is ook ondersoek.
'n Fisiese ekstraksie metode is gebruik om die ECP-inhoud van UASB
granules vanaf ses verskillende bronne te bepaal. Die optimale ekstraksietyd is
geneem as die tyd benodig voordat sellise sal plaasvind en die intrasellulêre
materiaal 'n bydrae sal lewer tot die ECP-inhoud van granules. Dit is afgelei dat
die ECP-samestelling beïnvloed word deur die samestelling van die afvalwater wat
vir die oorspronklike UASB bioreaktors gevoer is. Voorts is gevind dat die
aktiwiteitstoets resultate indirek gebruik kan word vir die voorspelling van aktiwiteit
van die verskillende trofiese groepe wat in die UASB granules teenwoordig is. 'n
Korrelasie is gevind tussen die aktiwiteitstoets resultate en die totale ECP-inhoud
wat aangedui het dat granules met hoër ECP opbrengste, beter biogas (SB) en
metanogeniese (SM) aktiwiteit getoon het. Volgens die aktiwiteitsdata en totale
ECP-inhoud het dit egter geblyk dat 'n proteïen:koolhidraat verhouding < 1 die
aktiwiteit van granules beïnvloed het.
Die slykbron wat as inokulum gebruik is vir lot-kweking van' anaërobiese
granulêre slyk het 'n noemenswaardige invloed gehad op granulevorming. Die gebruik van 'n rou anaërobe slyk wat reeds 'n mate van granulasie getoon het,
soos die Paarl-slyk, het 'n hoër toename in granule getalle aan die einde van die
kwekingsperiode teweeg gebring. Die asynsuur aktiwiteitsprofiele het aangedui
dat die asetoklastiese metanogene, wat hoofsaaklik betrokke is by inisiëring van
granulasie deur kernvorming, onaktief of afwesig was in al die verskillende lotsisteme,
met die uitsondering van die roltafel glukose-gekultiveerde Kraaifonteinslyk
(RKG) lot-sisteem.
Die toevoeging van glukose as koolstofbron vir lot-kweking het nie alleenlik
die aktiwiteit van die asidogene populasie verhoog nie, maar het ook bygedra tot
die vestiging van 'n groter verskeidenheid van granule trofiese groepe. Die
toevoeging van vrugtekelkie-uitvloeisel as koolstofbron het die produksie van ECP
verhoog in die Paarl-slyk gekweekte lot-sisteme. Die toevoeging van
koolstofsubstrate het egter geen merkbare verandering getoon in granulasie
opsigself nie. Die rol-tafel kwekingstegniek het 'n hoër toename in granule getalle
tot gevolg gehad, en dit is gespekuleer dat die meer kragtige skud-waterbad
tegniek waarskynlik die kontaktyd tussen die substraat en biomassa verkort het.
Groot variasies is gevind in die ECP-samestelling van die verskillende lotsisteme,
en dit is toegeskryf aan die heterogene samestelling van die verskillende
slyke. Vir toekomstige navorsing is dit raadsaam om slyk voor gebruik as
inokulum beide chemies en mikrobiologies te karakteriseer. Die keuse van 'n geskikte slyk-inokulum sal bydra tot die optimisering van die granulasie proses.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52841 |
| Date | 03 1900 |
| Creators | Van Eeden, Alida Elizabeth |
| Contributors | Britz, T. J., Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 105 p. : ill. |
| Rights | Stellenbosch University |
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