CONTINUOUS CONTROL OF TOTAL AMMONIA NITROGEN (TAN) IN

SEAWATER AQUACULTURE TANKS

I. Masaló1, J. Oca1, L. Reig1, M. Pujadas2, R. Gómez2, M. Batlle2

1Departament d’Enginyeria Agroalimentària i Biotecnologia (DEAB).

UPC-BARCELONATECH (Spain). 2ADASA Sistemas S.A.U.

www.adasaproducts.com

Oca, J.; Flo, V.; Masaló, I. (2013) Daily evolution of TAN liquid excretion rate in

sea bass (Dicentrarchus labrax). Elsevier Aquaculture Conference 2013, Las

Palmas de Gran Canaria, Spain.

Fig. 1: Aquamonia A103 autonomous analyzer.

An autonomous analyzer (AquaMonia A103), based on the FIA (Flow Injection Analysis) system with potentiometric

measurements was used. The analyzer determines TAN concentration within a range 0.01-4mg L-1. It combines a

selective electrode with a semi-permeable membrane that avoids the sample coming into direct contact with the

electrode. The sample is mixed with sodium hydroxide to achieve pH 12, transforming the ammonium to ammonia

gas, which diffuses through the semi permeable membrane. In this side, a solution with neutral pH transforms the

ammonia to ammonium, which is measured with the selective electrode, avoiding any type of interference due to

the sodium chloride. The equipment works continuously and includes a self-calibration system. Each measurement

lasts around 9 min, which is the minimal interval between consecutive readings.

Water quality monitoring is essential in land based aquaculture systems, since the accumulation of inorganic and organic compounds limit the carrying capacity.

Dissolved Oxygen (DO) and Total Ammonia Nitrogen (TAN) are the most critical parameters to be controlled. An accurate monitoring is needed due to the strong

variation of these parameters over the day.

Continuous TAN determination in seawater is difficult. Most of the methods used are time consuming and their automation is difficult. Otherwise, the use of

automated samplers is complicated due to the fast chemical and microbiological transformations that occur in the samples.

The objective of the present work is to analyze the suitability of a commercial autonomous analyzer to continuously determine the TAN concentration in a seawater

aquaculture tank.

-After feeding concentration rises, achieving the maximum concentration 5h

later.

-During the period without feeding (weekend) ammonium concentration was

maintained at low levels (below 0.3ppm).

-On 23th July at 20:30h, when the water supply failed, TAN concentration

levels increased rapidly, achieving concentrations above 1.5ppm (Fig. 2).

Fig. 2. Ammonium concentration evolution. Determinations were made automatically by

AquaMonia A103 analyzer every 1h during 10 days.

This work was funded by Spanish Ministerio de Economía y Competitividad

(AGL2013-41868-R).

ACKNOWLEDGMENTS

REFERENCES

MATERIAL AND METHODS

RESULTS AND DISCUSSION

0

1

2

3

4

5

6

7

8

0

0,5

1

1,5

2

2,5

Oxygen

(p

pm

)

Am

mo

niu

m (

pp

m)

Ammonia Feeding (50gr) Oxygen failure Oxygen

Weekend (no feeding)

y = 1,0281x

R² = 0,8522

0

0,5

1

1,5

2

2,5

0,0 0,5 1,0 1,5 2,0 2,5

Ph

oto

met

er (

YS

I 9

50

0)

AquaMonia A103

Ammonium (ppm) Comparing the determinations with

the photometer (YSI 9500) and the

AquaMonia A103 analyzer a high

correlation (R2=0.85) is obtained

(Fig. 3).

Fig. 3. Correlation between determinations

with the photometer (YSI 9500) and the

AquaMonia A103 analyzer.

In the present work the suitability of an autonomous analyzer (AquaMonia A103) was evaluated in a tank with Sea bass (36‰). The TAN concentration peak

observed 5h after feeding was in agreement with the results reported by Oca et al. (2013) taking and freezing samples hourly and determining TAN concentration by

fluorimetry (Biotek DR2000). A high correlation is shown between concentrations measured by AquaMonia A103 and by the indophenol method.

AquaMonia A103 has shown to be a useful tool to monitorize TAN concentrations in seawater aquaculture facilities and also to conduct scientific studies about

biofiltration efficiency or daily liquid excretion patterns. Data collected can be sent in real time to a local or remote control center for analysis and use.

Along the experiment, some samples were taken and analyzed

using the indophenol method with a photometer (YSI 9500) to

contrast the results obtained from the AquaMonia A103.

Experiments

-Circular tank with Sea bass (size: 618±197g; stocking density: 15,5 kg m-3)

-Feed ration: 0.8% (from Monday to Friday)

-Flow rate: 400L h-1

-Temperature: 26±1.2ºC; Water salinity 36‰; DO concentration: 6.4±0.7ppm

-Length of the tube sample from the tank to the analyzer: 3m (protected by a mesh of 100μm)

-Sampling frequency 1 hour; self calibration every 10h.