The fulvic acid fraction as it changes in the mature phase of vegetable oil-mill sludge and domestic waste composting.

Sludge resulting from the treatment of effluent from a vegetable oil mill, was composted mixed with domestic waste in a pile for five months. Different proportions of sludge and dry waste were mixed: M1 (1v/2v) and M2 (1v/1v). Monitoring different physical-chemical parameters showed the effect of the substrate on the microbiological activity and on the formation of fulvic acids, affecting the maturity of the final compost.

Sequential extraction of heavy metals during composting of sewage sludge.

The major limitation of soil application of sewage sludge compost is the total heavy metal contents and their bioavailability to the soil-plant system. This study was conducted to determine the heavy metal speciation and the influence of changing the physico-chemical properties of the medium in the course of composting on the concentrations, bioavailability or chemical forms of Cu, Zn, Pb and Ni in sewage sludge. Principal physical and chemical properties and FTIR spectroscopical characterization of sludge compost during treatment show the stability and maturity of end product.

Characterization of fulvic acids by elemental and spectroscopic (FTIR and 13C-NMR) analyses during composting of olive mill wastes plus straw.

Elemental, functional and spectroscopic analyses (FTIR, 13C-NMR) were performed to study fulvic acids of composted olive mill wastes plus cereal straw, in order to follow the maturity of the final product during composting. The extracted fulvic acids were characterized by high nitrogen, acidic functional group and phenolic hydroxyl contents that might have resulted from the high degree of humification and the synthesis of more condensed humic complexes. This was confirmed by a decrease of alcoholic and aliphatic structures and an increase of aromatic structures, as shown by the FTIR and 13C-NMR analyses.