Ion Selective Electrodes

Transcription

1 Products Solutions Services Ion Selective Electrodes For Monitoring Ammonium and Nitrate in Wastewater Treatment Plants Slide 1 Sara Fisk

2 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants Ensuring Aeration is only carried out when necessary Aeration is the biggest user of electricity in a wastewater facility Anaerobic Gravity Thickening, Digestion, 11 1 Lighting and Buildings, 6 Belt Press, 3 Wastewater pumping, 12 Chlorination, 1 Return Sludge Pumping, 1 Aeration, 60 Screens, 1 Grit Removal, 1 Clarifiers, 3 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 Slide 2 Sara Fisk

3 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants Other costs of Aeration Aeration equipment itself Cost for keeping equipment running (maintenance) Slide 3 Sara Fisk

4 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants Application Story 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 Slide 4 Sara Fisk

5 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants Application Story (continued) 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 Slide 5 Sara Fisk

6 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants Application Story (continued) 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) 30,000 29,000 28,000 27,000 26,000 25,000 24,000 23,000 22,000 Power cost Slide 6 Sara Fisk

7 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants 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

8 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants 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 Slide 8 Sara Fisk

9 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants 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 (NH 4 +). Slide 9 Sara Fisk

10 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treatment Plants What is nitrification & de-nitrification? Process to convert ammonia to nitrogen gas Nitrification: First, ammonium is converted (oxidized) to nitrite (NO 2 -) with oxygen Then, in a second process to nitrate (NO 3- ) 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 Slide 10 Sara Fisk

11 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants 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

12 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants 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

13 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants 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

14 Ion Selective Electrodes for Monitoring Ammonium and Nitrate in Wastewater Treament Plants Measuring Principle Slide 14 Sara Fisk

15 Products Solutions Services Package 3: Aerobic wastewater treatment COD and Nutrient removal Slide 15 Dr. H. Tippe

16 Water Management in Food Production Aerobic Treatment target Cooling system Processing Product Boiler Safe discharge limits (COD and optionally nutrient parameter as Nitrogen and Phosphorous) Process optimization regarding operational costs e.g. chemical usage, energy demand Waste water pretreatment Advanced WW treatment: 1. Anaerobic treatment 2. Aerobic Treatment Slide 16 Dr. H. Tippe

17 Water Management in Food Production 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% Slide 17 Dr. H. Tippe

18 Water Management in Food Production Oxygen Ammonia - Nitrate Orgabic Carbon + Oxygen Carbon Dioxyde + Water + Bacteria C n + O 2 CO 2 + H 2 O + new Bacteria Aeration ON Aeration Off Ammonia + Oxygen Nitrate NH 4 + O 2 NO 2 NO 3 Nitrate + organic Carbon Nitrogen ( ) NO 3 + C org N 2 NITRIFICATION DE- NITRIFICATION Slide 18 Dr. H. Tippe

19 Water Management in Food Production Cost factor oxygen demand Below 1 mg/l the bacteria activity is decreasing significantly limits and process in danger! Rel. performance of nitrified bacteria [%] Oxygen concentration mg/l 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! To optimize the aeration process, the Oxygen concentration range between mg/l has the ideal cost efficiency ratio! Slide 19 Dr. H. Tippe

20 Water Management in Food Production 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 Nitrification (~ 30 min) Denitrification Aeration Stirring 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 Filling Aeration Stirring Sedimentation Discharge Slide 20 Dr. H. Tippe

21 Water Management in Food Production Main important aerobic process technologies for F&B Membrane Bio Reactor 1 2 Advantages Substantial removal of Total Suspended Solids and organic compounds. Less land space required (only version 1) Disadvantage higher specific energy demand Slide 21 Dr. H. Tippe

22 Water Management in Food Production Example SBR Reactors Slide 22 Dr. H. Tippe

23 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% 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 Energy demand: 0,5 kwh/m3 waste water Slide 23 Dr. H. Tippe

24 Basic process units and their instrumentation Instrumentation of an aeration basin 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 ph Potentiometric CPS11D Liquiline CM4X Memosens technology Temperature Pt100 Suspended Solids optical CUS51D Ammonia NH4 ISE CAS40D Nitrate NO3 optionally: COD / SAC ISE Optical Optical (Analyzer) CAS40D CAS51D CAS51D inlet control Slide 24 Tippe/ Schmidt

25 Water Management in Food Production Process Control in the Aeration Slide 25 Dr. H. Tippe

26 Water Management in Food Production Process Control Blower/Aeration System T-mass in the air pipe Pressure at the blower system Slide 26 Dr. H. Tippe

27 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 Air 02 NO3 NH4 2-parameter ISE Return Activated Sludge Parameter: Oxygen - no over-aeration! Ammonia - indicates end of Nitrification - optimize aeration time Nitrate - indicates end of Denitrification Slide 27 Dr. H. Tippe

28 Water Management in Food Production Appendix: Process Optimization NH4 and NO3 measurements allows an automatic adjustment of the O 2 setpoint by load detection safe outlet limits with minimal energy costs Save the limits also in case of high load! Using energy saving potential during low load NH 4 comparative aeration basin NH 4 control by Endress+Hauser Specific O2 concentration set point Slide 28 Dr. H. Tippe

29 Water Management in Food Production Appendix: Process Optimization (Liquicontrol) Concentration [mg/l] Intermittent Reactor - WWTP Germany DO NH4 Before installation: Time-based controller Irregular blower activity Tremendously high oxygen and ammonium values No load-dependency 0 0:00 4:48 9:36 Time 14:24 19:12 0:00 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 Energy saving: 21.7 % Concentration [mg/l] Intermittent Reactor WWTP Germany DO NH4 0 0:00 4:48 9:36 Time 14:24 19:12 0:00 Slide 29 Dr. H. Tippe

30 Aerobe waste water treatment 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. Starting point Energy costs 110,000 CHF End point Energy costs: 63,0000 CHF Yearly energy saving effect CHF/a Needed investment CHF (blower, instrumentation, installation, software ) ROI = 17 months Slide 30 Tippe/ Schmidt