Biological Phosphorous Removal Is Coming! Michigan Water Environment Association Annual Conference, June 23, 2008; Boyne Falls MI

Transcription

1 Biological Phosphorous Removal Is Coming! Michigan Water Environment Association Annual Conference, June 23, 2008; Boyne Falls MI

2 EUTROPHICATION CHOPNS CO 2 H 2 0 PO 4 NH 4 SO 4 CHOPNS NO 3 1 lb P grows 138 lbs COD -2 1 lb P grows lbs algae

3 Chemical Phosphorus Removal Chemicals Ferric Chloride Alum Lime Advantages Proven technology Low capital costs High process reliability Enhanced primary treatment Reduced odor potential Disadvantages Chemical costs - extremely expensive with low P limit Increased sludge production Increased solids processing costs B&V - 3

4 How Do We Prepare? Sampling Needed Influent Total and Ortho Phosphorus Perform Jar Tests Compare chemical costs Determine benefits from enhanced primary treatment (TSS and BOD removal) Reduced odor potential Estimate additional solids production and loss of alkalinity B&V - 4

5 Biological Phosphorus Removal B&V - 5

6 Why consider biological treatment? Relative Life Cycle Cost Chemical Addition Conversion to BNR Effluent TP in mg/l B&V - 6

7 Benefit of Combined Systems It is practically possible to reduce soluble phosphorus to levels as low as 0.12 to 0.15 mg/l as P by biological means only Further polishing with chemicals can reduce this to an effluent total P of less than 0.05 mg/l Durham used 175 mg/l of Alum when operating chemical only This was reduced to 25 mg/l when applying biological plus chemical polishing to get 0.07 mg/l as P B&V - 7

8 What are the benchmarks in phosphorus removal? Effluent TP How can it be met mg/l <1 BPR and good clarifiers <0.5 BPR, good clarifiers and filtration <0.1 BPR, filtration and standby chemicals <0.05 BPR, Post chemical plus filtration <0.01 BPR, Chemical, Adsorption, membranes B&V - 8

9 Factors Effecting Biological Nutrient Removal B&V - 9

10 Bio-P Organisms Store PHB and Release P in the Anaerobic Zone rbcod Influent Modified JHB Process Facultative heterotrophs Energy Poly-P Phosphate These are obligate aerobes. They can store but not process Influent Volatile Fatty Acids PHB No dissolved oxygen or nitrates -10

11 Where are VFA Formed? Primary Sources Sludge goes anaerobic and makes VFA H 2 S formed as a byproduct Underground Small Diameter Anaerobic Tubular Reactors Most commonly called a Sewer VFA Supernatant/ Overflow Slime grows on sewer walls and make VFA H 2 S formed as a byproduct PC or Gravity Thickener Sludge B&V - 11

12 Wastewater Characteristics COD Soluble Biodegradable Non-biodegradable rbcod Fus Particulate Biodegradable Non-biodegradable Fbp Fup B&V - 12

13 Carbon to Phosphorus Ratios for Successful BPR Ratios for ensuring Phosphorus Removal COD/P > 40 rbcod/p > 15 VFA/P > 8 to16 B&V - 13

14 rbcod/p ratio Estimate of VFA and rbcod Requirements for Phosphorus Removal Eagle s Point VIP McDowell Creek Durham Reedy Creek These plants are getting fantastic results This line is used in BNR models At this point essentially all rbcod is VFA Fraction of rbcod that is VFA, (VFA expressed as COD) B&V - 14

15 Where Do We Start? Initiate sampling program on raw influent or primary effluent Analyze at a minimum for: VFA ffcod and effluent COD Total and ortho phosphorus Develop plant simulation model This a pre-design activity DO NOT WAIT FOR DESIGN TO START More data is better and reduces unknowns B&V - 15

16 What is ffcod and rbcod? Filtered flocculated COD is a better measure of the truly soluble COD Method uses zinc to enhance precipitation of colloidal solids and then sample is filtered. Filtrate is analyzed for COD. rbcod is a subset of ffcod and is the readily biodegradable material that is a precursor of VFA rbcod = ffcod non-biodegradable COD in plant effluent Effluent COD minus the biodegradable COD (effluent BOD converted into COD basis) B&V - 16

