Optimizing Nutrient Removal With Instrumentation. John Rutledge Hach RSM-Wastewater in NC & SC

Transcription

1 Optimizing Nutrient Removal With Instrumentation John Rutledge Hach RSM-Wastewater in NC & SC

2 Nutrients Nitrogen & Phosphorus Both are essential for plant & algae growth Both are present in municipal wastewater plant effluents Some industrial applications require the addition of nutrients

3 Lack of Nutrients What if your water doesn t have enough nutrients (N or P) to support the microbial growth? C:N:P Ratio The microorganisms have a high demand for N & P If the wastewater is low in N and/or P then the removal of C is inhibited. Desired Ratio: 100:5:1 (BOD to Nitrogen to Phosphorus)

4 Managing the C:N Ratio If the C:N ratio is smaller than 25:1, then excess ammonia (NH3/NH4+) will be generated. If the C:N ratio is larger than 35:1 then the biological removal of organics (BOD) will be inhibited.

5 C:N:P Ratio Strategies In wastewater plants when there is not enough carbon to cause nitrification / denitrification then methanol is often added as a carbon source. In plants where there is not enough nitrogen to facilitate organic removal (BOD) then ammonia (gas or liquid) is often added as a nitrogen source. In plants where there is not enough phosphorous to facilitate organic removal (BOD) then phosphorous (phosphoric acid) is often added as a phosphorous source.

6 Nitrogen Inorganic nitrogen Ammonia, NH 3 Nitrate, NO 3 - Nitrite, NO 2 - Nitrogen gas, N 2

7 Organic Nitrogen Organic nitrogen is found in living organisms: Proteins Peptides Nucleic acids (DNA, RNA) Urea Also found in decaying dead organisms.

8 Nitrogen Inorganic nitrogen changes forms by the processes of nitrification and denitrification.

9 Forms of Nitrogen Denitrification: Nitrate Nitrite Ammonia Nitrogen Gas Microbially mediated Anaerobic bacteria are able to use nitrate (rather than oxygen) in respiration

10 Ammonia (NH 3 ) Occurs naturally due to breakdown of organic nitrogen compounds in water. Ammonia (NH 3 ) can be toxic to aquatic life.

11 Nitrite (NO 2- ) Intermediate step of the nitrification process. NH 3 ó NO 2 - ó NO 3 - Nitrite is not highly stable Tends to be either oxidized to nitrate or reduced to ammonia

12 Nitrate (NO 3- ) Present naturally in surface and ground waters Essential nutrient for plants

13 Why Test for Nitrogen? Why monitored in municipal wastewater? Regulatory purposes Plant efficiency Why monitor in industrial wastewater? Regulatory purposes Process efficiency Must fertilize the microorganisms

14 Why is Nitrogen a Problem? Excess nitrogen in wastewater can be problematic because it: Stimulates algae growth and promotes eutrophication Which can lead to depleted oxygen levels in receiving waters May increase toxicity of water due to ammonia Interferes with chlorine disinfection

15 How do we remove it? Biological Nitrification/Denitrification Breakpoint Chlorination Selective Ion Exchange Air Stripping

16 Biological Removal Equalization Basin Primary Clarifier Aeration Basin Secondary Clarifier Nitrification Basin Plant Inlet (Influent) Gravity Sludge Thickener Return Activated Sludge (RAS) Waste Activated Sludge (WAS) Final Filtration Aerobic / Anaerobic Sludge Digester Sludge Dewatering By controlling DO Levels! 1 Centrate Sludge Disposal Disinfection Plant Effluent 1

17 Biological Removal - Nitrification Nitrification Basin + Ammonia or Nitrite (NO 2- ) + Oxygen (O 2 ) Nitrate (NO 3- ) Microbially mediated process Nitrosomonas oxidize ammonia to nitrite Nitrobacter oxidize nitrite to nitrate ph: (optimal) If less than 6.5 nitrification ceases Temperature: Warmer is better Optimal F No activity < 39 F Alkalinity: 50 mg/l needs to be maintained D.O. levels need to be 4 mg/l or higher

18 Nitrification Basin Biological Removal Denitrification The conversion of nitrates to nitrogen gas + Food + Nitrate (NO 3- ) Nitrogen gas (N) This requires D.O. levels of <1.0 mg/l

19 Nitrogen Forms During Wastewater Treatment NO 3- -N NH 4+ -N Org-N Nitrogen, mg/l Influent

20 Nitrogen Forms During Wastewater Treatment NO 3- -N NH 4+ -N Org-N Nitrogen, mg/l Influent Primary Effluent

21 Nitrogen Forms During Wastewater Treatment NO 3- -N NH 4+ -N Org-N Nitrogen, mg/l Influent Primary Effluent Nitrification

