COMPARATIVE STUDY OF ORGANIC MATTER DEGRADATION OF COMPOSTED SLUDGE AND SLUDGE LANDFILLED / ETUDE COMPARATIVE DE LA DEGRADATION DE LA MATIERE ORGANIQUE DES BOUES COMPOSTEES ET BOUES MISES EN DECHARGE

The results of the biotransformation of organic matter for three trials A (500 kg sludge + 400 kg turf + 100 kg of straw), B (1000 kg sludge composted alone), and C (1000 kg sludge landfilled) after six months show a good degradation rate for trial A, compared to B, and C. C/N ratio decrease from 30 to 12 for mixture A, from 32 to 19 for B, and from 32 to 24 for C. An important decomposition rate, about 74 %, for mixture A has been reached after six months. The final compost for mixture A exhibited a high concentration (151.7 g·kg-1) of humic substance and a low concentration of heavy metal contents, compared to the AFNOR standard (NF U 44-041). The efficiency of the composting is confirmed by the germination index (GI), which exceeds 90 % for the trial A. However, phytotoxicity for trials B and C remains less important (GI does not exceed 40 %). The results of trial A will open the way for the agricultural use of sludge

MONITORING OF ORGANIC POLLUTION AND MATURITY OF ORGANIC MATTER FROM SLUDGE LANDFILLING

The biotransformation during the 3 years of sludge landfilling was evaluated by physicochemical analysis and phytotoxicity test. The final product exhibited a high degree of decomposition rate (51.06 %) than the controls as shown by a decrease of C/N ratio of about 19.67. The results showed that the lipid, surfactant and polyphenol as main compound of the sludge were breakdown over time. The concentrations decreased from 29.9 to 11.8 mg·g-1 and 3.4 to 0.6 mg·g-1, respectively for surfactant and polyphenols after 3 years of landfilling. This corresponds to a reduction of 80.2 % for polyphenols and 60.4 % for surfactant, due to the microorganisms activity. Total lipids decrease from 16.5 to 6.27 mg·g-1 of dry matter, representing an abatement rate of about 62 %. The evolution of organic matter reflects the progress of the humification process, which judging by the increase in the polymerization degree, is about 20 %. The landfilling efficiency to reduce phytotoxicity of sludge was confirmed by the germination index, which reached 52 and 59 %, respectively for alfalfa and cress after 3 years of landfilling. These results are promising and pave the way for agricultural spreading of sludge