Abdelilah Meddich

Structural study of humic acids during composting of activated sludge-green waste: elemental analysis, FTIR and 13C NMR.

The humic acids extracted from a compost of activated sludge at different stages of maturity were characterized by various chemical techniques. Elemental analysis showed the reduction of H, and the H/C and C/N ratios and an increase in the proportion of N and S. At the end of composting C% and O% presented the same values as initially, although they increased in the intermediate stage. Based on the ratios of FTIR absorbance it was shown that the end product was enriched in etherified and peptidic compounds absorbing at 1384, 1034 and 1544 cm(-1). The alkyl and other N-rich and oxidized recalcitrant structures compose the new humic polymers produced during composting. In principal components analysis, the first axis, PC1: 49.75% considers the variability between structures in decomposition from the other parameters that concern the stable new humic polymers formed after composting. PC2 (40.5%) shows a negative correlation between (aromatic carbon, FA level) and (aliphatic carbon, HA level) during composting.

Impact of applying composted biosolids on wheat growth and yield parameters on a calcimagnesic soil in a semi-arid region

A field trial in a semi-arid climate was carried out on wheat ( Triticum aestivum var. Marchouch) growing on a calcimagnesic soil using compost applied at 42 T/ha during the three years of study, but in different ways: C1, C2 and C3. Over this period, the level of total Kjeldhal nitrogen (TKN) increased in the soil amended by high doses (C2 and C3, by about 33 and 50%) compared with steady low amendment (C1) and to both controls NF (soil without fertilisation) and MF (soil receiving mineral fertilization). Adding compost also led to a positive influence on cation exchange capacity (CEC) by increasing humic substance levels (HS) which doubled in plots C2 and C3 compared with both controls. In NF soil, the TKN, total organic carbon (TOC) and the pH of soil showed a clear negative correlation with the agronomic parameters. In the MF soil, most physico-chemical parameters correlated well with the agronomic parameters: input of mineral elements balancing export through harvest. In amended soil, especially in C3 plots, HS and CEC showed significant correlations with most agronomic parameters (P1: 69.1%) due to enhanced CEC and sequestration of available carbon in the form of stable humic structures. Key words: Compost, wheat growth, calcimagnesic soil, semi-arid region.

Assessment of Biodegradation of Oleandrin during Co-composting of Nerium oleander L. Wastes

ABSTRACT Variations in the levels of the highly toxic oleandrin molecules were studied during composting of Nerium oleander L. waste mixed with clippings of the grass Pennisetum clandistenum L. The thermophilic phase is characterized by a rise in temperature, which reached 70°C. After 150 days of co-composting, the C/N ratio was 11, the pH was 8, the NO3−/NH4+ ratio was greater than 1 and overall decomposition reached 70%. During the successive stages of co-composting, oleandrin concentrations were monitored by HPLC. The relative abundance of oleadrin was 26.84% at T0 with 10% abatement during the first month and 90% after two months (stabilization phase), reaching 100%, i.e., total removal after 90 days of co-composting (maturation phase). The biodegradation of the toxic substance was largely attributed to the activity of actinomycetes and fungi. The germination index of lettuce and watercress seeds exceeded 50% after 90 days and reached 95% after 150 days, confirming that the final compost was mature, stable, and free from phytotoxicity in spite of the highly poisonous starting material.