Diferentes relações C/N inicial para tratamento de lodo de curtume via compostagem

Abstract

The river sludge is one of the solid waste generated in tanneries and has a high organic load, which can cause impacts to the environment if disposed of incorrectly. Composting can be used to treat this waste. It is recommended, in the literature, that the initial C/N ratio of the process be 30:1. However, this relationship may be unfeasible, since residues considered as a source of nitrogen are the biggest challenges for industries and are generated in greater quantities. The aim of this study was to evaluate the efficiency of two initial C/N ratios in the composting of river sludge with tree pruning and wood shavings, in the presence and absence of boiler ash. Sixteen windrows were set up, with an initial calculated C/N ratio of 16:1 and 12:1. Over 60 days, the following were monitored: pH, temperature, electrical conductivity, C/N ratio, material appearance and reduction in mass and volume. The pH of all compounds was alkaline. Only T5 (sludge and pruning, C/N 16:1) reached a temperature above 55ºC. Tree pruning treatments were more efficient in reducing the C/N ratio, with T5 and T6 (sludge, pruning and ash, C/N 16:1) standing out with 41.52% and 42.02% reduction, respectively. All treatments suffered a reduction in volume and mass, especially for T5 and T6. There was greater mischaracterization of the waste with tree pruning in its composition. Therefore, the compounds T5 and T6 stood out, showing that the best C/N ratio to start the process is 16:1, and the carbon source is tree pruning.