New insights on abatement of organic matter and reduction of toxicity from landfill leachate treated by the electrocoagulation process

Abstract

In this work, new insights on organic matter (OM) removal performance along with the assessment of the toxicity of landfill leachate (LL) treated by Electrocoagulation (EC) method were investigated. In the context of response surface methodology (RSM), the optimal EC experimental conditions were sought by applying a 33 complete factorial design, regarding pH, current density and electrolysis time as operational parameters. The sum of dissolved organic and inorganic carbon, namely as dissolved total carbon (DTC), was chosen as a global response parameter. Other EC experiments were performed, keeping fixed pH and current density at local optimal values and varying the electrolysis time. Determination of the median lethal concentration (LC50) from bioassays based on Artemia salina and Lactuca sativa indicators was performed. A second-order polynomial function was statistically validated with good predictions of the DTC data, indicating best removals by setting values of pH, current density, and electrolysis time at 5, 128.57 Am−2 and 120min, respectively. Additionally, removals above 90% were achieved for color, turbidity, iron concentration and dissolved inorganic carbon, whereas reductions on related-to-organic matter parameter values were around 60%. Although the EC treatment reduced the LL effluent toxicity, as verified by toxicity bioassays, 90min treatment times showed best results on LC50, but higher toxicity was persistent in electrolysis times below 40min. Thus, a second stage of treatment based on a biological process could be suitably included in order to abate recalcitrant OM and decrease remaining toxicity in a more efficient integrated treatment system.