For Monitoring Ammonium and Nitrate in Wastewater ... Products Solutions Services Ion Selective...
Transcript of For Monitoring Ammonium and Nitrate in Wastewater ... Products Solutions Services Ion Selective...
02/27/2015
Products Solutions Services
Ion Selective Electrodes
For Monitoring Ammonium and Nitrate in Wastewater Treatment Plants
Slide 1 Sara Fisk
02/27/2015
Ensuring Aeration is only carried out when necessary • Aeration is the biggest user of electricity in a wastewater facility
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Slide 2 Sara Fisk
Aeration , 60
Clarifiers, 3 Grit Removal, 1
Screens, 1
Wastewater pumping, 12
Lighting and Buildings, 6
Belt Press, 3
Anaerobic Digestion, 11
Gravity Thickening, 1
Chlorination, 1 Return Sludge Pumping, 1
Note: For this chart Aeration includes activated sludge aeration in addition to dissolved air flotation thickening process From: How we use energy at Wastewater plants and how we can use less; Marco R Menendez, P. E. Black & Veatch
02/27/2015
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Other costs of Aeration
Sara Fisk Slide 3
• Aeration equipment itself • Cost for keeping equipment running (maintenance)
02/27/2015
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Application Story
Sara Fisk Slide 4
• Demonstrated cost savings by a wastewater reclamation facility • Result of applying pH, DO, ammonium, nitrate and potassium
analytical measurements and shifting control of the aeration blower system based on ammonium measurement in place of DO measurement
• 3 stage activated sludge treatment process • Originally designed to treat up to 20 MGD, currently processing 8 MGD • Secondary treatment has 3 passes
• Pass A for Phosphorus removal and partial denitrification • Pass B Nitrification • Pass C Nitrification
• Must ensure compliance while reducing cost
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Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Application Story (continued)
Sara Fisk Slide 5
• Issues: • Being close to customers was causing rapid fluctuations in ammonia • Operators had a desire to run effluent levels at 0 mg/L to ensure
compliance • Deficiency in BOD • Low alkalinity in system occasionally caused pH excursions outside
acceptable levels • Energy usage high
• Solution: • Source for additonal carbon found (whey) • Analytical instruments evaluated to measure ammonium, nitrate and pH
continuously • Use ammonia data to set aeration levels
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Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Application Story (continued)
Sara Fisk Slide 6
• Customer saw a 17% reduction in energy costs year over year • Even as the average flow passing through the facility increased from
6.4 MGD to over 7.6 MGD (18% increase in flow)
22,00023,00024,00025,00026,00027,00028,00029,00030,000
Power cost
20092010
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Some background – Biological Wastewater Processing
Current Methodology for controlling amount of DO in aeration basins for nitrification • Process or hand held/laboratory DO sensors/systems
What is Biological nitrification or biological nutrient removal? • Process in Wastewater plants to remove harmful ammonia from
wastewater before it can be discharged into receiving bodies of water (lakes, rivers, and streams)
• Ammonia is harmful to the environment. Criteria on ammonia discharge set by US EPA
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Slide 7 Sara Fisk
02/27/2015
Why is Biological Wastewater Processing difficult?
• Flows and times of influent to a wastewater plant are unpredictable • Dependent on time of day, week days vs. weekends, etc. • Precipitation (rain or melting snow) – never constant in timing, duration
or levels • Industrial plants that sent effluent to wastewater plants are dependent
on production schedules, timing of critical processes, different processes on different days/times, level of production
• Wastewater plants must design and incorporate methods and systems to accept a large variable influent and treat accordingly
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Sara Fisk Slide 8
02/27/2015
Nitrogen in Biological or Secondary Treatment
• As influent enters the Biological Treatment process – operators must be aware of level of nutrients within the organic load
• Nitrogen enters the sewer system in many forms • Most prevalent – urea • Food processing wastes • Industrial wastes • In water – organic nitrogen hydrolyzes into ammonium (NH4+).
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Sara Fisk Slide 9
02/27/2015
What is nitrification & de-nitrification?
