Domestication and pilot-scale culture of mixed bacteria HY-1 capable of heterotrophic nitrification-aerobic denitrification

Enhanced nitrogen removal from low C/N ratio wastewater by coordination of ternary electron donors of Fe0, carbon source and sulfur: Focus on oxic/anoxic/oxic process

Insufficient organics was the major obstacle for total nitrogen (TN) removal in conventional pre-anoxic denitrification when treating low carbon to nitrogen (C/N) ratio wastewater. This study constructed a novel ternary-electron donors (Fe0, organics and S0) enhanced oxic/anoxic/oxic (O/A/O) process, integrating simultaneous nitrification and denitrification and autotrophic denitrification (ADN), and evaluated its feasibility to achieve efficient nutrient removal under organics-deficient condition. Long-term operation results showed that TN removal was lower (9.9 %) when Fe0 added individually, then raised to 27.3 %∼46.0 % in simultaneous presence of Fe0 and organics. And the highest TN removal (82.0 %) was obtained by coordination of ternary-electron donors, with 8.46 ± 0.43 mg/L TN in effluent. Meanwhile, the O/A/O process exhibited excellent total phosphorous (TP) removal (84.8 %∼98.4 %) derived from chemical precipitation by Fe0, of which the effluent was <0.76 ± 0.04 mg/L TP. Metabolic characteristics indicated that the coordination of multi-electron donors improved microbial metabolism and denitrifying enzymatic activities, thereby promoting ammonia assimilation and enhancing TN removal. And the secretion of EPS was also stimulated, which favored the bio-utilization of Fe0 and S0 and alleviated organics dependence. Besides, the notable increase in abundances of aerobic denitrifiers (23.95 %∼27.37 %), autotrophic denitrifiers (9.31 %) and denitrifying genes further verified the synergy effect of multi-electron donors on TN removal. This study revealed the enhancement mechanism of O/A/O process by coordination of ternary-electron donors, verified its cost-effectiveness and provided innovative insights on low C/N ratio wastewater remediation.

Strategies to enhance production of metabolites in microbial co-culture systems

Increasing evidence shows that microbial synthesis plays an important role in producing high value-added products. However, microbial monoculture generally hampers metabolites production and limits scalability due to the increased metabolic burden on the host strain. In contrast, co-culture is a more flexible approach to improve the environmental adaptability and reduce the overall metabolic burden. The well-defined co-culturing microbial consortia can tap their metabolic potential to obtain yet-to-be discovered and pre-existing metabolites. This review focuses on the use of a co-culture strategy and its underlying mechanisms to enhance the production of products. Notably, the significance of comprehending the microbial interactions, diverse communication modes, genetic information, and modular co-culture involved in co-culture systems were highlighted. Furthermore, it addresses the current challenges and outlines potential future directions for microbial co-culture. This review provides better understanding the diversity and complexity of the interesting interaction and communication to advance the development of co-culture techniques.

Enhanced ammonia removal in tidal flow constructed wetland by incorporating steel slag: Performance, microbial community, and heavy metal release

Utilizing alkaline solid wastes, such as steel slag, as substrates in tidal flow constructed wetlands (TFCWs) can effectively neutralize the acidity generated by nitrification. However, the impacts of steel slag on microbial communities and the potential risk of heavy metal release remain poorly understood. To address these knowledge gaps, this study compared the performance and microbial community structure of TFCWs filled with a mixture of steel slag and zeolite (TFCW-S) to those filled with zeolite alone (TFCW-Z). TFCW-S exhibited a much higher NH4+-N removal efficiency (98.35 %) than TFCW-Z (55.26 %). Additionally, TFCW-S also achieved better TN and TP removal. The steel slag addition helped maintain the TFCW-S effluent pH at around 7.5, while the TFCW-Z effluent pH varied from 3.74 to 6.25. The nitrification and denitrification intensities in TFCW-S substrates were significantly higher than those in TFCW-Z, consistent with the observed removal performance. Moreover, steel slag did not cause excessive heavy metal release, as the effluent concentrations were below the standard limits. Microbial community analysis revealed that ammonia-oxidizing bacteria, ammonia-oxidizing archaea, and complete ammonia-oxidizing bacteria coexisted in both TFCWs, albeit with different compositions. Furthermore, the enrichment of heterotrophic nitrification-aerobic denitrification bacteria in TFCW-S likely contributed to the high NH4+-N removal. In summary, these findings demonstrate that the combined use of steel slag and zeolite in TFCWs creates favorable pH conditions for ammonia-oxidizing microorganisms, leading to efficient ammonia removal in an environmentally friendly manner.

Research progress of novel bio-denitrification technology in deep wastewater treatment

Excessive nitrogen emissions are a major contributor to water pollution, posing a threat not only to the environment but also to human health. Therefore, achieving deep denitrification of wastewater is of significant importance. Traditional biological denitrification methods have some drawbacks, including long processing times, substantial land requirements, high energy consumption, and high investment and operational costs. In contrast, the novel bio-denitrification technology reduces the traditional processing time and lowers operational and maintenance costs while improving denitrification efficiency. This technology falls within the category of environmentally friendly, low-energy deep denitrification methods. This paper introduces several innovative bio-denitrification technologies and their combinations, conducts a comparative analysis of their denitrification efficiency across various wastewater types, and concludes by outlining the future prospects for the development of these novel bio-denitrification technologies.