PAHs balance in solid and liquid phase of sewage sludge during fermentation process

Abstract

The results of the quantitative and qualitative analysis of PAHs both in sewage sludge and in supernatants before, during, and after methane fermentation process are presented in this paper. The investigations were carried out under laboratory scale in two series. The sludge samples originated from a municipal treatment plant. The process of fermentation was conducted using batch tests (a one-off batch supplemented with sludges). The content of 16 PAHs, listed by the US EPA, was determined using GC–MS technique. The aim of this investigation was to study changes in contribution groups of hydrocarbons (2-, 3-, 4-, 5-, and 6-ring) in relation to total concentration in PAHs. The objective of these investigations was to follow the changes in the PAHs content not only in sewage sludge (drymass) but also in supernatants (in the liquid phase), and to follow changes in concentration of PAHs during the methane fermentation process as well. The balance of PAHs load in sewage sludge and supernatants mixture was also calculated. An approximate two-fold decrease in dry matter of sludge was observed during the methane fermentation process. During sewage sludge digestion process 3- and 4-ring compounds were released from a solid phase to supernatants.

Keywords:

• PAHs
• sewage sludge
• supernatants
• fermentation process

Acknowledgments

This research was supported by the Committee of Scientific Research grant 3T09C 03319.

This paper was presented at the CEMEPE conference held on June 24–28, 2007 at the Skiathos Island, Greece