A novel strategy for anammox consortia preservation: Transformation into anoxic sulfide oxidation consortia

Perchlorate bioreduction in UASB reactor: S2--autotrophic granular sludge formation and sulphate generation control

Perchlorate (ClO4-) industrial wastewater requires efficient removal to prevent adverse environmental impacts, however, high concentration and low biodegradability give rise to poor ClO4- bioreduction performance. S2--autotrophic granular sludge (S2--AuGS) was firstly cultivated for high concentration perchlorate (ClO4-) removal in the upflow anaerobic sludge blanket (UASB) reactor (ClO4-: 150 mg L^-1). Simultaneously, the S2- was utilized to control the SO42- generation as electron donor, the effluent SO42- concentration (190 mg L^-1) was satisfied with drinking water standard (250 mg L^-1). Under the optimized condition of hydraulic retention time (HRT) (6 h) and S2-/ClO4- molar ratio (2.2), more EPS was secreted, which promoted the S2--AuGS formation and stability. Though acclimation of 146 d, the S2--AuGS was formed with a large average granular sludge size (612 μm) and an excellent settleability (sludge volume index: SVI₅/SVI₃₀= 1). With the mature S2--AuGS formation, the highest ClO4- and S2- loading was increased to 1.06 and 0.75 kg m^-3 d^-1. Interestingly, Georgfuchsia, Methyloversatilis, Sulfurisoma, and Exiguobacterium were the main microbial community in the S2--AuGS. This study proposed to form a novel S2--AuGS for developing the high ClO4- concentration removal performance and to utilize the S2- as an electron donor for controlling the excessive SO42- generation.

Recent Advances in Autotrophic Biological Nitrogen Removal for Low Carbon Wastewater: A Review

Due to carbon source dependence, conventional biological nitrogen removal (BNR) processes based on heterotrophic denitrification are suffering from great bottlenecks. The autotrophic BNR process represented by sulfur-driven autotrophic denitrification (SDAD) and anaerobic ammonium oxidation (anammox) provides a viable alternative for addressing low carbon wastewater. Whether for low carbon municipal wastewater or industrial wastewater with high nitrogen, the SDAD and anammox process can be suitably positioned accordingly. Herein, the recent advances and challenges to autotrophic BNR process guided by SDAD and anammox are systematically reviewed. Specifically, the present applications and crucial operation factors were discussed in detail. Besides, the microscopic interpretation of the process was deepened in the viewpoint of functional microbial species and their physiological characteristics. Furthermore, the current limitations and some future research priorities over the applications were identified and discussed from multiple perspectives. The obtained knowledge would provide insights into the application and optimization of the autotrophic BNR process, which will contribute to the establishment of a new generation of efficient and energy-saving wastewater nitrogen removal systems.

Storage without nitrite or nitrate enables the long-term preservation of full-scale partial nitritation/anammox sludge

Bioaugmentation with summer harvested sludge during winter could compensate for bacterial activity loss but requires that sludge activity can be restored after storage. This study assesses the effect of temperature and redox adjustment during the storage over 180 days of partial nitritation/anammox (PN/A) granular resp. floccular sludge from potato processing resp. sludge reject water treatment. Anoxic storage conditions (in the presence of nitrite or nitrate and the absence of oxygen) resulted in a loss of 80-100% of the anammox bacteria (AnAOB) activity capacity at 20 °C and 4 °C, while anaerobic conditions (without oxygen, nitrite, and nitrate) lost only 45-63%. Storage at 20 °C was more cost-effective compared to 4 °C, and this was confirmed in the sludge reactivation experiment (20 °C). Furthermore, AnAOB activity correlated negatively with the electrical conductivity level (R² > 0.85, p < 0.05), so strong salinity increases should be avoided. No significant differences were found in the activity capacity of aerobic ammonia-oxidizing bacteria (AerAOB) under different storage conditions (p > 0.1). The relative abundance of dominant AnAOB (Candidatus Brocadia) and AerAOB genera (Nitrosomonas) remained constant in both sludges. In conclusion, preserving PN/A biomass without cooling and nitrite or nitrate addition proved to be a cost-effective strategy.