Decomposition of Sewage Sludge in Drying Beds and the Potential Role of the Earthworm, Eisenia foetida

Abstract

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 O2, CH4, and CO2, 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 CH4 evolution vs. O2 consumption, decreased with time and were inversely related to sludge moisture content. O2 consumption rates, when standardized to 15°C, ranged from 10 to 80 µliter/g dry wt. For both LC and MB sludge, aerobic and anaerobic bacteria were abundant (3 × 107 to 6 × 108 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.

Microbial diversity of vermicompost bacteria that exhibit useful agricultural traits and waste management potential

“…The duration of the active phase depends on the species and density of the earthworms involved (Ndegwa et al 2000; Lazcano et al 2008; Aira et al 2011). A wide range of oganic wastes viz., horticultural residues from processed potatoes (Edwards 1988); mushroom wastes (Edwards 1988; Tajbakhsh et al 2008); horse wastes (Hartenstein et al 1979; Edwards et al 1998); pig wastes (Chan and Griffiths 1988; Reeh 1992); brewery wastes (Butt 1993); sericulture wastes (Gunathilagraj and Ravignanam 1996); municipal sewage sludge (Mitchell et al 1980; Dominguez et al 2000); agricultural residues (Bansal and Kapoor 2000); weeds (Gajalakshmi et al 2001); cattle dung (Gunadi et al 2002); industrial refuse such as paper wastes (Butt 1993; Elvira et al 1995; Gajalakshmi et al 2002); sludge from paper mills and dairy plants (Elvira et al 1997; Banu et al 2001); domestic kitchen wastes (Sinha et al 2002); urban residues and animal wastes (Edwards et al 1985; Edwards 1988) can be vermicomposted (Sharma et al 2005). …”

Effects of vermicomposts and composts on plant growth in horticultural container media and soil

“…The ability of some earthworms to consume a wide range of organic residues such as sewage sludge, animal wastes, crop residues, and industrial refuse has been fully established (Mitchell et al 1980;Edwards et al 1985;Chan & Griffiths 1988;Hartenstein & Bisesi 1989). In the process of feeding, earthworms fragment the waste substrate, enhance microbial activity and the rates of decomposition of the material, leading to a composting or humification effect by which the unstable organic matter is oxidized and stabilized.…”

Changes in biochemical properties of cow manure during processing by earthworms (Eisenia andrei, Bouché) and the effects on seedling growth

“…The ability of some earthworm species to consume a wide range of organic residues such as sewage sludge, animal wastes, crop residues, and industrial refuse has been well-established (Mitchell et al 1980;Edwards et al 1985;Chan & Griffiths 1988;Hartenstein & Bisesi 1989). The earthworm species most commonly utilized for the breakdown of organic wastes are Eisenia fetida (Savigny) and its related species Eisenia andrei (Bouché).…”