Feasibility of Olive Mill Wastewater treatment by Multi-Soil-Layering Ecotechnology

Tthis work aims to examine for the first time, the treatment of olive mill wastewater (omw) by multi-soil-layering (msl) ecotechnology. omw studied is a very acidic (ph 4.44) and highly concentrated of organics (25.15 g l⁻¹of cod) and toxic phenolic compounds (1.496 g l⁻¹). moreover, omw contained low concentrations of electrical conductivity and total suspended solids (4895 µs cm⁻¹ and 1.454 g l⁻¹ successively). the msl system is composed of soil mixture blocks (soil-sandy texture + sawdust + metal iron + charcoal) arranged in a brick- like pattern and surrounded by permeable gravel layers to avoid clogging. in our study, omw diluted by urban wastewater was loaded to the system, at continuous hydraulic loading rate (hlr) of 100 l m⁻²day⁻¹. during the experiment, the percentage of omw was gradually increased from 10% to100%.results showed that, between 10% and 50% of omw in the feeding of msl induced a ph alkalizing (from 7.9 to 8.5) of the treated water and reduced successfully tss (from 95.73% to 99.06%), cod (from 85.03% to 91.76%), bod (from 54.39% to 82.63%), total phosphorus (from 55.46% to 90.06%), nh₄⁺ (from 69.25% to 98.58%) and phenolic compounds (from 91.47% to 100%).the total oxygen demand for organic matter biodegradation and nitrogen oxidation was completely satisfied in the msl and residual dissolved oxygen still high at the outlet. however, when exceeding 60% of omw in the inlet, the efficiency of the msl system decreased for all parameters and a clogging starting sign (acidic ph, very low residual oxygen in the outlet) appeared although stability of outflow. therefore, the msl ecotechnology could be a good option for omw treatmentwhen mixing of omw to urban wastewater was less than50% corresponding to a um superficial organic load feeding of 1.068 kg cod m⁻²day⁻¹ and 0.516kg bod₅ m⁻²day⁻¹.