Nutrient Removal Processes MARK GEHRING TECHNICAL SALES MGR., BIOLOGICAL TREATMENT

Transcription

1 Nutrient Removal Processes MARK GEHRING TECHNICAL SALES MGR., BIOLOGICAL TREATMENT

2 Presentation Outline 1. Nutrient removal, treatment fundamentals 2. Treatment strategies Treatment methods: CAS, SBR, Ox Ditch Case stories Mixing integration 2

3 Wastewater Treatment Basics Biological Oxygen Demand (BOD)» Depletes oxygen» Relatively Easy to Remove Nutrients» Nitrogen and Phosphorus» More difficult to remove» Promote aquatic plant growth, resulting in Hypoxia = Low dissolved oxygen caused by decaying aquatic plant life Point and non-point sources» Point (WWTP)» Non-point (run-off) 3

4 Technologies Available Biological Activated Sludge Removal of BOD, TSS, Nitrogen & Phosphorus Physical & Chemical Tertiary Filtration Removal of TSS, which also captures N and P that are contained in the mixed liquor solids 4

5 Activated Sludge what is this stuff? Culture of microorganisms mixed with wastewater in an aerobic/anoxic/anaerobic environment for the removal of organic matter and nutrients. 5

6 Basic Terminology MLSS: Mixed Liquor Suspended Solids, biomass or microorganism mass including other particulates. F/M Ratio: F is the food or biodegradable organic matter (BOD 5 ). M are the microorganisms or MLSS. SRT (or MCRT): solids retention time or mean cell residence time is the average duration of time an organism spends in the system. Often the first step in plant design, dictated by need to nitrify and wastewater temperature. 6

7 Solids Retention Time (SRT) MLSS (lbs) = V (MG) * [MLSS] (mg/l) * MLSS Volume (lbs) Effluent TSS (lbs) WAS (lbs/d) SRT = SRT = MLSS (lbs) WAS (lbs/d) V (MG) * [MLSS] (mg/l) Q (MGD) * [MLSS] (mg/l) WAS (lbs/d) = Q was (MGD) * [MLSS] (mg/l) * SRT Defines Tank Volume 7

8 Sludge Age Impacts - Oxygen Demand (endogenous respiration) - Sludge Quantity & Composition - Nitrification - Phosphorus Removal - Alkalinity 8

9 Bacteria Impact of SRT 9

10 Basic Terminology Anaerobic: Absent of dissolved oxygen and chemically bound oxygen. Anoxic: Aerobic: Absent of dissolved oxygen, chemically bound oxygen present (NO 3 -N). Dissolved oxygen and chemically bound oxygen present. 10

11 Bacteria who and what are they? HETEROTROPHS (BOD OXIDIZING ORGANISMS) Microorganisms that use organic carbon compounds as their C source. Most absorb the C as soluble material from environment. AUTOTROPHS (AMMONIA OXIDIZING ORGANISMS) Microorganisms that use CO 2 as their (only) C source. Most absorb the C as soluble inorganic material from aqueous or gaseous environment. 11

12 Influent Parameters and Design Impacts 1. Flow» Basin size 2. BOD 5 Mass Load» Basin size» Aeration system size 3. TSS» Basin Size 4. Nitrogen» Aeration system size» Aerobic/anoxic environment 5. Phosphorus» Anaerobic environment 6. Temperature» Basin size 12

13 Nitrification Temperature 4-45 C For every 10 C drop, nitrifier growth rate will drop by 50% Alkalinity 50 mg/l as CaCO 3 min. ph D.O mg/l (>2.0) ORP +250 mv SRT days (temp dependent) Nitrifiers (autotrophic) are more susceptible to toxicity than BOD removers (heterotrophic) and slowest growing. 13

14 Denitrification Nitrate and organic carbon in presence of facultative heterotrophs + anoxic conditions results in O 2 + N 2» 2.86 g O 2 recovered / g NO 3 -N denitrified External carbon source (requirements based on influent) - ratio of 5 to 1 BOD to TKN is ideal Alkalinity recovered» 3.54 g as CaCO 3 / g of NO 3 -N denitrified Oxidation reduction potential (ORP) -50 to +50 mv 14

15 Phosphorus Macronutrient for biomass (100C:2P) Domestic sewage total-p 6-20 mg/l Typical U.S. municipal = 8 mg/l or lb/d/cap Organic-P (organically bound-tissue) 2-5 mg/l Inorganic-P (ortho- and poly-p) 4-15 mg/l P content in sludge 2% - 7% Biological, chemical, and physical removal processes 15

16 Enhanced Biological Phosphorus Removal Create environment favorable to Phosphorus Accumulating Organisms (PAO s) Step 1: Anaerobic Phase Phosphorus release Step 2: Aerobic Phase Phosphorus uptake and creation of new PAOs Phosphorus removal by sludge wasting 16

17 Enhanced Biological Phosphorus Removal Successful bio-p removal depends on: - Anaerobic conditions (zero dissolved oxygen and zero nitrate) - Volatile fatty acids (VFA, rbcod) - Solids management (SRT, WAS, and side streams) 17

