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Decomposition of Sewage Sludge in Drying Beds and the Potential Role of the Earthworm, Eisenia foetida
Author(s) -
Mitchell M. J.,
Hornor S. G.,
Abrams B. I.
Publication year - 1980
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1980.00472425000900030009x
Subject(s) - earthworm , decomposition , sewage sludge , anaerobic exercise , chemistry , dry weight , anaerobic digestion , activated sludge , environmental chemistry , moisture , wastewater , sewage , zoology , pulp and paper industry , environmental engineering , biology , botany , agronomy , environmental science , physiology , organic chemistry , methane , engineering
Decomposition of sewage sludge in drying beds at Ley Creek (LC) and Meadowbrook‐Limestone (MB) Wastewater Treatment facilities in metropolitan Syracuse, N.Y. was monitored. LC and MB beds were derived from an anaerobically digested, primary sludge and an aerobically digested, activated sludge, respectively. Fluxes of O 2 , CH 4 , and CO 2 , as determined by in situ incubation of cylinders and analysis by gas chromatography, showed that at LC, aerobic and anaerobic, decomposition and photosynthesis occurred concomitantly due to high moisture. Similar analyses for two separate trials at MB found that both total decomposition rate and percentage of anaerobic decomposition (1 to 90%), as indexed by CH 4 evolution vs. O 2 consumption, decreased with time and were inversely related to sludge moisture content. O 2 consumption rates, when standardized to 15°C, ranged from 10 to 80 µ liter/g dry wt. For both LC and MB sludge, aerobic and anaerobic bacteria were abundant (3 × 10 7 to 6 × 10 8 colony‐forming units/g dry wt) and dominant bacteria were not enteric. Nematode densities ranged from 7 to 814 individuals/g dry wt. A computer simulation model on the role of macroinvertebrates in decomposition was used for analyzing the effects of the earthworm, Eisenia foetida . This oligochaete was introduced into one‐half of the MB cylinders and was shown to accelerate decomposition and decrease the proportion of anaerobic decomposition if the sludge was below 375% moisture dry weight and 40% anaerobic decomposition. This stimulation was also reflected in increased nematode density and elevated Eh . Flooding of drying beds caused mortality to E. foetida .