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Nutrient Removal and Power Savings in Wastewater Treatment Systems Todd L. Steinbach, PE Aero-Mod ® Wastewater Process Solutions.

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Presentation on theme: "Nutrient Removal and Power Savings in Wastewater Treatment Systems Todd L. Steinbach, PE Aero-Mod ® Wastewater Process Solutions."— Presentation transcript:

1 Nutrient Removal and Power Savings in Wastewater Treatment Systems Todd L. Steinbach, PE Aero-Mod ® Wastewater Process Solutions

2 Energy Consumption What determines the amount of aeration required in an activated sludge plant? What determines the amount of aeration required in an activated sludge plant? It can be the organic loading (Organic Requirement)… It can be the organic loading (Organic Requirement)… but it is often the amount of energy required to keep the basin(s) in suspension (Mixing Requirement). but it is often the amount of energy required to keep the basin(s) in suspension (Mixing Requirement). How does an under-loaded plant operate energy-efficiently? How does an under-loaded plant operate energy-efficiently? How does this relate to Nitrogen Removal? How does this relate to Nitrogen Removal?

3 Organic Requirement Oxygen required by the bacteria to break down BOD and ammonia. Oxygen required by the bacteria to break down BOD and ammonia. For Extended Aeration: For Extended Aeration: 1 lb of BOD requires from 1.33 to 1.5 lbs of O 2. 1 lb of BOD requires from 1.33 to 1.5 lbs of O 2. 1 lb of ammonia requires 4.6 lbs of O 2. 1 lb of ammonia requires 4.6 lbs of O 2.

4 Organic Requirement 1.0 MGD Typical Example: 1.0 MGD Typical Example: BOD: 240 mg/l, NH 3 -N: 35 mg/l, 1.5 lbs O 2 /lb BOD, 24 hr HRT, 11’ water depth, fine bubble efficiency of 2.0%/ft of subm., 5.5 psi, 1,000 FASL, summer temp. BOD: 240 mg/l, NH 3 -N: 35 mg/l, 1.5 lbs O 2 /lb BOD, 24 hr HRT, 11’ water depth, fine bubble efficiency of 2.0%/ft of subm., 5.5 psi, 1,000 FASL, summer temp. O 2 for BOD would be 325 lbs/hr, O 2 for BOD would be 325 lbs/hr, …or 1,409 scfm (1,656 icfm) of blower air. O 2 for NH 3 -N would be 145 lbs/hr, O 2 for NH 3 -N would be 145 lbs/hr, …or 630 scfm (741 icfm) of blower air.

5 Organic Requirement 1.0 MGD Typical Example: 1.0 MGD Typical Example: Blower Power Required, assuming pd 70% efficiency Blower Power Required, assuming pd 70% efficiency BHP for BOD= (icfm) * (psi) / (229 * eff%) BHP for BOD= (icfm) * (psi) / (229 * eff%) = (1,656 icfm) * (5.5 psi) / (229 * 70%) = 57 HP BHP for NH 3 -N= (icfm) * (psi) / (229 * eff%) BHP for NH 3 -N= (icfm) * (psi) / (229 * eff%) = (741 icfm) * (5.5 psi) / (229 * 70%) = 25 HP 82 HP Total (sizing program gave me 79 HP) 82 HP Total (sizing program gave me 79 HP)

6 Mixing Requirement 1.0 MGD Typical Example: 1.0 MGD Typical Example: Side-roll aeration, 20 cfm/1,000 cf, 24 hr HRT, 11’ water depth, 5.5 psi, 1,000 FASL, summer temp. Side-roll aeration, 20 cfm/1,000 cf, 24 hr HRT, 11’ water depth, 5.5 psi, 1,000 FASL, summer temp. Air required for mixing would be: Air required for mixing would be: cfm= (1 Mgal) / 7.48 cf/gal / 1,000 cf * 20 cfm = 2,674 cfm BHP= (2,674 cfm) * (5.5 psi) / (229 * 70%) = 92 HP (sizing program gave me 89 HP)

7 Energy Consumption What determines the amount of aeration required in an activated sludge plant? What determines the amount of aeration required in an activated sludge plant? It can be the organic loading (Organic Requirement)… It can be the organic loading (Organic Requirement)… but it is often the amount of energy required to keep the basin(s) in suspension (Mixing Requirement). but it is often the amount of energy required to keep the basin(s) in suspension (Mixing Requirement). How does an under-loaded plant operate energy-efficiently? How does an under-loaded plant operate energy-efficiently? How does this relate to Nitrogen Removal? How does this relate to Nitrogen Removal?

