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Stable long-term operation and high nitrite accumulation of an endogenous partial-denitrification (EPD) granular sludge system under mainstream conditions at low temperature

Ji, Jiantao, Peng, Yongzhen, Li, Xiyao, Zhang, Qiong
Bioresource technology 2019 v.289 pp. 121634
anaerobic ammonium oxidation, denitrification, nitrate nitrogen, nitrites, nitrogen dioxide, polymers, sludge, temperature
In this study, the robustness of an endogenous partial-denitrification (EPD) system was demonstrated during a 105 days operation under mainstream conditions at low temperature. The results showed a high nitrate-to-nitrite transformation ratio (NTR) of 88.7%, a suitable NO2−-N/NH4+-N ratio of 1.09, and no residual NO3−-N in the effluent, as reactor temperature was decreased from 25 °C to 13.5 °C. The stable morphology of the EPD granular sludge with high extracellular polymeric substance content (273.6–308.1 mg/g VSS) contributed to the steady performance of the EPD system. Bath tests revealed that the maximum NTRs (95.6% and 96.3%) were slightly higher at 10 °C and 15 °C than those (90.4% and 92.0%) at 20 °C and 30 °C, resulting from the lower poly-β-hydroxyvalerate degradation rate or the negligible denitrifying dephosphatation activity at low temperatures. Thus, the EPD system has the potential to provide stable nitrite for mainstream anammox at low temperature.