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Activated Sludge Aeration Control Systems Do We Need 2.0 mg/L? Dave Kinnear HDR Engineering Charlotte, NC.

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Presentation on theme: "Activated Sludge Aeration Control Systems Do We Need 2.0 mg/L? Dave Kinnear HDR Engineering Charlotte, NC."— Presentation transcript:

1 Activated Sludge Aeration Control Systems Do We Need 2.0 mg/L? Dave Kinnear HDR Engineering Charlotte, NC

2 Outline Wastewater Treatment Aeration Requirements The Activated Sludge Landscape Aeration Control System Evolution Ammonia-Based Aeration Control Literature on DO effect on Performance 2.0 mg/L: Requirement or Myth?

3 Wastewater Aeration Requirements Biochemical Oxygen Demand 1.0 lb Oxygen/lb BOD Ammonia Removal 4.8 lb Oxygen/lb NH 3 Denitrification COD utilized for denitrification does not require oxygen 2.8 lb oxygen recovered/lb NO 3 removed Increased SRT increases transfer efficiency Increased Tank Depth increases transfer efficiency Decreased DO concentration increases transfer efficiency Energy Saving Benefits of Denitrification (Rosso and Stenstrom, 2007)

4 ASM Model MLSS 14 Major Components Ordinary Heterotrophic Bacteria Ammonia Oxidizing Bacteria Nitrite Oxidizing Bacteria Endogenous Products Endogenous Products Slowly- Biodegradable Colloidal COD Particulate Inert Particulate Inert N N P P COD Inert Suspended Solids Inert Suspended Solids rara rhrh rgrg Soluble N N P P COD rdrd Chemicals/ Precipitation Chemicals/ Precipitation Methylotrophic Bacteria Methylotrophic Bacteria Transformation Rates a: adsorption g: growth h: hydrolysis d death Poly-P Heterotrophic Bacteria Slowly - Biodegradable Particulate N N P P COD Fed to reactor Grown in reactor O2O2

5 Wastewater Treatment Energy Requirements WERF: Energy Efficiency in Wastewater Treatment: North American OWSO4R07e $2.8 B spent on WW Energy in 2009 $1.51 B spent on WW Aeration 2009 US GDP = $14 T Aeration Energy = 0.01% of GPD

6 Wastewater Processes Cycle Metabolic Conditions ANR ANR: 1-3 hours ANX: 1-2 hours AER:4-12 hours ANX: 1-2 hours AER: 0.5 hours ANR: 2–12 hours Oxidation Ditch SCL

7 Autotrophic Oxygen Half-Saturation  =  max (DO/(Ks + DO))

8 Temperature and Other Affects

9 Aerobic SRT Requirement for Autotrophs Don’t really care about , you care that system SRT w/ safety factor (aerobic SRT) > washout SRT. Nitrification capacity can be adjusted by: Increasing DO Changing aerobic SRT Adjusting aerobic volume SRT = 1/  Grady, Daiger and Lim. Biological Wastewater Treatment

10 Outline Wastewater Treatment Aeration Requirements The Activated Sludge Landscape Aeration Control System Evolution Ammonia-Based Aeration Control Literature on DO effect on Performance 2.0 mg/L: Requirement or Myth?

11 The Activated Sludge Landscape DO (and other substrates) and MLSS component concentration not constant throughout reactor. Allows “Simultaneous Nitrification/Denitrification” (SND) to occur. Steve Liss

12 Outline Wastewater Treatment Aeration Requirements The Activated Sludge Landscape Aeration Control System Evolution Ammonia-Based Aeration Control Literature on DO effect on Performance 2.0 mg/L: Requirement or Myth?

13 Aeration Control System Evolution Pre 1970: limited DO control due to lack of accurate, maintainable DO sensors 1990s?: Accurate, maintainable DO sensors allow feedback control to maintain a DO set point, saving energy. DO setpoint typically 2.0 mg/L Aeration Control – A Review (Amand, Olsson, Carlsson) WS&T Improving Nutrient Removal While Reducing Energy at Three Swiss WWTPs (Reiger, Takacs, Siegrist) WER

14 Aeration Control System Evolution Current Trend: Ammonia-Based Aeration Control DO setpoint changes based on effluent ammonia More SND Volume DO drops less than 0.5 mg/L Saves Energy Saves Carbon Improving Nutrient Removal While Reducing Energy at Three Swiss WWTPs (Reiger, Takacs, Siegrist) WER

15 Outline Wastewater Treatment Aeration Requirements The Activated Sludge Landscape Aeration Control System Evolution Ammonia-Based Aeration Control Literature on DO effect on Performance 2.0 mg/L: Requirement or Myth?

16 Ammonia-Based Aeration Control Provides benefits and Reiger reports no: Deterioration of settling properties (increased SVI) Increased nitrite in effluent Deterioration of effluent quality (increase effluent particulate phase, effluent TSS) [PC] Previous authors report these problems with low DO in aerobic bioreactor

17 Outline Wastewater Treatment Aeration Requirements The Activated Sludge Landscape Aeration Control System Evolution Ammonia-Based Aeration Control Literature on DO effect on Performance 2.0 mg/L: Requirement or Myth?

18 Palm, Jenkins and Parker (1980)

19 HRSD CE Pilot A-Stage Data Mark Miller, HRSD/Virginia Tech PhD Candidate

20 HRSD CE Pilot Data

21 Echeverria, Seco, Ferrer (1992) WS&T

22 Starkey and Karr (1984, JWPCF) DO reduced from 5.0 mg/L to 0.4 mg/L. At low dissolved oxygen concentrations, changes in suspended solids and BOD could be large enough to violate discharge permits

23 Outline Wastewater Treatment Aeration Requirements The Activated Sludge Landscape Aeration Control System Evolution Ammonia-Based Aeration Control Literature on DO effect on Performance 2.0 mg/L: Requirement or Myth?

24 Thorough literature review would be useful Student Professor with a student looking for a topic WERF or other research effort – reproduce previous efforts and apply literature review to laboratory References in papers cited here were not checked. When do we need 2.0 mg/L DO in bioreactor and when do we not? References in paper or me.

25 Dave Kinnear


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