Compostagem em reatores de tabaco de cigarros contrabandeados e lodo de ETE industrial: estudo da estabilidade e maturidade por meio de parâmetros físico-químicos, biológicos e espectroscópicos

Abstract

The composting in reactors has presented an efficient and low-cost technology to treat different organic solid residue. The preoccupation about the growing generation of these residue has aroused interested in relation to administration and its reuse, with the intention to minimize the effects of impacts when discarded improperly in the environment. Facing this problem, the present research has the objective to assess the stability and maturity of smuggled cigarettes tobacco compound and sludge from WTP industrial produced in composting reactors. The stability of the compounds was evaluated by results of temperature, pH and humidity, while the maturity was verified by data of electrical conductivity (EC), C/N ratio, cation exchange capacity (CEC) and seed germination index (SGI). The final compounds were evaluated for nutrient content, concentration of potentially toxic metals, percentage of nicotine removed and human pathogens. The increase of the humic acid fraction was characterized by spectroscopic techniques: UV/Vis, FTIR and NMR 13C-CP/MAS. It was verified that composting in facultative reactors was efficient in the self-control of humidity and aeration, which contributed to higher exposures of thermophilic temperatures (above 52ºC), resulting in the elimination of pathogenic microorganisms from the three compounds. The low initial C/N ratios for the R2 and R3 reactors enabled the treatment of large amounts of SCT residues and industrial WTP sludge and the decrease over the composting showed that the three compounds reached maturity. The increase in SGI and CEC values during the composting process, conferred maturity and high degree of humification to the compounds, indicating an increase in ionizable functional groups (carboxylates, phenolics and methoxylics). The subtraction of the E2/E6 and E4/E6 ratios, the increase of peaks and bands in the FTIR spectra, the characteristics of aromatic groups and the increase in the percentage of the main groups of aromatic C in the NMR 13C-CP/MAS analysis indicated increased fracture of humic metals and oxygen groups linked to their structure. The compounds of reactors R2 and R3 showed a tendency towards higher proportions of oxygenated and nitrogenated groups, possibly due to the greater tobacco composition of smuggled cigarettes and industrial WTP sludge in the initial mixtures. The final compounds (180 days of process) presented levels of (NPK) considered beneficial for the development of plants. Furthermore, it was found that concentrations of potentially toxic metals: Co, Ni, Cu, Mn, Fe, Cd, Pb and Cr were below the maximum allowed limit for organic compound and that the compounds were absent from pathogenic microorganisms or below the established limits. The percentage of nicotine withdrawal of 72; 96.4; 99.6% for the compounds of R1, R2 and R3, respectively, indicated the efficiency of the process in the degradation of this substance and formation of materials with absent toxicity. In view of the results, the smuggled cigarettes tobacco and sludge from WTP industrial produced in composting, through facultative reactors, produced compounds that are absent of toxicity, with a high degree of stability, maturity and richness in nutrients.