Improved Anaerobic Digestion by a Thermal Pretreatment

Abstract

The experimental study was conducted in order to evaluate the effects of thermal pre-treatment of secondary sludge on anaerobic digestion using as substrate a dairy discharge consisting primarily of whey (Numidia Constantine) made up mainly of lactoserum. The inoculums was subjected to heat treatment 120 °C, 160 °C, 180 °C for 2 hours, while considering the mud without treatment with a corresponding temperature equal to 20 °C.
The trials were conducted in a series of reactors of 250 ml in thermophilic phase at 55 °C. The effect of heat treatment on the physicochemical parameters of the sludge before incubation shows that: In all cases, heat treatment brings about an important solubilisation of matter: The concentration in soluble matter greatly increases the required minimum time of treatment to achieve the highest rate of solubilisation which is equal to 60 min.The solubilisation of the CDO (Chemical Demand of Oxygen) increases proportionally with the treatment temperature. An increase in the treatment temperature of 120 °C results in a CDO with a solubilisation ratio of 7% and for a temperature of 180 °C it is 25%, with a solubilisation rate reaching 34% for a temperature of 18 °C.
The best treatments (160 °C and 180 °C) result in a production of biogas from 2.7 to 3.5 times that of the untreated sludge for duration equal to 25 days.