17 Analyze Data to Determine the Potential for Good BPR If rbcod /P is above the line, proceed with Modeling If rbcod/p is below the line, consider fermentation or carbon supplementation rbcod/p ratio Below the line means rbcod is limited and BPR May not work very well Above the line means plenty of rbcod for BPR Fraction of rbcod that is VFA B&V - 17

18 Make ffcod or Add It? Is One Way Better? In a perfect world either approach would work equally well. Microbial competition clouds the issue We want PAOs (Phosphorus Accumulating Organisms) GAOs (Glycogen Accumulating Organisms) do not remove phosphorus but consume acetic acid. Competition for substrate. High GAO accumulation = must add more rbcod = Costs more to operate and makes more sludge The answer is FERMENTATION! B&V - 18

19 Fermentation Makes ffcod and VFA A fermenter is a pickled anaerobic digester Acid formation desired; Avoid Methane formation Propionic Acid Complex Wastes 15% 65% 15% 20% 17% 35% Acetic Acid 72% 13% 15% Methane Other Intermediates VFA and ffcod Concentration, mg/l 4,500 4,000 3,500 3,000 2,500 2,000 1,500 1, B&V - 19 VFA and ffcod Production y = x - 1E+07 R 2 = VFA Linear (VFA) y = x - 1E+07 R 2 = /30/05 12/2/05 12/4/05 12/6/05 12/8/05 12/10/05 Date ffcod Linear (ffcod) VFA Concentration (mg/l) 3,000 2,750 2,500 2,250 2,000 1,750 1,500 1,250 1, /2/05 11:05 AM NO SAMPLE 12/4/05 12:00 PM 12/5/05 10:45 AM 12/6/05 10:55 AM Duplicates 12/6/05 10:55 AM Individual Samples 12/7/05 10:55 AM 12/8/05 10:55 AM 12/9/05 10:55 AM Acetic Acid Propionic Acid Isobutyric Acid Butyric Acid 2-Methylbutyric Acid Isovaleric Acid Valeric Acid

20 Composition of Fermentation Products Butyric 12% Valeric 4% Other 4% Isobutyric 2% Acetic 43% Propionic 35% A large portion of propionic acid is desired to prevent GAO accumulation. B&V - 20

21 GAO out-perform PAO when 1. The temperature is high 2. The ph is low 3. The SRT is too long GAO Domination 4. Acetic acid only is fed to the plant? 5. Glucose is fed to the plant PAO Domination 6. The unaerated zones retention zone is too long B&V - 21

22 McDowell Creek WWTP - Effluent Phosphorus January 2001 through April 2005 Phosphorus, mg/l Effluent TP (mg/l) 30 per. Mov. Avg. (Effluent TP (mg/l)) Historical Monthly Avg P Limit = 1 mg/l 1999 Average = 0.40 mg/l 2000 Average = 0.28 mg/l 2001 Average = 0.20 mg/l 2002 Average = 0.14 mg/l 2003 Average = 0.15 mg/l 2004 Average = 0.13 mg/l 2005 Average = 0.21 mg/l 12 mgd Avg. P Limit = 0.27 mg/l B&V /1/99 3/1/00 6/1/00 9/1/00 12/1/00 3/1/01 6/1/01 9/1/01 12/1/01 3/1/02 6/1/02 9/1/02 12/1/02 3/1/03 6/1/03 9/1/03 12/1/03 3/1/04 6/1/04 9/1/04 12/1/04 3/1/05 6/1/05 9/1/05 12/1/05 3/1/06

23 To Protect PAO Reduce the SRT to the minimum, especially when the temperature is high Do not over-design the plant unaerated zones Add alkalinity when the ph drops below 7 Feed a combination of Propionic and Acetic Acid to the plant Add molasses to fermenter it ferments rapidly to acetic and propionic acid B&V - 23

24 Other Activities Make sure long term data is collected for BOD, TSS, VSS, TKN and TP Develop a good plant hydraulic profile Examine biosolids processing and sidestream return loads Anaerobic Digestion = recycle of P and N Develop advanced process model for the plant and evaluate alternatives B&V - 24

25 Conclusions and Recommendations Initiate sampling program to collect data needed for advanced process modeling Determine probable new permit limits for phosphorus and nitrogen Develop advanced process model for the liquid and biosolids processing facilities Develop plant hydraulic model Make decisions for plant configuration prior to new permit How much will it cost? B&V - 25

26 QUESTIONS? B&V - 26