Biological nitrogen removal from wastewater via partial nitrification
2010
Pornpak Thanasawate(Kasetsart University, Bangkok (Thailand). Faculty of Science. Department of Environmental Science) E-mail:[email protected] | Piyapawn Somsamak(Kasetsart University, Bangkok (Thailand). Faculty of Science. Department of Environmental Science)
Biological nitrogen removal from wastewater via partial nitrification of ammonia to nitrite, instead of conventional nitrate, is an alternative process to reduce energy consumption during nitrification and necessities of external organic carbon compounds for denitrification. In the present study the nitrogen removal from synthetic wastewater by partial nitrification-denitrification system was investigated. In the first stage the operation of nitrifying reactor was focused on the study of the optimal conditions to obtain an effluent with nitrite as a main nitrogen compound. Continuous experiments were carried out with three different operational conditions tested. Upon feeding synthetic wastewater with 250 mg NH4+ -N/L and methanol 790 mg/L at HRT of 24 hr, the ammonia-N : nitrite-N : nitrate-N ratio of 32 : 51 : 17 in the nitrifying reactor effluent was obtained. Partial nitrified synthetic wastewater was further treated by fixed-bed denitrification reactor. 90 precent of nitrite and nitrate in the feeding solution was removed. Significant amount of ammonia, however: was detected in denitrified effluent as a result of incomplete oxidation of ammonia in nitrifying reactor. Even though methanol concentration influenced the rate of denitrification, complete denitrification of partial nitrified synthetic wastewater was achieved at methanol to nitrogen ratio as low as 1.
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