Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Many South African farmers are forced to use water from nearby rivers for crop irrigation, since it is
the most affordable and sometimes only source of water available to them. During this research
project, a baseline study was performed on a farm irrigating fresh produce with water obtained
from the Eerste River. The baseline study was done over a five month period, at six preselected
sampling points, to determine the microbial and physico-chemical parameters of the water so a
baseline could be established to compare the results to when the ultraviolet (UV) apparatus was
installed (February 2013). Aerobic colony count (ACC), total coliforms (TC) and Escherichia coli
(E. coli) were tested for during the microbiological study, while the physico-chemical analysis
comprised of temperature, pH, conductivity, chemical oxygen demand (COD), alkalinity and total
soluble solids (TSS). The UV treatment study was also performed over a five month timeline, at
eight different sampling points (original six sampling points, with additional sampling points before
and after UV). The same microbiological tests were performed during the UV treatment study, but
turbidity and percentage ultraviolet transmittance (% UVT) were performed additionally during
physico-chemical analysis.
During the baseline study ACC, TC and E. coli counts as high as 9 600 cfu.mL-1, 13 799
MPN.100 mL-1 and 2 098 MPN.100 mL-1 were isolated at the river (Sampling Point 1), respectively.
While performing the UV treatment study ACC, TC and E. coli counts as high as 142 000 cfu.mL-1,
241 960 MPN.100 mL-1 and 6 867 MPN.100 mL-1 were isolated at the river, respectively. As a
result it was concluded that the Eerste River was mostly unsuitable for irrigation of fresh produce
that are consumed raw. The higher counts in the river, during the UV treatment study might be
attributed to the increase in rainfall that occurred in the sampling months (March to July 2013).
The counts as measured at the point of irrigation are considered of greater importance,
since the counts present in the river might still decrease to below the guideline levels after passing
through sand filters and the addition of hydrogen peroxide (current mode of treatment) or after
passing through the UV in the UV treatment study. The ACC, TC and E. coli counts during the
baseline study were as high as 8 800 cfu.mL-1, 24 196 MPN.100 mL-1 and 85 MPN.100 mL-1 at the
point of irrigation (Sampling Point 6), respectively. After hydrogen peroxide addition average logreductions
ranging between 0.65 and 1.13 were seen, but reduction was never constant. The counts at the point of irrigation remained more or less constant compared to the river
due to contamination that occurred at the sand filters, making the water unsuitable for irrigation of
fresh produce in terms of ACC and TC counts. In the UV treatment study ACC, TC and E. coli
counts were as high as 35 000 cfu.mL-1, 10 462 MPN.100 mL-1 and 63 MPN.100 mL-1 at the point
of irrigation (Sampling Point 8), respectively. Average log-reductions in the range of 0.90 to 1.25
were achieved, but it was inconsistent. After treatment with chlorine and re-sanding of the sand
filters, no further contamination occurred and counts decreased to below guideline limits, making
the water safe for irrigational use in terms of all of the microbiological parameters. Not only is UV treatment more effective in reducing microbiological counts than H2O2, it is also relatively less
expensive in the long term. Hydrogen peroxide treatment of water amounts to a very high capital
expense every month, whereas UV may seem expensive when starting up, but the monthly
operating cost thereafter is marginally less than for H2O2.
It is of great importance to farmers to find a treatment that would reduce the counts in the
river water to below the guideline limits required for safe irrigation since pathogens can be carried
over from water onto fresh produce, resulting in an increase in produce-associated foodborne
outbreaks and loss of consumer trust. / AFRIKAANSE OPSOMMING: Menigte Suid-Afrikaners is afhanklik van nabygeleë riviere om hulle oeste te besproei aangesien
dit meestal die mees bekostigbare en soms enigste bron tot hul beskikking is. Tydens hierdie
projek is ‘n grondslag sowel as ‘n UV behandelingsmetode studie uitgevoer op ‘n plaas wat vars
vrugte en groente besproei met water water wat hul vanuit die Eersterivier verkry. Die
grondslagstudie is oor ‘n tydperk van vyf maande uitgevoer by ses voorafgekose punte. Dit is
gedoen om die mikrobiologiese sowel as chemiese parameters van die water te bepaal sodat ‘n
grondslag beskikbaar kon wees om met resultate te vergelyk wat met behulp van die
ultravioletmasjien verkry is (in Februarie 2013 geïnstalleer). Tydens die mikrobiologiese studie is
daar vir aerobiese koliform tellings (ACC), totale koliforme (TC) en Escherichia coli (E. coli)
getoets. Tydens die chemiese analise is temperatuur, pH, konduktiwiteit, chemiese suurstof
benodiging, alkaliniteit en totale oplosbaie vastestowwe in die water getoets. Die UV
behandelingsmetode studie is ook oor ‘n tydperk van vyf maande uitgevoer, met twee addisionale
toetspunte by. Presies dieselfde mikrobiologiese analises as wat tydens die grondslag studie
uitgevoer is, is tydens die UV behandelingsmetode studie uitgevoer, maar vir die chemiese analise
het turbiditeit en persentasie ultraviolet transmissie van die water bygekom.
