Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The potential use of the upflow anaerobic sludge blanket (UASB) bioreactor is
limited by the extended start-up periods due to the time-consuming granulation
process and the fact that seeding inoculum is not freely available in most
developing countries like South Africa. The mass cultivation of granules would
provide the waste water treatment industry with suitable seeding inoculum and,
therefore, an efficient waste water treatment option would be more easily
available. By applying 'stress' conditions on a bioreactor system seeded with raw
anaerobic sludge, the population dynamics of the anaerobic community change
and the acidogens start to produce extracellular polymers, which in turn enhance
the granulation process by providing a matrix for the bacterial cells to adhere to.
These "environmental stress" conditions include changes in the C:P:N ratio's. The
aim of this study was, therefore, to assess the impact of different carbon and
nitrogen sources on the enhancement of granulation in a batch system, and to
determine the best preservation technique in terms of retainment of activity.
It was found that the carbon source and concentration had a significant
influence on batch granule enhancement. Low concentrations (2.g.l ̄ ¹)
of glucose
gave the best granule enhancement over a 14 day incubation period. Fruit
cocktail effluent was found to be a cheap and effective carbon source for batch
granule cultivation. It was found that different nitrogen sources did not have the
same impact on granule enhancement, however, urea, at all concentrations
tested, gave the best granule enhancement.
A major problem encountered during the study was the standardisation of
the inoculum. Significant granule enhancement comparisons between the
different carbon sources were impeded by the lack of a suitable and reliable form
of sludge standardisation. Future research needs to address this problem of the
standardisation of the sludge inoculum as this would lead to more kinetically
comparable results.
Mass granule culturing will require granule preservation without risking the
loss of activity. In the second study, six different preservation techniques and
storage periods were evaluated in terms of the retainment of activity. These
involved freeze-drying, vacuum freeze-drying, vacuum-drying, freezing, cold storage and room temperature preservation. Activity testing was used for
comparing the efficiency of the different preservation techniques in terms of the
tempo of biogas and methane production. Freeze-drying the granules, with
storage for up to 90 days was found to give the best retainment of activity,
followed by vacuum freeze-drying. The room temperature preserved samples
showed a sudden increase in activity by day 120, which could possibly be
explained by cell hydrolysis of the granules after day 90.
The highest activity was achieved after 10 h of incubation, and it was,
therefore, suggested that activity testing for evaluation purposes should use an
incubation time of only 10 h. Furthermore, only the basic test medium with added
glucose should be used for activity testing as it was observed that the addition of
lactate and acetic acid played no decisive role in determining the level of activity of
the granules.
This study recommends the use of low concentrations of glucose for
optimum granule enhancement during the mass cultivation of granules, and the
addition of low concentrations of lactate to ensure a stable system with no
acidification. It is also advisable to use a standardised sludge inoculum, as this
will allow more efficient comparisons. Freeze-drying is recommended as
preservationtechnique as this technique showed the best retainment of activity. A
storage period of 90 days is, however, too short to be of much use for the industry.
This will have to be investigated, together with the phenomenon of increased
activity after 90 days as shown by the room temperature preserved granules. / AFRIKAANSE OPSOMMING: Die potensiële gebruik van die "uptflow anaerobic sludge blanket" (UASB)
bioreaktor word beperk deur verlengde aansitprosedure as gevolg van die
tydsame granulasieproses en die feit dat geskikte inokulums nie vrylik beskikbaar
is in die meeste ontwikkelende lande, bv. Suid-Afrika nie. Die massa-kweking van
granules sal die afvalwater-industrie voorsien van 'n geskikte inokulum, en
sodoende 'n effektiewe opsie vir die behandeling van afvalwater beskikbaar stel.
Deur die aanwending van "stres" toestande op 'n reaktor, wat geinokuleer is met
rou anaerobe slyk, vind daar 'n verandering in die samestelling van die anaerobe
populasie plaas. Die laktaat-benuttende asidogene begin om ekstrasellulêre
polisakkariede te produseer wat die granulasieproses versnel deur 'n matriks te
voorsien waaraan die bakteriële selle kan heg. Hierdie "omgewings stres"
toestande sluit veranderinge in die C:P:N verhoudings in. Die doel van hierdie
studie was om die invloed van verskillende koolstof- en stikstofbronne op die
vermeerdering van granules te bepaal, asook om die beste preserveringstegniek
in terme van die behoud van aktiwiteit te bepaal.
