Incorporating microbial inoculants to reduce nitrogen loss during sludge composting by suppressing denitrification and promoting ammonia assimilation.

To address the challenge of increasing nitrogen retention in compost, this study investigated the effects of microbial communities on denitrification and ammonia assimilation during sludge composting by inoculating microbial inoculants. The results showed that the retention rates of total Kjeldahl nitrogen (TKN) and humic acid (HA) in MIs group (with microbial inoculants) were 4.94 % and 18.52 % higher than those in the control group (CK), respectively. Metagenomic analysis showed that Actinobacteria and Proteobacteria were identified as main microorganisms contributing to denitrification and ammonia assimilation. The addition of microbial agents altered the structure of the microbial community, which in turn stimulated the expression of functional genes. During cooling period, the ammonia assimilation genes glnA, gltB and gltD in MIs were 15.98 %, 24.84 % and 32.88 % higher than those in CK, respectively. Canonical correspondence analysis revealed a positive correlation between the dominant bacterial genera from the cooling stage to the maturity stage and the levels of NO3--N, NH4+-N, HA, and TKN contents. NH4+-N was positively correlated with HA, indicating NH4+-N might be incorporated into HA. Heat map and network analyses revealed NH4+-N as a key factor affecting functional genes of denitrification and ammonia assimilation, with Nitrospira identified as the core bacteria in the microbial network. Therefore, the addition of microbial agents could increase nitrogen retention and improve compost product quality.

Regulating sludge composting with percarbonate facilitated the methylation and detoxification of arsenic mediated via reactive oxygen species.

This study purposed to demonstrate the impact of reactive oxygen species (ROS) on arsenic detoxification mechanism in sludge composting with percarbonate. In this study, sodium percarbonate was used as an additive. Adding sodium percarbonate increased the content of H2O2 and OH, which the experimental group (SPC) was higher than the control group (CK). In addition, it decreased the bioavailability of arsenic by 19.10%. Metagenomic analysis found that Firmicutes and Pseudomonas took an active part in the overall compost as the dominant bacteria of arsenic methylation. ROS positively correlated with arsenic oxidation and methylation genes (arsC, arsM), with the gene copy number of arsC and arsM increasing to 7.74 × 1012, 5.24 × 1012 in SPC. In summary, the passivation of arsenic could be achieved by adding percarbonate, which promoted the methylation of arsenic, reduced the toxicity of arsenic, and provided a new idea for the harmless management of sludge.

Transmission and regulation insights into antibiotic resistance genes in straw-sludge composting system amended with calcium peroxide.

This study developed a Fenton-like system by adding calcium peroxide (CaO2) to a composting system containing straw and sludge. The objective was to examine the influence of antibiotic resistance genes (ARGs) and the structure of the bacterial community. The findings indicated that the inclusion of CaO2 facilitated the reduction of ARGs. ARGs abundance in the test group (T) with CaO2 was 19.02% lower than that in the control check group (CK) without CaO2, and the abundance of ARGs in both groups after composting was lower than the initial abundance. Additionally, the structure of bacterial community in both groups underwent significant changes. Redundancy analysis (RDA) revealed that the CaO2-induced Fenton-like reaction predominantly affected temperature, pH, and the bacterial community by means of reactive oxygen species (ROS). In conclusion, the addition of CaO2 enhanced the removal of ARGs from sewage-sludge and improved compost quality in the composting.

A novel carbon-nitrogen coupled metabolic pathway promotes the recyclability of nitrogen in composting habitats.

This study revealed a novel carbon-nitrogen coupled metabolic pathway. Results showed that the addition of inorganic carbon sources slowed down the decomposition of urea and conserved more nutrients in composting. Metagenomic analysis showed that the main bacteria involved in this new pathway were Actinobacteria, Proteobacteria and Firmicutes. During the late composting period, the dominant genus Microbacteium involved in denitrification accounted for 22.18% in control (CP) and only 0.12% in treatment group (T). Moreover, ureC, rocF, argF, argI, argG were key genes involved in urea cycle. The abundance of functional gene ureC and denitrification genes decreased in thermophilic and cooling phases, respectively. The genes hao, nosZ, ureA and nifH were more closely associated with Chloroflexi_bacterium and Bacillus_paralichenformis. In conclusion, composting habitats with additional inorganic carbon sources could not only weaken denitrification but also allow more nitrogen to be conserved through slow-release urea to improve resource utilization and decrease the environmental risk.

[Effects of continuous blood purification on hemodynamics and oxygenation in patients with acute respiratory distress syndrome].

OBJECTIVE: To evaluate the effects of continuous blood purification on the hemodynamics and oxygenation in patients with acute respiratory distress syndrome (ARDS). METHODS: Twenty-one patients with ARDS were treated with continuous veno-venous hemofiltration (CVVH) combined with plasma exchange. Hemodynamics and oxygenation were measured or calculated at scheduled intervals using Swan-Ganz catheters. RESULTS: The mean arterial pressure, partial pressure of arterial oxygen, oxygen delivery, oxygen consumption increased, heart rate, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, blood lactate concentration all decreased significantly after the treatment, and the oxygen extraction ratio underwent no obvious changes. CONCLUSIONS: Continuous blood purification can increase blood and oxygen supply but has no significant effects on oxygen extraction ratio in ARDS patients.

[Suppression of geomagnetic field interference in the magnet locating system of the micro-magnetic capsule inside the alimentary tract].

A method for the suppression of geomagnetic field interference is here-in introduced. It is designed for use in the magnet locating system of the engineering-based microcapsule inside the alimentary tract. This method marks the geomagnetic field interference levels by getting the static value. Then subtracting the static value from the dynamic value. The results of the experiment show that the method can assess the geomagnetic fi eld interference levels around thelocating waistcoat accurately. And the three-dimensional tracking trajectory shows that the method has greatly improved the accuracy of the capsule location inside the alimentary tract.