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


Other costs of Aeration

Sara Fisk Slide 3

• Aeration equipment itself • Cost for keeping equipment running (maintenance)

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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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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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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

02/27/2015

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


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


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+).


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


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


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


Slide 13 Sara Fisk

02/27/2015

Measuring Principle


Slide 14 Sara Fisk

Products Solutions Services

02/27/2015

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


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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)


Carbon in wastewater

100%

Carbon in CO2 ∼ 50%

Carbon in activated sludge

∼ 50%

Carbon in the outlet ∼ 1%


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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


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Cost factor ‘oxygen demand’

Below 1 mg/l the bacteria activity is decreasing significantly limits and process in danger!


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!


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!

02/27/2015

Main important aerobic process technologies for F&B


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


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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


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Example SBR Reactors



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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


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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



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Process Control Blower/Aeration System


T-mass in the air pipe Pressure at the blower system


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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


02/27/2015



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!


02/27/2015

Appendix: Process Optimization (Liquicontrol)


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 %


02/27/2015


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

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