In Integrated ed Ac AcoD oD system em of of the the or organic nic fr fractio tion of of MSW and MSW and se sewage sl sludg udge: e: Case Case study udy A. Piasentin 1 , L. Girotto 1 , G. Moretto 2 , F. Ardolino 3 & F. Cecchi* *Innoven srl, Spinoff University of Verona 1 Alto Trevigiano Servizi S.r.l., Montebelluna (TV) 2 Department of Environmental Sciences, Informatics and Statistics, University Ca’ Foscari of Venice 3 Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Contents 1. Introduction AcoD system overview • Feasible routes for OFMSW recovery • AcoD integration within existing WWTPs • 2. Materials and Methods Case study presentation • Mixtures characterization • Steady state conditions operating parameters • Steady state conditions performance parameters • Energy considerations • Preliminary LCA study • 3. Conclusions
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 ACoD: as territory service was discussed in the 2 th IC ‐ SSWM according to the following schemes TERRITORY Cecchi F., et Al. (1994). Water Science & Technology; Cecchi and Cavinato (2015), Waste Management and Research
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Two main objectives for OFMSW recovery and valorisation trough AcoD: 1 Maximisation of energy recovery 2 Maximisation of matter recovery 1 2 The choice is driven by territory diversity and available technologies
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Case Study Approach Screw press flowchart Squeezed wet biowaste contains approx. 15 ‐ 20% TS • This approach could favour ACoD with SS in nearby WWTPs •
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Case study: full ‐ scale implementation of OFMSW ‐ SS AcoD Treviso WWTP Squeezed OFMSW from door ‐ to ‐ door separate collection ensures high quality organic waste Parameter Mean ± St. Dev. Max Min TS, g/kg 135 ± 52 211.0 33.2 TVS, g/kg 113 ± 44 176.6 24.9 Organic waste recycling in Treviso Province = 85.3% TVS/TS, % 84 ± 3 97 75 (ARPAV, 2017)
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Case study: full ‐ scale implementation of OFMSW ‐ SS AcoD Treviso WWTP Treviso (TV) • A.T.S. S.r.l. WWTP
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Feedstock mixture characterization Parameter Mean ± St. Dev. Max Min TS, g/kg 33.8 ± 5.3 48.9 19.4 TVS, g/kg 24.9 ± 3.8 34.9 13.8 TVS/TS, % 74 ± 4 88 55 pH 5.4 ± 0.25 5.92 5.08 COD, gCOD/kgTS 811 ± 52 979 693 TKN, gN/kgTS 41.3 ± 6.2 48.9 19.2 P org , gP/kgTS 11.0 ± 3.1 20.0 4.8 Effluent characterization 2000 m 3 anaerobic digester CSTR Parameter Mean ± St. Dev. Max Min TS, g/kg 18 ± 2.7 28.0 13.5 TVS, g/kg 12.1 ± 2.3 19.0 8.0 TVS/TS, % 67 ± 7 88 52 COD, gCOD/kgTS 736 ± 53 906 648 TKN, gN/kgTS 40.0 ± 8.1 49.1 19.1 P org , gP/kgTS 13.7 ± 3.7 27.1 9.1
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Steady state conditions operating parameters Hydraulic Retention Time 50 40 30 HRT (d) 20 10 0 300 350 400 450 500 550 600 650 700 Days During steady state conditions an average HRT = 20 days was mantained
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Parameters of steady state operating conditions OFMSW flow rate fed to digester 14,0 OFMSW flow rate (m 3 /d) 12,0 9.5 m 3 /d 10,0 8,0 6,0 4,0 2,0 0,0 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Periods Sludge flow rate fed to digester 140 Sludge flow rate (m 3 /d) 88 m 3 /d 120 100 80 60 40 20 0 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Periods
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Parameters of steady state operating conditions Organic Loading Rate 3,0 Total OLR (kgVS/m 3 d) 2,5 1.8 kgVS/m 3 d 2,0 1,5 1,0 0,5 0,0 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Periods OFMSW OLR Sludge OLR Average OFMSW OLR = 0.7 kgVS/m 3 d • Average Sludge OLR = 1.1 kgVS/m 3 d • *All results shown are related to steady state conditions and based on an average of 20 days Steady state conditions cover a time period from 22/04/17 to 28/02/18
