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• A. Piasentin1, L. Girotto1, G. Moretto2, F. Ardolino3 & F. Cecchi*

*Innoven srl, Spinoff University of Verona

1Alto Trevigiano Servizi S.r.l., Montebelluna (TV) 2Department of Environmental Sciences, Informatics and Statistics, University Ca’

Foscari of Venice

3Department of Environmental, Biological and Pharmaceutical Sciences and

Technologies, University of Campania “Luigi Vanvitelli”

Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

• 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

Contents

ACoD: as territory service was discussed in the 2th 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

6th 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 The choice is driven by territory diversity and available technologies

1 2

Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

• Squeezed wet biowaste contains approx. 15‐20% TS
• This approach could favour ACoD with SS in nearby WWTPs

Case Study Approach

Screw press flowchart Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

Parameter Mean ± St. Dev. Max Min

TS, g/kg 135 ± 52 211.0 33.2 TVS, g/kg 113 ± 44 176.6 24.9 TVS/TS, % 84 ± 3 97 75

Squeezed OFMSW from door‐to‐door separate collection ensures high quality organic waste Organic waste recycling in Treviso Province = 85.3%

(ARPAV, 2017)

Case study: full‐scale implementation of OFMSW‐SS AcoD Treviso WWTP

Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

• Treviso (TV)

A.T.S. S.r.l. WWTP

Case study: full‐scale implementation of OFMSW‐SS AcoD Treviso WWTP

Naxos 2018

6th 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 Porg, gP/kgTS 11.0 ± 3.1 20.0 4.8

Effluent characterization

2000 m3 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 Porg, gP/kgTS 13.7 ± 3.7 27.1 9.1

Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

10 20 30 40 50 300 350 400 450 500 550 600 650 700 HRT (d) Days

Hydraulic Retention Time

Steady state conditions operating parameters

During steady state conditions an average HRT = 20 days was mantained Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

Parameters of steady state operating conditions

0,0 2,0 4,0 6,0 8,0 10,0 12,0 14,0 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 OFMSW flow rate (m3/d) Periods

9.5 m3/d OFMSW flow rate fed to digester Sludge flow rate fed to digester

20 40 60 80 100 120 140 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Sludge flow rate (m3/d) Periods

88 m3/d Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

Organic Loading Rate

*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

• Average OFMSW OLR = 0.7 kgVS/m3d
• Average Sludge OLR = 1.1 kgVS/m3d

0,0 0,5 1,0 1,5 2,0 2,5 3,0 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Total OLR (kgVS/m3d) Periods OFMSW OLR Sludge OLR

1.8 kgVS/m3d

Parameters of steady state operating conditions

Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

Steady state conditions performance parameters

Biogas production

500 1000 1500 2000 2500 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Biogas production (m3/d) Periods

Biogas main composition 1800 m3/d

200 400 600 800 1000 55 60 65 70 75 80 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 H2S (ppm) % CH4 Periods Methane percentage Hydrogen Sulfide concentration

65% CH4 ; 400 ppm H2S Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 SGP (m3/kgVSd) Periods

Steady state conditions performance parameters

Specific Gas Production Stable SGP was observed with an average value of 0.5 m3/kgVSd Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

Steady state conditions: process stability parameters

Steady state conditions were characterized by stable pH, alkalinity, ammonium and VFA concentrations Parameter Mean ± St. Dev. Max Min

pH 7.4 ± 0.19 7.7 7.1 Alk pH6, mgCaCO3/l 2015 ± 258 2326 1387 Alk pH4, mgCaCO3/l 2932 ± 290 3208 2303 N‐NH4

+, mgN‐NH4 +/l

530 ± 84 726 365 VFA, mgCOD/l 58 ± 23 232

500 1000 1500 2000 2500 3000 3500 4000 6,5 7,0 7,5 8,0 8,5 9,0 9,5 10,0 17 22 27 32 Alkalinity (mgCaCO3/l) pH Periods pH Partial Alkalinity Total Alkalinity 100 200 300 400 500 600 700 800 900 1000 100 200 300 400 500 600 700 800 900 1000 17 22 27 32 VFA (mgCOD/l) N‐NH4

+ (mgN‐NH4 +/l)

Periods Ammonium concentration VFA

Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018

Energy consumption and recovery

Electric energy consumed and produced

• Electric energy is autoproduced through a 185 kWel CHP motor
• Energy produced accounts for 50% of the total plant energy demand

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Energy coverage (%) EE consumed (kWh/d) Periods EE consumption Energy coverage

Naxos 2018

6th 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

6th 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

6th IC ‐ SSWM

13 – 16 June 2018

Preliminary LCA study

"Past" scenario "Present" scenario Delta

(Present‐Past) Specific electrical consumption, kWh/tIN Input, tIN/d Electrical consumption, kWh/d Input, tIN/d Electrical consumption, kWh/d Electrical consumption, kWh/d Composting 69 138 9515 129 8880 ‐635 Wastewater line 0.04 180000 6667 180000 6667 Recovered EE, kWh/tBiogas to CHP Biogas to CHP, tIN/d Recovered EE, kWh/d Biogas a CHP, tIN/d Recovered EE, kWh/d Recovered EE, kWh/d Recovered EE from CHP 1771 ‐ ‐ 1.89 3345 3345

Total electrical consumption kWh/d kWh/d kWh/d 16182 12202 ‐3979

Global Warming Potential of the Italian electrical mix:

0.437 kg CO2 eq for the production of 1 kWh (from: IPPC 2001 500a, and IEA 2016) Potential avoided GWP: 1739 kg CO2 eq. per day

Naxos 2018

6th 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

6th IC ‐ SSWM

13 – 16 June 2018

THANK THANK YO YOU FO FOR YO YOUR ATTENTI TENTION! N!

Naxos 2018

6th IC ‐ SSWM

13 – 16 June 2018