Developing A Better Method for Anaerobic Digestion Process Monitoring at a Large Wastewater - PowerPoint Presentation

1. Developing A Better Method for Anaerobic Digestion Process Monitoring at a Large Wastewater Treatment Plant - Volatile Fatty Acids by Ion Chromatography with Inline UltrafiltrationXin Xu, Research Chemist, EBMUDAug. 11, 2021

2. ObjectivesValidate instrumental analysis of target VFAsTest new method on various matricesDigester Influent and effluent Blend tank R2WaterOther wastewater (landfill leachates, N/DN, activated sludge etc.)Method comparison (traditional SM vs. IC method)Digester performance monitoring

3. BackgroundAnaerobic digestion process4 stagesAcetic acid, butyric acid, isobutyric acid, isovaleric acid, and propionic acid Inhibition effectMain WWTP2 Blend tanksTwo stages thermophilic AD (8+3)Denitrification Conc. (mg/L) or ratioTransfer Sludge (TSL, after 1st stage digesters)Digested Sludge (DSL, after 2nd stage digesters) Alk. (mg/L as CaCO3)8,855 8,945 VA (mg/L as HAc)491.8 292.1 VA / ALK0.06 0.03 1. Cited from L. Appels et al. / Progress in Energy and Combustion Science 34 (2008) 755–7812. Cited from MWWTP master plan 2020VA in Digesters2 Subsequent steps in AD process1

4. Method comparisonMethodPrincipleSpeciationPros and ConsCitationDistillation50mL-250mL distill @ 1 atmXCumbersomeAzeotropic issue causing poor individual recoveryConversion factorHeat and chemical hazardsSOP473 (SM5560C)SpectrophotometricMontgomery methodXCritical pH control reagentLess accurate due to various interferencesCumbersomeMontgomery et al., 1962GCDI-GC method (DB-WAX column+ FID)GC-MS√Filtration required; negative biases; matrix effectSample extraction, DMC or SPELimitation and matrix interferenceManni and Caron 1995Ullah MA 2014Hayoung Kim 2019HPLCcation exchange column selectively separate VFAs according to their respective pKa values.√Special column (Supelcogel 610H, Aminex HPX87H, and ORH 801)Carbonate interferenceGuerrant et al. 1982ICColumn SuppressorCarbonate removal autosampler+ filtration√ Separates weakly ionized acids Elutes strong acid anions Reduce carbonate interference Operational ease Thermo application noteMetrohm application note

5. Instrument SelectionFactors to considerThermoMetrohmBasic performanceColumnAutosamplerCarbonate removalSuppressorDetectorsulfonated polystyrene/divinylbenzene resin, , particle size 7.5 µm (pH: 0-7)Inline filtration with fritCRDChemical suppressorConductivity detector Polystyrene-divinylbenzene copolymer, particle size 9 µm (pH:0-13)Inline filtration with ultrafiltration systemMCSChemical suppressorConductivity detector Sensitivity Selectivity8 VFAs @ 0.2-0.8 mg/L; 20-80 mg/L6 VFAs @ 0.1-50 mg/Lwilling to customize methodCostIC UnitFive yrs costConsumablesServiceLong term maintenance32K76KColumn+ suppressor/yrNeed to purchaseFiltration extra 4K/year, manually36K67KColumn/2yrService contractAutomatic filtration and filters are easy to changeSoftware/hardware 4K, more training neededFree and more familiarData transfer to LIMSNeed to develop Upload script readyStaff experiencelimitedsignificant

6. Metrohm IC Setup Scheme930 Compact IC Flex, includingMetrohm Carbon Suppressor (MCS)919 IC autosampler plusMetrosep Organic Acids - 250/7.8Metrosep Organic Acids Guard/4.6850 conductivity detector930 Compact IC Flex, includingMetrohm Suppressor Module (MSM)

7. Method SetupInstrument MethodEluent: 0.5mM H2SO4 @flow: 0.5 mL/minRegenerate: 0.5mol/L LiCl @flow: 0.5mL/minInjection volume: 50 uLColumn temp. 32°CMSM interval 10 minsAnalytical MethodIdentify target compounds (speciation by individual acids)Sensitivity (IDL, MDL), Linear Calibration Range (LCR), Limit of Quantification(LOQ)Accuracy & precision: recovery, RSD, RPD. Sample preparationPreservation, holding time etc.Rapid handlingData report

