An integrated ethanol-methane fermentation coupled system characterized with full wastewater reutilization was proposed. The waste distillage originated from ethanol distillation was treated with anaerobic digestion and then recycled for medium preparation in the next ethanol fermentation run. This process could enhance wastewater reutilization, save fresh water and reduce energy consumption in the cassava-based ethanol production. The results indicated that, when using anaerobic effluents from the digestion process with only one tank, an ethanol concentration of 10.5% (v/v) compatible with that of conventional one could be achieved, but ethanol fermentation was partially inhibited and operation time gradually prolonged from 48 to 105 h. Using anaerobic effluents from the digestion process with two subsequently connected tanks, ethanol fermentation performance could be largely improved, and the fermentation lag could be completely eliminated. The performance enhancement was due to the concentrations reduction in organic acids, such as acetic and propionic acids in the digestion effluents using two digestion tanks in-series.

Health risk assessment (HRA) methodologies of three stages of Municipal Solid Waste Landfill (MSWL), including operation period, maintenance and management period after closure, and usage period without any restricted limits were built in this paper. The major exposure pathways to environmental contaminants were considered: inhalation of gas and dust during operation period, and ingestion of four food pathways categories (plant foods, meat, milk, and fish), groundwater and dust during usage period without any limits. The endpoints of HRA of MSWL are individual lifetime carcinogenic risk for all the carcinogenic chemical contaminants, and hazard index (HI) for all the non-carcinogenic chemical contaminants to the landfill worker (only at the operation period), and to the public near to the landfill (at all the three stages) respectively. The parameter values of calculation model are conservatively chosen. This is the first time in China that an integrated risk assessment methodology for landfill gas and leachate is attempted to develop. HRA methodologies will facilitate rapid estimation of the risk level of MSWL.