Report: anaerobic digestion of a sulphate-rich high-strength landfill leachate: the effect of differential dosing with FeCl3.

The effect of different dose concentrations of FeCl3 on the performance of a mesophilic anaerobic digester treating a highly alkaline, high-strength and sulphate-rich landfill leachate was tested. The results indicated that sulphate reduction was the predominant reaction and methanogenic processes were entirely inhibited in the reactor without FeCl3 addition. Adding FeCl3 into the reactor restored some methanogenic activity and also improved the rates of sulphate reduction. A combination of sulphate reduction and methanogenic activity resulted in up to 75% chemical oxygen demand (COD) removal and 85% sulphate removal. Sulphate reduction remained the principle mechanism by which COD removal took place with a methane yield of only between 0.14 and 0.18 m3 CH4 kg(-1) COD removed being achieved. The process was, however, stable and offered advantages for the further treatment or conveyance of the anaerobically treated leachate.