Ammonia Controlled Aeration. CSWEA 85 th Annual Conference. Don Esping, P.E. May 15, 2012

Transcription

1 Ammonia Controlled Aeration CSWEA 85 th Annual Conference Don Esping, P.E. May 15,

2 Ammonia Controlled Aeration Goals Reduced energy consumption Reduced total nitrogen Rieger, WEFTEC 2010 Brown and Caldwell May 15,2012 2

3 Outline Ammonia Sensors Ammonia Aeration Control Strategies Case Studies Close Brown and Caldwell May 15,2012 3

4 Ammonia/Nitrogen Sensors WTW Hach Endress + Hauser Brown and Caldwell May 15,2012 4

5 Santa Clara/San Jose Ammonia Sensor Evaluation Brown and Caldwell May 15,2012 Source: WEFTEC

6 Typical Aeration Basin Control Strategy DO Setpoint DO Controller/PLC Airflow M D.O. Set point Brown and Caldwell May 15,2012 6

7 Ammonia/Aeration Basin Control Strategies NH 4 Setpoint NH 4 Controller/PLC DO Setpoint DO Controller/PLC NH 4 Controller/PLC Airflow M NH 4 Airflow M D.O. NH 4 Set point Set point Ammonia Feedback Control Cascade to DO set point (or visa versa) Example NH4 < 1.5 mg/l then DO setpoint = 0.5 mg/l NH4 >1.6 mg/l then DO setpoint = 2.0 mg/l Brown and Caldwell May 15,2012 7

8 Ammonia Feed Forward Feedback Control NH 4 Controller/PLC NH 4 Setpoint(Max) NH 4 Airflow M NH 4 Set point Brown and Caldwell May 15,2012 8

9 Ammonia Feed Forward Feedback Control NH 4 Controller/PLC NH 4 Setpoint(Max) NH 4 Airflow M D.O. NH 4 Set point Brown and Caldwell May 15,2012 9

10 Case Example: J.D. Phillips WRF Flow: 8 mgd Design Capacity: 23.6 mgd MLE facility Blowers Small/Large Permit Ammonia ph Brown and Caldwell May 15,

11 Case Example: J.D. Phillips WRF Flow, mgd Primary Effluent Am mmonia, mg N/L Time, hours Flow Ammonia Brown and Caldwell May 15,

12 Case Example: J.D. Phillips WRF Initial Driver: Monitoring NH 3 Brown and Caldwell May 15,

13 Case Example: J.D. Phillips WRF Initial Control Strategy Ammonia cascade loop w/do control DO Setpoint Airflow DO Controller/PLC M D.O. NH 4 Controller/PLC NH 4 Set point Findings Biological response to ammonia slug was fast Control slow to adjust DO setpoint More complexity & difficult to control and tune Brown and Caldwell May 15,

14 Case Example: J.D. Phillips WRF NH 3 NO 3 DO NH 3 Primary Effluent) NH 3 DO NO 3 Brown and Caldwell May 15,

15 Case Example: J.D. Phillips WRF Base Aeration Control Strategy Item Pass B D Ammonia Control Value Effluent NH 4 Setpoint 1.5 mg /L 0.2 mg/l (am only) Comments Operator input Pass B Middle NH 4 Setpoint EffNH4 target * CF1 Algorithm from Historical (70% removal) trends Pass C NH 4 Setpoint EffNH4 target * CF2 (90 % removal) Check on Pass B Sensor Target D.O (Secondary) mg /L Filament control Pass C DO Control D.O Setpoint >0.5 mg /L Prevent denitrification in secondary clarifiers Brown and Caldwell May 15,

16 Case Example: J.D. Phillips WRF Pass B ammonia Pass B D.O. 3.0 Effluent Ammonia setpoint Source: WEFTEC 2010 Brown and Caldwell May 15,

17 Case Example: J.D. Phillips WRF Lessons Learned Sensors are reliable with proper maintenance Calibrate monthly 1 D2 hours/calibration/probe (recommend Hach kits ) Replace sensor caps every 6 months Algorithm takes time to develop and change 20% energy savings Save during offdpeaks Blower turndown essential Beneficial for plant nitrifier upsets PE difficult sensor application head of bioreactor for feed forward control Brown and Caldwell May 15,

18 Case Example 2 U.K. 42Stage Bardenpho Optimized DO Zone 1 = 2.0 mg/l Zone 2 = 2.1 mg/l Zone 3 = 1.6 mg/l Zone 4 = 0.5 mg/l Source: WST, 61.9,2010 Brown and Caldwell May 15,

19 Case Example 2 Aerated Zone Control Primary loop NH 4 Controller/PLC Secondary loop NH 4 Setpoint NH 4 Controller/PLC DO Setpoint DO Controller/PLC NH 4 Airflow M D.O. NH 4 Set point Aerated Zone DO setpoints based upon FeedDForward anoxic zone ammonia using process model correlations Brown and Caldwell May 15,

20 Case Example 2 U.K. 42Stage Bardenpho Min DO or airflow Source: WST, 61.9,2010 Brown and Caldwell May 15,

21 Case Example 2 U.K. 42Stage Bardenpho 20% airflow savings overall Source: WST, 61.9,2010 Brown and Caldwell May 15,

22 Case Example 2 U.K. 42Stage Bardenpho RTC Effluent ammonia setpointof of 1 mg/l Source: WST, 61.9,2010 Brown and Caldwell May 15,

23 Ammonia Aeration Control 2 General Need reliable and accurate sensors test sensors for requirements Control can be more complex Sensor outlay and maintenance More monitoring More maintenance (0.5 to 3 hours/week/device) Cascade loops lag times/fine tuning Historical treatment or process model algorithms FeedDforward provides greater safety w.r.t peak loadings Blower turndown Low D.O. bulking a concern especially if 1 st aerobic zone D.O. <2.0 mg/l Brown and Caldwell May 15,

24 Close Special Thanks Jay Hardison and Bill Hoyt, Colorado Springs Utilities Questions Brown and Caldwell May 15,