Effects of disposal of a food industry wastewater treatment plant sludge on soil: case study

Sludge from wastewater treatment plants usually contains high levels of organic matter and nutrients, and therefore it can be used as fertilizer and soil conditioner. However, its disposal on the soil has to be properly managed because it can contain contaminants. The aim of this work was to study the effects of food industry sludge disposal on the soil, as well as to assess the sludge application viability. The results show that the sludge characteristics are adequate for its application on latosol according to Brazilian federal regulation (Resolucao CONAMA n degrees 375/2006). There was no statistically significant difference for toxic organic substances between the amended and unamended soil treatments. There was a small concentration increase of inorganic compounds (Al, Ba, B, Co, Cu, Fe, Mn, Ni, Zn) in the soil area with sludge, but it was not statistically confirmed. Soil fertility, sum of bases, cation exchange capacity, and organic matter values increased with sludge application, and exchangeable Al and Al saturation values decreased.