Evolution of the fulvic acid fractions during co-composting of olive oil mill wastewater sludge and tree cuttings.
Fulvic acids (FAs) were isolated by a conventional procedure from two mixtures of the sludge residue obtained from olive oil mill wastewater (OMW) evaporated in open-air pond and tree cuttings (TC) at different stages of the co-composting process. The FAs were analyzed for elemental (C, H, N, S, O) and acidic functional group (carboxylic and phenolic) composition, and by ultraviolet/visible, Fourier transform infrared and fluorescence spectroscopies. At the initial stage of composting, FAs from the OMW sludge-TC mixtures were characterized by a prevalent aliphatic character, large contents of C, S-containing groups, proteinaceous materials and polysaccharide components, extended molecular heterogeneity, small O and acidic functional group contents, and small degrees of aromatic ring polycondensation, polymerization and humification. As composting proceeded, C, H and S contents, C/N ratio, and aliphaticity decreased, whereas N, O, COOH and phenolic OH contents, C/H and O/C ratios, and aromaticity increased. These results suggested that, with increasing the composting time, the chemical and structural properties of the FA components of the two OMW sludge-TC mixtures approached the characteristics typical of native soil FAs. Thus, co-composting of OMW sludge mixed with TC may represent a suitable treatment for enhancing the quality of organic matter in these materials when used as soil amendments.
Plaza
César
C
Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, Serrano 115 dpdo., 28006 Madrid, Spain. c.plaza@ccma.csic.es
Senesi
Nicola
N
Brunetti
Gennaro
G
Mondelli
Donato
D
D001578:Benzopyrans / Q000737:chemistry* / Q000302:isolation & purification; D005591:Chemical Fractionation; D019649:Food Industry; D006812:Humic Substances; D007220:Industrial Waste; D000069463:Olive Oil; D010938:Plant Oils; D012037:Refuse Disposal; D012722:Sewage / Q000737:chemistry*; D012987:Soil; D017550:Spectroscopy, Fourier Transform Infrared; D014197:Trees / Q000737:chemistry; D014865:Waste Disposal, Fluid
D001578:Benzopyrans; D006812:Humic Substances; D007220:Industrial Waste; D000069463:Olive Oil; D010938:Plant Oils; D012722:Sewage; D012987:Soil; C005023:fulvic acid