A Combined Denitrification Sludge Bed-Suspended-Growth Nitrification Reactor System Treating High-Strength Nitrogen Wastewater

A combined denitrification sludge bed-suspended-growth nitrification reactor system treating high-strength nitrogen wastewater (similar to anaerobically pretreated piggery wastewater; COD = 2,010 - 3,610 mg/L, NH₄⁺-N = 1,000 mg/L, TP = 115 -122 mg/L) was performed to generate experimental data. In the combined reactor system, the upflow denitrification sludge bed (DSB) proceeds denitrification (together with the utilization of inflow organics) that required electron acceptors (NO₂^-and NO₃^-) are recycled from the supernatant of the suspended-growth nitrification reactor (SNR). IUnder proper operating conditions (NH₄⁺-N loading, NO_x^--N loading, recycle ratio of nitrified-effiuent, HRT, and MCRT), the combined reactor system was very effective for nitrification-denitrification. According to material-balance calculations using operating conditions and performance data of the steady-state combined reactor systems (eight test runs), the specific nitrification rates and the specific denitrification rates were 0.39 -0.48 mg NH₄⁺-N /mg VSS-d and 0.18 - 0.30mg NO_x^--N/mg VSS-d, respectively. The measured alkalinity consumption in the SNR reactor was close to the theoretical, while the measured alkalinity production in the DSB reactor was close to the theoretical. In other words, the measurement of alkalinity changes can be adequately used for monitoring a combined reactor system. Sludge granulation did occur in the DSB reactor under the superficial flow velocity of 2 m/h (eight test runs).When steady states were reached in the combined reactor system, sludge and granules were respectively removed from the SNR and DSB reactors, respectively. From independent batch experiments using such sludge (granules), the estimated fn2 and fdn2 values were 0.30 - 0.68 and 0.62 - 0.87, respectively. A combined denitrification sludge bed-suspended-growth nitrification reator system treating similar to anaerobically pretreated piggery wastewater, NH₄⁺-N removal were 98.5%-99.9%. Accordingly this system were very efficient and appropriate with treating high-strength nitrogen wastewater.