8 Ammonia toxicity to aquatic organisms Ammonia toxicity to aquatic organisms Nitrite toxicity to aquatic organisms Nitrite toxicity to aquatic organisms Nitrate toxicity to humans Nitrate toxicity to humans Methemoglobinemia (blue baby syndrome) Methemoglobinemia (blue baby syndrome) Eutrophication Eutrophication Fertilization Fertilization Nutrient Discharge Limits

9 Ammonia Aero-Mod ® Wastewater Process Solutions

10 Hydrolysis of urea Hydrolysis of urea Adds water to the molecule Adds water to the molecule Urea + H 2 O > 2NH 3 + CO 2 Ammonia Production

11 De-amination of organic compounds De-amination of organic compounds Organism breaks protein into amino acids Organism breaks protein into amino acids Removes NH 2 - group from amino acids Removes NH 2 - group from amino acids Amino Acid > Keto Acid (fatty acid) + NH 3 Ammonia Production

12 Oxidation of Ammonia Oxidation of Ammonia Urea (CH 4 N 2 O) => NH 3 => NO 3 - Urea (CH 4 N 2 O) => NH 3 => NO 3 - Protein => Amino Acid => NH 3 => NO 3 - Protein => Amino Acid => NH 3 => NO 3 - Ammonia Reduction

13 Nitrification is accomplished by two unrelated groups of autotrophic microorganisms Nitrification is accomplished by two unrelated groups of autotrophic microorganisms Ammonia-oxidizing bacteria such as Nitrosomonas Ammonia-oxidizing bacteria such as Nitrosomonas Nitrite-oxidizing bacteria such as Nitrobacter Nitrite-oxidizing bacteria such as Nitrobacter Nitrification

14 Consumes 4.6 grams of O 2 per gram of NH 3 -N oxidized Consumes 4.6 grams of O 2 per gram of NH 3 -N oxidized Consumes 7.1 grams of alkalinity per gram of NH 3 -N oxidized Consumes 7.1 grams of alkalinity per gram of NH 3 -N oxidized Forms 0.15 grams of new cells per gram of NH 3 -N oxidized Forms 0.15 grams of new cells per gram of NH 3 -N oxidized Nitrification

15 Nitrite oxidizers cannot proliferate until the ammonia oxidizers have produced enough nitrite for the nitrite oxidizers Nitrite oxidizers cannot proliferate until the ammonia oxidizers have produced enough nitrite for the nitrite oxidizers Different species nitrify at different D.O. levels Different species nitrify at different D.O. levels Clusters of ammonia oxidizers and nitrite oxidizers appear to grow close together within the floc Clusters of ammonia oxidizers and nitrite oxidizers appear to grow close together within the floc Nitrifiers need NH 3 -N, not NH 4 +-N Nitrifiers need NH 3 -N, not NH 4 +-N Nitrifying Bacteria

16 SRT SRT Temperature Temperature pH pH Alkalinity Alkalinity D.O. D.O. Wastewater Characteristics that Impact Nitrification

17 SRT SRT Typically, at least 5 days will be required for stable nitrification Typically, at least 5 days will be required for stable nitrification Wastewater Characteristics that Impact Nitrification

18 Temperature Temperature Colder temperatures require an older sludge age because reproduction slows down Colder temperatures require an older sludge age because reproduction slows down Colder temperatures cause more of the ammonia to be ionized (NH 4 +) Colder temperatures cause more of the ammonia to be ionized (NH 4 +) Wastewater Characteristics that Impact Nitrification

19 pH pH Nitrifiers are sensitive to changes in pH Nitrifiers are sensitive to changes in pH As pH decreases, ionization increases and less NH 3 -N is available As pH decreases, ionization increases and less NH 3 -N is available Wastewater Characteristics that Impact Nitrification

20 pH vs. Alkalinity pH vs. Alkalinity pH is a measure of hydrogen ion concentration pH is a measure of hydrogen ion concentration Alkalinity is a measure of a water’s ability to neutralize acid Alkalinity is a measure of a water’s ability to neutralize acid Water with high alkalinity will always have an elevated pH, but a water with elevated pH does not always have a high alkalinity Water with high alkalinity will always have an elevated pH, but a water with elevated pH does not always have a high alkalinity Both measurements are needed Both measurements are needed Wastewater Characteristics that Impact Nitrification

21 Why Low Alkalinity Affects Nitrifiers Why Low Alkalinity Affects Nitrifiers pH pH Alkalinity neutralizes acid Alkalinity neutralizes acid Inadequate alkalinity results in low pH Inadequate alkalinity results in low pH Carbon Source Carbon Source Nitrifiers cannot use organic compounds for synthesis and growth Nitrifiers cannot use organic compounds for synthesis and growth Bicarbonate/carbonate alkalinity may satisfy their need for an inorganic carbon source Bicarbonate/carbonate alkalinity may satisfy their need for an inorganic carbon source Wastewater Characteristics that Impact Nitrification

