Water Science & Technology Vol 42 No 3-4 pp 369–376 © IWA Publishing 2000
Nitrogen removal from hydroponic culture wastewater by autotrophic
denitrification using thiosulfate
R Yamamoto-Ikemoto*, T Komori**, M Nomuri***, Y Ide**** and T Matsukami*****
*
Dept. of Civil Engng., Kanazawa Univ., 2-40-20 Kodastuno, Kanazawa City, 920-8667, Japan
**
Dept. of Civil Engng., Kanazawa Univ., 2-40-20 Kodastuno, Kanazawa City, 920-8667, Japan
***
Meiwa Kogyo Co. Ltd., 29 Yakushido, Kanazawa City, 920-0052, Japan,
****
Dept. of Civil Engng., Kanazawa Univ., 2-40-20 Kodastuno, Kanazawa City, 920-8667, Japan
*****
Dept. of Civil Engng., Kanazawa Univ., 2-40-20 Kodastuno, Kanazawa City, 920-8667, Japan
ABSTRACT
Using the upflow biological filter reactor, sulfur denitrification using
thiosulfate of hydroponic culture wastewater was examined. Start-up periods
of the reactor were one to two weeks. About 90% of nitrogen removal ratio
were achieved over 80 days, at 6.3 kg/m3.days of nitrogen
loading. Shock loading among 0.56-2.8 kgN/m3.m3day did
not affect the reactor performance. However, when temperature went below
15°C, the effluent characteristics became poor. Suitable S/N and IC/N
ratios were calculated as 3.3 and 0.15, respectively. The activities of
sulfur denitrification, heterotrophic denitrification and sulfur reduction
were examined by the bath experiments under several conditions using
biomass grown in the reactor. In the anoxic conditions, denitrification
using thiosulfate was occurred stoichiometrically in the presence of
thiosulfate. The denitrification activity was highest
(17 mgN/gBiomass.hr). When the electron donor was not added to the
substrate, denitrification occurred using sulfur granules accumulated in the biomass. Seventy mg of sulfur granule were accumulated in one g of
biomass. The denitrification activity using sulfur granules was
2.9-5.0 mgN/gBiomass.hr. Heterotrophic denitrification occurred in
the presence of organic matter. The activities were
1.4-5.4 mgN/gBiomass.hr. In the anaerobic conditions, the
accumulated sulfur was reduced to sulfide at a rate of
1.4 mgS/gBiomass.hr. These results suggested that sulfur
denitrification, heterotrophic denitrification and sulfur reduction
bacteria coexisted in the biofilm and sulfur cycle was established in
the reactor. Accumulated sulfur plays an important role in the sulfur
denitrification.
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