• Process to convert ammonia to nitrogen gas • Nitrification:
• First, ammonium is converted (oxidized) to nitrite (NO2-) with oxygen • Then, in a second process to nitrate (NO3-)
• De-nitrification: • oxygen is reduced (anoxic) • bacteria (heterotrophic) feed on the nitrate and produce benign nitrogen
gas which bubbles up through the process and is released into the atmosphere
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treatment Plants
Slide 10 Sara Fisk
02/27/2015
Keys to the Conversion Process
• Oxygen • Bacteria need time to thrive • pH (typically in the 6.8 to 7.5 range) • Temperatures
• Example: High temperature and high DO makes for best conversion
rate
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Slide 11 Sara Fisk
02/27/2015
How much Oxygen is enough?
• Too much oxygen is a waste of energy, pump/compressor usage and resulting maintenance
• Too little – and microorganisms become oxygen deprived, process slows, or at worst dies off
• Using Ion Specific Electrode Sensors with DO measurement ensures the right amount of oxygen is maintained
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Slide 12 Sara Fisk
02/27/2015
Ion Selective Electrodes (ISE)
• Directly measure ammonium and nitrate levels during nitrification & de-nitrification
• Use with DO sensors • Together provide wastewater plants with accurate trending
information on the aeration tank
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Slide 13 Sara Fisk
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Measuring Principle
Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants
Slide 14 Sara Fisk
Products Solutions Services
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Package 3: Aerobic wastewater treatment
• COD and Nutrient removal
Slide 15 Dr. H. Tippe
02/27/2015
Aerobic Treatment target
• Safe discharge limits (COD and optionally nutrient parameter as Nitrogen and Phosphorous)
• Process optimization regarding operational costs e.g. chemical usage, energy demand
Water Management in Food Production
Boiler Cooling system
Processing
Product
Waste water pre-treatment
§
Advanced WW treatment:
1. Anaerobic treatment 2. Aerobic Treatment
Slide 16 Dr. H. Tippe
02/27/2015
Carbon Balance in Aerobic Processes
Why does the aerobic process produce so much sludge? Huge specific energy gain for bacteria Fast cell reproduction
(generation time in h)
Advantage Fast process and “complete”
COD (and nutrient) removal Disadvantage Energy demand for aeration
(costs) Sludge production (costs)
Water Management in Food Production
Carbon in wastewater
100%
Carbon in CO2 ∼ 50%
Carbon in activated sludge
∼ 50%
Carbon in the outlet ∼ 1%
Slide 17 Dr. H. Tippe
02/27/2015
Water Management in Food Production
Oxygen – Ammonia - Nitrate
Orgabic Carbon + Oxygen Carbon Dioxyde + Water + Bacteria
Cn + O2 CO2 + H2O + new Bacteria
Ammonia + Oxygen Nitrate
NH4 + O2 NO2 NO3
Nitrate + organic Carbon Nitrogen ()
NO3 + Corg N2
Aeration ON Aeration Off
NITRIFICATION
DE- NITRIFICATION
Slide 18 Dr. H. Tippe
02/27/2015
Cost factor ‘oxygen demand’
Below 1 mg/l the bacteria activity is decreasing significantly limits and process in danger!
Water Management in Food Production
100 100
Oxygen concentration mg/l
Rel.
perf
orm
ance
of
nitr
ified
bac
teria
[%]
0 1 2 3 4
50
0
50
0
1 2
To optimize the aeration process, the Oxygen concentration range between 1.2 … 2.5 mg/l has the ideal cost efficiency ratio!
Slide 19 Dr. H. Tippe
O2 concentrations above 2,5 … 3,0 mg/l don´t result in higher bacteria activity and better results but increase the energy demand waste of energy!
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Main important aerobic process technologies for F&B
Water Management in Food Production
Intermitted Aeration Aerated and non-aerated periods in one basin, but separated by time Sludge removal separately mainly in clarifiers
Aeration Stirring
Denitrification Nitrification (~ 30 min)
Filling Aeration Stirring Sedimentation Discharge
Sequence Batch Reactor (SBR) All important process steps including sludge separation are executed in the same basin. Several SBR reactors are working in parallel with in different stages
Slide 20 Dr. H. Tippe
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Water Management in Food Production
Main important aerobic process technologies for F&B
Advantages
Substantial removal of Total Suspended
Solids and organic compounds.
