Thesis (MSc Food Sc )--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The South African apple juice processing industry is growing rapidly and during the
harvesting season the wastewater volumes and organic loads increase significantly with a
considerable environmental impact. These larger apple juice processing wastewater
(AJPWW) volumes and chemical oxygen demand (COD) loads subsequently lead to faster
increases in the organic loading rate (OLR) of an upflow anaerobic sludge bed (UASB)
wastewater treatment system and it is necessary to know if the treatment system can
handle such drastic increases over short periods. The objective of the study were to
evaluate the efficiency of the UASB process in the treatment of an AJPWW; to determine
what effect a substrate viscosity increase, based on a pectin calcium gel has on the
performance of an UASB system, and to determine what impact ozonation has on the
pectin content, gelformation ability and biodegradability of the AJPWW.
The ability of the UASB to maintain stability during the apple-processing season
was investigated by increasing the OLR from 2.9 to over 14.0 kg COD.m-3.d-1 in 131 days.
During this time the COD removal remained constant at 85%, while the pH and alkalinity
remained at levels indicative of good reactor stability. It was thus concluded that the
UASB reactor could operate successfully during the apple-harvesting season when
wastewater volumes and organic loads increase significantly.
In the study it was found that the viscosity of the AJPWW, containing 750 mq.L-1
pectin, increased from 8.5 to 47.0 cps after a 312 rnq.L-1 Ca2
+ addition. This increased
viscosity substrate was then fed to an UASB reactor at an OLR of 15.0 kg COD.m-3.d-1.
During a 12 day increased viscosity (47 cps) feeding stage the COD removal decreased
from 94 to 11%, while the reactor pH decreased from 7.5 to 4.9. During this period, pectin
accumulated in the UASB and led to biomass washout and rapid UASB failure. The
possible elimination of pectin by ozonation was thus investigated, and a 77% decrease in
pectin content and 76% decrease in gel formation ability occurred after ozonation.
The effect of pre- and post-ozonation on the efficiency of the UASB system was
subsequently investigated. It was found that a 10 min pre-ozonation decreased the
AJPWW COD by 19% and the total suspended content by 36%, while the soluble portion
of the total COD was increased from 81.7 to 92.4%. This increase in soluble COD content
should lead to increased wastewater biodegradability. The ozonated AJPWW was then
used to replaced the raw non-ozonated AJPWW as reactor feed. Results showed that the
COD removal increased from 78 to 90% within 24 h of starting with the ozonated feed. It
was also found that the reactor stability improved after AJPWW pre-ozonation as an OLR
increase from 10.0 to 16.6 kg COD.m-3.d-1 in 23 days did not detrimentally influence the stability of the reactor. This reactor effluent (COD = 465 rnq.L-1) was then post-ozonated
which resulted in 64.8% COD and 79.0% colour reductions. The final effluent had a COD
of 180 rnq.L-1 (98% reduction).
The ability of the ozonation/digestion system as described in this study to degrade
AJPWW at a higher OLR is of value to the apple industry, as it may lead to larger organic
pollutant removals and thus a more effiecient treatment system. Increased reactor
performance will directly improve the quality of the final wastewater produced, which in
turn will have a significant impact on the treatment ability of the South African apple
processing industry currently limited by the production of large wastewater volumes. / AFRIKAANSE OPSOMMING: Gedurende die oesseisoen word groot volumes afvalwater met 'n hoe organiese lading in
die vinnig groeiende Suid-Afrikaanse appelsapprosesseringsbedryf geproduseer. Dit het 'n
groot impak op die omgewing. Die groter volumes appelsapprosesseringsafvalwater
(ASPAW) met 'n hoë organiese lading het 'n vinniger verhoging in organiese
ladingstempo's (OLT) van 'n UASB-waterbehandelingstelsel tot gevolg. Daarom is dit
belangrik om te weet of die stelsel die drastiese verhoging oor kort tydperke kan hanteer.
Die doel van hierdie studie was die evaluering van die effektiwiteit van die UASB-proses in
die behandeling van ASPAW; om te bepaal watter effek 'n substraatviskositeitsverhoging,
gebaseer op 'n pektien-kalsium-jel, op die doeltreffendheid van 'n UASB-stelsel het; en om
te bepaal watter impak osonering op die pektieninhoud, jelvormingsvermoe en
bioafbreekbaarheid van ASPAW het.
