Mixed Sludge Reactor Research Articles

Performance and microbial community analysis of two sludge type reactors in achieving mainstream deammonification with hydrazine addition

The deammonification process is a promising and energy efficient nitrogen removal technology. Since deammonification process has succeeded in high-strength ammonia nitrogen wastewater treatment (sidestream deammonification) but its application in treating low-strength ammonium nitrogen wastewater (mainstream deammonification) remains a great challenge. In this study, mainstream deammonification process in two reactors maintained stability with hydrazine (N2H4) addition. The two reactors consisted of a deammonification granular reactor and a mixed ammonia oxidizing bacteria (AOB) flocculent with anaerobic ammonia oxidizing bacteria (AnAOB) granular reactor. Deammonification granular reactor had a more efficient total nitrogen removal efficiency (TNRE, 80.5 ± 5.8%) and nitrogen removal rate (NRR, 0.33 ± 0.04 g/(L·day)). The advantage of retain biomass in granular sludge reactor lead to a more balanced ex-situ activity between AOB (0.37 mg N/(g VSS·h)) and AnAOB (0.43 mg N/(g VSS·h)). Candidatus Brocadia and Nitraspira were detected the dominant genus responsible for the observed AnAOB and nitrite oxidizing bacteria (NOB), respectively. The more obvious effect of N2H4 on enhancing AnAOB and suppressing NOB both in ex-situ activity and genus abundances in mixed sludge reactor were also founded may due to loose spatial distribution among species.

Comparison of Simultaneous Nitrification and Denitrification for Three Different Reactors.

Discharge of high NH4-N containing wastewater into water bodies has become a critical and serious issue due to its negative impact on water and environmental quality. In this research, the performance of three different reactors was assessed and compared with regard to the removal of NH4-N from wastewater. The highest nitrogen removal efficiency of 98.3% was found when the entrapped sludge reactor (ESR), in which the sludge was entrapped in polyethylene glycol polymer, was used. Under intermittent aeration, nitrification and denitrification occurred simultaneously in the aerobic and anaerobic periods. Moreover, internal carbon was consumed efficiently for denitrification. On the other hand, internal carbon consumption was not found to occur in the suspended sludge reactor (SSR) and the mixed sludge reactor (MSR) and this resulted in nitrogen removal efficiencies of SSR and MSR being 64.7 and 45.1%, respectively. Nitrification and denitrification were the main nitrogen removal processes in the aerobic and anaerobic periods, respectively. However, due to the absence of sufficient organic carbon, denitrification was uncompleted resulting in high NO3-N contents in the effluent.