Seeking the Optimum Approach to Generate VFA/rbCOD to Ensure Reliable EBPR at the Robert W. Hite Treatment Facility

Transcription

1 Seeking the Optimum Approach to Generate VFA/rbCOD to Ensure Reliable EBPR at the Robert W. Hite Treatment Facility Kim Cowan, Lab Support Specialist Kurt Carson, O&M Engineer RMWEA JTAC December 17 th, 2015

2 Outline RWHTF facility EBPR upgrades Calculated VFA deficit SCVFA definition VFA/rbCOD: Five options overview Bench testing & process modeling results Pilot testing Conclusions

3 Robert W. Hite Treatment Facility

4 Robert W. Hite Treatment Facility

5 Robert W. Hite Treatment Facility Split Secondary Treatment Different configurations South Secondary is conventional A2O Process North Secondary is a Modified Ludzak-Ettinger retrofitted with a sidestream EBPR Process South Secondary uses VFA/rbCOD in the Primary Effluent North Secondary utilizes VFA/rbCOD in the Gravity Thickener Overflow

6 RWHTF Plan South Plant Mainstream A2O PE is carbon source

7 RWHTF Plan North Plant Gravity Thickener Overflow is the carbon source

8 EBPR Upgrade 1.0 mg-p/l 2018 Tertiary Treatment planned $377M in the CES VFA deficit 2-3 tpd (1,800 to 2,700 kg/day) Our SCVFA (short-chain volatile-fatty acids) definition: Rossle and Pretorius (2001) SCVFA unit: mg-cod/l SCVFA = sum of acetic, propionic, valeric & caproic COD equivalents; normalized as acetic

9 SCVFA What is it? SCVFA = One usable data point Acetic Acid Butyric Acid Iso-butyric Acid Caproic Acid Iso-caproic Acid Propionic Acid N-valeric Acid Iso-valeric Acid SCVFA = Σ(Each SCVFA analyte, converted to COD equivalents, then weighted as acetic) Units = mg/l(acetic)cod

10 SCVFA What is it? Wow, 300 lbs of dogs! That s a lot of dogs! it WOULD be a lot of chihuahuas, but not a lot of mastiffs let s get these dogs on an equivalent standard dog unit. Standard Canine Volume Factor A ok going too far with the metaphor

11 SCVFA What is it? VFA analyte VFA analyte (mg/l) COD equivalent ratio VFA analyte COD equivalent Acetic COD equivalent VFA analyte Acetic COD equivalent SCVFA Acetic Acid Butyric Acid Iso-butyric Acid Caproic Acid Iso-caproic Acid N-valeric Acid Iso-valeric Acid Propionic Acid

12 SCVFA Where does it come from?

13 RWHTF Design Tertiary Polishing The more effective EBPR is in the Secondary Processes, the more aggressive we can get in our design assumptions for tertiary treatment MAJOR potential cost savings if we can optimize reliable Bio-P. $377M currently budgeted.

14 Calculating VFA deficit RWHTF influent 3.4 tons/day PO 4 Centrate return 1.5 tons/day PO 4 Available VFA and rbcod in the Primary Effluent and Gravity Thickener Overflow VFA:P ratio Source SSEC 8:1 WEF, 2010 NSEC 5:1 PAR 1171 field data

15 Total VFA deficit for North and South lb-vfa/day 6784 North VFA deficit lb-vfa/day 3740 South VFA deficit lb-vfa/day 3044 Influent PO4 units average Influent flow mgd 130 inputs Influent PO4 mg-p/l 4.2 calcs flow split to south % 40 output recycle load PO4 flow mgd 1 PO4 concentration mg-p/l 400 P-sequestration efficiency % reduction of recycle P 85 flow split of recycle stream to south % 50 Pre-fermenter available carbon assumed South VFA/PO4 ratio mg-vfa/mg-p 7.5 VFA in Primary Effluent mg-cod/l 25 assumed North VFA/PO4 ratio mg-vfa/mg-p 5 VFA in GTO mg-cod/l 175 GTO flow to SAR mgd 6.9 North calcs flow split to north % 60 influent PO4 mass to north lbs-p/day 2732 flow split to north % 50 recycle PO4 mass to north lbs-p/day 30 pre-fermenter mass VFA in north lbs-vfa/day total North PO4 lb-p/day 2762 estimated required VFA - PAR 1171 observed lb-vfa/day total North VFA lb-vfa/day South Calcs influent PO4 mass to south lbs-p/day 1821 recycle PO4 mass to south lbs-p/day 30 pre-fermenter mass VFA in south lbs-vfa/day total South PO4 lb-p/day 1851 estimated required VFA - literature value lb-vfa/day total South VFA lb-vfa/day 10842

