Use of municipal and industrial sludge in agricultural soil: Responses of soil microbials and soil enzymes

Abstract

Industrialization has contributed to the increase in the generation of potentially toxic solid residues. Textile and tannery industries produce residues, called sludge, with high organic and inorganic content, including heavy metals. The most widely-used method for disposal of tannery, textile and sewage sludge is sanitary sites, presenting a high risk for environmental contamination. Concerns about environmental quality have led to the introduction of alternative disposal methods, such as the use of sludge as a nutrient source for plants and as soil conditioners. However, the use of sludge in agricultural soils needs defined action, in order to avoid damage to the environment, mainly to the soil. The knowledge of short- and long-term effects of soil amendments becomes essential when considering, for example, the conservation of soil quality. In recent years, soil microbiological parameters, as such microbial activity and biomass, along with soil enzyme activity, have been seen to be early and sensitive indicators of soil stress and can be used to predict long-term trends in soil quality. Several studies have been done aiming to evaluate the effects of use of these sludges in agricultural soil. In this way, this chapter describes the state of the art about the effect of textile, tannery and sewage sludge on soil microorganisms and soil enzyme activity.