Integrated two-phase purification procedure for abatement of pollutants from sanitary landfill leachates

Abstract

The improvement of pollutant removal, in addition to low toxicity and a high biodegradability index, from sanitary landfill leachate (SLL) effluents treated in a two-process purification system was investigated. As a purification strategy, an electrocoagulation (EC) process followed by a biological purification step was applied. The response surface methodology was used to study the best EC process performance as a function of initial pH, current density and electrolysis time. The maximum removal of turbidity, chemical oxygen demand (COD) and iron concentration were achieved at an initial pH of 5, a current density of 128.57 A m−2 and an electrolysis time of 120 min. Regarding the best EC conditions, toxicity, based on an Artemia salina bioassay, and biodegradability, based on the Zahn-Wellens test, were assessed in raw SLL effluents and after their treatment with EC and biological processes. After stripping almost 98% ammonia of the concentration after EC experiments at 0, 5 and 120 min electrolysis times, the toxicity was also assessed. From the bioassay tests, the best result for the toxicity level was achieved for a 5 min electrolysis time. The Zahn-Wellens test showed that the EC process as a first stage of a two-phase treatment system was sufficient and provided a biodegradability index above 70%. By treating with a biological process, a significant improvement in toxicity was attained. However, most probably, the remaining toxicity could be attributed to ammonia. Thus, a pre-treatment based on the EC process integrated to a biological one can be considered as a promising and challenging alternative.