22 Nitrogen Forms During Wastewater Treatment NO 3- -N NH 4+ -N Org-N Nitrogen, mg/l Influent Primary Effluent Nitrification Denitrification

23 Biological Removal Key monitoring parameters: Dissolved Oxygen ph 7.5 to 8.0 Temperature Warmer is better Alkalinity Buffers ph NO 3 - Alkalinity is destroyed in nitrification process N 2 NO 2 - NH 3

24 Nitrogen Analysis Laboratory Analysis Can test for NH 3 -N, NO 3-, NO 2-, or Total N Total Kjeldahl Nitrogen = NH 3 -N + Organic N Does not measure Nitrate or Nitrite TOTAL N TKN Nitrate & Nitrite Organic N Ammonia

25 NH 3 N Analysis Several different procedures available Colorimetric Requires Distillation Nesslerization Method Salicylate Method Electrochemical Ammonia (NH 3 ) gas sensing electrode Ammonium (NH 4+ ) ISE

26 NH 3 N Analysis Colorimetric Nesslerization Method Portable Spectrophotometer Lab Spectrophotometer Salicylate Method PP, TNT, and TNT+ Test Kits PCII Portable Spectrophotometer Lab Spectrophotometer

27 NH 3 N Analysis - ISE Ammonia Electrode Combination type Air gap Assembly

28 Ammonia Analyzer (1) GSE: Gas Sensitive Electrode as detector (2) Air pump to move liquids 5 8 (3) Dosing pump for reagent (4) Electrolyte storage (5) Cleaning solution (6) 2 standard solutions (7) Reagent (8) Membrane storage

29 NH 3 N Analysis Ammonia Analyzer Online analysis Controller/Transmitter Requires filtration Uses Gas Sensitive Electrode Typical sample ranges mg/l NH4-N mg/l NH4-N mg/l NH4-N mg/l NH4-N minute measurement interval 3 months 5 min. interval Accuracy: +/- 2% of measured value or +/- 0.02mg/L NH4-N +

30 Ammonia Analyzer Gas Sensitive Electrode (GSE) (1) Electrode (2) Removable membrane cap (3) Gas Sensitive Membrane

31 Ammonium (NH4) Probe The Economical Insitu Ammonium ISE Sensor

32 Ammonium (NH4) Probe Low cost ammonium probe for trending applications (5% accuracy) Onboard potassium electrode, reference & temp sensors ensure accuracy Sensors use one replaceable cartridge Optional air blast system to extend cleaning interval Range: 0.2 to 1000 mg/l NH4-N

33 Ammonium Probe System calibrates all three sensors against each other Factory calibrated, but validation should be performed 12 hrs after installation Allows for adjustment to wastewater matrix

34 NH4 System Components Controller/Transmitter Sensor for insitu installations + Optional: Cleaning Unit Optional: Any available pressured air or High Output Cleaning System compressor

35 Nitrate NO 3 Analysis Can also be determined by UV light absorbance Nitrate dissolved in water absorbs ultra-violet light at 210nm Reference absorbance measurement taken at 350nm Corrects for organic matter and turbidity

36 Nitrate Probe- NO 3 Analysis Sample Requirements Pressure 0.5 bar Temperature 2 40 C Probe Pathlength & Range 1, 2, and 5 mm pathlength mg/l NO 2+3 -N (1 mm) mg/l NO 2+3 -N(2 mm) mg/l NO 2+3 -N(5 mm) Accuracy ± 3% of the mean ± 0.5 Probe Pathlength & Range 1 mm pathlength mg/l NO 2+3 -N Accuracy ± 5% of the mean ± 1.0 Probe Pathlength & Range 5 mm pathlength mg/l NO 2+3 -N Accuracy ± 5% of the mean ± 0.5

37 Nitrate (NO3) Probe The Economical Insitu Nitrate ISE Sensor

38 Nitrate (NO3) Probe Low cost Nitrate probe for trending applications (5% accuracy) Onboard chloride electrode, reference & temp sensors ensure accuracy Sensors use one replaceable cartridge Optional air blast system to extend cleaning interval Range: 0.5 to 1000 mg/l NO3-N

39 Nitrate (NO3) Probe System calibrates all three sensors against each other Factory calibrated, but validation should be performed 12 hrs after installation Allows for adjustment to wastewater matrix

40 NO3 System Components Controller/Transmitter Sensor for insitu installations + Optional: Cleaning Unit Optional: Any available pressured air or High Output Cleaning System compressor

41 P H O S P H O R U S

42 Phosphorus Phosphorus is a nutrient, essential to growth. Phosphorus can occur as orthophosphate, condensed phosphate, or organic phosphate. Only orthophosphate can be measured directly

