Salinity acclimation of immobilized freshwater denitrifier. [Erratum: Aug 2002, v. 26 (3), p. 215.]
2001
Park, E.J. | Seo, J.K. | Kim, M.R. | Jung, I.H. | Kim, J.K. | Kim, S.K.
To develop a marine recirculating aquarium system, the marine denitrification process was evaluated for the effects of salinity, temperature and hydraulic retention time (HRT) on marine denitrification processes. Denitrifier consortium was collected from a continuous denitrification tank operated for 120 days and was immobilized by the PVA-boric acid method. Four reactors were simultaneously operated to determine the effect of salinity. One of them, R-1, was supplied with tap water as a control, and others, R-2, R-3 and R-4 were supplied with sea water diluted with tap water by 3 steps (7.5, 15, 30 ppt), 2 steps (15, 30 ppt) and 1 step (30 ppt), respectively. The loading rate of nitrate-nitrogen averaged 20.6 g/m(3)/day. Salinity caused nitrite-nitrogen formation at the early stage of acclimation, even though the conversion rates of nitrate for high salinites were similar to that of the control (freshwater). Addition of salt to the system might cause a damage to denitrifiers that convert nitrate to nitrogen gas, however the activity was recovered after 10 days of operation. Also, the direct acclimation method to seawater was more efficient than the stepwise acclimation method when the freshwater denitrification system was converted to the marine system. As the HRT was reduced, the nitrate removal rate increased and denitrification efficiency decreased. The optimum HRT was 3 h with a nitrate removal rate of 34 g/m(3)/day. Any further decrease in HRT decreased the nitrate removal rate due to the rapid drop of nitrate removal efficiency and high flow rate.
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