Abstract

SONICATION STUDIES OF FEED SLUDGE TO ANAEROBIC DIGESTER

A Mani*and S. Sundaramoorthy

ABSTRACT

Anaerobic digestion has been the preferred method for reducing and stabilizing waste sludge from biological wastewater treatment for over a century; however, as sludge volumes and disposal costs increase, there has been a desire to develop various methods for reducing the volume of sludge to be treated, improving the performance of the digesters, and increasing the energy value of the sludge. Sonication of primary sludge, waste activated sludge and mixed sludge samples from an existing activated sludge sewage treatment plant of 40 million liters per day dry weather flow design capacity operating at full load at Chennai city, India was studied to find out the response to sonication. The sonicator yielded an output power was 20 kHz and the power supply was 500 watts. The probe was of Titanium and 13 mm in diameter. The sonication was performed for 5, 10 and 20 minutes with 60% intensity. The sample volume was 150 ml. The relationship of sonication time to the ratio of soluble COD to volatile solids was inferred. The results indicate that this ratio increases with the time of sonication as a linear measure for primary sludge. The ratio increases polynomially for both waste activated sludge as well as mixed sludge to about 15 minutes of sonication and reduces thereafter. The increase is about 2.5, 4 and 2.5 times during this period for primary, waste activated and mixed sludges respectively. The study of this nature proved its efficiency of the method employed.

Keywords: Anaerobic digestion; Sewage; Sonication; Volatile solids; COD.