Microthrix parvicellaandGordona amaraein mesophilic and thermophilic anaerobic digestion systems

Abstract

The scope of the study presented in this paper is to determine the fate of the filamentous bacteria Gordona amarae and Microthrix parvicella in anaerobic digestion operating under mesophilic and thermophilic conditions. In order to detect and quantify foaming bacteria in the anaerobic digesters, a fluorescent in situ hybridization (FISH) method was developed and applied. This paper presents the results of a laboratory-scale study that involved the operation of four lab-scale anaerobic digestion systems operating in the mesophilic (35 degrees C) and thermophilic (55 degrees C) temperature ranges at 20 days' detention time. According to the FISH counts of G. amarae and M. parvicella, it appears that thermophilic conditions resulted in a higher destruction of both filamentous bacteria, averaging approximately 97% and 94% for the single thermophilic digester and the dual thermophilic/mesophilic system, respectively. Within the context of this study, the overall performance of the four different anaerobic digestion systems was evaluated in terms of biogas production per mass of volatile solids destroyed, COD destruction, sludge dewaterability and foaming characteristics. The dual stage systems used in this study outperformed the single stage digesters.

Foaming Phenomenon in Bench‐Scale Anaerobic Digesters

“…The filamentous organisms attach onto the gas bubbles present in anaerobic digesters and rise to the surface of the liquid creating a foam blanket (Jenkins et al 2003). Fragmented filamentous organisms can more evenly distribute foam-associated compounds throughout the digester, increasing foam (Marneri et al 2009). Correlation analysis on Phase 2 data showed that alkalinity (R 2 =0.737), pH (R 2 =0.381), percent total solids (R 2 =0.731), percent volatile solids (R 2 =0.740), and filament counts (R 2 =0.333) that correlated with the Alka-Seltzer foaming potential results.…”

“…Allowing dual-stage anaerobic digestion to be economical to operate since the majority of the sludge stabilization is performed in the mesophilic stage (Cheunbarn and Pagilla 2000). Marneri et al (2009) investigated the foaming potential of dual-stage anaerobic digesters.…”

“…The greater destruction of filamentous organisms in thermophilic and acid phase-thermophilic anaerobic digesters increases the concentration of colloidal hydrophobic compounds, like mycolic acid in the digesters (Marneri et al 2009). Mycolic acid is located on the cell walls of these filamentous organisms allowing the filamentous organisms to attach to solid particles rendering them hydrophobic.…”

“…Many researchers have used the Alka-Seltzer foaming potential test that is designed to determine the foaming potential of influent and effluent streams (de los , Marneri et al 2009, and Oerther et al 2001. Jenkins et al (2003) modified this test using two Alka-Seltzer tablets, which are placed into a 500 mL graduated cylinder containing 250 mL of sample, simulating foam that exist in the wastewater treatment plant.…”

“…: Operating parameters of bench-scale anaerobic digesters (Marneri et al 2009)……….28 Table 4: Analytical measurements………………………………………………………………. 49 Table 5: ANOVA foaming classification………………………………………………………...51 Table 6: Performance characteristics of phase 1 to 4…………………………………………….53 Table 7: Foaming classifications of phase 1 to 4………………………………………………... 55 …”