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Biological treatment of pulp mill wastewater using sequencing batch reactors
C V Dubeski1, R M Branion, K V Lo
1Department of Chemical & Biological Engineering, University of British Columbia, Vancouver, Canada.
Summary
Sequencing batch reactors effectively reduced chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in chemithermomechanical pulping wastewater. Extended settling times significantly improved pollutant removal, though complete detoxification was not achieved.
Area of Science:
- Environmental Engineering
- Wastewater Treatment Technologies
- Biotechnology
Background:
- Chemithermomechanical pulping (CTMP) wastewater presents significant treatment challenges due to high organic loads.
- High chemical oxygen demand (COD) and biochemical oxygen demand (BOD) necessitate efficient treatment methods.
- Pulping effluents contain inhibitory compounds like resin and fatty acids.
Purpose of the Study:
- To evaluate the efficacy of sequencing batch reactors (SBRs) for treating CTMP wastewater.
- To determine the impact of settling time on COD and BOD removal efficiency.
- To assess the reduction of specific inhibitory compounds.
Main Methods:
- Lab-scale sequencing batch reactors (SBRs) were operated with a 24-hour cycle time and 34.3-hour hydraulic retention time.
- Wastewater with high COD (5,980–8,990 mg/L) and BOD (2,240–3,190 mg/L) was treated.
- SBR performance was compared using 1-hour and 4-hour settling periods.
Main Results:
- A 4-hour settling period achieved significantly higher COD (53–62%) and BOD (88–94%) reductions compared to a 1-hour settling period (30–41% COD, 67–78% BOD).
- The majority of oxygen demand reduction occurred within the initial 16 hours of aeration.
- Resin and fatty acid concentrations were reduced, but effluent remained partially toxic.
Conclusions:
- SBRs are a viable technology for reducing organic load in CTMP wastewater.
- Optimizing settling time in SBRs is crucial for maximizing treatment efficiency.
- Further treatment steps may be required for complete detoxification of CTMP effluent.