Meso-thermophilic acidogenic biotreatment of mixed wastewater from toilets and coffeeshop: Effect of temperature on the efficiency of organic removal and VFA productions

This study aimed to investigate the effects of temperatures (meso-thermophilic range) on the removal of chemical oxygen demand (COD), fat oil and grease (FOG) and caffeine, and volatile fatty acids (VFA) production in acidogenic biotreatment of a mixed wastewater from toilets and a coffee shop. The mixed wastewater was prepared from 90% of toilet wastewater and 10% of coffee shop’s greywater. A series of batch acidogenesis experiments in treating the mixed wastewater was conducted under mesophilic (30 and 40 °C) and thermophilic (50 and 60 °C) conditions. The results found that temperatures of 30–60 °C could remove total chemical oxygen demand (TCOD) about 30–80%, while the FOG removal efficiencies were 70–80% at the temperatures of 30–50 °C. The highest total VFA production was achieved at the temperature of 40 °C, which could be further biodegraded into biogas by the methanogenesis reactions. The initial caffeine concentrations of the mixed wastewater were about 0.6–0.7 mg/L and the results revealed that these concentrations did not change much during the meso-thermophilic acidogenic biotreatment.