Nitrogen removal from high nitrogen soybean wastewater by simultaneous nitrification and denitrification via nitrite

An innovative technology for nutrient removal from high nitrogen soybean wastewater was developed by controlling dissolved oxygen(DO) concentration in sequencing batch reactor (SBR). The experimental results showed that when DO concentration was maintained at 0.5 mg·L -1 during aeration, nitrosation rate (NO-_2-N/NO-__x-N) was always more than 93% during nitrification, and ammonia removal via simultaneous nitrification-denitrification was up to 87.6% when aeration was ended. So nitrification-denitrification via nitrite and simultaneous nitrification-denitrification (SND) were achieved in a single reactor by controlling DO concentration at 0.5 mg·L -1. Based on theoretical analysis and calculations of the new technology, the specific growth rate of ammonium oxidizers was about 2.22—2.43 times than nitrite oxidizers at DO=0.5 mg·L -1, and the anoxic area for denitrification was easily built in activated sludge in the DO condition.In conclusion,stable nitrogen removal from wastewater by simultaneous nitrification-denitrification via nitrite at normal temperature could be achieved so long as DO was controlled at 0.5 mg·L -1.