This document summarizes the results of a project that developed a two-phase anaerobic digestion (AD) system to treat high-salinity wastewater and produce biogas. The system uses granular sludge that can withstand salt concentrations up to 58 g/L in the acidogenic phase and 14 g/L in the methanogenic phase. Testing at a demonstration site in Slovenia treated saline hides wastewater and produced up to 9.3 m3 of biogas per m3 of wastewater. This provides a sustainable way to treat saline industrial wastewater while generating renewable energy in the form of biogas.

1. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
1
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
High salinity Anaerobic Digestion
Final stakeholder event
25th September 2019
Ljubljana (Slovenia)
Mónica Carvalheira

2. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
2
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Problem statement
Saline industrial wastewater (WW), such as
leather pickling WW, are high organically
polluted WW:
Fig 1. Salted hides (KOTO, Slovenia)
• high COD content
• high concentration of salt
Need to be treat to avoid
the soil and water
contamination

3. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
3
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Saline wastewater treatment
Two-phase Anaerobic Digestion
&
Granular sludge
Conventional biological treatment inhibited by salt
High cost
Physicochemical processes as alternative
More economical and feasible alternative
Wastewater treatment & Biogas production
Advantage

4. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
4
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Anaerobic Digestion
Complex organic matter
(carbohydrates, proteins, fats)
Soluble organic matter
(sugars, aminoacids, fatty
acids)
Fermentative intermediates
(propionate, butyrate, lactate,
ethanol)
Acetate H2 and CO2
CH4 and CO2
HYDROLYSIS
ACIDOGENESIS
ACETOGENESIS
METHANOGENESIS

5. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
5
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
2-phase anaerobic granular sludge process
Granular sludge
• More robust, shielding inner cells from high salinity effect
2-phase anaerobic digestion
• Acidogenic and methanogenic organisms have different pH requirements, growth
kinetics, and resistance to environmental stresses
• Separate phases increases stability, higher OLR, higher biogas production rate, and
BOD removal efficiency

6. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
6
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Two-phase AD
Wastewater
Acidogenic
phase
Methanogenic
phase
VFAs & Ethanol
Biogas
(CH4 & CO2)
Treated
Effluent
Anaerobic Granules

7. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
7
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Acidogenic reactor performance
0
20
40
60
80
100
30 gNa+/L
1.55 gCOD/L.d
58 gNa+/L
1.55 gCOD/L.d
58 gNa+/L
0.85 gCOD/L.d
58 gNa+/L
2.56 gCOD/L.d
58 gNa+/L
1.24 gCOD/L.d
Acidificationdegree(%)
Such a high salinity was never reported in acidogenic UASB bioreactors.
• Operational conditions affect the
acidification degree and the
profile of the fermentation
products.
• Acidification degree up to
80.7±19.2% was obtained with
sodium concentrations of 58 g
Na+/L at OLR of 1.24 gCOD/L.d
and pH of 6.5.

8. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
8
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Methanogenic reactor performance
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 20 40 60 80
Na+(g/L)
EffCOD(gCDO/L)
QCH4(L/d)
OLR(gCOD/L.d)
t (d)
It is possible to produce 0.6Lbiogas/day with a methane productivity
of 0.23 LCH4/L.day in a lab scale reactor (2.2 L).
• Slow adaptation of the
methanogenic community
to salinity is needed.
• Methanogenic activity was
still detected at levels of 14
gNa+/L

9. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
9
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Take home message
• The two phase AD system is robust and can operate efficiently under
dynamic feeding of saline wastewaters with no apparent destruction of
granules.
» Anaerobic granules were able to withstand with salinities up to 58 gNa+/L and
14 gNa+/L in acidogenesis and methanogenesis stages, respectively.
» The phase separation allowed to obtain high acidification degree in the 1st
stage.
» 0.6Lbiogas/day with a methane productivity of 0.23 LCH4/L.day was produced with
a 2.2L 2nd stage reactor.
This system can be used to treat saline wastewater and
produce biogas (energy source), adding a new value to the
wastewater.

10. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
10
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Slovenian demo site in industrial environment
AD2 methanogenic
reactor
Salted hides –
wastewater source
AD1 acidogenic reactor

11. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
11
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Slovenian demo site in industrial environment
• Continuous operation of AD system in industrial environment was reached.
» Successful adaptation of microbial culture in the granules to high salinity (in
AD1 up to 38.7 g Na+/L in AD2 up to 25.1 g Na+/L.
» Biogas production varies, between 0 - 380 L/h in stable operation up to 9.31
m3Biogas/d can be produced in two phase AD (reactor volume 1.8 m3, working
volume 1,.52 m3) at inflow to AD1 346.56 L/day of saline wastewater.
» 9.3 m3 CH4/ m3 wastewater (maximally 23.4 m3 CH4/ m3 wastewater)
The implementation in industrial environment was
successfully achieved

12. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
12
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Slovenian demo site output
With a constant inflow and stable process temperature (30 ⁰C ) we
can estimate that
at inflow of 1 m3 WW 9 m3 biogas can be produced and
9 kWhe electricity at CH4 content > 85%.
contribution to electric energy = 9.08 kWh/day,
maximally 68.4 kWh/day per 1 m3 of wastewater
contribution to thermal energy = 18.15 kWh/day,
maximally 136.8 kWh/day per 1 m3 of wastewater

13. This project has received funding from the European Union’s Horizon 2020
Innovation Action programme WATER under grant agreement no 689785
H2020-Water-
1b-2015
13
Final STK event
25-Sept-2019 Ljubljana. Slovenia
www.saltgae.eu
Thank you for the attention
Final stakeholder event
25th September 2019
Ljubljana (Slovenia)
Mónica Carvalheira