What is it about?
Vermicomposting of sewage sludge using spent mushroom compost from grey oyster mushroom as feed material was conducted to determine the effect on the concentration of heavy metals, namely Chromium, Cadmium, Lead, Copper, and Zinc. We conducted vermicomposting by employing red worms, Lumbricus rubellus, with a combination of different percentages of sewage sludge and spent mushroom compost for 70 days subsequent to 21 days of precomposting. The vermicompost produced in treatments with a low percentage of sewage sludge were fine in texture, dark in colour and odourless in contrast to the initial physical characteristics. The heavy metals contained in vermicompost were 0.25 ~ 11.57-fold higher than the initial concentration due to mineralization and excretion of non-accumulated heavy metals existent in the earthworms’ gut, which were present prior to treatments. Even so, the concentration was below the limits set by EU and US biosolid compost standards and safe to be utilized as a biofertilizer and soil conditioner.
Photo by Neslihan Gunaydin on Unsplash
Why is it important?
Vermicomposting is a realistic and practical solution for solving the problem of sewage sludge and spent mushroom compost disposal. The present findings showed that increases in earthworm numbers and growth were maximum in a 25 : 75 ratio of sewage sludge : spent mushroom compost, suggesting that adding an appropriate amount of sewage sludge (25 ~ 50%) to spent mushroom compost can be used as feed material for vermicomposting. A lower percentage of sewage sludge in vermibeds is recommended if the main objective is vermiculture (i.e. earthworm production). Notably, applying sewage sludge vermicompost as a soil stabilizer or fertilizer would not have an adverse impact on heavy metal content.
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This page is a summary of: Vermicomposting of sewage sludge by Lumbricus rubellus using spent mushroom compost as feed material: Effect on concentration of heavy metals, Biotechnology and Bioprocess Engineering, September 2011, Springer Science + Business Media, DOI: 10.1007/s12257-011-0147-y.
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Vermitechnology enriching plant nutrient elements and removing pollutants
Other related publication of our works on testing the potential of the earthworms, Lumbricus rubellus in vermitechnology by converting organic waste into a biofertiliser and removing pollutant (potentially toxic elements in sewage sludge and polycyclic aromatic hydrocarbons in soil).
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