Effect of thermophilic pre-composting of olive mill wastewaters on reproduction and growth of earthworms Eisenia andrei

Lombric

Barhoum Kharbouch, Hicham Lakhtar, Sandrine Amat, Abdelhamid El Mousadik, Claude Perissol, Steven Criquet, Nathalie.Dupuy_, Sevastianos Roussos

The aim of the present work was to test the effect of thermophilic pre-composting of olive by-products on reproduction and growth of earthworms Eisenia andrei. Three mixtures were composed of olive cake (600 kg), horse manure (300 kg) and wheat straw (100 kg). Olive Mill Wastewater (OMWW), was added different ratio (0%, 25%, and 50%), to prepare three treatment T1, T2 and T3 respectively, then placed in trapezoidal piles with dimensions (1m height and 3×2m base) and pre-composted for two months. Three vermibed were made using 200 kg of mixtures previously pre-composted and inoculated with 2 kg of earthworms. Another three vermibed were made from same non pre-composted mixture to test the effect of thermophilic pre-composting of olive by-product on earthworm’s growth and reproduction rate. Earthworm’s growth and chemical composition changes of each treatment were measured during vermicomposting process.

The growth rate mg (worm^-1day^-1) was better in pre-composted treatment. Indeed pre-composted T₁ (control mixture) present maximum value of growth rate (11.79 mg worm^-1 day^-1), against non-pre-composted T₄ (10.04 mg worm^-1 day^-1), followed by T₂ (10.93 mg worm^-1 day^-1), against non-pre-composted T₅ (7.54 mg worm^-1 day^-1), and T₃ (8.57 mg worm^-1day^-1). In fact these results could be attributed to the OMWW’s toxicity reduction.