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Effects of temperature transient conditions on aerobic biological treatment of wastewater
- Source :
- Water research. 37(15)
- Publication Year :
- 2003
-
Abstract
- The effects of temperature variations on aerobic biological wastewater treatment were evaluated with respect to treatment efficiency, solids discharges, sludge physicochemical properties and microbiology. The effects of controlled temperature shifts (from 35 degrees to 45 degrees C; from 45 degrees to 35 degrees C) and periodic temperature oscillations (from 31.5 degrees C to 40 degrees C, 6-day period, for 30 days) were assessed in 4 parallel, lab-scale sequencing batch reactors (SBRs) that treated pulp and paper mill effluent. Overall, the temperature shifts caused higher effluent suspended solids (ESS) levels (25-100 mg/L) and a decrease (up to 20%) in the removal efficiencies of soluble chemical oxygen demand (SCOD). Lower ESS levels were triggered by a slow (2 degrees C/day) versus a fast (10 degrees C/12h) temperature shift from 35 degrees to 45 degrees C, but the SCOD removal efficiencies decreased similarly in both cases (from 66+/-3% and 65+/-2% to 49+/-3% and 51+/-3%). Temperature oscillations caused an increased deterioration of the sludge settleability [high sludge volume indices (SVI); low zone settling velocities (ZSV)], high ESS levels and lower SCOD removals. The temperature transients were associated with poor sludge settleability (SVI100 mL/g MLSS, ZSV1 cm/min), more negatively charged sludge (up to -0.35+/-0.03 meq/g MLSS), increased filament abundance (approximately 4 to 4.5, subjective scale equivalent to very common), and decreased concentrations of protozoa and metazoa (25,000-50,000 microorganisms/mL sludge). The controlled, periodic temperature oscillations had a slight impact on SCOD removal efficiency (5% decrease), and did not seem to select for robust microorganisms that withstood the temperature shift. Sludge deflocculation and filament proliferation caused by these temperature transients may explain the higher ESS levels.
- Subjects :
- Paper
Periodicity
Environmental Engineering
Population Dynamics
Industrial Waste
Waste Disposal, Fluid
Bioreactors
Animals
Aerobic digestion
Waste Management and Disposal
Effluent
Water Science and Technology
Civil and Structural Engineering
Suspended solids
Sewage
Chemistry
Ecological Modeling
Chemical oxygen demand
Environmental engineering
Temperature
Eukaryota
Pulp and paper industry
Pollution
Bacteria, Aerobic
Oxygen
Activated sludge
Volume (thermodynamics)
Wastewater
Sewage treatment
Subjects
Details
- ISSN :
- 00431354
- Volume :
- 37
- Issue :
- 15
- Database :
- OpenAIRE
- Journal :
- Water research
- Accession number :
- edsair.doi.dedup.....aecb81ecaff4257a52db19cfe258dc07