[Pollution Characteristics and Risk Assessment of Antibiotics in Lianhua Reservoir].

Thirteen typical antibiotics in surface water of the Lianhua Reservoir were analyzed using HPLC/MS/MS to assess the pollution characteristics and risk levels. Ten antibiotics except for erythromycin, sulfadiazine, and sulfamethoxazole were detected in surface water and the total concentration of antibiotics varied between non-detectable (n.d.) and 925.26 ng ·L-1. Azithromycin had the highest concentration (n.d.-232.61 ng ·L-1) with the detection frequency of 75%, followed by enrofloxacin (n.d.-187.69 ng ·L-1), tetracycline (n.d.-155.05 ng ·L-1), and ciprofloxacin (n.d.-83.66 ng ·L-1) with the detection frequencies over 60%. The spatial distribution of antibiotics was as follows: total concentration of upstream (sampling point 1) > Aoxi River stream tributary (sampling point 2) > reservoir downstream (sampling point 3) > reservoir entrance (sampling point 4) > reservoir area (sampling point 5). The seasonal variations in the concentrations of antibiotics were evident; total concentrations in the dry season were significantly higher than those in the wet and normal seasons. The results of the environmental risk assessment indicated that ofloxacin, enrofloxacin, and ciprofloxacin pose significant risks to the environment. In the Lianhua Reservoir, ciprofloxacin showed high potential risk to the ecological environment, while the environmental risks of other antibiotics in the reservoir were below the medium level. The combined risk value of the antibiotics in the dry season was higher than that in the wet and normal seasons.

Effects of bulking material types on water consumption and pollutant degradation in composting process with controlled addition of different liquid manures.

This study was conducted to examine the effects of different bulking materials (corncob and ricehusk) on liquid manure consumption, organic matter degradation and pollutants retention in composting process under controlled addition of different types of liquid manures (LM). The results indicated that under the controlled addition of LM, bulking materials with higher content of biodegradable carbon (corncob) and LM with a higher concentration of organic pollutants (swine effluent) were more beneficial for biological heat generation and thus were more efficient for water evaporation, organic matter degradation, LM consumption and pollutants retention during the cocomposting process. Consequently, the optimization of these major influencing factors could compensate for efforts geared towards better utilization of the cocomposting process.

Higher Temperatures Do Not Always Achieve Better Antibiotic Resistance Gene Removal in Anaerobic Digestion of Swine Manure.

This study employed high-throughput quantitative PCR and 16S rRNA sequencing to evaluate the effect of temperature and residual antibiotics on the dynamics of antibiotic resistance genes (ARGs) and microbial communities during anaerobic digestion of swine manure. The abundances of total ARGs and 16S rRNA genes significantly decreased in all of four treatments (25°C, 37°C, and 37°C with 50 mg of wet weight antibiotics of body weight, and 55°C). The abundances of most ARG types were significantly correlated with those of the 16S rRNA gene and transposase gene (P < 0.01). However, the abundances of total ARGs at 55°C were much higher than those of other treatments. Meanwhile, the microbial communities at 55°C, where the Streptococcus pathogen remained at a relatively high abundance and cellulose degraders and hydrogen producers, such as Ethanoligenens and Coprococcus bacteria, increased, were markedly different from those of other treatments. Redundancy analysis indicates that temperature, pH, and the genus Streptococcus had the highest explanation for ARG variation among experimental factors, chemical properties, and representative genera, respectively. Network analysis further showed that the genus Streptococcus contributed greatly to the higher ARG abundance at 55°C. The moderate antibiotic residue only caused a slight and transitory inhibition for microbially diverse populations and promotion for ARG abundance, probably due to the degradation of antibiotics and microbial adaptability. Our results clarify the cooperativity of gene transfer-related items on ARG variation and intensively prove that higher temperature cannot always achieve better ARG removal in anaerobic digestion unless pathogens and gene transfer elements are more efficiently inhibited.IMPORTANCE Antibiotic resistance genes (ARGs) are frequently detected with high abundance in manure-applied soils. Anaerobic digestion is one of widely used processes for animal waste treatment. Thus, it is critical to understand the potential of anaerobic digestion to attenuate ARGs. Although some previous studies recommended thermophilic digestion for ARG removal, they did not get sufficient evidence to support this view. The antibiotics applied to animals are mostly excreted through feces and urine because of incomplete metabolism. It is indispensable to know whether residual antibiotics in manure will hinder ARG attenuation in anaerobic digesters. The significance of our research is in comprehensively understanding the evolution and mechanism of ARGs in anaerobic digestion of swine manure affected by temperature and residual antibiotics, which will allow the development of an ARG elimination strategy before their release into the environment.

Effects of compost characteristics on nutrient retention and simultaneous pollutant immobilization and degradation during co-composting process.

This study was conducted to examine the effects of controlled addition of liquid (LM) to solid (SM) manure compost using a volume-model technique on the co-composting of SM and LM, and further to investigate the major effects of bulking material sizes and LM types on the co-composting process and final compost characteristics. Results indicated that this volume-model technique played a critical role in reducing leachate generation and improving the overall efficiency of the co-composting process. Specifically, the developed model enhanced the evaporation rates of windrows during the co-composting process. For improved final compost properties, small bulking materials and swine-effluent-based LM were found to be more efficient for organic matter degradation, LM consumption, hazardous metals immobilization, and essential nutrients retention than large bulking materials and biogas-based LM. Thus, process parameter optimizations represent major research options for successful co-composting applications for the future.

Development of algae-bacteria granular consortia in photo-sequencing batch reactor.

The development and properties of algae-bacteria granular consortia, which cultivated with the algae (Chlorella and Scenedesmus) and aerobic granules, was investigated in this experiment. The results indicated that the granular consortia could be successfully developed by selection pressure control, and the algal biomass and extracellular polymeric substances (EPS) concentration in the consortia showed notable correlation with the operating parameters of reactor. The maximum specific removal rates of total nitrogen and phosphate were obtained from the granular consortia with the highest algal biomass, yet the correlation between the fatty acid methyl esters yield and the algal biomass in the consortia was not markedly observed. The seed algae maintained dominance in the phototroph community, whereas the cyanobacteria only occupied a small proportion (5.2-6.5%). Although the bacterial communities with different operational strategies showed significant difference, the dominated bacteria (Comamonadaceae, 18.79-36.25%) in the mature granular consortia were similar.