Autotrophic growth activity of complete ammonia oxidizers in an upflow biological contact filter for drinking water treatment

Utilization and applications of stable isotope analysis for wastewater treatment systems: A review

Stable isotopic analysis (SIA), traditionally crucial in ecological and geochemical studies, has recently expanded its applications to include wastewater management among other fields. This method is instrumental in verifying natural attenuation processes and deepening understanding of operations within engineering systems, such as groundwater, drinking water, and wastewater treatment. This review explores recent advancements in SIA, emphasizing its significance and potential applications in wastewater treatment. We highlight how this analysis can trace various sources within wastewater treatment processes, elucidate the mechanisms responsible for organic matter and nutrient removal in biological treatments, and facilitate the analysis of microbial communities. The review discusses a wide range of isotopic analytical methods, from bulk analysis and compound-specific approaches, covering sample preparation and extraction techniques. We also examine advanced tools like gas chromatography - isotope ratio mass spectrometer (IRMS) and liquid chromatography-IRMS which enhance the accuracy of source identification and address the limitations of bulk analysis. Literature shows a positive correlation between δ15N assimilation in activated sludge and nitrogen removal performance in reactors. Additionally, the review assesses the role of SIA in identifying active microbes involved in the degradation of specific pollutants in biological wastewater treatment. Finally, we discuss current limitations of SIA in wastewater treatment and propose potential research directions to broaden its applicability.

Altitudinal patterns of alpine soil ammonia-oxidizing community structure and potential nitrification rate

Nitrogen availability limits the net primary productivity in alpine meadows on the Qinghai-Tibetan Plateau, which is regulated by ammonia-oxidizing microorganisms. However, little is known about the elevational patterns of soil ammonia oxidizers in alpine meadows. Here, we investigated the potential nitrification rate (PNR), abundance, and community diversity of soil ammonia-oxidizing microorganisms along the altitudinal gradient between 3,200 and 4,200 m in Qinghai-Tibetan alpine meadows. We found that both PNR and amoA gene abundance declined from 3,400 to 4,200 m but lowered at 3,200 m, possibly due to intense substrate competition and biological nitrification inhibition from grasses. The primary contributors to soil nitrification were ammonia-oxidizing archaea (AOA), and their proportionate share of soil nitrification increased with altitude in comparison to ammonia-oxidizing bacteria (AOB). The alpha diversity of AOA increased by higher temperature and plant richness at low elevations, while decreased by higher moisture and low legume biomass at middle elevations. In contrast, the alpha diversity of AOB increased along elevation. The elevational patterns of AOA and AOB communities were primarily driven by temperature, soil moisture, and vegetation. These findings suggest that elevation-induced climate changes, such as shifts in temperature and water conditions, could potentially alter the soil nitrification process in alpine meadows through changes in vegetation and soil properties, which provide new insights into how soil ammonia oxidizers respond to climate change in alpine meadows.IMPORTANCEThe importance of this study is revealing that elevational patterns and nitrification contributions of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) communities were primarily driven by temperature, soil moisture, and vegetation. Compared to AOB, the relative contribution of AOA to soil nitrification increased at higher elevations. The research highlights the potential impact of elevation-induced climate change on nitrification processes in alpine meadows, mediated by alterations in vegetation and soil properties. By providing new insights into how ammonia oxidizers respond to climate change, this study contributes valuable knowledge to the field of microbial ecology and helps predict ecological responses to environmental changes in alpine meadows.