16 VFA/RBCOD: 5 Options 1. Acetic Acid 2. APD 3. Local Recycle Stream 4. Elutration and/or SML addition 5. Repurposed fermenter

17 Option 1 - Acetic Acid Benefits Operational ease Consistency/purity Drawbacks $870K $1.3M Lack of propionic & other SCVFA compounds

18 Option 2 - Acid Phase Digester Effluent Characterization SCVFA = 10,564 mg-cod/l 25% acetic, 38% propionic 442 mg-p/l 569 mg-n/l of total ammonia nitrogen - Net gain 7,470 mg-cod/l 90,000 to 130,000 gallons per day 16 dry tpd or 19% increase in solids loading

19 Option 3 - Locally Generated Recycle Stream 4,000 6,000 gallons per day >90% Packaged beer (off-spec, expired, etc.) o <10% Soft drinks & water Direct dose vs. additional fermentation Characterization of the recycle stream

20 Option 4 - Elutriation and/or Settled Mixed Liquor Addition Dual purposing for solids separation and fermentation Hydrolysis is rate limiting Practical limitation on return streams

21 Option 5 - Repurposed Fermenter Existing tank GTU vs GTI ex-situ fermentation

22 Process Modeling Approach Technical merit of settled mixed liquor inoculation (Option 4) Determine relative settled mixed liquor volume ratios Fermentation of GTI and GTU (Option 5) Determine the APD characterization (Option 2) SCVFA and nutrients

23 Process Modeling Results Option 4 Option 5

24 Bench Scale Prescreening

25 Bench Scale Prescreening

26 Bench Scale Method: Fermentation

27 Bench Scale Method: Fermentation Method Application Option 3: Locally Generated Waste Stream LGWS addition to GVT Underflow at 30%, 60% & 90% Compare against control (distilled water) Compare against EtOH Option 4: SML Addition to GVT Underflow SML addition to GVT Underflow at 1:100, 1:1,000 & 1:10,000 Compare against control (Secondary Effluent) Option 5: GVT standalone fermentation GVT Underflow compared to GVT Influent

28 Locally Generated Recycle Stream (Beer) Initial Stream Characterization Data High COD Low solids Low nutrient load (COD:N, COD:P) ~4% EtOH

29 Locally Generated Recycle Stream (Beer)

30 SCVFA Produced, lb/day 1,600 1,400 Locally Generated Recycle Stream 30% Locally Generated Recycle Stream 60% locally Generated Recycle Stream 90% Locally Generated Recycle Stream 1,200 1, Start 1 day 2 days 3 days

31 Locally Generated Recycle Stream Lower concentrations, higher yield Inhibitory substances? Test <30% in future 24 Hour SRT sufficient Test shorter SRT in future

32 Elutriation/Settled Mixed Liquor

33 Elutriation/Settled Mixed Liquor 100:1 and 1,000:1 dilution ratios Settled mixed liquor effectiveness: 12% increase in SCVFA SCVFA: 3716 mg-cod/l 4168 mg-cod/l Return flow: 0.23 MG to MG Return solids load: 53.8 tpd 48.0 tpd

34 Fermented Primary Sludge

35 Fermented Primary Sludge

36 Fermented Primary Sludge Bench testing results confirm traditional fermenter production ranges 17% - 25% increase in solids Fermenter capacity limitations allow for GVT Underflow, not GVT influent

