Vermicomposting of sewage sludge by Lumbricus rubellus using spent mushroom compost as feed material: Effect on concentration of heavy metals

Abstract

Vermicomposting of sewage sludge (SS) using spent mushroom compost from Pleurotus sajor-caju as feed material was conducted to determine the effect on the concentration of heavy metals, namely Cr, Cd, Pb, Cu, and Zn. Previous studies have reported the feasibility of brandling worms, Eisenia foetida, for vermicomposting SS, whereas we conducted vermicomposting by employing red worms, Lumbricus rubellus, with a combination of different percentages of SS and spent mushroom compost (SMC) for 70 days subsequent to 21 days of precomposting. The vermicompost produced in treatments with a low percentage of SS were fine in texture, dark in colour and odourless in contrast to the initial physical characteristics. Results indicate that growth in earthworm numbers and biomass gain was maximum at 25 : 75 (T D ) of SS : SMC compared to other treatments with 5 and 8-fold increases, respectively. 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.

Changes in nutrient and heavy metal content levels of sawdust due to vermicomposting by Allomyrina dichotoma subsp. tunobosonis

“…Furthermore, Cr, Ni, and Pd were detected at low concentrations (< 7%) compared to Cu (12.73%) and Zn (71.32%) in vermicompost. Our results differ from those of other studies thatshowed increase in heavy metal content during vermicomposting of sludge (Bakar et al, 2011;Hait and Tare, 2012;Kaur et al, 2010). However, the reduction in Cd is in agreement with the findings of Suthar (2009), who also reported a decrease in Cu and Zn concentrations during vermicomposting of sewage sludge spiked with sugarcane trash.…”

Comparison of heavy metals content in compost against vermicompost of organic solid waste: Past and present

“…Vermicompost can be used effectively as a natural absorbent for heavy metal accumulation (Landgraf et al, 1998;Matos and Arruda, 2003). Several studies (Abu Bakar et al, 2011;Gupta and Garg, 2008) pertaining to vermistabilization of sewage sludge have reported decrease in total heavy metals content in the vermicompost. According to Saxena et al (1998), earthworms (E. fetida) accumulate higher concentration of heavy metals during vermicomposting of sewage sludge.…”

Vermicomposting of coal fly ash using epigeic and epi-endogeic earthworm species: nutrient dynamics and metal remediation

“…E. fetida has shown its ability in increasing bioavailability of major nutrient elements such as P and N in FA 11,12 on one hand and minimizing the solubility of heavy metals on the other. 13 The efficiency of E. eugeniae and L. rubellus in rapid degradation of waste material has been well documented by 14,15 respectively. Suthar et al 2008 (ref.…”