Effect of temperature and feedstock size on biogas production of water hyacinth used for phytoremediation of rural domestic wastewater in Shanghai

Biogas is a renewable primary energy source. The aim of the current study was to quantify the effect of temperature and feedstock size on biogas production of water hyacinth used for phytoremediation of rural domestic wastewater using anaerobic digestion (AD) process on a batch scale. This experiment consisted of two factors: AD temperature (mesophilic, 35°C) and thermophilic (55°C) and feedstock size (water hyacinth chopped to 6-10 mm, or 15-20 mm). The biogas production, pH, TOC, TKN, TS, and VS contents of the effluents (substrates) were investigated. The results showed that: Higher temperature with smaller size could improve the water hyacinth biogas productivity. The highest biogas production rate was obtained in T6-10 treatment and is higher by 12%, 42%, and 59% in average compared to the biogas production rate from T_15-20, M_6-10 and M_15-20, respectively. However, the production rate of biogas from M_6-10 and M_15-20 are no different. The VS content in the effluent was increased slowly with the time, but the VS content reduction in the working substrates ultimately. The initial pH of substrates was 6.7 being well suited for AD process. the ratio of C/N was kept going down fell from 27.4 to 21.5, 22.3, 25.3 and 25.7 with the T_6-10, T_15-20, M_6-10 and M_15-20 treatment, respectively, and thereafter variation less than 5%. Based on the analysis of the results, a conclusion can be made: thermophilic condition with smaller size can be more benefit for the biodegradation of water hyacinth AD process.