Short‐term and long‐term effects of increasing temperatures on the stability and the production of volatile sulfur compounds in full‐scale thermophilic anaerobic digesters

Abstract

This study compares the effect of a rapid increase of the digester temperature (from 54 degrees C to 58 degrees C in 2 weeks) with a slow increase (from 53.9 degrees C to 57.2 degrees C at a rate of 0.55 degrees C per month) on full-scale thermophilic anaerobic digestion at Hyperion Treatment Plant. The short-term test demonstrated that rapidly increasing the digester temperature caused elevated production of volatile sulfur compounds, most notably methyl mercaptan, but volatile solids destruction and methane production were not significantly affected. The increase of the volatile fatty acid to alkalinity ratio from 0.1 to over 0.3 indicated a transient change in digester biochemistry, which was reversed by lowering the temperature. In the long term-test, a slow increase of digester temperature, the production of hydrogen sulfide increased above temperatures of 56.1 degrees C, but was controlled by increased injection of ferrous chloride. Methyl mercaptan was detected in trace amounts at the highest temperature tested (57.2 degrees C). This test showed insignificant effects on other digestion parameters, although some temperature-independent changes were observed that could have been seasonal effects over the year that the long-term test lasted. Thus a slow temperature increase was preferable. This observation contrasts with previous results showing the desirability of a rapid temperature rise to first establish a thermophilic culture when converting from mesophilic operation. Further research is warranted on temperature limits and process changes to optimize thermophilic anaerobic digestion.

Literature review of air pollution control biofilters and biotrickling filters for odor and volatile organic compound removal

“…This may be of particular importance in biotrickling filters, in that the packing, contrary to compost, does not initially contain a native population of microorganisms and alternative substrates that can be used to sustain heterotrophic organisms. Waste air from liquid processes at POTWs typically contains relatively high concentrations of H 2 S, whereas waste air from solids-handling processes can be highly odorous and have a more complex composition [83][84][85]. We believe that there are many opportunities for using biofilters and biotrickling filters as a replacement of the chemical scrubbers that are currently used for these waste air streams at many POTWs.…”

Anaerobic Codigestion of Municipal, Farm, and Industrial Organic Wastes: A Survey of Recent Literature

“…Likewise, anaerobic digesters at municipal wastewater treatment plants (WWTPs) potentially are available for codigestion of organic wastes. For example, the City of Los Angeles Bureau of Sanitation (California) currently operates two WWTPs (Hyperion and Terminal Island) that process municipal wastewater sludge (MWS) in large digesters ( Iranpour et al, 2003 ; 2004a , b ; 2005 ; 2006 ; Oh et al, 2005 ; Shao et al, 2002 ). The methane produced during anaerobic digestion is recovered and used for heating of the digesters and for electricity production.…”

Thermophilic‐Anaerobic Digestion to Produce Class A Biosolids: Initial Full‐Scale Studies at Hyperion Treatment Plant

“…These studies were similar to a wide variety of others during this period (e.g., Andrews and Pearson, 1965 ; Fair and Moore, 1934 ; McCarty, 1964 ; Pohland and Bloodgood, 1963 ), in being motivated, to a large degree, by the hope that the more rapid metabolism of thermophilic organisms would translate into advantages in digestion speed or operational efficiency, if process stability could be maintained. Recent interest in thermophilic‐anaerobic digestion at the HTP is driven by stricter regulations for removal of pathogens from wastes being digested for final use as a soil amendment ( Ahring et al, 2001 ; Ghosh, 1998 ; Iranpour and Cox, 2005 ; Iranpour et al, 2002 , 2004 , 2005a , b , and c ).…”