Enzyme and Earthworm Activities during Vermicomposting of Carbaryl‐Treated Sewage Sludge

Abstract

The feasibility of vermicomposting pesticide contaminated refuses was evaluated. A mixture of sewage sludges was amended, at a ratio of 1:1 (v/v), with a garden refuse artificially contaminated with carbaryl, a carbamate insecticide commonly used in farming and gardening. Ten clitellated earthworms were then placed in this material. We determined the evolution of earthworm ( Eisenia foetida , Savigny) biomass and changes in enzyme activities during an 18‐wk period of sewage sludge vermicomposting. The carbaryl produced a chronically toxic effect on the earthworms, measured by weight gain and sexual maturity. The growth was slower in the presence of pesticide. In addition, carbaryl treatments showed inhibited enzyme activity in the first weeks of the vermicomposting process, slowing down organic matter biodegradation. The dynamics of the vermicomposting process can be followed by combining easily detectable parameters related to the global microbial metabolism: a traditional chemical (water‐soluble C/water‐soluble N) and biochemical (dehydrogenase activity/water‐soluble C) index, were calculated. In particular, this last seemed more useful in characterizing the vermicomposting process even a longer maturation time (10–18 wk).