43 Why is Phosphorus Important? Essential to the growth of organisms Limiting factor for photosynthesis Excess quantities can cause eutrophication

44 How does Phosphorus Occur? Phosphorus occurs in natural waters and wastewaters primarily in the form of phosphate. Orthophosphate Condensed phosphate Organic phosphate

45 How does Phosphorus Occur? Phosphate ion is also known by the names: O 3 - Orthophosphate Reactive phosphate O P O O

46 How does Phosphorus Occur? Condensed phosphate Metaphosphate polyphosphate pyrophosphate..

47 Where are Condensed Phosphates Found? Condensed phosphates are used in a variety of applications: Corrosion inhibitor for water treatment Laundry or cleaning detergent Treatment of boiler waters

48 How does Phosphorus Occur? Organic phosphate CH 3 CH 2 O S N Cl CH 3 CH 2 O P O Cl Cl Chlorpyrifos

49 Where are Orthophosphates Found? Wastewater plant effluents Fertilizers for agricultural or domestic use Phosphates are carried into surface waters by storm runoff and melting snow.

50 Phosphorus Removal CHEMICAL treatment processes Flocculation & sedimentation Lime (Ca(OH) 2 ), Alum (Aluminum Sulfate), Iron Ferric Chloride, Ferric Sulfate Ferrous Sulfate BIOLOGICAL treatment processes Luxury uptake with chemical addition

51 Chemical Phosphorus Removal Chemical Precipitation Lime, Alum, or Iron is added to the effluent These chemicals bind the Phosphorous and cause it to settle out into a final clarifier and then it s pumped out LIME Plant Effluent CLARIFIER RAPID MIX FLOCCULATION Phosphorus-rich sludge

52 Chemical Phosphorus Removal With Alum, a filter may be necessary: ALUM Plant Effluent RAPID MIX FLOCCULATION CLARIFIER Phosphorus-rich sludge FILTER Effluent

53 Chemical Phosphorus Removal Key Monitoring Parameters: ph 11 or higher Efficiency of phosphate removal

54 Biological Phosphorus Removal Bacteria consume phosphorus for: cell synthesis maintenance energy transport.

55 Biological Phosphorus Removal Key Monitoring Parameters: D.O. levels Anaerobic zones and aerobic zones ph Efficiency of phosphorus removal

56 PhosphorusAnalyzer (1) 2-beam-LED-photometer with well proofed colorimetric method (yellow), two ranges (2) Air pump to move liquids (3) Dosing pump for reagent (4) Cleaning solution (5) Reagent

57 PO4 Analysis Phosphorus Analyzer Online analysis Controller/Transmitter Requires filtration Colorimetric Finish 2 sample ranges LR mg/l PO4-P HR mg/l PO4-P minute measurement interval

58 Sampling System with Filter-Type 1 Mounting pipe Heated hose (5m or 10m) Filtration modules (2) (Click in) Continuous air bubble cleaning Upward flow

59 Sampling System with Filter-Type 2

60 Operating Principle Sample Filtration System Unit prepares the sample through two ultra-filtration membranes (0.15 µ) that are immersed in the process tank

61 Ammonia and Phosphorus Installation with Sampling System (Outdoor/Indoor) NH4-N PO4-P Sample preparation Sample preparation Analyzer Outdoor or Indoor Two Analyzers connected to one sample

62 Ammonia and Phosphorus Installation with Sampling System (2 Parameters and 2 Channels) NH4-N PO4-P Max. 20 m (115V) Max. 30 m (230 V) Max. 20 m (115V) Max. 30 m (230 V)

63 Phosphate Control System Optimizes Phosphate Removal Reduces precipitation sludge Reduces chemical costs 63

64 Phosphate Real Time Control Module (RTC) è Minimized consumption of precipitation agent è Reduced amount of precipitation sludge è Reliable control based on validated measurements è Simple integration into existing plant structure 64

65 Recommended measurement and dosing points è Good mixing of waste water at dosing point è Measurement and dosing point close to each other to reduce reaction time è PO4-P measurement for automated control of precipitant dosing è Ptot measurement for control of effluent quality Vor- Not yet hydrolyzed to PO4-P Simultan- Nachfällung dosing PO4-P Ptot PO4-P Nitrate Internal Recirculation Ptot Rezirkulation Flocculation reactor Sedimentation VK ana anox aerob NK Flockungsreaktor Return Activated Sludge Rücklaufschlamm 65

66 What does it do? Components Analyzer + Filter System Controller Control RTC parameters Signal validation All communication capabilities RTC Calculating set-points in real time Interface for dosing pump Install in PLC cabinet Dosing pump Control pump feed of precipitant based on PO4 concentration Services Installation and setup Instrumentation service contracts On-going service for adjustments and trouble shooting via remote connection supporting installation, optimization and after sales support 66

