Day 0 Day 63 Day 120 Day 185

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0.25

10 15 20 25 30 35

NO

B a

ctiv

ity (

g N

/(g

VSS d

))

Temperature (ºC)

Total

Flocculent fraction

Granular fraction

0.00

0.01

0.02

0.03

0.04

0.05

0

20

40

60

80

100

0 50 100 150 200

NO

R (

g N

/(L d

))

Tota

l N

itro

gen

Rem

oval

(%

)

Time (d)

TN removal

NOR

AOB

NOB

Anammox

Secondary settlerAerobic SRT: 2 d

Anaerobic digester

Digested Sludge

Biogas

Annammox based processes unit

Annammox based processes unit

Reject Water

Modifications of a conventional WWTP

with the inclusion of ELAN® process

Primary settler Mainstream

T 15º C80% of total N

NH4

+ 50 mg N/L

Sidestream

T 30º C20% of total N

NH4

+ 1000 mg N/L

AOBNOBAnammox

NOB activity suppression in the anammox based process ELAN® applied to the water line of a WWTP

Acknowledgments:

This work is enclosed in the ITACA project which is funded by the Spanish Ministry of Economy

throught the DCTI INNPRONTA program. The authors belong to the Galician Competitive Group

GRC 2013-12

Referents:

[1] Volcke et al. (2010), Enviromental Technology, 31(11), 1271-1280

[2] Vázquez-Padín et al. (2014), Wter Sciencie and Technology, 69 (6), 1151-1158

Introduction and Objective

Materials and Methods

Results

A. Val del RíoJ.L. CamposA. Mosquera-Corral

R. Méndez

Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain. e-mail: mangeles.val@usc.es, Tel.: +34 881816739

involves the reduction of the aeration costs, diminishes the sludge production [1]

and reduces the need of organic carbon for denitrification.

sludge anaerobic digesters that normally accounts for 20% of the total nitrogen in

a WWTP.

is applied to the mainstream line of a WWTP: the low a mmonia concentration and

the low temperatures of municipal wastewater.

Objective: the present work is focused on the study of the feasibility of the ELAN®

(“ELiminación Autótrofa de Nitrógeno”) process applied to the main stream of a

WWTP. The ELAN® process consists of a one-stage autotrophic nitrogen removal

process based on granular biomass.ELAN®: Partial nitrification + anammox in a single stage with granular biomass

REACTOR: A laboratory scale sequencing batch reactor (SBR)

with a useful volume of 4 L was operated in cycles of 3 hours

comprising: 150 min of feeding+aeration+stirring, 28 min of

settling and 2 min of withdrawal.

FEEDING: Supernatant from an anaerobic sludge digester diluted

to simulate an urban wastewater, which COD was previously

removed. The average ammonia inlet concentration was 50 mg

NH4+-N/L.

The applied nitrogen loading rate (NLR) was of 0.10 g NH4+-N/L·d

and the hydraulic retention time (HRT) of 0.5 days.

INOCULUM: 9 g VSS/L of granular biomass from an ELAN® pilot

plant [2] treating reject water from a anaerobic digester of a

municipal WWTP.

N. Morales J.R. Vázquez-Padín R. Fernández-González

Aqualia (FCC Group), Guillarei WWTP, Camino de la Veiga s/n, E-36720 Tui, Spain

Parameter Stage I Stage II Stage III

Days 0 – 40 41 – 170 171 – 220

Settling velocity imposed (m/h) 0.13 0.13 0.36

VSSreactor

(g/L) 10.4 ± 2.4 10.5 ± 1.8 11.7 ± 1.7

Average granules diameter (mm) 2.4 ± 0.1 2.4 ± 0.2* -

NOB activity mainly present on the flocculent fraction

Biomass evolution through the operational period (size bar 2 mm).

During the first 40 operational days with the granular

sludge the nitrogen removal efficiency achieved was

around 80%.

Nitrite oxidizing bacteria (NOB) were present in the

inoculum in a low proportion (2 – 3%), but with a

negligible activity at macroscopic scale.

The structure of the granular biomass was progressively

damaged and the detachment of biomass from the granule

surface occurred. The increase of the surface for oxygen

liquid-solid transfer promoted the access of NOB to the

substrates, and an increase of the nitrite oxidation rate

(NOR) was observed.

Biomass activity assays showed that NOB were more active

in the flocculent fraction than in the granular one.

An increase of the imposed settling velocity in the SBR

removed most of the NOB, which were mainly present in

the flocculent biomass. This action favored the recovery

of the nitrogen removal efficiency (from values of 20% to

60%).

An ELAN® reactor at pilot plant scale treating primary

settled wastewater is being operated in a municipal WWTP

in order to further assess the performance of the process.

Discussion and Conclusions

3

Thermostatic system

Air pump

Effluent

Feeding

11

9

8

2

1

5

4

6

7

Photograph of the laboratory

SBR and scheme of the

experimental set-up:

1.- Effluent pump.

2.- Influent pump.

3.- Dissolved oxygen indicator.

4.- Thermostatic bath.

5.- Gas diffuser.

6.- Air pump.

7.- Effluent port.

8.- Dissolved oxygen probe.

9.- Influent port.

10.- Recycled air port.

11.- Mechanical stirring

system.

S-I S-II S-III

Stage III: increase on the settling velocity imposed to remove the flocculent fraction characterized by a high NOB activity