SHOULD WE KEEP DO FOR NITRIFICATION CONTROL?

Transcription

1 SHOULD WE KEEP DO FOR NITRIFICATION CONTROL? The proof is in the Ammonium Electrodes Standards Certification Education & Training Publishing Conferences & Exhibits Speaker: Robert Lagrange 2012 ISA Water & Wastewater and Automatic Controls Symposium August 7-9, 2012 Orlando, Florida, USA

2 Thanks to Sue Baert Amanda Poole David Green Nick Camin 2

3 Presentation Outline Wheaton Sanitary District Air flow control DO control NH 4 control Colorado Springs Others 3

4 Description Wheaton Sanitary District Design flow 8.9 MGD Peak Flow 19.1 MGD Ammonia Load 16.7 mg/l BOD Load 150 mg/l Process Primary Trickling Filters Aeration Secondary Clarifiers Filters Discharge in Spring Brook 4

5 Wheaton Aeration Flow 5

6 Conditions at Wheaton 2011 from Multistage to Turbo Blower Same capacity This forces the plant to adjust air flow distribution among the tanks to prevent tripping Minimum total air flow (approximately scfm) Step 1: constant air flow Use Thermal Mass Flow One per tank 6

7 Thermal Mass Flow A second transducer is heated A temperature sensor monitors the process temperature The transducer power is proportional to the gas mass flow rate A control loop maintains a defined differential temperature As the massflow increases the cooling of the heated sensor requires an increase of power to maintain the differential temperature. 7

8 Tank 2 Airflow Control Airflow (scfm) FIT-111 (airflow to tank 2) ACP_WTW_NH4N_AVG (NH3 upstream) AIT_110 (D.O. tank 2) Concentration (mg/l) Date - Time 8

9 Tank 3 Air Flow Control FIT-121 (airflow to tank 2) EH_NH4N (NH3 downstream) AIT_120 (D.O. tank 3) Airflow (scfm) Concentration (mg/l) Date - Time 9

10 Conditions at Wheaton Step 2: DO Control Use Optical DO One per tank 20 feet toward the end of the tank 10

11 Optical Dissolved Oxygen Low oxygen High Oxygen 11

12 PID Loop for DO DO Controller DO Set Point Flow Flow 12

13 Tank 3 DO Control FIT-121 (airflow to tank 2) EH_NH4N (NH3 downstream) AIT_120 (D.O. tank 3) Airflow (scfm) Concentration (mg/l) Date - Time 13

14 Installation Tank 3 DO ISE 14

15 Example : Energy Saved with DO reference: TVA Before Installation of DO and Variable Frequency Drive Savings: Peak 39% from 130 kw to 79kW Consumption kwh 13% from 1,550 to 1,350 kwh/d After 15

16 Is DO the real story? Example Hannover DO Flow NADH

17 Hannover DO NADH ISE 17

18 Is DO the real story? Example Hannover NH 4 -N

19 Is DO the real story? Example Hannover DO-- Flow-- NADH-- NH 4 -N-- NO 3 -N-- 19

20 Conditions at Wheaton Step 2: DO Control Use Optical DO One per tank 20 feet toward the end of the tank Step 3: NH 4 control Tank 2 ISE 15 feet into the tank Tank 3 ISE 15 feet toward the end of the tank 20

21 Ion Selective Electrode 21

22 PID control for predictive NH 4 NH 4 Controller NH 4 Set Point Limit on Minimum Airflow v 22

23 Tank 2 NH 4 Control Airflow (scfm) FIT-111 (airflow to tank 2) ACP_WTW_NH4N_AVG (NH3 upstream) AIT_110 (D.O. tank 2) Concentration (mg/l) Date - Time 23

24 Results Step 1 Air flow - 28% Energy (10% of which due to control, 18% to blower) Step 2 DO +9% Energy compared with Step 1 Step 3 NH 4 +6% Energy compared with Step 1 When taking into account flow and BOD load Step 2 consumes 5% more energy (but very high ammonia) Step 3 consumes 6% less energy 24

25 Details FIT-111 (airflow to tank 2) ACP_WTW_NH4N_AVG (NH3 upstream) AIT_110 (D.O. tank 2) Airflow scfm :00:00 0:30:00 1:00:00 1:30:00 2:00:00 2:30:00 3:00:00 3:30:00 4:00:00 4:30:00 5:00:00 5:30:00 6:00:00 6:30:00 7:00:00 7:30:00 8:00:00 8:30:00 9:00:00 9:30:00 10:00:00 10:30:00 11:00:00 11:30:00 12:00:00 12:30:00 13:00:00 13:30:00 14:00:00 14:30:00 15:00:00 15:30:00 16:00:00 16:30:00 17:00:00 17:30:00 18:00:00 18:30:00 19:00:00 19:30:00 20:00:00 20:30:00 21:00:00 21:30:00 22:00:00 22:30:00 23:00:00 23:30:00 Concentration mg/l 25

26 Conditions at Wheaton Finally Feedforward control based on NH 3 (NH 4 ) ISE in the influent splitter box ahead of the aeration tanks Elimination of trickling filters Objectives Very low ammonia in the effluent Discharge to a very small creek Faster response at high flow More stable process 26

27 Another Approach COLORADO SPRINGS UTILITIES 27

28 Influent Ammonia Variations 28

29 Installation points Colorado Springs 29

30 PID control for NH 4 NH 4 Controller High and Low limits on DO NH 4 Set Point v 30

31 Energy Savings Nov vs

32 Other Approaches OTHERS 32

33 PID for DO with Ammonium Cascade NH 4 Controller DO Controller DO Set Point NH 4 Set Point v 33

34 Peoria Beardsley Plant NH 4 DO DO Anoxic Aerobic Filter UV Courtesy Dabkowski Workshop 105 WEFTEC

35 DO + ammonium feed-forward/feed-back control. Controller Feed-forward Maximumcriteria Measured variable DO Controller Ref. variable NH 4 Press. air Manipulated variable NH 4 controller DO f(nh 4 ) O 2 M NH 4 Courtesy Rieger Water Environment Research, Volume 84,

36 Summary DO helps Acceptable for small plants (Eagle Lake: 0.3 MGD) NH 4 control better Feedforward, Feedback, Cascade with DO All 3 Maintenance needed 36