Comparative Study of Algae and Cactus as Bioflocculants in the Physico-chemical Treatment of Leachate from the Controlled Landfill

Landfilling is one of the most widely used methods of municipal solid waste (MSW) disposal. Up to 95% of the total municipal solid waste collected worldwide is landfilled. After landfilling, solid waste undergoes physico-chemical and biological changes. Consequently, the degradation of the organic fraction of the waste, combined with the percolation of rainwater, leads to the production of leachate. If not properly treated, leachate from a landfill can enter the underlying groundwater, posing potentially serious risks to the surrounding environment and public health. Consequently, the search for effective and efficient landfill leachate treatment technologies has intensified in recent years. Bioflocculants are a sustainable alternative to metal salts and synthetic polymers for the treatment of water by coagulation–flocculation (CF). The literature has mainly described the optimal parameters for the application of bio-based materials in CF. The present study is based on the use of ferric chloride FeCl3 in combination with two bioflocculants. The first bioflocculant is of Opuntia cactus origin, and the second is an algae bioflocculant. The flocculants were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The influence of various experimental parameters, such as: the quantities of coagulants and bioflocculants used, pH, turbidity, and Chemical Oxygen Demand (COD), were studied. The coagulation–flocculation tests show that with a mass of 3 g FeCl3, a COD abatement of 74% at pH = 6.55 and a turbidity reduction equal to 77% were achieved. The examination of the main parameters studied in the flocculation tests, in the presence of the two bioflocculants, Opuntia cactus and algae and ferric chloride FeCl3 with a dose of 3 g, shows that the degree of pollution decreases, which is confirmed by an elimination efficiency of 86% for COD and 83% for turbidity values with the use of the Opuntia cactus bioflocculant, and an elimination of COD 87% and turbidity 81% with the use of algae bioflocculant.