Choices to Address Filamentous Growth

Transcription

1 Michigan Water Environment Association Process Seminar November 12, 2015 Choices to Address Filamentous Growth Richard Beardslee City of Battle Creek Nathan Cassity Donohue & Associates

2 Outline Battle Creek Introduction Experiences Background Filament Facts Indicators Control Strategies Temporary Long Term Page 2 November 12, 2015

3 Battle Creek Wastewater Treatment Facility Design capacity 27 mgd Currently operating at 9 mgd Flows have decreased over the years Significant loadings from food processors and paper Influent BOD 580 mg/l ( ) 650 mg/l (2015) Page 3 November 12, 2015

4 Battle Creek Wastewater Treatment Facility Page 4 November 12, 2015

5 Battle Creek Wastewater Treatment Facility Nutrient deficiency Insufficient nitrogen and phosphorus for activated sludge based on high BOD loadings Initial control for filament blooms was chlorination of RAS Operators watched for indicators Microscopy, settling, and effluent characteristics Chlorination was started immediately if bloom was detected Page 5 November 12, 2015

6 Battle Creek Wastewater Treatment Facility Nutrient deficiency First attempt for nitrogen and phosphorus addition included monitoring the primary effluent Ortho-P analyzer UV-BOD probe Ammonia probe Nitrogen and phosphorus was dosed based on meeting a 100:5:1, BOD:N:P ratio Started talking with industrial customers Page 6 November 12, 2015

7 Battle Creek Wastewater Treatment Facility Nutrient deficiency Primary effluent monitoring equipment didn t work Recent strategy is manual feed of nitrogen and phosphorus based on lab data (COD, TKN, P) Nitrogen feed, UAN-28: 25 tons annually Phosphorus feed, phosphoric acid: 823 tons annually Page 7 November 12, 2015

8 Battle Creek Wastewater Treatment Facility Phosphorus removal Ferric chloride is regularly dosed for a settling aid in the mixed liquor Adds to the complexity of daily control balancing phosphorus addition and phosphorus removal Winter effluent limit 1 mg/l Summer voluntary TMDL limit of 0.5 mg/l Page 8 November 12, 2015

9 Battle Creek Wastewater Treatment Facility Filamentous bulking episodes Prior to dosing N and P, blooms were occurring every 2 weeks Current control has reduced frequency of blooms Control using RAS chlorination has always been an effective tool Page 9 November 12, 2015

10 Background on Filament Growth

11 Filaments Are Important Components of Mixed Liquor Too Few Filaments Moderate Filament Growth Filamentous Bulking Condition Page 11 November 12, 2015

12 Sludge Volume Index (SVI) An Indicator of ML Settleability SVI < 60 ml/g Too Low, Not Enough Filaments, Fine Solids in Effluent SVI = ml/g Good Settling ML, Clear Effluent, Compact Blankets SVI = ml/g Fair Settleability, Clear Effluent SVI = ml/g Marginal/Poor Settleability, Clear Effluent SVI > 250 ml/g Poor Settleability/Bulking Page 12 November 12, 2015

13 So you think you have filaments? Don t jump to conclusions Stepwise Approach: A. Identify the Filament (send sample to lab) RAS Chlorinate in the meantime B. Research the Filament (what does it like) C. Critique your Environment (what s causing it) D. Identify and Implement a Solution Page 13 November 12, 2015

14 Primary Causes of Bulking Needed Compound Lacking or in Short Supply Nutrient Deficiency Low Dissolved Oxygen Concentrations Low Substrate (Food/BOD) Concentrations High SRT Different causes result in the propagation of different filamentous organisms. Page 14 November 12, 2015

15 Why do filaments bloom Floc-forming organism Filament Filaments higher surface area provides a selective advantage when essential food / nutrients / DO are limiting. Page 15 November 12, 2015

16 Control Strategies

17 Bulking Control Strategies Kill the Filaments RAS Chlorination Baseline Provision Modify Environmental Conditions to Eliminate What s Causing the Filaments Nutrient Addition Basin Configuration/Feed Pattern Aeration Upgrades System SRT Page 17 November 12, 2015

18 RAS Chlorination Basics Preferred Feed Point Location RAS Line Good Mixing Contacts All Mixed Liquor Several Times Per Day Feed Rate Basis Pounds of Chlorine Applied Per Day Per 1,000 Pounds of Mixed Liquor Suspended Solids in the System Page 18 November 12, 2015

19 RAS Chlorination Feed Rates Maintenance Dosage 1-2 lbs Cl 2 /1,000 lbs MLSS/day Can Apply 24/7 Toxic Dosage Hit em Hard for Limited Periods Aggressive 4-8 lbs Cl 2 /1,000 lbs MLSS/day Very Aggressive 8-12 lbs Cl 2 /1,000 lbs MLSS/day Only Apply for 4-8 hours Every 3-4 days, Using Maintenance Dose Rest of Time Be Very Careful, Particularly at Very Aggressive Rates Page 19 November 12, 2015

20 Modify Environmental Conditions Nutrient Deficiency BOD:N:P Ratio of 100:5:1 is Good Target Nutrient Addition Page 20 November 12, 2015 Battle Creek Primary Effluent Date BOD TKN Tot-P 07/12/ /14/ /16/ /19/ /21/ /23/