18 Factors Affecting Biological Phosphorus Removal TPout = TPin - {(BODin - BODout) x Y x TPps} D.O. (aerobic phase) 2 mg/l D.O. (anaerobic phase) 0 mg/l ORP >- 50 mv SRT (Days) BOD / P 20 (minimum) Minimal Nitrate 18

19 2. Treatment Strategies

20 Nutrient Removal Heat Map EPA Identified Nutrient Removal Priority States*: WI, MN, FL, NY, NJ, MA, DE, RI, HI, NE, SC, WV Watersheds: Chesapeake Bay Mississippi River * ID as either 1, 2 or more waterways with N and/or P criteria

21 Nitrification Influent Aerobic Clarifier Effluent RAS WAS 1. Organic N in influent converted to Ammonia 2. Autotrophs oxidize ammonia to Nitrate in Aerobic zone 21

22 Denitrification Internal Recycle ( % Q) Influent (Q) Anoxic Aerobic Clarifier Effluent RAS (50-100% Q) WAS 1. Organic N in influent converted to Ammonia 2. Autotrophs oxidize ammonia to Nitrate in Aerobic zone 22

23 Denitrification Internal Recycle ( % Q) Influent (Q) Anoxic Aerobic Clarifier Effluent RAS (50-100% Q) WAS 1. Nitrates from Aerobic zone recirculated to Anoxic zone 2. Facultative Heterotrophs use Nitrates to oxidize influent BOD in Anoxic stage, producing Nitrogen Gas 23

24 Advanced Denitrification Internal Recycle (400 % Q) Influent (Q) Anoxic 1 Aerobic Anoxic 2 Post Aerobic Clarifier Effluent RAS (100% Q) WAS 1. Anoxic 2 zone reactions similar to zone 1, except BOD produced by endogenous respiration or carbon addition 2. Post aeration to promote aerobic conditions prior to clarifier 24

25 Basic Biological Phosphorus Removal Influent (Q) Anaerobic Aerobic Clarifier Effluent RAS (50-100% Q) WAS 1. Phosphorus release in Anaerobic Zone 2. Phosphorus uptake in Aerobic zone 25

26 Enhanced Biological Phosphorus Removal Internal Recycle ( % Q) Influent (Q) Anaerobic Anoxic Aerobic Clarifier Effluent RAS (50-100% Q) WAS 1. Phosphorus release in Anaerobic Zone 2. Denitrification in Anoxic Zone 3. Mixed liquor recycle from Anoxic to Anaerobic zone to minimize nitrate concentration in Anaerobic zone 26

27 Advanced Nitrogen and Phosphorus Removal Internal Recycle (400% Q) Influent (Q) Anaerobic Anoxic 1 Aerobic Anoxic 2 Post Aerobic Clarifier Effluent RAS (100% Q) WAS 1. Mixed liquor recycle from Anoxic zone to Anaerobic Zone is not necessary, as nitrate concentration in the RAS stream is low. 27

28 Limits of Enhanced Biological Phosphorus Removal With Anaerobic Zone, but without Anoxic Zone < 1 to 2 mg/l TP With Anaerobic and Anoxic zones < 0.5 to 0.8 mg/l 28

29 Chemical Phosphorus Removal Precipitation or adsorption with chemical addition - Ferric chloride (ferric) - Aluminum sulfate (alum) - Poly aluminum chlorides (PAC) Effluent soluble P concentrations Can be reduced to < 0.05 mg/l 29

30 Benefits of Tertiary Treatment Gravity separation (0.8 to 1.0 mg/l) Physical removal filter or membrane (0.05 mg/l to 0.5 mg/l) 30

31 Tertiary Treatment vs. MBR Tertiary Treatment Lower chemical cost, as biological process can be isolated from chemical precipitation process Larger footprint for filtration equipment MBR - Higher chemical cost, as chemicals added to precipitate phosphorus inhibit biological phosphorus removal - Smaller Footprint 31

32 Sanitaire Bioloop Oxidation Ditch Activated sludge process solving challenges of energy efficiency, nutrient removal, and flexibility with a complete system solution. Energy Efficient Operating Flexibility Tailored Process Design

33 Bioloop Energy Efficient Energy efficient equipment. Independent aeration & mixing dependency on aeration equipment for mixing is eliminated. Deeper tanks lead to increase aeration efficiency compared to mechanical surface aerators. AERATION MIXING RECYCLE PUMPS OSCAR

34 Bioloop Operating Flexibility Independent Aeration & Mixing + = Advanced Process Controls Optimize Treatment & Energy Performance AERATION MIXING OSCAR

35 Bioloop Tailored Process Design Activated sludge, often characterized as extended aeration Combination of anaerobic, anoxic, aerobic tanks Multiple processes available: NIT: aerobic only MLE (Modified Ludzack-Ettinger): anoxic + aerobic A 2 O: anaerobic + anoxic + aerobic Bardenpho 4-stage Bardenpho 5-stage Multiple Ditches Series

36 Combining Mixing and Aeration Optimized combination of aeration and mixer design is vital for the total efficiency Liquid velocity to overcome losses caused by aeration Optimize bubble retention time in the water Minimizing local energy losses with optimized placement of mixers and aeration