Die vermoe van die UASB om stabiliteit te handhaaf gedurende die
appelsapprosesseringseisoen is ondersoek deur die OLT van 2,9 tot bo
14,0 kg CSB.m-3.d-1 te verhoog oor 131 dae. Gedurende hierdie tyd het die chemiese
suurstofbehoefte- (CSB-) verwydering konstant gebly by 85%, terwyl die pH en alkaliniteit
ook op vlakke aanduidend van goeie reaktorstabiliteit gebly het. Daar is sodoende bewys
dat die UASB-reaktor suksesvol kan presteer tydens die appelsapprosesseringseisoen,
wanneer daar 'n beduidende verhoging in OLT plaasvind.
In die studie is daar gevind dat die viskositeit van die ASPAW, wat 750 mq.L-1
pektien bevat, van 8,5 tot 47,0 cps toeneem na die byvoeging van 312 rnq.L-1 Ca2+.
Hierdie verhoogde vikositeitsubstraat is tot die UASB-reaktor toegevoeg teen 'n OLT van
15,0 kg CSB.m-1.d-1. Gedurende 'n 12-dae toevoer van verhoogde viskositeit (47 cps), het
die CSB-verwydering van die reaktor afgeneem van 94% na 11%, terwyl die pH gedaal het
van 7,5 na 4,9. Gedurende hierdie tydperk het pektien in die UASB geakkumuleer, wat
gelei het tot die uitspoel van biomassa en vinnige UASB-reaktormislukking. Die moontlike
eliminasie van pektien, deur osonering, is daarom ondersoek. 'n Verlaging van 77% in
pektieninhoud en 76% in jelvormingsvermoe het na osonering plaasgevind.
Die effek van pre- en post-osonering op die effektiwiteit van 'n UASB-stelsel is
gevolglik ondersoek. Daar is gevind dat 'n 10 minute pre-osonering die CSB van die
ASPAW met 19% verlaag en die totale inhoud van gesuspendeerde vaste stowwe met
36% verlaag, terwyl die oplosbare gedeelte van die totale CSB van 81,7% tot 92,4%
gestyg het. Die verhoging in oplosbare CSB-inhoud behoort tot verhoogde
bioafbreekbaarheid van ASPAW te lei. Die geosoneerde ASPAW is gebruik om die rou,
ongeosoneerde ASPAW as reaktorsubstraat te vervang. Die resultate het getoon dat die CSB-verwydering verhoog het van 78% na 90% na 'n 24-uur toevoer van geosoneerde
substraat. Daar is ook gevind dat die reaktorstabiliteit toegeneem het na ASPAW
osoneering, aangesien 'n OLT-verhoging van 10,0 na 16,6 kg.CSB.m-3.d-1 in 23 dae nie die
stabiliteit van die reaktor nadelig beinvloed het nie. Hierdie reaktoruitvloeisel (CSB = 465
rnq.L-1) is hierna gepost-osoneer, wat 'n 64,8% CSB- en 79,0% kleurverlaging tot gevolg
gehad. Die finale uitvloeisel het 'n CBS-inhoud van 180 rnq.L-1 gehad (98,1%
verwydering).
Die vermoe van die osonering-/verteringstelsel om ASPAW te degradeer teen 'n hoër OLT,
soos beskryf in hierdie studie, is van waarde tot die appelsapprosesseringsbedryf,
aangesien dit tot groter organiese afvalstofverwydering kan lei en dus 'n meer effektiewe
behandelingstelsel tot gevolg kan hê. Verhoogde reaktordoeltreffendheid sal 'n direkte
verbetering tot gevolg hê in die gehalte van die finale afvalwater wat geproduseer word,
wat op sy beurt 'n beduidende impak sal hê op die behandelingsvermoe van die
appelsapprosesseringsbedryf, wat tans beperk word deur die produksie van groot volumes
afvalwater.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50124 |
| Date | 12 1900 |
| Creators | Van Schalkwyk, Nico |
| 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 | 108 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0029 seconds