Coagulation-flocculation treatment is often used for the treatment of stabilized landfill leachate. However, uses a non-environmentally friendly chemical coagulant which is a threat to environment quality, therefore Cactus opuntia is proposed to replace the use of current chemical coagulants such as aluminium sulphate in order to achieve sustainable growth. In this regard, the comparative suitability of Cactus opuntia and alum as coagulants for the treatment of the stabilised leachate of the Padang Siding Landfill Site was evaluated via a series of Jar Test experimental works with a rapid mixing speed of 100 rpm for 3 minutes, a slow mixing speed of 30 rpm for 10 minutes and a set-up period of 30 minutes. In addition, the sludge volume index (SVI) of the treated leachate sample was calculated under optimised conditions. Cactus opuntia was able to remove 66.8 per cent turbidity and 42 per cent COD at optimal pH 2 with a favourable dose of 8000 mg / L, while the optimal pH 5 with a coagulant dose of 8000 mg / L induced 94.5 per cent turbidity and 69 per cent COD reduction from the same leachate sample. In addition, the SVI of alum coagulant was 42.2 while the Cactus opuntia was 4.45 with a relative ratio of alum to opuntia of 9:1. Cactus opuntia may also be proposed as a plentiful coagulant of metal cationic ions such as aluminium, iron and silica elements for the treatment of leachate.
