Gang Fang

In China, studies on the regional risk assessment of hazardous chemicals have been carried out for only a few years, and there are few studies on hazardous chemicals leaking into seas. Previous regional-risk-assessment methods considered a single risk factor for most assessment targets, and comprehensive considerations of risk sources and sensitive resources for a study area are not sufficiently included. Based on previous work, this study established a regional-risk-assessment method for hazardous chemicals leaking into seas. This method considered the hazards of hazardous chemicals and the tolerance of the regional environment by means of a case study in Tianjin. The results showed that the risk level of the enterprise was Grade I, classified as a high-risk source of hazardous chemicals; the main reasons were the strong toxicity and large quantity of hazardous chemicals. This method provides technical support for scientifically assessing marine-environmental-risk levels for hazardous-chemical-leakage areas and for carrying out risk-prevention and restoration assessments of hazardous chemicals leaking into seas.

High-solid anaerobic digestion (HS-AD) technology is a promising technique to treat organic residues as its advantages of excellent processing capacity, less water usage and small reactor volume. The efficiency of HS-AD is affected by mass transfer and other environmental factors, which could reflect by variation of microbial communities. Revealing of the relationship among the variations to operational parameters of HS-AD will sharpen the strategies of HS-AD and raise efficiency. However, the methanogenic community of HS-AD is much more complicated than conventional liquid AD (L-AD) as its limit of mass transfer. It is therefore important to reveal the interactions among those factors on AD performance and variation of the microbial community to enlighten the operational strategies. In this study, three leach bed reactors (LBRs) feeding of ensiled straw were operated with the leachate circulation. High-throughput sequencing was applied to monitor the dynamics of the methanogenic community and their interactions. Results demonstrated that mass transfer had only a limited impact on the methanogenic community. In addition, species that adapt quickly to the environment could survive in batch cultivation, which shorted the lag time and improved process stability. Co-occurrence network and statistical analysis suggested that symbiosis was the principle of most of the surviving species, while the interspecies competition of dominated species guided the community assembly. This study revealed the impact of environmental factors and the interactive principle of species, which could enhance the understanding of methanogenesis in HS-AD.