Conversion of Municipal Wastewater Treatment Plant Residual Sludges into Earthworm Castings for Use as Topsoil

摘要

Vermicomposting, or biodegradation of waste water sludge from the San Jose and Santa Clara Wastewater Treatment Plants in California, was accomplished by the use of earthworms of the redworm (Eisenia foetida) species. Ninety tons of earthworm manure were produced from the sludge over a five-year period. Different size windrows were populated with different densities of earthworms, and castings were harvested by passing windrow contents through a rotating screen which separated the worms from the castings for reuse. Plants in castings outgrew plants in topsoil by a factor of 4 to 1. Cost analysis showed the system to be cost effective at a cost of $29.45 per dry ton in a 10 ton per day facility, and to return a profit of $3.34 per dry ton if castings were produced at the rate of 50 tons per day.