Fate of volatile organic compounds in municipal activated sludge plants

Abstract

ABSTRACT: The fate of volatile organic compounds (VOCs) in municipal activated sludge plants was investigated at pilot and full scale. More than 80% of the mass flow of nonchlorinated compounds was observed to be biodegraded while less than 20% was removed by stripping. Conversely, 46% of the mass flow of chlorinated compounds was biodegraded and 47% was removed by stripping. Adsorption of VOCs onto waste sludge was not a significant removal mechanism. The pilot plant employed was found to effectively emulate the liquid‐gas phase partitioning and overall compound removals observed in a full‐scale plant. Little difference in liquid‐gas phase partitioning was observed for coarse and fine pore diffusers in spite of differing mass‐transfer characteristics as demonstrated by oxygen‐transfer measurements. This implies that equilibrium between the liquid and gas‐phase concentrations was achieved with both diffuser types. Stripping of VOCs was observed to increase with airflow; however, the extent of stripping increased at a declining rate.