Remediation of ammonia-contaminated groundwater in landfill sites with electrochemical reactive barriers: A bench scale study

Leachate plumes originating from leaking landfills often cause the contamination of groundwater in subsurface. Ammonia nitrogen in the contaminated groundwater is usually hard to be attenuated due to the hypoxic condition in subsurface environment. In this study, an active chlorine mediated electroc...
Ausführliche Beschreibung

Leachate plumes originating from leaking landfills often cause the contamination of groundwater in subsurface. Ammonia nitrogen in the contaminated groundwater is usually hard to be attenuated due to the hypoxic condition in subsurface environment. In this study, an active chlorine mediated electrochemical reactive barrier (ACM-ERB) consisting of inert electrodes is proposed for the remediation of ammonia-contaminated groundwater because an elevated level of chloride ions was often found in the groundwater polluted by leachate plumes. Bench-scale experiments were conducted to evaluate the prototype of this remedial technology and to study the variables affecting the performance of ACM-ERB. The results showed that ammonia in the simulated groundwater can be effectively converted into nitrogen rather than undesirable nitrite/nitrate. RuO2/Ti anode was better than PbO2/Ti anode for the sake of ammonia removal. In the presence of naturally occurring level of bicarbonate, the electrode arrangement with an upstream cathode offered weak alkaline pH and therefore favored the removal of ammonia in the initial stage of experiment. Higher current densities and bicarbonate concentrations were favorable to the removal of ammonia. An ammonia removal efficiency up to 70% was achieved for 20 mg/L NH4 +-N influent, when the operating conditions were 250 mg/L chloride ions, 500 mA current, −80 mm water level and 6 mL/min flow rate. Polarity reversal could prevent the formation of scale on electrodes, thereby allowing the long-term operation of the ACM-ERB system in groundwater. Moreover, in the experiment using diluted leachate as influent solution, ammonia was preferentially removed relative to the organic contaminants. The present study demonstrates that ACM-ERB is a promising method to cope with the ammonia-contaminated groundwater in landfill sites. Ausführliche Beschreibung