Effects of thermal pretreatment on the anaerobic digestion characteristics of fruit waste liquids

Fruit waste is one of the main components of municipal waste. To study its potential and characteristics in anaerobic digestion, this study took fruit waste and its waste liquid as raw materials, investigate the influence of thermal pretreatment on the anaerobic digestion characteristics under 35 ± 17 °C. The anaerobic digestion materials were fruit waste liquid (group A1), fruit waste liquid after thermal pretreatment (group A2), fruit slurry (group A3), and the material of A2 and A3 mixed with municipal sludge (groups A4 and A5) has also been involved. The results showed that the thermal pretreatment is in favor of increasing the total gas production rate, which the waste liquid after thermal pretreatment (A2) was the highest one with 767.09 mL/gVS which 6.51% higher than A1; while it has not obviously influence on the total hydrogen production rate of waste liquid; the addition of municipal sludge increased the total methane production rate of fruit waste or its liquid. After thermal pretreatment, the pH of fruit waste was 0.37 lower than initial pH; VFAs and SCOD content were both increased, which are benefit for anaerobic digestion. In addition, the experimental data were verified by the modified Gompertz model.