Prof. Dr. Elena Ficara

1. The Microalgae hub project:
how to use microalgae for agro-industrial wastewater
bioremediation and valorisation of the algal biomass
E. Ficara, M. Bellucci, F. Marazzi, V. Mezzanotte K. Parati

2. The project – The microalgae hub
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Collaborations:
Partners:
Consortium
Funding:

3. The motivation/context
Cremona Province
• Agriculture: 15.5% of companies belong to the
agricultural sector, breeding 887,000 pigs,
288,000 cows, e 1,800 buffalos  intensive
breeding
• Anaerobic digestion: prompted by national
incentive  more than 140 biogas plants
Nitrate directive (676/91/CE)
56% of the Cremona province is
classified as vulnerable to nitrate
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4. Dairy by-
products
Zootechnical
waste
Microalgae Biomass
transformation
processes
transformation
processes
Effluent
Organic material, nittrogen,
Phosphor and salts
Cosmesis
Animal feed
Biofuels
Bioplastics
Biostimulants
WP2: Implementation of the Hub
WP 3: research and
technological development
activities
WP4 4: Training and
monitoring
WP5: Services
WP 6: Dissemination
CO2

5. The case study
Piggery farm
(20.000 capi)
W1
Biogas
Biogas
RW
2 digesters
V = 3,000 m3
HRT ≈ 30 d
T = 40°C
330 kWel
2 digesters + 2
post digesters
V = 9,000 m3
HRT ≈ 55 d
T= 42°C
1 MWel
WWTP
W2W3 5

6. The case study
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• Low optical density/turbidity
• Physiological pH
• Non –inhibiting N-NH4
• N:P=10-30
W1
piggery
W2
digestate
W3
digestate
TQ SL TQ SL TQ SL
TS g/L 5 2 73 7,5 591 53
VS (g/l) 3 0.74 51 2 37 32
pH 7.4 7.3 7.7 8.1 7.8 8.2
N-NH4 (mg/l) 152 148 1 920 1 300 2 240 2 150
P (mg/l) 25 19 142 26 239 271
Turbidity (FAU) 148 191 4 280 70 3 660 4 460
COD sol (mg/l) 1 390 1 070 4 220 1 920 4 240 5 070
COD tot (mg/l) 4 550 1 000 72 440 3 400 5 560 50 000
Ideal

7. Pilot scale tests
Experimental campaigns:
• 2016: diluted digestate (1:5  1:3)
• 2017: piggery wastewater
• 2018: undiluted digestate
Assessment of:
• N and P forms
• Organic contamination (COD)
• Algae growth parameters (counts, TSS, OD680,
turbidity)
Raceway
A = 3.8 m2 (V =0.9 m3),
• paddlewheel
• pH control by bubbling CO2
• CO2 sump
• feeding pump
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0
50
100
150
200
250
300
350
400
0
5
10
15
20
25
30
35
15/4 29/4 13/5 27/5 10/6 24/6 8/7 22/7 5/8 19/8 2/9 16/9 30/9 14/10
I(W/m2)
T(°C)
data
Averagedaily Temp°C Averagedaily irradiance W/m2