8. Analytical Workflowpreservation/preparationInstrument analysisReportAcidification CentrifugeDilution Inline UltrafiltrationSeparationQuantitationexternal calibration Data generationMagIC Net XLIMS 1:1 H2SO4 to pH<250 mL @ for 12,100rpm for10 mins@ 4°CDilute 2-20 timesAuto filtration 0.2 μmFlow @0.5-0.6 ml/minTemperature control @32°CPressure <7MPaBaseline conductivity: ~100µs/cmMagIC process data and generate report XLIMS IC script

9. Identify Target AnalytesTarget # (elution order)VFACAS#RT @0.5 mL/min (mins)RT @0.6 mL/min (mins)Calibration Range* (mg/L)1Lactic acid79-33-411.6TBDTBD2Formic Acid64-18-614.812.512-1003Acetic Acid64-19-716.914.210.5-1004Propionic Acid79-09-419.516.390.5-1005Isobutyric Acid79-31-221.718.090.5-1006Butyric Acid107-92-623.519.711-1007Isovaleric acid503-74-226.722.322-1008Valeric Acid109-52-432.927.501-1009Caproic Acid142-62-150.041.755-100*: Linear regression, weighting 1/x, R2>0.999

10. Instrument IDOCAcceptance criteria (request to Metrohm): Accuracy: 80%-120%; Precision (RPD)%≤20% Target #VFAspiked conc. (mg/L)IDOC 1 readingIDOC 2 readingIDOC 3 readingIDOC 4 readingAve. (mg/L)Ave. rec.%StdevRSD%2nd source check rec. %2Formic Acid5050.350.250.450.250.3101%0.080.2%98%3Acetic Acid5050.350.250.450.050.2100%0.150.3%94%4Propionic Acid5050.150.050.249.750.0100%0.210.4%93%5Isobutyric Acid5049.949.950.149.849.9100%0.140.3%94%6Butyric Acid5050.050.150.249.850.0100%0.170.3%95%7Isovaleric acid5050.150.049.849.449.8100%0.350.7%92%8Valeric Acid5049.849.849.549.949.799%0.170.3%93%9Caproic Acid5050.148.848.248.148.898%0.952.0%75%

11. Instrument Detection Limit (IDL)ParameterFormic AcidAcetic AcidPropionic AcidIsobutyric AcidButyric AcidIsovaleric acidValeric AcidCaproic AcidIDLlcs(mg/L)0.50.10.10.20.60.50.42.0IDLMB(mg/L)0.70.00.10.20.51.00.34.0IDL(mg/L)0.70.10.10.20.61.00.44.0Acceptance Criteria (mg/L)0.510.5--1------MDL calculation based on https://www.epa.gov/sites/production/files/2016-12/documents/mdl-procedure_rev2_12-13-2016.pdfParameterFormic AcidAcetic AcidPropionic AcidIsobutyric AcidButyric AcidIsovaleric acidValeric AcidCaproic AcidRL (mg/L)20.50.50.51215Acceptance Criteria (mg/L)12011

12. Sample matrix interferenceSample Formic AcidAcetic AcidPropionic AcidRecovery%RPD%L239937-2 Supernatant0.8554.653.79L239937-2 MS 0.88550.443.4499.1%0.2%L239937-2 MSD0.88549.383.4298.9%L239937-2 centrifuge @3000 RPM for 30 mins, and then supernatant centrifuge @ 11,000 RPM for 10 mins. Dilute and spiked with 50 mg/L of acetic acid.Sample Formic AcidAcetic AcidPropionic AcidRecovery%RPD%L240333-5 Supernatant5.2558.374.10L240333-5 MS 5.24462.913.8581%4.2%L240333-5 MSD5.24482.583.8385%L240333-5 acidified, centrifuge @3000 RPM for 30 mins, and then supernatant centrifuge @ 11,000 RPM for 10 mins. Dilute and spiked with 50 mg/L of acetic acid.

