Nitrogen removal in Urban Wastewater using Scendesmus sp.

grown in different media condition

Carlo Pozza M. Sc.1, Dipl.-Ing. Sebastian Schmuck M. Sc.

1*,

Dr.-Ing. Thorsten Mietzel1

1Urban Water and Waste Management, Faculty of Engineering Sciences

Building Sciences, University of Duisburg-Essen, Universitätsstr. 15, 45141 Essen

*Presenting Author: Sebastian Schmuck e-mail: sebastian.schmuck@uni-due.de

Introduction Why microalgae in wastewater treatment?

• Microalgae grow naturally in wastewater

Microalgae remove N and P during their grow (proteins are 45-60% of microalgae dry weight)

• Assimilation of CO2 for photosynthesis

(about 2 tons of CO2 for 1 ton of microalgae; high tolerance to high CO2 concentration; the use of flue gas

enhance the grow of the microalgae)

• Synergic effects

(O2 production (bacteria); rising of the pH for metals and phosphorus precipitation, ammonia volatiliza-

tion)

• Biomass production

(Biogas production, biofuels, fertilizer)

Many experiments have been conducted with microalgae and wastewater but always the wastewater was

filtered and/or sterilized in order to show the ability of microalgae to live and remove nutrients. The pur-

pose of this experiment was to assess the ability of microalgae to remove nutrients in a not pre-treated

wastewater.

Naturally other microorganisms are present in wastewater and they can cooperate or compete with mi-

croalgae. Two main groups of bacteria have effects on microalgae growth and nutrient removal: the het-

erotrophic bacteria and the nitrifying bacteria. Heterotrophic bacteria use the organic carbon and oxy-

gen as a source of energy. Nitrifying bacteria are autotrophic and they use the ammonia as a source of

energy and the CO2 as a source of carbon. The presence of these two groups affected the nutrient re-

moval and the microalgae growth.

Reactor C

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16 18

Time (d)

Co

nce

ntr

ati

on

(m

gN

/L)

TNbN-NH4N-NO2N-NO3

Reactor D

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16 18

Time (d)

Co

nce

ntr

ati

on

(m

gN

/L)

TNbN-NH4N-NO2N-NO3

Reactor B

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16 18

Time (d)

Co

nce

ntr

ati

on

(m

gN

/L)

TNbN-NH4N-NO2N-NO3

Reactor A

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16 18

Time (d)

Co

nce

ntr

ati

on

(m

gN

/L)

TNbN-NH4N-NO2N-NO3

Figure 9. COD concentration in the four reactors. The profiles

are similar because most of the biodegradation can be re-

lated to the heterotrophic bacteria. Their activity is enhanced

due to the oxygen provided from the microalgae.

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18 20

Time (d)

Bio

ma

ss c

on

cen

tra

tio

n (

mg

TS

S/L

)

A

B

C

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18

Time (d)

CO

D (

mg

O2/L

)

A

B

C

D

Parameter Concentration

COD (mgO2/L) 280

TNb (mgN/L) 27,2

N-NH4 (mgN/L) 21,1

N-NO2 (mgN/L) <0,2

N-NO3 (mgN/L) <0,5

P-PO4 (mgP/L) 3,1

TIC (mgC/L) 31,3

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

0 2 4 6 8 10 12 14 16 18

Time (d)

P-P

O4 (

mg

P/L

)

A

B

C

D

Results and discussion

The experiment:

• 1-L photobioreactor;

• fluorescent lights with chlorophyll spectrum (45-55 µmol/m2/s);

• 20:4 day:night cycle;

• pH control areating with pure CO2 (pH in the range 7,0-9,0);

• Microalgae starting concentration: 350 mgTSS/L.

The wastewater:

The effluent of the primary treatment of wastewater treatment plant

of Duisburg-Kaßlerfeld was used in the experiment (In Table 1 the

composition).

Carlo Pozza, M.Sc.

Universität Duisburg-Essen

Urban Water and Waste Manage-

ment

Universitätstraße 15

45141 Essen (DE)

Tel: +49(0)201 183 2856

Fax: +49(0)201 183 3465

carlo.pozza@uni-due.de

www.uni-due.de/siwawi

Acknowledgments This research was founded by the EU in the framework of the Marie Cu-

rie Initial Training Network, (ATWARM, Advanced Technologies for Water

Resource Management).