37 Bioloop Applications Municipal & industrial wastewater Retrofit existing surface mechanical facilities Biological phosphorus removal BOD 5 & TSS reduction Nitrification & denitrification

38 Bioloop System Scope of Supply Diffused aeration Blowers Mixers Recycle Pumps Controls & Instrumentation Process Design Performance Guarantee 38

39 Advanced Process Control Solution (OSCAR)

40 Retrievable Aeration Systems Removal of the aeration system out of the basin without basin dewatering 40 Benefits: Fits where you can t build a second basin Lowers CAPEX Reduces Footprint

41 Conversion of Ditches with Mechanical Aerators to Fine Bubble with Submersible Mixers South Water Reclamation Facility, Orlando, FL 78 MLD 52% energy savings Eunice, LA 4 MLD 50% energy savings 41

42 Ditch in Series Retrofit Tifton, Georgia 6 MGD Previous mechanical surface aerator/mixer Process design System responsibility Integrated control package DO/ORP control 42

43 Optional Performance Guarantees Capable of BNR Effluent Quality: - TN < 5 mg/l (<3 with filter) - TP < 1 mg/l (<0.05 mg/l with chemical polishing & filter) Effluent quality guarantee based on 30-day performance test Two options for energy guarantee: Clean water shop test followed by field blower power test at design airflow rate 30-day field performance test 43

44 Why Bioloop? Energy efficiency Independent aeration and mixing. Wide range of operation Deeper tanks (smaller footprint) Proven effluent quality Avoids misting / icing in cold climates

45 ICEAS Intermittent Cycle Extended Aeration System Continuous Flow Sequencing Batch Reactor ICEAS Single Basin Reactor

46 Comparative requirements - SBR vs ASP Conventional ASP HEAD WORKS PC PC ASP FC FC SBR Plant HEAD WORKS SBR 1 SBR 2 SBR 3 SBR 4 RAS BENEFITS 30-50% Less land area Lower Construction costs Less mechanical equipment Reduced pipework complexity

47 SBR Fill and Draw Theory Influent 1. Fill (Aerobic / Anoxic) 2. React 3. Settle 4. Draw Effluent Influent valves required 5. Idle Waste Sludge

48 ICEAS Operating Cycle Continuous Flow 1. React 2. Settle Continuous Flow 3. Decant Treated Effluent Waste Sludge

49 49 Complete System: Process Equipment & Controls

50 Conventional SBR vs. ICEAS Screened Degritted Influent SBR 1 SBR 2 Shortcomings of Batch SBR vs. ICEAS: Need 2 reactors or balancing tank Complicated valve arrangements & control Final Effluent Cannot easily remove basin from service for maintenance Carbon source interrupted in react phase reducing ability to remove nitrogen and phosphorus Unequal loading of basins during diurnal cycle causes control problems. Each tank is a treatment plant.

51 ICEAS/SBR vs. Conventional BNR 51

52 ICEAS vs. Conventional SBR Smaller Footprint Aerobic, Anoxic, Anaerobic & Settling Occurs in Same Basin Time Based Control Built in Decanter High Peak to Average Flow Ratio (5:1) Less Mechanical Components Ease of Process Upgrades 52

53 Summary Planning for future BNR requirements during initial design will ease the upgrade process. Preparing: Basin Size Blower and Grid Size Control Panel Mixers Can lead to meeting and exceeding design parameters. 53

54 ICEAS Experience Operating in the U.S since 1985 Over 600 ICEAS Facilities in USA (>900 worldwide) 10,000 GPD MGD ADF Municipal and Industrial Applications Proven BNR Effluent Quality - TN < 5 mg/l (<3 with filter) - TP < 1 mg/l (<0.05 mg/l with chemical polishing & filter)

55 Optional Performance Guarantees Effluent quality guarantee based on 30-day performance test Two options for energy guarantee Clean water shop test followed by field blower power test at design airflow rate 30-day field performance test 55

56 Mixers in wastewater treatment digesters sludge holding pump station grit chamber biological treatment retention basin

57 Flygt Mixer portfolio Submersible compact mixers Compact HE 4650 LSPM Top entry agitators Submersible midsize Submersible low-speed mixers kW Jet mixers Hydro ejectors JT4710 JT4715 JT4720 JT4730 JT4735 JP4710 JP4715 JP4720 Ultra-low-head pumps PP4630-PP4680 Installation Equip.

58 Oxidation ditch blending, circulation, suspension

59 BNR blending, solids distribution, suspension

60 Selection guidelines - summary 4400 series 4600 series 4800 series JT4700 series JP4700 series Wastewater Liquid Thick sludge (> 4%) - Abrasive or corrosive fluid Horizontal flow, flat tank - Tank Vertical flow, tall tank - - Sealed tank - Low liquid level (< 1 m) - - Energy efficient Economy Lean installation Easy service Durability Other Motor type integrated integrated standard integrated integrated = excellent = good = average - = typically not recommended Exceptions apply. Each case must be considered individually.

61 Questions?