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Effects of high operating temperatures, hydraulic retention time and solids residence time on activated sludge treatment of kraft pulping effluent Barr, Tanya Alexandra
Abstract
Laboratory scale research on the effects of hydraulic retention time (HRT), solids residence time (SRT), high operating temperatures and temperature shocks on activated sludge (AS) treatment of kraft pulping effluent was performed. This research was conducted as four separate experiments using two 5 litre continuously fed bioreactors. Each unit consisted of a bioreactor and a clarifier which were fully automated, using pumps and timers, to control feed, waste and recycle rates. Feed consisted of weekly shipments of primary clarified effluent (PCE) from Western Pulp's (WP) Squamish pulp mill. Six standard assays were routinely performed in order to assess treatment performance and efficiencies. These assays included biochemical oxygen demand (BOD), chemical oxygen demand (COD), volatile suspended solids (VSS), specific oxygen uptake rate (SOUR), Microtox - toxicity test, and adsorbable organic halides (AOX). The first experiment was start up and steady state operation of a bioreactor. The unit was run at 35°C for a period of two months in order to attain results which could be used as a set of baseline data for comparison purposes for the three following studies. The HRT and SRT were 10-12 hours and 12-15 days respectively. The assay results indicated treatment performance was very comparable to full scale pulp mill AS treatment facilities. The second experiment studied the effects of varying HRT and SRT on treatment efficiencies. Nine different operating conditions were examined based on a 2x3 factorial design method. HRT was varied between 12, 8 and 4 hours, while SRT was varied from 15, 10, 5 days. The results from this study indicated that HRT had more of an effect on treatment performance than SRT. Longer HRTs led to improved BOD, COD, toxicity and AOX removal, while longer SRTs were not shown to significantly affect the removal of these. Shorter HRTs and longer SRTs led to significant increases in SOURs. The third experiment studied the effects of increased operating temperatures on bioreactor performance. Operating temperatures were increased 1°C every 1-2 weeks from 41°C up to 50°C over a period of four months. BOD, COD, toxicity and AOX removal were within normal operating parameters as determined by the steady state study. SOURs were somewhat lower than the rates at 35°C, however microbial activity was well within an acceptable range. The fourth and final experiment analysed the effects of induced temperature shocks on the AS system. Four separate temperature decreases occurred from a baseline temperature of 50°C over a period of five weeks. These decreases were 7°C, 16.5°C, 32°C and 40.5°C. Each temperature decrease lasted 8-10 hours, after which the temperature of the bioreactor was returned to 50°C. Immediately after each temperature shock the same six assays, used in the previous experiments, were performed on the unit. Analysis was performed prior to the temperature shock and then just after the shock at periods of 1, 6, 12, 24 and 72 hours. Results indicated that smaller temperature shocks had no detrimental effects on treatment performance, while the larger shocks did. For the two smaller temperature shocks (7°C and 16.5° C), recovery from the effects occurred within 12-24 hours. Approximately 72 hours was needed for the system
Item Metadata
Title |
Effects of high operating temperatures, hydraulic retention time and solids residence time on activated sludge treatment of kraft pulping effluent
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1995
|
Description |
Laboratory scale research on the effects of hydraulic retention time (HRT), solids
residence time (SRT), high operating temperatures and temperature shocks on
activated sludge (AS) treatment of kraft pulping effluent was performed. This
research was conducted as four separate experiments using two 5 litre continuously
fed bioreactors. Each unit consisted of a bioreactor and a clarifier which were fully
automated, using pumps and timers, to control feed, waste and recycle rates. Feed
consisted of weekly shipments of primary clarified effluent (PCE) from Western
Pulp's (WP) Squamish pulp mill. Six standard assays were routinely performed in
order to assess treatment performance and efficiencies. These assays included
biochemical oxygen demand (BOD), chemical oxygen demand (COD), volatile
suspended solids (VSS), specific oxygen uptake rate (SOUR), Microtox - toxicity test,
and adsorbable organic halides (AOX).
The first experiment was start up and steady state operation of a bioreactor. The unit
was run at 35°C for a period of two months in order to attain results which could be
used as a set of baseline data for comparison purposes for the three following studies.
The HRT and SRT were 10-12 hours and 12-15 days respectively. The assay results
indicated treatment performance was very comparable to full scale pulp mill AS
treatment facilities.
The second experiment studied the effects of varying HRT and SRT on treatment
efficiencies. Nine different operating conditions were examined based on a 2x3
factorial design method. HRT was varied between 12, 8 and 4 hours, while SRT was
varied from 15, 10, 5 days. The results from this study indicated that HRT had more
of an effect on treatment performance than SRT. Longer HRTs led to improved BOD,
COD, toxicity and AOX removal, while longer SRTs were not shown to significantly
affect the removal of these. Shorter HRTs and longer SRTs led to significant
increases in SOURs.
The third experiment studied the effects of increased operating temperatures on
bioreactor performance. Operating temperatures were increased 1°C every 1-2 weeks
from 41°C up to 50°C over a period of four months. BOD, COD, toxicity and AOX
removal were within normal operating parameters as determined by the steady state
study. SOURs were somewhat lower than the rates at 35°C, however microbial
activity was well within an acceptable range.
The fourth and final experiment analysed the effects of induced temperature shocks on
the AS system. Four separate temperature decreases occurred from a baseline
temperature of 50°C over a period of five weeks. These decreases were 7°C, 16.5°C,
32°C and 40.5°C. Each temperature decrease lasted 8-10 hours, after which the
temperature of the bioreactor was returned to 50°C. Immediately after each
temperature shock the same six assays, used in the previous experiments, were
performed on the unit. Analysis was performed prior to the temperature shock and
then just after the shock at periods of 1, 6, 12, 24 and 72 hours. Results indicated that
smaller temperature shocks had no detrimental effects on treatment performance,
while the larger shocks did. For the two smaller temperature shocks (7°C and 16.5°
C), recovery from the effects occurred within 12-24 hours. Approximately 72 hours
was needed for the system
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Extent |
6093478 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-01-14
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0058556
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1995-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.