(B) Scenedesmus sp. cultivated

with high concentration of ammonia

(A) Scenedesmus sp. cultivated

in a conventional media (D) Control reactor

(C) Indigenous microalgae cultivated

from the wastewater of Duisburg

COD Biomass concentration P-PO4

Figure 8. Algae biomass concentration in the three reactors.

The Scenedesmus sp. grown with high concentration of am-

monia had the highest biomass production (360 mgTSS/L, 27

mgTSS/L/d in 6,7 days).

Figure 10. P-PO4 concentration in the four reactors. The phos-

phorous is assimilated by the microalgae and bacteria. The

starting concentration was 3 mgP-PO4/L and the removal was

82%, 60% and 80% for reactors A, B and C respectively.

Conclusions The results show that microalgae growing and nutrient re-

moval in wastewater is feasible and the selection of the bio-

mass, using a different grow media for Scenedesmus sp., im-

proves the efficiency of the treatment. Moreover the microal-

gae have a synergic effect, enhancing the bacteria activity,

achieving a faster nitrogen removal rate compared to the re-

moval rates found in literature (Park, Jin et al. 2010).

Bibliography Choi, O., A. Das, et al. (2010). "Nitrifying bacterial growth inhibition in the pres-

ence of algae and cyanobacteria." Biotechnology and Bioengineering 107(6): 1004-

1011.

Park, J., H.-F. Jin, et al. (2010). "Ammonia removal from anaerobic digestion efflu-

ent of livestock waste using green alga Scenedesmus sp." Bioresource Technology

101(22): 8649-8657.

Pittman, J. K., A. P. Dean, et al. (2011). "The potential of sustainable algal biofuel

production using wastewater resources." Bioresource Technology 102(1): 17-25.

Wang, L., M. Min, et al. (2009). "Cultivation of Green Algae Chlorella sp. in Differ-

ent Wastewaters from Municipal Wastewater Treatment Plant." Applied Biochem-

istry and Biotechnology 162(4): 1174-1186.

In the Figure 4 to 8 show the profiles of the nitrogen removal are presented for the different

photobioreactors.

The Scenedesmus sp. cultivated with a high concentration of ammonia was more effective treating

the wastewater: 99% removal of TN in 6.7 days, 3.8 mgN/L/d.

The Scenedesmus sp. grown achieved a 95% of removal of TN in 14 days.

The indigenous mix of microalgae had a removal of 98% in 14 days (removal rate: 1.8 mgN/L/d).

Figure 4. Nitrogen removal profiles using Scenedesmus sp.

grown in a normal media.

Figure 5. Nitrogen removal profiles using Scenedesmus sp.

cutivated with high concentration of ammonia.

Figure 6. Nitrogen removal profiles using indigenous micro-

algae cultivated from the wastewater of Duisburg.

Figure 7. Nitrogen removal profiles in the control reactor.

The wastewater was not sterilized before the experiment and the indigenous bacteria influenced the

nitrogen composition.

After 2-3 days ammonia oxidising bacteria developed in all reactors due to the aerobic condition

caused by the photosynthetic activity.

The nitrifying bacteria converted the ammonia to nitrite and then nitrate. Both were assimilated by

the microalgae in the last days of the experiment.

Materials and Methods Table 1. Parameters of the wastewater

used in the experiment.

Figure 3. (C) Indigenous microalgae

cultivated from the wastewater of

Duisburg. Mainly Chlorella sp. and

Scenedesmus sp.

Figure 2. (B) The same Scenedes-

mus sp. as (A) but cultivated with

high concentration of ammonia

(1200 mgN-NH4/L in a modified BG-

11 media).

Figure 1. (A) Scenedesmus sp. culti-

vated in a modified BG-11 media.

The microalgae

(A) Scenedesmus sp. grown in a normal media;

(B) Scenedesmus sp. grown with high concentration

of ammonia;

(C) Indigenous microalgae cultivated from the wastewater of

Duisburg;

(D) Control reactor (no microalgae).

50 µm 30 µm 30 µm