37 Future Testing: Bench Scale (locally generated recycle stream) Direct-dose Phosphorus release & uptake testing Test dosing site options (PE vs. RAS) HRT optimization Initial testing of micro-aerobic 24-hr HRT promising 48-hr fully aerated HRT = massive increase in acetic acid SCVFA = 422% increase ( mg-cod/l) But, only 12% as propionic (ratio <0.2 Propionic:Acetic)

38 Pilot Scale Carbon Augmentation Study (CAS) 6 Month Pilot with Waste Management (WM) Logistical and Technical considerations December 2015, CDPHE pilot authorization approved Use existing acetic acid dosing point 2 tanks, parallel testing QC parameters & performance evaluation ~ gpd

39 Carbon Augmentation Study Characterization of the Beer Waste Bench-scale: Evaluate the Beer Waste as a carbon Source In-situ P-release and uptake profiles In-situ specific process rates Ex-situ - can we make it better, ferment it more Full-scale: Demonstrate a full-scale P release in the anaerobic zones Microbial population shifts; more or less stability RAMEN, DAPI, DNA, FISH analysis Assess the efficacy of a long-term relationship with WM.

40 Baseline versus Acetic Acid Dosing Pre-Testing

41 Preliminary CAS results

42 CAS Considerations The logistical considerations are just as important as the technical Full-scale profiling is critical to understand the process dynamic of alternative carbon sources

43 Conclusions of Various Options Acetic Acid (Option 1) Costly Lack of propionic & other SCVFA Availability lends to possible backup carbon source Acid Phase Digester (Option 2) High recycle nutrient load Steals carbon from methanogens in meso-phase digesters Odor concerns Locally Generated Recycle Stream (Option 3) Promising results, more study needed for dosing parameters Inhibition noted at higher concentrations Logistic considerations (QC, M&E, contractual agreements, etc.) Pilot to run from December June 2016.

44 Conclusions of Various Options, cont. Elutriation & Settled Mixed Liquor (Option 4) May be undesirable to dual purpose gravity thickeners Modest yield of SCVFA Fermentation (Option 5) GTI more productive while GTU more concentrated Intensive O&M nature may prove undesirable

45 References Carson K Evaluation of Performance for a Novel Sidestream Enhanced Biological Phosphorus Removal Configuration at a Full-scale Wastewater Treatment Plant. Master of Science Thesis, University of Colorado, Boulder, Colorado. Cavanaugh L., Carson K., Lynch C., Philips H., Barnard J. and McQuarrie J. (2012) A Small Footprint Approach for Enhanced Biological Phosphorus Removal: Results from a 106 mgd Full-scale Demonstration. Proceedings of the 85th Annual Water Environment Federation Technical Exhibition and Conference [CD-ROM], New Orleans, Louisiana, Sep 29 Oct 3; Water Environment Federation: Alexandria, Virginia. Lopez-Vazquez CM, Oehman A, Hooijmans CM, Brdjanovic D, Gijzen HJ, Yuan Z, van Loosdrecht MC. (2009) Modeling the PAO-GAO Competition: Effects of Carbon Source, ph and Temperature. Water Res Feb; 43(2): (Epub 2008 Nov 1). Metcalf and Eddy. Wastewater Engineering Treatment and Resource Recovery. McGraw Hill Education, Print. Oehmen A, Lemos PC, Carvalho G, Yuan Z, Keller J, Blackall LL, Reis MAM. Advances in enhanced biological phosphorus removal: from micro to macro scale. Water Res. 2007; 41(11): Rossle WH, Pretorius WA. (2001) A Review of Characterisation Requirements for In-line Prefermenters, Paper 1: Wastewater Characterization. Water SA Vol. 27 No. 3 July 2001, ISSN

46 Thank you Questions? Kimberly Cowan, CWP Kurt Carson, CWP, EIT Laboratory Support Specialist O&M Engineer Associate (303) (303) Metro Wastewater Reclamation District 6450 York St., Denver CO 80229