The document describes a study on using bioreactors with citrus woodchips to denitrify saline drainage water under semi-arid conditions in Spain. Three pilot-scale bioreactors were tested with hydraulic retention times of 8, 16, and 24 hours. Woodchip bags were extracted from different depths and zones of the bioreactors after 6, 12, and 18 months. The weight of the woodchips generally decreased over time, indicating biodegradation, but decreased more for bags buried shallower in the bioreactors. Nitrate removal efficiencies were highest for the 24-hour hydraulic retention time bioreactor.

1. The magic of bioreactors
arrives in Spain for
denitrification of saline
drainage under semi-arid
conditions
Carolina Diaz-Garcia, Laura E. Christianson,
Juan Jose Martinez-Sanchez, Jose Alvarez-Rogel
Technical University of Cartagena
University of Illinois at Urbana-Champaign

2. Scarce water resources
50 000 ha agricultural fertigation
ESPAÑA
Campo de Cartagena
Spain- Campo de Cartagena
• Major supplier to European Markets -
horticulture products and citrus.
• Environmental impacts since the brine
(wastewater resulting from desalination)
contains a high concentration of nitrate.
Dryland until 1990 Irrigation since 2000
Mar
Menor
Mar
Menor
Campo de
Cartagena
Campo de
Cartagena
Reverse osmosis plant

3. Scarce water resources
50 000 ha agricultural fertigation
ESPAÑA
Campo de Cartagena
Spain- Campo de Cartagena
Dryland until 1990 Irrigation since 2000
Mar
Menor
Mar
Menor
Campo de
Cartagena
Campo de
Cartagena
Most of the nutrients present in the water
bodies have reached the Mar Menor lagoon
through surface and subsurface discharges.
The Mar Menor is the largest coastal
hypersaline lagoon in the Mediterranean basin.
@MarmenorKO

4. Eutrophication
NO DESALINATION
WITHOUT DENITRIFICATION
Objetive:
Search low-cost and efficient denitrification
systems that are easy for farmers to manage

5. Pilot plant. Wetlands and Denitrifying Bioreactors
placed in WWTP Los Alcázares
Drainage channel D7
Pilot plant
Bioreactors

6. Bioreactors
3 bioreactors: 8 h, 16 h y 24 h.
566 days (80 weeks) – May 29
2019 to November 17 2020
7 m3 of citrus woodchips
Flow 3 m3/day per bioreactor
Electrical conductivity 7.2 mS/cm
24 h
16 h
8 h
Denitrifying bioreactors with citrus woodchips
6 m
0,98 m

7. LATERAL VIEW
Bioreactors

8. Woodchip bags
LATERAL VIEW
200 g of citrus woodchip per bag

9. LATERAL VIEW
200 g of citrus woodchip per bag
Extraction of 1 bag from each zone
and height every 6, 12 and 18 months
Woodchip bags

10. Dissolved Organic Carbon

11. Woodchips bags
Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
100
120
140
160
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom

12. Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
100
120
140
160
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

13. Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
100
120
140
160
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

14. Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
100
120
140
160
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

15. Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
100
120
140
160
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

16. Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
100
120
140
160
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

17. Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
100
120
140
160
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

18. Lateral views of the bioreactors
SALIDA
TRH
16 H
BOLSAS
SALIDA
TRH
24 H
BOLSAS
HRT 8 h
HRT 16 h
HRT 24 h
SALIDA
TRH
8 H
BOLSAS

19. Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

20. Moorman (2010)
Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

21. Moorman (2010)
Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips
weight
(g)
100
120
140
160
180
200
Bioreactor HRT 8 h
a b
ab a a a a a a
B B B B A
B B A A
Months from the beginning
6 months 12 months 18 months
Woodchips
weight
(g)
100
120
140
160
180
200
Months from the beginning
6 months 12 months 18 months
Months from the beginning
6 months 12 months 18 months
a b
ab a a a
a a a
A A A A A A A A A
A) Bags buried at 70 cm from the bottom
Bioreactor HRT 16 h Bioreactor HRT 24 h
Bioreactor HRT 8 h Bioreactor HRT 16 h Bioreactor HRT 24 h
B) Bags buried at 20 cm from the bottom
Woodchips bags

22. Woodchips level before and after
Beginning of the experiment
After 1.5 years of performance
24 h 16 h
8 h
24 h
16 h
8 h