Less land space required
(only version 1)
Disadvantage
higher specific energy demand
1
2
Membrane Bio Reactor
Slide 21 Dr. H. Tippe
02/27/2015
Example SBR Reactors
Water Management in Food Production
Slide 22 Dr. H. Tippe
02/27/2015
Water Management in Food Production
Example Industrial WWTP (brewery Rothaus, Germany)
10 SBR-Reactors with following membrane filtration • Flow performance: 2400 m3/d • COD Reduction 99,2% • BOD Reduction 99,9% • P-Reduction 95% • N-Reduction 98,5%
Energy demand: 0,5 kWh/m3 waste water
4 Membrane filters in operation:
16 x MID; 4 x Level hydrostatic; 4 x pressure; 4 x Temperature;
4 x suspended solids, 4 x pH; 4 x air flow
Slide 23 Dr. H. Tippe
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Instrumentation of an aeration basin
Basic process units and their instrumentation
Tippe/ Schmidt Slide 24
What Technology Sensor Remarks Flow inlet and sludge pipes
Magmeter PromagL400 PU or HR liner
Flow air pipe thermal tmass 150 optionally Pressure air pipe pressure Cerabar PMC51
/ 131 blower control, indicates blocking
Oxygen optical COS60D Multichannel transmitter Liquiline CM4X Memosens technology inlet control
pH Potentiometric CPS11D Temperature Pt100 Suspended Solids optical CUS51D Ammonia NH4 ISE CAS40D Nitrate NO3 ISE
Optical CAS40D CAS51D
optionally: COD / SAC
Optical (Analyzer)
CAS51D
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Process Control in the Aeration
Water Management in Food Production
Slide 25 Dr. H. Tippe
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Process Control Blower/Aeration System
Water Management in Food Production
T-mass in the air pipe Pressure at the blower system
Slide 26 Dr. H. Tippe
02/27/2015
Water Management in Food Production
Appendix: Process Optimization
Benefit of a NH4/NO3 based control strategy:
• Possibility to ensure outlet limits independent of the
inlet load (peak situations!)
• make energy saving potential visible and usable to
operate under optimal energy conditions
Return Activated Sludge
NO3
NH4
02
Air
Parameter: Oxygen - no over-aeration!
Ammonia - indicates end of Nitrification
- optimize aeration time
Nitrate - indicates end of Denitrification
2-parameter ISE
Slide 27 Dr. H. Tippe
02/27/2015
Water Management in Food Production
Appendix: Process Optimization
NH4 – comparative aeration basin
NH4 – control by Endress+Hauser
Specific O2 concentration set point
NH4 and NO3 measurements allows an automatic adjustment of the O2 – setpoint by load
detection
safe outlet limits with minimal energy costs
Using energy saving potential during low load
Save the limits also in case of high load!
Slide 28 Dr. H. Tippe
02/27/2015
Appendix: Process Optimization (Liquicontrol)
Water Management in Food Production
Before installation: • Time-based controller • Irregular blower activity • Tremendously high oxygen
and ammonium values • No load-dependency
After installation: • Load-based controller
depending on ammonium trigger value 2 mg/l
• Dynamic oxygen setpoint -> load-dependency
• Regular blower activity with less aeration duration
0
0.5
1
1.5
2
2.5
0:00 4:48 9:36 14:24 19:12 0:00
Conc
entr
atio
n [m
g/l]
Time
Intermittent Reactor – WWTP Germany 02.11.2011 DO NH4
0
1
2
3
4
5
6
7
0:00 4:48 9:36 14:24 19:12 0:00
Conc
entr
atio
n [m
g/l]
Time
Intermittent Reactor - WWTP Germany 27.06.2011 DO NH4
Energy saving: 21.7 %
Slide 29 Dr. H. Tippe
02/27/2015
Appendix: Process Optimization
Life Cycle Costs analysis of a municipal WWTP (Switzerland) demonstrates huge costs saving effect and better treatment efficiency thanks to online O2 and NH4 measurement and control.
Aerobe waste water treatment
Slide 30 Tippe/ Schmidt
Starting point Energy costs 110,000 CHF End point Energy costs: 63,0000 CHF Yearly energy saving effect ∆ + 47.000 CHF/a Needed investment 68.000 CHF (blower, instrumentation, installation, software…) ROI = 17 months