ARVI Getting most out of the thermal drying of sewage sludge, Deviatkin

1. Getting most out of the thermal
drying of sewage sludge
to stay within the planetary
boundaries for the nitrogen cycle
16.01.2016
Ivan Deviatkin
Doctoral student,
Department of
Sustainability Science,
School of Energy
Systems, Lappeenranta
University of Technology

2. Planetary boundaries
1.0-2.5 mg N/L – limit to prevent eutrophication.
To keep it such, the planetary nitrogen fixation
boundary is set to 62-82 Mt N/year.
Currently, the fixation rate is 121 Mt N/year, where
82 Mt N comes from synthetic fertilizers.
Therefore, 20-26 Mt N from synthetic fertilizers
should be avoided.

3. Where to get N, if not a synthetic one?
Stream N content, mg/L
Liquid manure fractions ≈ 3,500
Digested manure ≈ 3,500
Organic waste ≈ 1,200
Reject water from WWTP ≈ 750
Industrial waste streams *
Condensate from sludge drying *
N-fertilizer
N-food
N-wastewater
N-sludge
N-NO3
N2
N-
Anam
mox
N-Anammox
Shortcircuit
N-Haber-Bosch
van Eekert, M., Weijma, J., Verdoes, N., de Buisonje, F., Reitsma, B., van den Bulk, J.,
van Gastel, J., 2012. Explorative research on innovative nitrogen recovery.
Great attention was drawn to N recovery from liquid
flows neglecting direct recovery from gaseous flows!

4. Research idea (!) and questions (?)
(!) sludge drying and incineration is a common
practice, so nitrogen recovery during thermal drying
of sludge (and similar streams) was seen favorable.
(?) how much N is released from sewage sludge,
digestate, and biosludge from a pulp and paper mill
(?) what is the impact of T on the N release
(?) which recovery methods could be practiced
(?) intensifying N release through condensate
stripping
Legend
N-NH3
Sewage sludge
(1)
(2)
(4)
(3)
Nitrogen fertilizer
Hot air/
steam
Fumes for
treatment
Energy
Ash for
recycling
Solid flow
Liquid flow
Gas flow
Energy flow
(1)
(2)
(3)
(4)
- sludge bunker;
- drier;
- incineration plant;
- absorber/adsorber.
drier
bunker recovery
Incineration plant

5. Nitrogen release during batch drying 1
Experimental setup on the Figure →
Sewage sludge Toikansuo WWTP, LPR
Digestate Kouvolan Vesi Oy, Kouvola
Biosludge UPM Kymmene, LPR
b
a
c
d
e
f
g
Legend:
a – vessel with sludge
b – inletpipe
c – outlet pipe
d – electric oven
e – thermometer
f – praparation unit
g – Gasmet analyzer
Nitrogen species Digestate Exhaust fumes Condensate
Total nitrogen (𝑁"#") Modified Kjeldahl
test
n.d. Nitrogen (total)
cell test
Soluble nitrogen (𝑁$#%) WE + Nitrogen
(total) cell test
n.a. n.d.
Ammonium (𝑁𝐻'
() WE + Ion
chromatography
n.a. Ion
chromatography
Ammonia gas (𝑁𝐻)) n.a. FTIR n.a.

6. Nitrogen release during batch drying 2
100°C 130°C 160°C
70°C 100°C 130°C 160°C
130°C 180°C 210°C
Sewage sludge
Digestate
Biosludge
0
10 000
20 000
30 000
40 000
50 000
60 000
Sewage sludge Digestate Biosludge
Total Nitrogen Soluble Nitrogen N-NH4
70°C 100°C 130°C
160°C 180°C 210°C
19%
58%
7%
mg/kgTS

7. Nitrogen release during batch drying 3
100°C 130°C 160°C
70°C 100°C 130°C 160°C
130°C 180°C 210°C
Sewage sludge
Digestate
Biosludge
0
5 000
10 000
15 000
20 000
Sewage sludge Digestate Biosludge
Total Nitrogen Soluble Nitrogen N-NH4
70°C 100°C 130°C
160°C 180°C 210°C
mg/kgTS
55%
4900 −
6200
9000 −
9900
1300 −
1700
50%
65%

8. Nitrogen release during continuous drying 1
Experimental setup on the Figure →
Two (+1) tests. Feeding at 1.38±0.17 kg/h.
MC of raw sludge was 83.7±0.1% and of dried
sludge – 31.1±0.1%.
Each experiment lasted for 8 hours.
Ammonia measurement at 2h, 4h, 5h, 6h, 7h, 8h.
Acid traps for NH3 capture. Ion chromatography.
Biochar was used for ammonia capture

9. Nitrogen release during continuous drying 2
0
400
800
1 200
1 600
2 000
0.00
0.30
1.00
1.30
2.00
2.30
3.00
3.30
4.00
4.30
5.00
Cumulativemassofdrysludge,g
Test I Test II Test III
100
200
300
400
500
1h 2h 3h 4h 5h 6h
Driedsludgeoutput,g·h-1
Test I Test II Test III
- calculated dried
sludge output (280±10 g/h)
R² = 0,99413
R² = 0,99861
0,0
200,0
400,0
600,0
800,0
1000,0
1200,0
1400,0
0 1 2 3 4 5 6 7 8 9
CumulativeNinexhaustfumes,mg
Time, h
So we get:
0.53±0.01 mg N/
g dried sludge
0.21±0.01 g dried sludge/
g wet sludge.
Therefore, we can get:
110±6 g N/t wet sludge.

10. Adsorption on biochar:
organic materials doped with N
Absorption:
• ammonium sulphate solution,
• ammonium nitrate solution,
• ammonium chloride solution,
• etc.
Aqua ammonia
General recovery methods
Packed adsorption Packed absorption
Sprayed absorption Droplet absorption

11. Thus, there is the need
to release 30% N
back for recovery!
Intensifying ammonia release
100%90%
TEST IITEST I
30% in
condensate
70% goes
for recovery
Let us strip it!
14ºC 31ºC

12. Sludge is a reliable source of nitrogen as its amount is
ever-growing worldwide.
When we incinerate sludge, we have a good possibility to
recover nitrogen.
50-65% of soluble nitrogen is release as ammonia during
the drying process.
Nitrogen released could be recovered by ad/absorption.
Moreover, great possibilities for symbiosis exist. The
process could be retrofitted to:
• a sludge incineration plant to get nitrogen released;
• a WWTP for nitrogen stripping from condensate.
What do we get after all?
Legend
N-NH3
Sewage sludge
(1)
(2)
(4)
(3)
Nitrogen fertilizer
Hot air/
steam
Fumes for
treatment
Energy
Ash for
recycling
Solid flow
Liquid flow
Gas flow
Energy flow
(1)
(2)
(3)
(4)
- sludge bunker;
- drier;
- incineration plant;
- absorber/adsorber.
drier
bunker recovery
Incineration plant

13. 1. Technical study on recovery possibilities
2. Economical analysis
3. Environmental impact assessment
Future research needs
Social
acceptance
Environmental
impact
Economic
conditions
SYSTEM ANALYSIS

14. Thank you for your attention!
Questions?