Daar is gevind dat die koolstofbron en konsentrasie 'n betekenisvolle
invloed op granule-vermeerdering het. Lae konsentrasies glukose (2 g.I ̄ ¹) het tot
die grootste vermeerdering in granules oor 'n 14 dae inkubasieperiode gelei.
Vrugtekelkie-afvalwater is geidentifiseer as 'n goedkoop en effektiewe koolstofbron
wat ook gebruik kan word vir die kweking van granules. Voorts is gevind dat die
stikstofbron en konsentrasie nie so 'n groot invloed op granule-vermeerdering het
nie. Urea het nietemin die beste granule-vermeerdering vir al die konsentrasies
wat getoets is, gegee.
Standaardisasie van die inokulum was 'n groot probleem gedurende die
studie. Betekenisvolle vergelykings tussen die granule-vermeerderings verkry met
die verskeie groeimedia is bemoeilik deur die afwesigheid van 'n geskikte en
betroubare standaardisasie-metode. Toekomstige navorsing moet hierdie
probleem aanspreek aangesien dit sal lei tot meer kineties vergelykbare resultate.
Massa-kweking van granule sal 'n metode van granule-preservering vereis
sonder enige verlies van aktiwiteit. In die tweede studie is ses verskillende
preserverings-tegnieke en opbergings-periodes in terme van die behoud van aktiwiteit geëvalueer. Die tegnieke sluit in: vriesdroging; vakuum-vriesdroging;
vakuumdroging; bevriesing; koelopberging en kamertemperatuur-preservering.
Aktiwiteitstoetsing is gebruik vir die vergelyking van die effektiwiteit tussen die
verskillende preserverings-tegnieke in terme van die tempo van biogas- en
metaanproduksie. Die granules wat met behulp van die vriesdroogtegniek
gepreserveer is, het die beste behoud van aktiwiteit getoon, gevolg deur die
vakuum-gevriesdroogde granules. Die monsters wat by kamertemperatuur
gepreserveer is, het 'n skielike toename in aktiwiteit na 120 dae van opberging
getoon en 'n moontlike verklaring vir hierdie verskynsel kan sel-hidrolise van die
granules na 90 dae van opberging wees.
Die meeste aktiwiteit is behaal na 'n 10 h inkubasietyd, en dus word hierdie
inkubasietyd aanbeveel indien aktiwiteitstoetse vir evaluerings-doeleindes gedoen
word. Verder word aanbeveel dat slegs die glukose-verrykte basiese toetsmedia
vir aktiwiteitstoetsing gebruik word aangesien die byvoeging van laktaat en
asynsuur geen noemenswaardige rol speel in die bepaling van die vlak van
aktiwiteit van die granules nie.
Hierdie studie beveel die gebruik van lae glukosekonsentrasies aan vir
optimale vermeerdering van granules tydens die massakweking daarvan, asook
die byvoeging van lae konsentrasies laktaat om 'n stabiele sisteem met geen
versuring te verseker. Die gebruik van 'n gestandaardiseerde slyk-inokulum word
sterk aanbeveel aangesien dit meer vergelykbare resultate lewer. Vriesdroging
(as preserveringstegniek) het die beste behoud van aktiwiteit in die granules
getoon en word dus as preserveringstegniek aanbeveel. 'n Opbergingsperiode
van 90 dae is egter te kort om van veel waarde vir die industrie te wees. Hierdie
probleem, asook die verskynsel van 'n verhoging in aktiwiteit na 90 dae van die
granules wat by kamertemperatuur gepreserveer is, moet verder ondersoek word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51886 |
| Date | 12 1900 |
| Creators | Cameron, Michelle |
| 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 | Unknown |
| Type | Thesis |
| Format | 118 p. : ill. |
| Rights | Stellenbosch University |
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