Tenebrio molitor L. bioaccumulation of heavy metal in municipal sewage sludge

By using an orthogonal design, the effects of four breeding factors (temperature, larva breeding density, municipal sewage sludge to wheat-bran ratio, and larva average weight) on the growth rate, mortality and heavy metal accumulation in T. molitor larva bred on sewage sludge were investigated. The results showed that larva growth rate and mortality increased with increasing breeding temperature. However, larva growth rate and mortality were not obviously affected by breeding density, and municipal sewage sludge to wheat-bran ratio. Optimal breeding conditions for larva bioaccumulation of Cu, Se and Hg were 15 ℃, 0.2 g·cm^-2, sewage sludge to wheat-bran ratio of 1∶2, and larva average weight of 85.4±5.9 mg. Those for larva bioaccumulation of Cd were 15 ℃, 0.4 g·cm^-2, sewage sludge to wheat-bran ratio of 1∶0, and larva average weight of 85.4±5.9 mg. Optimal larva bioaccumulation of Zn occurs under the breeding conditions of 20 ℃, 0.4 g·cm^-2, sewage sludge to wheat-bran ratio of 1∶0, and larva average weight of 34.9±4.9 mg. Obvious symptoms of Cu, Cd, Se, Hg and Zn bioaccumulation were noted in T. molitor larva fed with sewage sludge.