Shinya ONO
Development of biological nitrogen removal technology in recirculating system for oceanarium
Takashi YAMAGUCHI
As for the recirculating system used in the aquarium, nitrogenous constituent of the aquatic life origin such as fishes is not removal now. The breeding water has been diluted with seawater in the oceanarium, because of the nitrogen removal. However, it costs a lot of costs to such a water-purity control. Therefore, the nitrogen removal technology that the decrease of the dilution volume of water is possible is requested.
The present study for the biological waste treatment might influenced from the composition and the density of the wastewater. Cause the synthetic seawater was used as breeding water. We aimed at the development of a biological nitrogen removal process of the no dilution type that combines a nitrification reactor with DHS reactor and few findings with a denitrification reactor with UASB reactor that can be used under the salinity condition.
The pilot machine was composed of water tank 200L that fish breeding had been assumed, UASB tank 10L , and DHS tank 34L.UASB seeding sludge is denitrification sludge that raised up synthetic seawater of salt concentration 3.0% and methane fermentation sludge, industrial wastewater treatment sludge. Seeding sludge of DHS used the activated sludge. HRT of the UASB tank is 5.0 h that shortened gradually. HRT of DHS is 0.09 h. The artificial breeding water has been adjusted to become 3.0% in the density of the salt by using the synthetic seawater. Moreover, ammonium chloride was added 1.24 mg-N/L/day in the water tank, that assumed ammonia sources generated from the fish of 3 kg/m3.In the water tank pH has been adjusted by using the hydrochloric acid to become 8.0. Sodium acetate (g C/g N = 3.0) was used for the electron donor in UASB.
As a result of experimenting, according to the nitrification of DHS, ammonia in the water tank is 0.1(¡Þ0.31) mg-N/ L. The average nitrite is 0.02(¡Þ0.02) mg-N/L. Remarkable accumulation of ammonia and nitrite in the water tank was not confirmed and nitrification was done enough. The performance of denitrification was evaluated by the theory settling density. The performance of denitrification by the HRT change was HRT 5.0, 2.5, 1.2 h that became below the theory settling density and an excellent result was obtained. Moreover, the bacterium bush of sludge was analyzed in UASB. As a result, Denitrifying bacteria accounted for 36% of the whole in uasb.
It was shown that this treatment process was able to be used from the above-mentioned result as a nitrogen removal technology of the no dilution type intended for the oceanarium.
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