23. Nitrate removal efficiency
3
0
3
3
3
5
3
7
4
1
4
3
4
4
4
7
4
9
5
1
5
4
5
6
5
8
6
1
6
3
6
5
6
8
7
0
7
2
7
6
8
2
8
4
8
9
9
2
9
7
9
9
1
0
3
1
0
7
1
1
0
1
1
3
1
1
7
1
1
9
1
2
5
1
3
2
1
4
2
1
4
7
1
5
4
1
6
1
1
6
7
1
7
3
1
8
0
1
8
7
2
0
2
2
0
8
2
3
1
2
4
3
2
5
2
2
5
8
2
7
9
2
9
9
3
1
3
3
8
5
3
9
4
4
0
6
4
1
1
4
2
1
4
2
8
4
3
3
4
4
1
4
4
8
4
5
3
4
6
1
4
6
8
4
7
5
4
8
2
4
9
0
5
0
4
5
1
0
5
1
7
5
2
5
5
3
2
5
3
4
5
3
8
5
4
7
5
5
1
5
5
2
5
5
9
5
6
6
NRE
(%)
0
20
40
60
80
100
Temperature
(ºC)
10
12
14
16
18
20
22
24
26
28
Effluent Bio8h
Effluent Bio16h
Effluent Bio24h
Temperature
Days, months and years
Jun.- Jul.- Aug. Sep.- Oct.- Nov. Dec.- Jan.-
Feb.
Mar.- Apr.-
May.- Jun.
Jul.- Aug.- Sep.
2019 2020
Oct.- Nov.

24. Sulphide
24h TRH
231
258
279
299
385
394
406
411
421
428
433
441
448
453
461
468
475
482
490
504
510
517
525
532
534
538
547
551
552
559
566
Sulphide
(mg
L
-1
)
0
1
2
3
4
5
Effluent Bio8h
Effluent Bio16h
Effluent Bio24h
Inflow
Dec.- Jan.- Feb. Mar.- Apr.- May.- Jun. Jul.- Aug.-Sep.
Days, months and years
2019 2020
Oct.- Nov.

25. Phosphate (SRP)
24h TRH
2
3
1
2
9
9
3
1
3
3
8
5
3
9
4
4
0
6
4
1
1
4
2
1
4
2
8
4
3
3
4
4
1
4
4
8
4
5
3
4
6
1
4
6
8
4
7
5
4
8
2
4
9
0
5
0
4
5
1
0
5
1
7
5
2
5
5
3
2
5
3
4
5
3
8
5
4
7
5
5
1
5
5
2
5
5
9
5
6
6
SRP
(mg
L
-1
)
0,0
0,1
0,2
0,3
0,4
0,5
0,6
Effluent Bio8h
Effluent Bio16h
Effluent Bio24h
Inflow
Dec.- Jan.- Feb. Mar.- Apr.- May.- Jun. Jul.- Aug.-Sep.
Days, months and years
2019 2020
Oct.- Nov.

26. Carbon Dioxide and Nitrous Oxide
Bioreactor
8 h HRT 16 h HRT 24 h HRT
CO
2
(mg
m
-2
h
-1
)
0
200
400
600
800
1000
1200
1400
1600
1800
Bioreactor
8 h HRT 16 h HRT 24 h HRT
N
2
O
(mg
m
-2
h
-1
)
0
20
40
60
80
100
120
140
160
180
SALIDA
TRH
8 H
BOLSAS
SALIDA
TRH
24 H
BOLSAS
HRT 8 h HRT 24 h
N2O
N2O N2O N2O
CO2
CO2
CO2
CO2

27. Conclusions
• Bioreactors are suitable for the denitrification of saline effluents from
intensive agriculture.
• Flooded woodchips (anoxic conditions) suffered less degradation and
greater production of N2O emissions compared to the woodchips that
were out of the water, which suffered greater degradation and favored
CO2 emissions.
• Potentially harmful formation compounds such as sulfides are a factor to
be considered.

28. Thanks for your
attention
Acknowledgments:
• Entidad Regional de Saneamiento
y Depuración de Aguas Residuales
(ESAMUR) (Spain)
• NRCS Conservation Innovation
Grant (NR213A750013G038)
• Illinois NREC (2021-3-360498-144)