Pilot-scale implementation of mainstream anammox for municipal wastewater treatment against cold temperature
Qi Zhao, Yongzhen Peng, Jianwei Li, Tipei Jia, Qiong Zhang, Liang Zhang
Abstract
Applying anammox to municipal wastewater treatment promises enormous energy and resource savings; however, seasonally cold conditions pose a considerable challenge, impeding its future applications towards non-tropical regions. In this study, we establish a pilot-scale wastewater treatment plant (50 m3/d) in northern China and implement the partial denitrification coupling anammox process on actual municipal wastewater. Despite seasonal cooling, the nitrogen removal efficiency remains high, ranging from 75.0 ± 4.6% at 27.8–20.0 °C to 70.4 ± 4.5% at 10–7.5 °C. This process exhibits remarkable low-temperature tolerance, achieving an in-situ anammox rate of 32.7 ± 4.7 g-N/(m3·d) at 10–7.5 °C and contributing up to 39.7 ± 6.7% to nitrogen removal. Further 15N stable isotope tracing and kinetic tests reveal that the partial denitrification is capable of supplying increasingly abundant NO2- to anammox with decreasing temperature, enabling robust mainstream anammox against seasonal cooling. From 27.8 °C to 7.5 °C, anammox bacteria not only survive but thrive under mainstream conditions, with absolute and relative abundances increasing by 429.1% and 343.5%, respectively. This pilot-scale study sheds fresh light on extending mainstream anammox towards non-tropical regions, taking a necessary step forward toward the sustainability goals of the wastewater treatment sector. Low temperatures pose challenges to applying sustainable anammox technology in non-tropical regions. Here, authors propose a partial denitrification coupling anammox process and conduct a pilot-scale evaluation, offering insights into extending anammox applications to colder locations.