| Anammox process, as an effective and economic denitrifying method to treat wastewater, has been accepted worldwide. However, this process needs nitrite as electron acceptor. Nitrite can be obtained in the process of heterotrophic denitrification. It studied the effects of carbon sourc on nitrite accumulation. And we studied the reason that nitrite could accumulate. Moreover, it observed the nitrite accumulation in SBR reactor. All those work is to serve more information to the “Partial Denitrification-Anammox”process.Denitrification experiment using common carbon source as electron donor showed that: when it was at 18±2℃ and carbon source was glucose, the nitrate degradation rate grew with C/N; Nitrate-to-nitrite transformation ratio(NTR) was high, while the conversion rates of nitrate and nitrite were relatively low, they grew with C/N and reached 70%, 46% and 32.2% at C/N=5.7, respectively. When carbon source was acetate, the nitrate degration rate grew with C/N, while nitrite accumulation rate got to the maximum value at C/N=3.4; nitrate conversion rate grew with C/N, while NTR and nitrite conversion rate achieved their maximum values(38.00% and 23.56%) at C/N=3.4. Using glucose as carbon source at 28±2℃, nitrate degration rate grew with C/N; NTR, nitrate and nitrite conversion rates all increased with C/N, achieved 71.0%, 96.0% and 68.2% at C/N=5.7, respectively. When carbon source was acetate, NTR values were high at all C/N systems, nitrate and nitrite conversion rates both grew with C/N increasing, and achieved 79.00% and 61.62%, respectively. High temperature benefited accumulation of nitrite, glucose had an advantage over acetate.Denitrifing enzyme activity experiment shows that: in 30 min, nitrate reductase activity was about twice as much as nitrite reductase, thus nitrite was accumulated.Denitrification experiment using unusual carbon source(straw leachate, ultrasonic disintegration liquid and sludge hydrolysate) as electron donor showed that: in the organic components of straw leachate and ultrasonic cracking liquid, volatile fatty acids accounted for above 55%, so they were applicable to be carbon sources. Combining nitrite accumulation with the removal of COD, the suitable C/N were 5.2 and 5.5~8.3, respectively. While in ultrasonic disintegration liquid, VFA only accounted for 16.5%.C/N=2.0~3.6, ultrasonic disintegration liquid benefited more for NTR、nitrate conversion rate and nitrite accumulation rate, than the other two carbon sources; C/N=5.0~8.3, nitrate conversion rate and nitrite accumulation rate of straw leachate and ultrasonic disintegration liquid were high; C/N=11.0~13.7, straw leachate had advantage over the other two carbon sources overall.The experiment of observing nitrite accumulation activated sludge in SBR showed that: when using glucose as carbon source, setting C/N=3.0, nitrate concentration as 19.0~23.0mg/L, reaction period as 3h, we could observe the long-term stable accumulation of nitrite. The nitrite concentration in effluent was 19.0~23.0mg/L, NTR was above 60%, nitrate conversion rate was above 89%, nitrite accumulation rate got 55%~65%. |
