Anammox upflow hybrid reactor: Nitrogen removal performance and potential for phosphorus recovery

Echoing to the call of recovering high-value-added chemicals from wastewater and achieving carbon-neutral operation in wastewater treatment, an anammox upflow hybrid reactor was successfully applied for nitrogen removal, and the potential for phosphorus recovery was put forward. Moreover, the spatial pattern of removal capacities, and distribution of biomass and HAP precipitates were recognized and demonstrated as height-oriented. The intensity of HAP precipitates was highly consistent with the amount of anammox biomass and the relative abundance of the Candidatus Kuenenia, indicating that HAP formation was encouraged by the anammox reaction itself and heterogeneous nucleation induced by organic matters (proteins and polysaccharides). The fixed bed also played an important role in immobilizing the anammox biomass, secreted organic matrix, and HAP precipitates. This finding also provoked the thought that in the anammox process, HAP precipitation was more achievable, effective and practicable using the fixed-carrier system.

Adaption and restoration of anammox biomass to Cd(II) stress: Performance, extracellular polymeric substance and microbial community

Cadmium (Cd) can cause the deterioration of biological systems through inhibiting the enzymes activity and disturbing the microbial metabolism. Although the influence of Cd on conventional wastewater treatment process has been studied, the response of anammox to Cd exposure still remains unclear. This study firstly investigated the adaption and restoration of anammox biomass to Cd(II) stress. Results showed that long-term exposure of anammox bacteria to 2 mg L^-1 Cd(II) was beneficial for the reactor performance, while 5 mg L^-1 Cd(II) would cause the decline of SAA, extracellular polymeric substance content and relative abundance of Candidatus kuenenia by 40%, 25% and 31%, respectively. Furthermore, these indexes could approximately recover to the initial status after withdrawing Cd(II) from the influent. Overall, the anammox biomass exhibited a certain adaption and restoration ability to the suppression of Cd(II). This study may provide key valuable information for the biological treatment of wastewater containing Cd(II).