67 Beaver Dam, WI: 53.4% Ferric Savings Original Dose P-RTC Dose Le Sueur, MN: 41.2% Ferric Savings Original Dose P-RTC Dose

68 Application example for closed loop control WWTP Statistics Size : Flow: Ptot Inflow (min/avg/max): 30,000 population 2 MGD daily average 8 MGD max 5 mg/l Ptot Outlet: 1 mg/l Dosing point: End of aeration Precipitant: FeAl Dosing (avg.) 10 l/h 68

69 Closed loop control of PO4-P 2,0 PO 4 -P [mg/l] Flow [1000 m 3 /h] 40 Dosing [l/h] 1,5 30 Flow [1000m 3 /h] 1,0 PO 4 -P 20 PO 4 -P set - point 0,5 0,0 savings 31. Aug Sep Sep Sep Sep Sep Sep Sep. 09 Compliant effluent values manual dosing [l/h] 10 dosing [l/h] 0 Significant reduction in chemicals and sludge disposal

70 Application example for open loop control WWTP Statistics Size : Flow: Ptot Inflow (min/avg/max): 220,000 population 8-13 MGD 3.43 / 8.46 / mg/l Ptot Outlet: 0.8 mg/l Dosing point: End of aeration Precipitant: FeCl3 Max. Dosing rate: 120 l/h Dosing rate: app. 40 l/h 70

71 Open loop control of PO4-P concentration 140 [mg/l] [l/h] 3,5 [1000 m3/h] 120 3, , Zufluss [1000m 3 /h] Inflow 2,0 1,5 40 Manual dosing 1,0 20 Setpoint 0,5 PO 4 -P Dosing RTC [l/h] 0 0,0 12. Jul Jul Jul Jul Jul Jul Jul Jul. 09 Weekly View - significantly lower dosing rate to meet regulatory requirements 71

72 Open loop control of PO4-P concentration 140 [l/h] 120 3,5 [mg/l] [1000 m3/h] 3,0 Dosis [l/h] 100 2,5 80 PO 4 -P 2,0 60 1,5 40 manual dosing Zufluss [1000m 3 /h] 1, % savings Sollwert 0,5 0, : : : :00 Savings precipitant: $3,700 /month Cost for P-RTC+PHOSPHAXsc: $25,000 Yearly costs: $900 Payback period (w/o sludge): 7 months

73 N/DN Real time control for intermittent and SBR Wastewater Treatment Plants Optimizes Intermittent and SBR denitrification Reduces energy cost Reliable control 73

74 RTC Control Module Nitrification / Denitrification è Minimized energy for aeration è Reliable control of / by NO3-N, NH4-N and Ntot è Balance between Ntot and NH4-N è Reliable control based on validated measurements è Easy integration into existing plant structure 74

75 Easy Installation N/DN Control System Components Signals for aeration: Step (24V) PID - Controller PLC, Instruments AN-ISEsc LDO Controller Setting parameters Signal validation All Controller communication capabilities RTC Calculation of aeration control signal Interface for dosing pump blower control 75

76 Oxidation Ditch WWTP 1 MGD average loading Two identical treatment lanes 2 surface aerators in each lane Loading of trains 50/50 Significant peak loads during rainy weather Aeration strategy lane 1: conventional fixed time schedule Aeration strategy lane 2: RTC N/DN control system Results based on 1 month of simultaneous operation of both lanes 76

77 Results of RTC N/DN Ammonium Control Ammonium AST effluent concentrations 24h composite sample Fixed time NH4-N reduced by: 25% 5 [mg/l] 4 3 WTOS

78 Results of RTC N/DN Nitrate Control Nitrate AST effluent concentrations 24h composite sample NO3-N reduced by: 65% [mg/l] Fixed time NO3-N AST1 - time based WTO S NO3-N AST2 WTOS N/DN 78

79 Results of RTC N/DN Total Nitrogen Control Ntot,inorg AST effluent concentrations 24h composite sample Fixed time 8 NTotal reduced by: 50% [mg/l] WTO S Ntot, inorg AST1 - time based Nges, anorg AST2 - WTOS 79N/DN

80 Summary RTC N/DN Nges,anorg 24h MP Ablaufwert Villau Sauerstoffkonz. 24h MP BB1 / BB2 Villau N O [%] 50 [%] Mittel Standardabw. 0 Mittel Standardabw. Zeitbasiert WTOS N/DN Zeitbasiert WTOS N/DN - Fast reaction to peak loads - Consistent low effluent concentrations - Reliable control 80

81 Optimizing Nutrient Removal With Instrumentation

82 Questions

83 John Rutledge- Hach RSM for wastewater Phone: (704)