The document discusses a project using microalgae to treat agro-industrial wastewater in Cremona Province, Italy. The project aims to bioremediate wastewater from intensive pig farming operations and valorize the algal biomass. Pilot tests were conducted on diluted and undiluted digestate from biogas plants as well as direct pig wastewater. Microalgae grew well and removed nitrogen, phosphorus, and COD. Productivity was up to 10 g/m2/day. The project aims to optimize cultivation conditions and valorize biomass as fertilizer, biofuel, or other products to improve sustainability.

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
2
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
3

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
6
• 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
7
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
8

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
9

10. Pilot scale tests - 2018: undiluted digestate
10
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)
11
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
12
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
13
• 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)
14

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)
16
Obiettivo: Ottimizzare rapporto C/N
della miscela
++
• Pretreatments are required
(cost/benefit balance)
• Co-digestion

17. Valorization - PHA
17
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
18