%0 Journal Article
%T Biosolid Soil Application: Toxicity Tests under Laboratory Conditions
%A Cintya Ap. Christofoletti
%A Annelise Francisco
%A Carmem S. Fontanetti
%J Applied and Environmental Soil Science
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/518206
%X A large volume of generated sewage sludge makes its disposal a problem. The usage of sludge in agriculture is highlighted by a number of advantages. However, heavy metals and other toxic compounds may exercise harmful effects to soil organisms. This study evaluated the possible toxic effects of a biosolid sample, under laboratory conditions, for 30 days, using diplopods Rhinocricus padbergi and plants Allium cepa (onion) as test organisms. The data obtained demonstrated that the biosolid raw sample had genotoxic potential for Allium cepa root tip cells. In the diplopods exposed to biosolid sample, epithelium disorganization in the midgut and a reduction of the volume of the hepatic cells were observed after 7 days of exposure. After 30 days, the animals still showed a reduction of the volume of the hepatic cells, but in minor intensity. Allium cepa analysis showed genotoxicity, but this effect was reduced after 30 days of bioprocessing by diplopods. This study was important to know the effects as well as to determine how this waste could be applied concerning the soil living organisms and plants. 1. Introduction In sewage treatment plants (STP), after the sewage had been treated, a sludge rich in organic matter and nutrients is generated as a waste, known as sewage sludge. The composition of this sludge is very variable since it depends on the source of the sewage treatment process and the seasonality [1]. Generally, the sewage sludge presents around 40% to 60% of organic matter, 4% nitrogen, 2% phosphorus, and other macro- and micronutrients, besides potentially toxic elements [2]. The generated sewage sludge still can go through processes in order to increase the solids and reduce the number of pathogenic organisms, generating a residue called biosolid, which is considered most innocuous than the sewage sludge itself [3]. Good quality fertilizers can be generated with the sludge stabilization, reducing its volume through the use of ¡°sludge thickeners drying beds,¡± filter presses, band presser, vacuum filters, and centrifugation [4]. According to Lambais and Do Carmo [5], chemical composition of the sludge depends on the origin of the wastewater. This way, the material is variable, but generally it is a compound rich in organic matter and essential nutrients for plants and microorganisms. Currently, sewage treatment plants in different Brazilian cities are facing the problem of sludge disposal. The alternatives to the sewage sludge usual fate are landfill disposal, reuse in industry (light-weight aggregate production, bricks and ceramics manufacturing,
%U http://www.hindawi.com/journals/aess/2012/518206/