Cattle manure composting driven by a microbial agent: A coupled mechanism involving microbial community succession and organic matter conversion.

Aerobic composting has been used as a mainstream treatment technology for agricultural solid waste resourcing. In the present study, we investigated the effects and potential mechanisms of the addition of a microbial agent (LD) prepared by combining Bacillus subtilis, Bacillus paralicheniformis and Irpex lacteus in improving the efficiency of cattle manure composting. Our results showed that addition of 1.5 % LD significantly accelerated compost humification, i.e., the germination index and lignocellulose degradation rate of the final compost product reached values of 92.20 and 42.29 %, respectively. Metagenomic sequencing results showed that inoculation of cattle manure with LD increased the abundance of functional microorganisms. LD effectively promoted the production of humus precursors, which then underwent reactions through synergistic abiotic and biotic pathways to achieve compost humification. This research provides a theoretical basis for the study of microbial enhancement strategies and humus formation mechanisms in the composting of livestock manure.

Deciphering the removal of antibiotics and the antibiotic resistome from typical hospital wastewater treatment systems.

Hospital wastewater treatment systems (HWTSs) are a significant source and reservoir of antibiotic resistance genes (ARGs) and a crucial hub for transmitting ARGs from clinical to natural environments. However, there is a lack of research on the antibiotic resistome of clinical wastewater in HWTSs. In this study, we used metagenomics to analyze the prevalence and abundance of ARGs in five typical HWTSs. A total of 17 antibiotics from six categories were detected in the five HWTSs; ß-lactam antibiotics were found at the highest concentrations, with up to 4074.08 ng·L-1. We further found a total of 21 ARG types and 1106 subtypes of ARGs with the highest percentage of multi-drug resistance genes (evgS, msbA, arlS, and baeS). The most abundant last-resort ARGs were mcr, which were detected in 100 % of the samples. HWTSs effluent is a major pathway for the transmission of last-resort ARGs into urban wastewater networks. The removal of antibiotics, antibiotic-resistant bacteria, and ARGs from HWTSs was mainly achieved by tertiary treatment, i.e., chlorine disinfection, but antibiotics and ARGs were still present in the HWTSs effluent or even increased after treatment. Moreover, antibiotics and heavy metals (especially mercury) in hospital effluents can exert selective pressure for antibiotic resistance, even at low concentrations. Qualitative analyses based on metagenome-assembled genome analysis revealed that the putative hosts of the identified ARGs are widely distributed among Pseudomonas, Acidovorax, Flavobacterium, Polaromonas, and Arcobacter. Moreover, we further assessed the clinical availability of ARGs and found that multidrug ARGs had the highest clinical relevance values. This study provides new impulses for monitoring and removing antibiotics and ARGs in the hospital sewage treatment process.

A self-cleaning photocatalytic membrane loaded with Bi2O2CO3/In(OH)3 S-scheme heterojunction composites for removing tetracycline from aqueous solutions.

Bi2O2CO3/In(OH)3 (BON) photocatalysts were synthesized by a one-pot method and loaded onto polyvinylidene fluoride (PVDF) membranes to obtain a Bi2O2CO3/In(OH)3/PVDF (BON-M) catalytic membrane system. The catalytic membranes demonstrated complete degradation of tetracycline within 40 min under visible light. They demonstrated robust photocatalytic activity across a broad pH range (5-11) and in the presence of coexisting ions. The membranes demonstrated excellent self-cleaning performance. Following exposure to light, the irreversible contamination decreased from 27.1% to 4.7% and the membrane's permeability was almost completely restored. Moreover, the charge transfer mechanism at the S-scheme heterojunction interface of BON was demonstrated by Density functional theory and in-situ X-ray Photoelectron Spectroscopy characterisation, and the active sites involved in tetracycline's degradation were identified. Meanwhile, the mechanism of the "anemone effect" of BON-M was demonstrated in conjunction with Electron paramagnetic resonance, and the intrinsic Some factors enhancing the membranes' photocatalytic activity are specified.

Aerobic co-composting of mature compost with cattle manure: Organic matter conversion and microbial community characterization.

The production of organic fertilizer by aerobic composting of cattle manure is an important way of its resource utilization. This study evaluated the effects of adding mature compost on the decomposition and microbial communities in the aerobic composting of cattle manure. The addition of mature compost shortens the composting cycle and results in a final lignocellulosic degradation rate of 35%. Metagenomic analysis showed that this was due to the proliferation of thermophilic and organic matter-degrading functional microorganisms, which enhanced the activity of carbohydrate-active enzymes. With the addition of mature compost, the microbial community exhibited stronger metabolic functions, especially carbohydrate and amino acid metabolism, which are the driving forces of organic matter degradation. This study deepens the understanding of organic matter conversion and microbial community metabolic functions when mature compost is used for livestock manure composting and provides a promising technology for livestock manure composting.