Experimental Vertical-flow Constructed Wetlands Treating Domestic Wastewater Contaminated by Diesel Spill

Wetlands are potential alternatives and cost-efficient supplementary systems to treat different types of oily-polluted water, wide spread particularly in areas where land costs are low. The aim of this study is to evaluate the effect of different variables: media size (gravel), contact time, empty time and loading rate (COD load) on the treatment performance of vertical-flow constructed wetland filters operated in batch flow mode and subjected to two diesel spills (20 g/L and 150 g/L) on September 2013 and September 2014, respectively. The objectives were to (i) test the impact of multi- doses of diesel concentrations on the overall treatment performance of the vertical-flow wetlands; and to investigate (ii) the effect of different design and operational parameters on the removal of diesel compounds and other water quality parameters for the period between September 2013 and January 2016. The results showed that the wetland filters were to be highly efficient for the removal of diesel concentrations in the first period of diesel spill (first dose of diesel) and moderate in the second period of diesel spill (second dose of diesel). Also, water quality parameters for wetlands were in a compliance with secondary wastewater treatment standards regarding ammonia-nitrogen (NH4-N), and suspended solids (SS), and non-compliance concerning orthophosphate-phosphorus (PO4-P). Moreover, wetland filters contaminated by hydrocarbon compounds showed drops in COD removal efficiencies. This study will enhance the perceptive of using constructed wetlands as best tool for hydrocarbon compounds treatment.