Organic and inorganic nitrogen removals by an ureolytic heterotrophic nitrification and aerobic denitrification strain Acinetobacter sp. Z1: Elucidating its physiological characteristics and metabolic mechanisms.

Although heterotrophic nitrification-aerobic denitrification (HN-AD) is promising in nitrogen removal, it remains unclear for most HN-AD strains in physiological characteristics and metabolic mechanisms. In this study, a newly isolated strain Acinetobacter sp. Z1 converted not only inorganic nitrogen, but also organic nitrogen to N2. Among them, urea was the preferential nitrogen substrate. Single-factor experiments showed that efficient HN-AD process occurred with acetate as carbon source, C/N ratios of 12 for NH4+-N and 15 for NO3--N, pH 8, 30 °C, DO of ∼5.8 mg/L and salinity less than 1.5 %. Subsequently, response surface analysis was applied to predict the optimal growth conditions. Its complete genome annotation in combination with enzymatic activity assay and nitrogen balance calculation showed that at least four pathways involved in nitrogen metabolism. This work indicates that ureolytic strain Z1 could be prepared as bacterial agents with other HN-AD strains to treat urea-containing wastewater like urine from urban community.

Low carbon-to-nitrogen ratio digestate from high-rate anaerobic baffled reactor facilitates heterotrophic/autotrophic nitrifiers involved in nitrogen removal.

In this study, baffled anaerobic-aerobic reactors (AOBRs) with modified basalt fiber (MBF) carriers and felt were used to treat domestic wastewater (DWW). The influent was first treated in anaerobic compartments, with the NH4+-N containing digestate refluxed into aerobic compartment for nitrification. The nitrified liquid was channeled to the anaerobic compartments for further denitrification. Under optimal conditions, AOBR with MBF carriers could remove 91% chemical oxygen demand (COD) and 81% total nitrogen (TN), with biomass production increased by 7.6%, 4.5% and 8.7% in three successive anaerobic compartments compared to the control. Biological viability analysis showed that live cells outnumbered dead cells in bio-nests. Metagenomics analysis showed that multiple metabolic pathways accounted for nitrogen conversion in anaerobic and aerobic compartments. More importantly, low COD/TN ratio digestate facilitated heterotrophic nitrification-aerobic denitrification (HN-AD) species growth in aerobic compartment. This study provides a promising strategy to source treatment of DWW from urban communities.

Calcium modified basalt fiber bio-carrier for wastewater treatment: Investigation on bacterial community and nitrogen removal enhancement of bio-nest.

Modified basalt fiber (MBF) is a sustainable material studied as novel wastewater treatment bio-carrier recently. This work studied the effects of calcium modification on the bacterial affinity of modified fiber (Ca-MBF), bacterial community, and nitrogen removal performance. Results showed that Ca-MBF with hydrophilic (62.66°) and positively-charged (7.80 mV) surface accelerated bacterial attachment. Volatile suspended solids on Ca-MBF (5.46 g VSS/g fiber) were increased by 2.61 times after modification, with high bacterial activity when bio-carriers were cultured in activated sludge. Extracellular polymeric substances on Ca-MBF was 4.35 times higher and consisted of more protein. Bio-nests with unique aerobic/anaerobic structure formed on the ultrafine carriers in bioreactor. Ca-MBF bioreactor exhibited total nitrogen removal efficiency above 72.2% and COD removal efficiency above 94.2% with more stable performance than unmodified carrier in long-term treatment using synthetic domestic wastewater.16S rRNA gene sequencing revealed enhanced abundance of nitrifying and denitrifying bacteria in Ca-MBF bio-nest.

Changes in community structure and metabolic function of soil bacteria depending on the type restoration processing in the degraded alpine grassland ecosystems in Northern Tibet.

The alpine grassland ecosystems in Northern Tibet is seriously degraded. The condition of the degraded alpine grassland ecosystems in Northern Tibet (DAGENT) triggers a serious threat to environmental health and ecological safety of the local society. Thus, restoring DAGENT is a pressing task presently to sustain social stability and sustainable development. Soil microorganisms act a vital role in the structure and function execution of ecosystems. Further, bacteria are sensitive to external disturbances. This study purposes to evaluate the effects of the three types of restoration processing (i.e., the separated plant sowing, the separated water-soluble polyurethane fertilization, and the combined plant sowing and water-soluble polyurethane fertilization) on soil bacterial communities in DAGENT by using high-throughput sequencing with Illumina Novaseq 6000. The separated plant sowing significantly elevations soil pH, and soil nitrogen and phosphorus contents in DAGENT. Additionally, the combined plant sowing and water-soluble polyurethane fertilization markedly improves soil nitrogen content in DAGENT. The combined plant sowing and water-soluble polyurethane fertilization antagonistically affect soil pH and soil phosphorus content in DAGENT. The three types of restoration processing have no obvious effects on the alpha diversity of soil bacteria in DAGENT. But the three types of restoration processing create obvious alterations in the beta diversity of soil bacteria and the relative abundance of soil bacterial proportions in DAGENT. The three types of restoration processing also cause significant modifications in metabolic function of soil bacteria in DAGENT. The leading reason for the altered community structure and metabolic function of soil bacteria may be attributed to the changes in plant growing condition as well as soil pH and nutrient contents in DAGENT. Consequently, the three types of restoration processing are mainly changed the community structure and metabolic function of soil bacteria, rather than the alpha diversity of soil bacteria, in DAGENT.