21 Modify Environmental Conditions Nutrient Deficiency BOD:N:P Ratio of 100:5:1 is Good Target Nutrient Addition UAN-28 and Phosphoric Acid Page 21 November 12, 2015 Battle Creek PE including N + P Dosing Date BOD TKN Tot-P 07/12/ /14/ /16/ /19/ /21/ /23/

22 mgn/l Modify Environmental Conditions Nutrient Deficiency Conceptual Profile Nitrogen Excess PE Pass 1 Pass 2 Pass 3 NH3-N NOX-N Page 22 November 12, 2015

23 mgn/l Modify Environmental Conditions Nutrient Deficiency Battle Creek: 3 of 6 days showed similar numbers /15/15 Nitrogen Profile Pass 1 Pass 2 Pass 3 NH3-N NOX-N Page 23 November 12, 2015

24 Modify Environmental Conditions Nutrient Deficiency Battle Creek initial recommendations Increase UAN-28 dosing Start monitoring effluent nitrate concentration Page 24 November 12, 2015

25 Recommended Chemical Dosing Strategy Pass 1 Zone 1 Pass 1 Zone 2 Pass 1 Zone 3 Ferric Chloride Primary Effluent Pass 2 Zone 2 Pass 2 Zone 1 Effluent Pass 3 Zone 1 Pass 3 Zone 2 Phosphoric Acid UAN FeCl 3 Metering Pump Speed WAS UAN Metering Pump Speed PLC NOx-N (mg/l) NH3-N (mg/l) Phos. Acid Metering Pump Speed PO 4 -P (mg/l) Page 25 November 12, 2015

26 Modify Environmental Conditions Select Against Filaments Example Convert From Complete Mix to Plug Flow PE Low F:M PE Variable F:M RAS RAS Complete Mix Bioreactor Plug Flow Bioreactor To Clarifiers To Clarifiers Page 26 November 12, 2015

27 Modify Environmental Conditions Add Selector Zones Upstream of Aeration Basins. In f W W (P E ) R A S M M L T o C la rifie r S e le c to r Z o n e B a ffle W a ll A e ra tio n Z o n e Page 27 November 12, 2015

28 Selectors Provide Environmental Conditions Which Promote Growth of Floc Formers High Substrate Concentration Eliminates Filament Size Advantage Short Detention Time Takes Advantage of Substrate Storage Capabilities of Floc Formers Anoxic or Anaerobic Conditions Takes Advantage of Floc Formers Anoxic or Anaerobic Respiration Capabilities Page 28 November 12, 2015

29 Typical Anoxic Selector Configuration M ix ed L iq u o r R ecycle In f W W (P E ) R A S M M L T o C larifier S electo r Z o n e B affle W all A eratio n Z o n e Nitrate is supplied to the selector zone via mixed liquor recycle and RAS. Page 29 November 12, 2015

30 Anoxic Selector Upstream of Plug Flow Aeration Basin Page 30 November 12, 2015

31 Anoxic Selectors Can Provide Additional Benefits Reduced Aeration Requirements 2.86 mg of oxygen equivalent is supplied for every 1 mg of nitrate denitrified to nitrogen gas Reduced Consumption of Alkalinity Nitrification consumes 7.1 mg alkalinity for each mg of ammonia nitrified to nitrate Denitrification produces 3.6 mg alkalinity for each mg of nitrate denitrified to nitrogen gas Page 31 November 12, 2015

32 Simple Anaerobic Selector In f W W (P E ) R A S M M L T o C la rifie r S e le c to r Z o n e B a ffle W a ll A e ra tio n Z o n e Anaerobic/aerobic cycling provides environment selecting for PAOs. Bio-P Bugs Settle Fast Page 32 November 12, 2015

33 Battle Creek West Aeration Tanks Recommended selector layout Baffle Wall (Typical of 16) Diffuser Modifications (Typical of 8) Selector Mixer (Typical of 16) Page 33 November 12, 2015

34 Selectors Are Not Always Effective You Must Prevent Bleed Through of Soluble Substrate to Bulk Aeration Basin Target < 60 mg/l Soluble COD (20-30 mg/l SBOD5) Function of Selector Loading and Configuration They Won t Cure Other Problems Nutrient Deficiency Some Filaments Are Immune to Selector Effect Long SRT Filaments Page 34 November 12, 2015

35 Concluding Thoughts Not All Filaments Can Be Controlled By Selectors Not All Bulking Caused By Filaments Microscopic Examination/Identification Provides Very Valuable Information Potential Causes Corrective Actions Key Fundamentals Can t Be Taken For Granted SRT Control Control P Removal Chemical Dosages to Avoid Nutrient Deficient Conditions Maintain Provisions for RAS Chlorination Page 35 November 12, 2015

36 Finally Use the Proven Stepwise Approach to Address the Problem A. Identify the Filament (or that it s not a filament) If It s Filamentous Bulking Start RAS Chlorination B. Research What Factors Favor That Filament (or Condition) C. Evaluate Your Situation For What Might Be Contributing D. Identify and Implement a Solution if Possible Page 36 November 12, 2015