Gedurende die grondslag studie was ACC, TC and E. coli tellings so hoog as 9 600
cfu.mL-1, 13 799 MPN.100 mL-1 en 2 098 MPN.100 mL-1 onderskeidelik uit die rivier geïsoleer
(Punt 1). Tydens die UV behandelingsmetode studie was ACC, TC en E. coli tellings so hoog as
142 000 cfu.mL-1, 241 960 MPN.100 mL-1 en 6 867 MPN.100 mL-1 onderskeidelik by die rivier
geïsoleer. Gevolglik is daar afgelei dat die Eersterivier se water meestal ongeskik is om te gebruik
vir die besproeiing van vars groente en vrugte wat rou geëet word sonder dat enige verdere
behandeling plaasvind. Die hoër tellings wat tydens die UV behandelingsmetode in die rivier
sigbaar was kan hoofsaaklik toegeskryf word aan die toename in reënval in daardie tyd (Maart tot
Julie 2013).
Tellings soos gemeet by die punt van besproeiing is wel van groter belang as die wat
aangeteken is by die rivier; aangesien die tellings wat in die rivier aangeteken is steeds kan
afneem tot onder aanvaarbare hoeveelhede soos in die standaarde uiteengesit, want die water
moet steeds deur sandfilters beweeg en word ook huidiglik deur waterstofperoksied behandel
tydens die die grondslagstudie of beweeg deur die UV apparaat in die UV behandelingsmetode
studie. Die ACC, TC en E. coli tellings soos gemeet by die besproeiingspunt (Punt 6) was so hoog
as 8 800 cfu.mL-1, 24 196 MPN.100 mL-1 en 85 MPN.100 mL-1, onderskeidelik. Na
waterstofperoksied byvoeging was die gemiddelde log-reduksies sigbaar, tussen 065 en 1.13,
maar afnames was nooit konstant nie. Die tellings by die punt van besproeiing het ongeveer
konstant gebly in vergelyking met die tellings wat by die rivier aangeteken is; moontlik as gevolg
van die hoë kontaminasie vlakke in die sandfilters. Kontaminasie van sandfilters het veroorsaak
dat die water ongeskik was vir die gebruik van besproeiing van vars groente as gevolg van die hoë ACC en TC vlakke. Tydens die UV behandelingsmetode studie is ACC, TC en E. coli tellings so
hoog as 35 000 cfu.mL-1, 10 462 MPN.100 mL-1 en 63 MPN.100 mL-1, onderskeidelik aangeteken
(Punt 8). Gemiddelde log-reduksies tussen 0.90 tot 1.25 was verkry, maar behandeling en
afnames in tellings was nie konstant nie. Nadat die sandfilters met chloor behandel is en die sand
daarin vervang is, het geen verdere kontaminasie by die punt voorgekom nie. Nadat al die
voorafgenoemde behandelings afgehandel is, het die tellings tot laer as die van die standaarde
gedaal en dus was die water nou veilig om te gebruik vir besproeiingsdoeleindes in terme van die
mikrobiologiese parameters. Die UV behandelingsmetode is nie net meer effektief in die verlaging
van mikrobiologiesese tellings as waterstofperoksied nie, dis ook heelwat goedkoper in die
langtermyn. Waterstofperoksied behandeling van water lei tot ‘n baie hoë kapitale onkoste per
maand, terwyl UV baie duur mag voorkom in die beginfase, maar die maandelikse kostes is
aansienlik laer as die van waterstofperoksied en maak sodoende op daarvoor.
Dit is van uiterste belang vir boere om ‘n water behandelingsmetode te vind wat die hoë
tellings in die rivier sal afbring tot laer as Suid-Afrikaanse en Kanadese riglyne; aangesien
patogene oorgedra kan word van vars vrugte en groente. Laasgenoemde kan tot ‘n drastiese
toename in vars voedsel geassosieerde siektes en gevolglik ‘n afname in die vertroue wat ‘n kliënt
in ‘n produk plaas, lei.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96867 |
| Date | 04 1900 |
| Creators | Kotze, Madelize J. |
| Contributors | Sigge, G. O., 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 | x, 114 pages |
| Rights | Stellenbosch University |
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