22 Chemical Sources of Alkalinity Chemical Sources of Alkalinity For every mg of _______ added, _______ mg of alkalinity as CaCO 3 is gained For every mg of _______ added, _______ mg of alkalinity as CaCO 3 is gained CaOQuick Lime1.8 Ca(OH) 2 Hydrated Lime1.4 Mg(OH) 2 Magnesium Hydroxide1.4 NaOHCaustic1.2 Na 2 CO 3 Soda Ash0.9 Wastewater Characteristics that Impact Nitrification

23 Dissolved Oxygen Dissolved Oxygen Nitrification is an aerobic process and elemental oxygen (O 2 ) is required Nitrification is an aerobic process and elemental oxygen (O 2 ) is required Nitrifiers may not compete as well for oxygen as heterotrophic bacteria Nitrifiers may not compete as well for oxygen as heterotrophic bacteria If not enough oxygen is present, the heterotrophs may get most of it first If not enough oxygen is present, the heterotrophs may get most of it first Wastewater Characteristics that Impact Nitrification

24 Large oxygen requirement Large oxygen requirement Potential low pH (if alkalinity is low) Potential low pH (if alkalinity is low) If pH is low, fungi can develop If pH is low, fungi can develop Discharge of nitrogen as Nitrate Discharge of nitrogen as Nitrate Potential for clarifier denitrification Potential for clarifier denitrification Sludge age range where filaments can develop Sludge age range where filaments can develop Problems Caused by Nitrification

25 Nitrogen Removal Aero-Mod ® Wastewater Process Solutions

26 The other half of biological nitrogen removal The other half of biological nitrogen removal Accomplished by many different kinds of facultative bacteria Accomplished by many different kinds of facultative bacteria Facultative bacteria can use oxygen or nitrate Facultative bacteria can use oxygen or nitrate Denitrifiers are facultative heterotrophs and must have an organic carbon food source Denitrifiers are facultative heterotrophs and must have an organic carbon food source Bacteria forced to use the oxygen in Nitrate Bacteria forced to use the oxygen in Nitrate Denitrification

27 Bacteria reuse about 60% of nitrification O 2 Bacteria reuse about 60% of nitrification O 2 Produces 3.6 grams of alkalinity per gram of Nitrate reduced (about 50%) Produces 3.6 grams of alkalinity per gram of Nitrate reduced (about 50%) Forms about 0.5 grams of new cells per gram of Nitrate reduced Forms about 0.5 grams of new cells per gram of Nitrate reduced Consumes about 2.9 grams of BOD per gram of Nitrate reduced Consumes about 2.9 grams of BOD per gram of Nitrate reduced Denitrification

28 Anoxic zone with nitrate recycle from aeration tank Anoxic zone with nitrate recycle from aeration tank High recycle rate of 2Q to 4Q High recycle rate of 2Q to 4Q Sequenced aeration Sequenced aeration Low D.O. operation Low D.O. operation D.O. Probes & Controller D.O. Probes & Controller VFD Motor Drives VFD Motor Drives PLC Process Controller PLC Process Controller Denitrification Methods

29 A 2 O and Bardenpho A 2 O and Bardenpho SBR SBR Oxidation Ditch w/ Mixed Anoxic Zone Oxidation Ditch w/ Mixed Anoxic Zone MBBR (Moving Bed BioReactor) MBBR (Moving Bed BioReactor) Step feed aeration Step feed aeration SEQUOX SEQUOX Denitrification Designs

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31 D.O. level too high will prevent bacteria from using NO 3 - D.O. level too high will prevent bacteria from using NO 3 - Lack of carbon source available for bacteria Lack of carbon source available for bacteria Recycle rate too low will not bring back enough Nitrate Recycle rate too low will not bring back enough Nitrate Recycle rate too high will shorten detention time of aeration basin Recycle rate too high will shorten detention time of aeration basin High peak flows in an SBR reduces allowed time for aeration on and aeration off High peak flows in an SBR reduces allowed time for aeration on and aeration off High fluctuations of BOD/ammonia disrupt D.O. level High fluctuations of BOD/ammonia disrupt D.O. level Denitrification Issues

32 RAS Clarification 1 st Stage Aeration (Air off) Aerobic Digestion WAS Supernatant Bio-Selector 2 nd Stage Aeration (Air-off) Aerobic Digestion 1 st Stage Aeration (Air on) 2 nd Stage Aeration (Air on) Clarification RAS WAS Supernatant Influent Effluent Aero-Mod SEQUOX Solution