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Steady state conditions performance parameters Biogas production 2500 Biogas production (m 3 /d) 2000 1500 1000 1800 m 3 /d 500 0 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Periods Biogas main composition 80 1000 65% CH 4 ; 400 ppm H 2 S 75 800 H 2 S (ppm) 70 600 % CH 4 65 400 60 200 55 0 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Periods Methane percentage Hydrogen Sulfide concentration
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Steady state conditions performance parameters Specific Gas Production 0,8 0,7 0,6 SGP (m 3 /kgVSd) 0,5 0,4 0,3 0,2 0,1 0,0 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Periods Stable SGP was observed with an average value of 0.5 m 3 /kgVSd
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Steady state conditions: process stability parameters 10,0 4000 1000 1000 900 900 3500 9,5 Alkalinity (mgCaCO 3 /l) 800 800 + /l) 3000 9,0 700 700 VFA (mgCOD/l) + (mgN ‐ NH 4 2500 600 600 8,5 pH 2000 500 500 8,0 400 400 1500 N ‐ NH 4 300 300 7,5 1000 200 200 7,0 500 100 100 0 0 6,5 0 17 22 27 32 17 22 27 32 Periods Periods Ammonium concentration VFA pH Partial Alkalinity Total Alkalinity Parameter Mean ± St. Dev. Max Min pH 7.4 ± 0.19 7.7 7.1 Steady state conditions were Alk pH6, mgCaCO 3 /l 2015 ± 258 2326 1387 characterized by stable pH, alkalinity, ammonium and VFA Alk pH4, mgCaCO 3 /l 2932 ± 290 3208 2303 concentrations + , mgN ‐ NH 4 + /l N ‐ NH 4 530 ± 84 726 365 VFA, mgCOD/l 58 ± 23 232 0
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Energy consumption and recovery Electric energy consumed and produced 10000 100% 9000 90% 8000 80% EE consumed (kWh/d) Energy coverage (%) 7000 70% 6000 60% 5000 50% 4000 40% 3000 30% 2000 20% 1000 10% 0 0% 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Periods EE consumption Energy coverage Electric energy is autoproduced through a 185 kW el CHP motor • Energy produced accounts for 50% of the total plant energy demand •
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Preliminary LCA study Two different LCA scenarios: past scenario VS present scenario Past scenario: OFMSW composting • Data are expressed in t/d
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Preliminary LCA study Two different LCA scenarios: past scenario VS present scenario Present scenario: OFMSW pretreatment → AcoD + Composting • Data are expressed in t/d
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Preliminary LCA study Delta "Past" scenario "Present" scenario (Present ‐ Past) Specific electrical Electrical Electrical Electrical consumption, Input, t IN /d consumption, Input, t IN /d consumption, consumption, kWh/t IN kWh/d kWh/d kWh/d Composting 69 138 9515 129 8880 ‐ 635 Wastewater line 0.04 180000 6667 180000 6667 0 Recovered EE, Biogas to Recovered Biogas a Recovered EE, Recovered EE, kWh/t Biogas to CHP CHP, t IN /d EE, kWh/d CHP, t IN /d kWh/d kWh/d Recovered EE 1771 ‐ ‐ 1.89 3345 3345 from CHP kWh/d kWh/d kWh/d Total electrical consumption 16182 12202 ‐ 3979 Global Warming Potential of the Italian electrical mix: 0.437 kg CO 2 eq for the production of 1 kWh (from: IPPC 2001 500a, and IEA 2016) Potential avoided GWP: 1739 kg CO 2 eq. per day
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 Conclusions OFMSW codigestion with SS ensures: Valorisation of organic wastes through energy recovery • Best territorial service for citizens • Simple operational work • Stable operating condition under SSC • Higher revenues • Slight increase in sludge production • High energy savings due to CHP biogas conversion • Undeniable overall convenience in terms of LCA • Applicable to any WWTP with reduced upgrading costs
Naxos 2018 6 th IC ‐ SSWM 13 – 16 June 2018 THANK THANK YO YOU FO FOR YO YOUR ATTENTI TENTION! N!
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