8. Pilot scale tests - 2016: diluted digestate
 Microalgae could grow in the liquid
fraction of agro-digestate and under
sub-optimal climatic conditions for
200 d
 Average productivity: 8.2 g TSS m-2 d-1
 N apportioning: 7±3% N was
assimilated; 61 ± 24% was nitrified
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9. 0
25
50
75
100
125
150
10/5 4/6 29/6 24/7 18/8 12/9 7/10 1/11 26/11HRT,SRT[d]
HRT → ∞
Pilot scale tests - 2018: undiluted digestate
Liquid recirculation
QIN(m3/d)
QOUT (m3/d)
Qevap
Qalgae (kgDW/d)
VRW(m3), Calgae (kgDW/m3)
Centrifuge
SRT = VRW× Calgae/ Qalgae
HRT = VRW/ QOUT
Undiluted
W2
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10. Pilot scale tests - 2018: undiluted digestate
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𝑑(𝑋 ∗ 𝑉)
𝑑𝑡
= 𝑄𝑖𝑛 ∗ 𝑋𝑖𝑛 − 𝑄𝑎𝑙𝑔𝑎𝑒 ∗ 𝑋𝑎𝑙𝑔𝑎𝑒 − 𝑄𝑜𝑢𝑡𝑋𝑜𝑢𝑡 +𝒓
Raceway mass balances:
V = Qin  t- Qout  t-Qalgae  t+  P – E
RW
Xout
Qin
Xin
Qout
Xout
Precipitation
(meteo data)
Evaporation
(estimated, Penman’s equation)

11. Pilot scale tests - 2018: undiluted digestate
Productivity: 6.2 gDM/(m2∙d) (< 8.2 ± 8.5 gDM/(m2∙d)
2016)
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Removal efficiencies:
• NH4
+-N: 95 ± 12 [%]
• N: 52 ± 13 [%]
• PO4
3--P: 80 ± 21 [%]
• CODs: 45 ± 35 [%] N-NH4
+: 0 ± 1 %  high removal
N stripped: 35 ± 7 %  poor pH
control  stripping (or denitrification)
N-NO2
-: 8 ± 4 %
N-NO3
-: 44 ± 12 %  nitrification
N-biomass: 13 ± 1 %

12. Pilot scale tests - 2017: piggery WW
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TSS
(g/L)
N-NH4
(mg/L)
N-NO3
(mg/L)
OD @680
(-)
sCOD
(mg/L)
P-PO4
(mg/L)
Cond.
(mS/cm)
Mean 0.2 200 3.6 0.15 658 20 3.5
Standard dev. 0.28 60 3.6 0.08 314 14 0.3
Stable growth but variable composition of algal community
Average productivity: = 10 gDM/m2/d  9 months = 27 tDM/ha/year

13. Pilot scale tests - 2017: piggery WW
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• Ammonium removal Mean: 90%
• P removal: More variable Mean: 46%
• sCOD removal: Mean: 67% (O2 from algae)
N apportioning
Biomass apportioning
16%
73%
10% 1%
Nbio
Nox
NH4
Nstripp
75%
2%
15%
8%
Algae
Nitrifiers
Het
debris

14. Conclusions/Perspectives
PROs
- Reduced N load to the fields ( reduced
arable land demand for N disposal)
- Lower energy request for aeration
- Production of valuable algal biomass (CO2
capture, organic C and nutrients to be returned
to soils)
CONs
- Large areal request for algae treatment
- Overall efficiency largely dependent on
climatic conditions (may imply
discontinuous operation)
- Long term stability still to be proven
 Integrated schemes are to be tested for final applicability assessment
 Biomass valorization
 Optimization of culturing (respirometry+modelling)
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15. Valorization
- Fertilisers,
biostimulants
- Biofuels
- Feed in aquacultures
- Biomaterials

16. Valorization – CH4
Biogas
Simple/straightforward
Reduces the overall N removal benefit
Low methane yield
(100-200 Nm3_CH4/ton_DM)
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Obiettivo: Ottimizzare rapporto C/N
della miscela
++
• Pretreatments are required
(cost/benefit balance)
• Co-digestion

17. Valorization - PHA
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Bioplastics/VFAs
More complex
Allows for N, P recovery
Low yield (0,08 -0,2 g_PHA/g_DM)
Fermentation
Struvite
Precipitation
PHA
accumulation
PHA
estraction
VFA
A
C
B
• Optimization of process parameters
• Co-fermentation

18. Thanks to
Francesca Marazzi
Valeria Mezzanotte
Micol Bellucci
Andrea Pizzera
All of you for listening
Katia Parati
Co-authors
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