33 RAS Clarification 1 st Stage Aeration (Air on) Aerobic Digestion WAS Supernatant Bio-Selector 2 nd Stage Aeration (Air on) Aerobic Digestion 1 st Stage Aeration (Air off) 2 nd Stage Aeration (Air Off) Clarification RAS WAS Supernatant Influent Effluent Aero-Mod SEQUOX Solution 2 hours later

34 Denitrification without mixers Denitrification without mixers Sequenced aeration with continuous clarification Sequenced aeration with continuous clarification Reclaim portion of oxygen & alkalinity consumed in nitrification Reclaim portion of oxygen & alkalinity consumed in nitrification Concentrated settled biomass consumes D.O. quickly Concentrated settled biomass consumes D.O. quickly Oxygen-starved biomass uses nitrates quickly when basin is re-aerated Oxygen-starved biomass uses nitrates quickly when basin is re-aerated Plug flow pattern ensures several cycles of sequenced aeration Plug flow pattern ensures several cycles of sequenced aeration Common-wall construction provides small footprint Common-wall construction provides small footprint SEQUOX Nitrogen Removal Process

35 SEQUOX Features SEQUOX controls: 1.Where we the air is placed (only 50% of basins aerated at a time) 2.When we aerate basins (simple timer control on typical 2-hour cycle) 3.How much air we provide via VFD control on the aeration blowers 4.How fast we allow the D.O. to rise in the Aeration Basins using a PLC-based D.O. control system to control each blower VFD

36 SEQUOX with DO 2 ptimizer Benefits 1.Energy Savings a. When D.O. is below low set point, blower output increases. ( O rganic Requirement) ( O rganic Requirement) b. When in-between low and high set points, blower output decreases to mixing requirement. ( M ixing Requirement) ( M ixing Requirement) c. When above high set point, blowers can be turned off. ( R est) ( R est) 2.Flexibility when organic loading is high, plant can automatically switch to SEQUOX (both 1 st Stage Aeration Basins aerating) and when the organic loading subsides – go back to SEQUOX-Plus. 3.Nitrogen Removal levels to Total N of 3 mg/l achieved.

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40 NEYCSA - Mt. Wolf, PA 1.70 MGD

41 Neligh, NE 210,000 gpd municipal facility 210,000 gpd municipal facility One 30 HP blower for process and aerobic digester One 30 HP blower for process and aerobic digester Blower operated with manual control of VFD for nine years Blower operated with manual control of VFD for nine years PLC-based D.O. control placed into operation in Fall of 2011 PLC-based D.O. control placed into operation in Fall of 2011 Average of 5,000 kWh reduction per month ≈ $500 savings per month Average of 5,000 kWh reduction per month ≈ $500 savings per month Along with the power savings, plant is also achieving TN reduction Along with the power savings, plant is also achieving TN reduction

42 Holton, Kansas MGD Bio-P

43 Ammonia is oxidized by nitrifying bacteria Ammonia is oxidized by nitrifying bacteria Bacteria use oxygen to strip carbon from alkalinity and hydrogen from ammonia Bacteria use oxygen to strip carbon from alkalinity and hydrogen from ammonia Bacteria use 7.1 mg alkalinity per mg ammonia reduced Bacteria use 7.1 mg alkalinity per mg ammonia reduced Bacteria use 4.6 mg oxygen per mg ammonia reduced Bacteria use 4.6 mg oxygen per mg ammonia reduced Nitrate is reduced product – NO 3 - Nitrate is reduced product – NO 3 - Ammonia Removal - Nitrification

44 Nitrate is reduced by heterotrophic bacteria Nitrate is reduced by heterotrophic bacteria Bacteria use the oxygen from nitrate Bacteria use the oxygen from nitrate DO must be controlled to force the bacteria to use the nitrate DO must be controlled to force the bacteria to use the nitrate Alkalinity is reclaimed – about 3.6 mg per mg of nitrate Alkalinity is reclaimed – about 3.6 mg per mg of nitrate A carbon source must be available for the bacteria to use A carbon source must be available for the bacteria to use Nitrogen Removal - Denitrification

45 Energy Consumption What determines the amount of aeration required in an activated sludge plant? What determines the amount of aeration required in an activated sludge plant?  It can be the organic loading (Organic Requirement),…  but it is often the amount of energy required to keep the basin(s) in suspension (Mixing Requirement)  How does an under-loaded plant operate energy-efficiently? USING SEQUOX & AERO-MOD’S DO 2 PTIMIZER

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47 Custom Designed Wastewater Treatment Solutions


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