Treatment of raw sanitary landfill leachate using a hybrid pilot-scale system comprising adsorption, electrocoagulation and biological process

The effectiveness of a three-stage pilot approach using adsorption (AD), electrocoagulation (EC) and biological (BIO) processes for the treatment of raw sanitary landfill leachate (SLL) was investigated. SLL is loaded with hazardous substances such as organic load and heavy metals with high ammonium nitrogen (NH4+-N) concen-trations and is also produced in large quantities, causing serious risks to both living organisms and the envi-ronment. In this study, column adsorption experiments were initially performed to examine the removal of toxic NH4+-N using different initial NH4+-N concentrations and recirculation flow rates. The adsorption process was then examined as a pre-treatment step in two sequential treatment scenarios, i.e., AD-EC-BIO and AD-BIO-EC, to determine which achieved the highest removal of pollutants and leachate toxic potential, thus ensuring the biosafety of these processes during the release of the respective effluents into surface waters. The overall removal efficiencies of NH4+-N, color, dissolved chemical oxygen demand (d-COD), manganese (Mn), nickel (Ni), zinc (Zn) and iron (Fe) achieved after the application of the AD-EC-BIO system were 95.5 +/- 0.1%, 98.8 +/- 0.1%, 85.7 +/- 0.8%, 100 +/- 0.1%, 71.4 +/- 1.7%, 63.8 +/- 1.9% and 94.2 +/- 0.2%, respectively, while the values for the AD-BIO-EC system were 98.5 +/- 0.2%, 98.7 +/- 0.1%, 85.7 +/- 0.4%, 98.9 +/- 1.2%, 67.7 +/- 1.7%, 76.1 +/- 1.6% and 94.8 +/- 0.1%, respectively. In accordance with the latter, the assessment of leachate toxic potential using a Thamnoce-phalus platyurus bioassay revealed that the AD-EC-BIO system could be considered a promising treatment strategy for the purification of raw SLL.