Performance of olive mill wastewater treatment using hybrid system combining sand filtration and vertical flow constructed wetlands

Abstract

Olive mill wastewater (OMWW) is a main source of noxious and recalcitrant organic pollutants of significant concern in environmental engineering. For this purpose, the current study assessed the performance of system combining sand filtration and vertical flow constructed wetlands (VF-CWs) in reducing the organic load of OMWW. Sand filter system wed in this study is composed of 6 plastic columns of 0.50 m in diameter and 120 L of capacity. The irrigation of sand filter columns was assured by 50 % diluted OMWW at flow rate of 5 L/day. VF-CWs system consists of a 1 m3 tank filled with soil and gravel in the bottom and planted of Typha latifolia, Phragmites australis and Arundo donax aquatic plants. The irrigation of VF-CWs system was assured with treated OMWW with a flow rate of 20 L twice in the week. Obtained results showed that sand filtration achieved a high removal rate of 76.42, 75.12, 79.7 and 78.10 %, respectively, for total suspended solid (TSS), dissolved COD (chemical oxygen demand), total COD and phenolic compounds. The usage of the combination of sand filter and VF-CWS improved significantly the elimination efficiency of total COD up to 91.44 %, dissolved COD up to 77.09 % and phenolic compounds up to 79.47 %, but it did not report any performance in the removal of TSS. Despite the high performance of hybrid system (sand filter+VF-CWs) in reducing the organic pollution, final effluent concentrations remained below the permitted limits for discharge into a municipal sewer system.