PERFORMANCE ANALYSYS OFINNOVATIVE UPFLOW ANAEROBICREACTOR AT THELAGOS AND LOULÉ WWTP1

Sara Barreto, Rui Correia, Manuel Soares, Joaquim Freire, António Martins, Raúl Barros, Ana Carvalho, Zouhayr Arbib, Jesús Rodríguez, Maikel FernándezJune 17-18, 2021

Presentation Index2

1. Introduction2.Objectives3.Results and Discussion4.Final Remarks

1. Introduction 3

Within the scope of IDIaqua e PREDAQUA - “INTERREG Spain-Portugal Cooperation Program(POCTEP) 2014-2020” with funding from the FEDER, Águas do Algarve S.A. installed anaerobicdigestion prototypes in the treatment of the liquid phase.In January 2019, Águas do Algarve SA, launched the Public Tender: “Design, Installation, Start-up and

Monitoring of the Upflow Anaerobic Reactor Prototype UASB (WWTP in Lagos - Lot 1 and WWTP in Loulé - Lot 2), and thecontracts were awarded at the end of May 2019 to the company FCC AQUALIA S.A, with aduration of 24 months. Anaerobic reactors designed and patented by FCC AQUALIA S.A., called Pulsed Solids Hydrolyser (PUSH®) – EP 3 009 408 B1• Liquid Upflow Velocity (6 to 12 m/h)• Static settling between pulses• High solids retention times• Minimization of greenhouse gas emissions• Low energy consumption

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Objective: To test the technology of anaerobic digestion in the liquid phase in two WWTPswith different affluence characteristics: At the Lagos WWTP with inflows subject to saline intrusion. At the Loulé WWTP, with relatively high concentrations of organic matter.LouléLagos

2. Objectives

3. Results and Discussion 5

Lagos WWTP (Lot I) Loulé WWTP (Lot II)Inoculation: January 14, 2020Continuous mode operation: February 5, 2020Months Hydraulicretentiontime (h) Flow(m3/day) VolumetricOrganic Load(kg COD/m3.dia)Feb to Jun-20 36 6 (3Q + 3Qr) 0.7Jun-20 to date 12 18 (9Q+9Qr) 2.4Months Hydraulicretentiontime (h) Flow(m3/day) VolumetricOrganic Load(kg COD/m3.dia)Feb to Jun-20 36 6 (3Q + 3Qr) 0.8Jun-20 to date 12 18 (9Q+9Qr) 1.2Prototypes equipped with probes for continuous monitoring: Conductivity in the affluent (Lagos WWTP) pH Temperature SolidsMonthly monitoring of feed and treated effluentCOD ,BOD5, TSS, VSS, SO4-2

3. Results and Discussion March-20 to December-20 6

Parameters PUSH® Lagos PUSH® LouléFeed effluent EffluentTreated Removal efficiencies Feed effluent EffluentTreated Removal efficienciespH 7.5 7.5 - 7.3 6.9 -COD (mg/L) 594 357 40% 1143 218 81%BOD5 (mg/L) 217 208 4% 631 105 83%TSS (mg/L) 214 42 80% 448 47 90%VSS (mg/L) 208 27 87% 373 38 90%SO4-2 (mg/L) 332 116 65% 45 10 78%COD/SO4-2 1.8 - - 25.4 - -

3. Results and Discussion March-20 to Dec-207

Loulé prototype with greatstability in COD removalefficiency. (Same pattern as the coldestmonths)Lagos prototype with great variabilityin COD removal efficiencies (bestmonth August 2020 with highertemperatures

3. Results and Discussion PUSH® Lagos8

Removal efficiencies in the Lagos prototype in the orderof 40% for COD e 4% for BOD5Poor performance of the prototypeFacts: COD/SO4-2 of 1.8 (low ratio). Reference value must be greater than 10 for anaerobicwastewater treatment to be successful Significant presence of sulfates in the residual water (332 mg/L) reveals a significantcontribution of undue inflows of saline water in the drainage network. Referencevalues 65% to 75% for COD and BOD5

3. Results and Discussion PUSH® Lagos9

Conductivity values ranged from 2 to30 mS/cm (characteristic average value ofwastewater in the Algarve and without salineintrusion 1,4 mS/cm)051015202530 1-6 4-6 7-6 10-6 13-6 16-6 19-6 22-6 25-6 28-6 1-7C (dS/m) Data Higher conductivity values coincident with greater tidal level amplitudes

3. Results and Discussion PUSH® Loulé10

Removal efficiencies in the Loulé prototype in the orderof 81% for COD and 83% for BOD5, Good performance of the prototypeFacts: COD/SO4-2 of 25.4 does not have saline intrusion.High average COD value for a typically urban waste water (1143 mg/L), favorable for the anaerobic digestion process. Referencevalues 65% to 75% for COD and BOD5

3. Results and Discussion Gaseous Phase11

Yield of Loulé's PUSH® methane production withaverage value of0.21 m3 CH4/kg CODGoodYield(theoretical value 0.35 m3 CH4/kg COD)Yield of Lagos's PUSH® methane productionwith average value of0.10 m3 CH4/kg CODPoorYieldIn the presence of sulphate there will be microbial activity of sulphate-reducing bacteria, which consume COD more efficiently than methanogenic bacteria, without forming methane and forming hydrogen sulphide (H2S)Inhibition of methanogenesis Average biogas composition PUSH® Lagos PUSH® LouléReactor Stripping Reactor StrippingMethane CH4 (%) 75 54 75 72Carbon dioxide CO2 (%) 6 4 9 10Oxygen O2 (%) 0 0 0 0Nitrogen N2 (%) 18 40 15 17Hydrogen Sulfide H2S (ppmv) 7428 7372 2251 2821

4. Final Remarks12

Effluent with a high concentration oforganic matter: Conditions that favor the process ofanaerobic digestion. This technology implemented in the liquid phase, after a screening system, proved to be quite attractive.Prototype at the Lagos WWTP showedlower performance, with organic matterremoval efficiencies in the order of 40% in COD and 4% in BOD5 and a yield of methaneproduction from 0.10 m3 CH4/kg CODEffluent with high salinity: Instability in the process of anaerobicdigestion, inhibition of microbial activity, difficulty in sedimenting thebiomass and consequently the escape of solids by the effluent. Prototype at the Loulé WWTP with highorganic matter removal efficiencies, in the orderof 81% for COD and 83% for BOD5, with anaverage yield of methane production from0.21 m3 CH4/kg COD

Acknowledgements13

The present work was developed within the scope of the projects IDIAQUA –Potenciación de la I+D+i de excelencia en materia de depuración de las águas en pequeñasaglomeraciones urbanas and PREDÁQUA - Pré-tratamientos en Depuración de AguasResiduales Industriales y Domésticas: Contribución al Desarrollo Económico, with funding fromthe FEDER “INTERREG Spain-Portugal Cooperation Program (POCTEP) 2014-2020”