13. Mass Balance Calculation (from IC analysis)10mL of 2000mg/L HAc std250mL DIW39.85 mg/L as HAc measured by IC51.26 mg/L as HAc measured by ICYspiked=20mg as HAc100 mL collected distillate 20 mL discarded distillate Ycalc.=6 mg as HOAcDistillation Recovery =30%

14. Impact of distillation on VFAs recoveryTarget #VFAs Boiling point (°C)Initial mass (mg) 100 mL distillate* 20 mL discarded distillate*Total rec. (%)IC w/o distillationMass (mg)Rec. %Mass (mg)Rec. %Recovery %2Formic Acid100.8504.269%0.51.0%10%98%3Acetic Acid117.912.3625%****25%94%4Propionic Acid141.224.6449%****49%93%5Isobutyric Acid99.520.6741%****41%94%6Butyric Acid163.527.7355%****55%95%7Isovaleric acid176.526.0352%****52%92%8Valeric Acid18629.0958%14.228.5%87%93%9Caproic Acid20517.5035%19.238.3%73%75%*: Data generated from IC run**: Distillate discarded.

15. Digester samples (collected on 11/30/20)Sample IDFormic Acid(mg/L)Acetic Acid(mg/L)Propionic Acid(mg/L)Valeric Acid(mg/L)Equal. to HAc(mg/L)Titration (mg/L as HAc)ALKALINITY: TOTAL ( CaCO3 mg/L)DIGESTER 12 L239768-841.6748.3815.48 115.39009700DIGESTER 11 L239768-741.6454.1215.56 121.06109700DIGESTER 10 L239768-641.7263.9616.06 131.411009900DIGESTER 9 L239768-542.0269.5717.41 138.58909700DIGESTER 8 L239768-442.7267.1817.92 137.49709700DIGESTER 7 L239768-346.7054.7917.4763.78167.4110010000DIGESTER 5 L239768-262.7056.8521.5275.90200.711009300DIGESTER 2 L239768-180.8953.3128.0880.21228.7110010000

16. Next stepsMethod validation on digester samples followed SOP 194 v1Lactic Acid Sample preservation, storage, sample prepSurrogate - Phenoxyacetic acidIDOC, MDL study, RLFinalize batch QC criteriaSOPFor digester samples Parallel study (IC vs. Distillation)Correlation with temperature, pH, Alkalinity, VS, NH3/NH4+ Analyze individual VFAs data to predict digester performance

17. Thank you! Brian P. BellefeuilleArtem A. Dyachenko, Jason P. Mitchell, Yun ShangMelissa LashKamara Vrandecic, Genesis Castellanos, Lauren E. Brougham

18. Referenceshttps://elibrary.asabe.org/abstract.asp?aid=31977https://www.liebertpub.com/doi/abs/10.1089/ees.2017.0190?journalCode=eeshttps://onlinelibrary.wiley.com/doi/epdf/10.1002/elsc.201600095New Approach for Determination of Volatile Fatty Acid in Anaerobic Digester Sample ENVIRONMENTAL ENGINEERING SCIENCE, Volume 35, Number 4, 2018L. G. M. Gorris, J. M. A. van Deursen, C. van der Drift, and G. D. Vogels, “Inhibition of propionate degradation by acetate in methanogenic fluidized bed reactors,” Biotechnology Letters, vol. 11, no. 1, pp. 61–66, 1989.L. Appels, J. Baeyens, J. Degrève, and R. Dewil, “Principles and potential of the anaerobic digestion of waste-activated sludge,” Progress in Energy and Combustion Science, vol. 34, no. 6, pp. 755–781, 2008.K. C. Wijekoon, C. Visvanathan, and A. Abeynayaka, “Effect of organic loading rate on VFA production, organic matter removal and microbial activity of a two-stage thermophilic anaerobic membrane bioreactor,” Bioresource Technology, vol. 102, no. 9, pp. 5353–5360, 2011.R. Gourdon and P. Vermande, “Effects of propionic acid concentration on anaerobic digestion of pig manure,” Biomass, vol. 13, no. 1, pp. 1–12, 1987.

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