COMBINED PROCESS OF ULTRASONIC PRE-TREATMENT AND ALKALINE HYDROLYSIS OF BIOLOGICAL SLUDGE FROM PURIFICATION PLANTS, FOR ENHANCING EFFICIENCY OF BIOGAS PRODUCTION BY ANAEROBIC FERMENTATION

摘要

The invention relates to a combined physical and chemical ultrasonic pre-treatment and alkaline hydrolysis of biological sludge from purification plants, for enhancing the efficiency of biogas production by anaerobic fermentation. According to the invention, the process uses the cavitation phenomenon generated by the application of ultrasonic field in pre-treating the biological sludge, alkalinized with NaOH at a pH = 10.5 which leads to obtaining sludge solubilization and disintegration degrees 3...4 times higher than in case of the sonication at a pH= 6...6.5 at a reduced sonication time of 10 min, the duration of triggering the production of biogas being of 6 days in conditions of anaerobic fermentation at 37.5°C, inclusively for old fermented sludge, stored in aerobic conditions, the amount of biogas being double as compared with the amount obtained in case of ultrasonically treated sludge without additional alkalinization.