Publication: Application of tin (IV) tetrachloride and jatropha curcas in coagulation-flocculation process for the treatment of stabilised landfill leachate
Date
2021-11-01
Authors
Syed Zainal, Sharifah Farah Fariza
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Abstract
Leachate is one of the most common problems faced by landfilling methods that can jeopardize the life and environment due to the excessive concentrations of pollutants. It must be treated first before discharge into the environment. The coagulation-flocculation (C-F) process has been extensively used in landfill leachate treatment. However, leachate needs high strength coagulant to remove higher pollutants. The application of tetravalent metal salts coagulant in combination with a natural coagulant and the effectiveness of tetravalent metal salts in a C–F process is still inclusive. This study was performed to determine the best C-F operational conditions such as pH and coagulant/flocculant dosage, rapid mixing, slow mixing, and settling on the removal of chemical oxygen demand (COD), colour, and suspended solids (SS) in a stabilised leachate from Alor Pongsu landfill site, Kerian, Perak as a case study site. Tin (IV) Chloride (SnCl4) and Jatropha curcas (JC) seed or ‘buah jarak’ was tested as a sole coagulant and later mixed with JC reacted as a flocculant. A series of jar tests were conducted, and the C-F mix was optimised using response surface methodology (RSM) and central composite design (CCD). Floc’s size and sludge properties were also evaluated, followed by an acute toxicity test on the raw and treated effluent. Excellent removals of 99.5 %, 98.4 %, and 71.5 % for SS, colour, and COD, respectively, were obtained by using 11.1 g/L of SnCl4 as coagulant alone at pH 8. JC seed was poor as a sole coagulant with only 33.9 % and 23 % reductions in colour and COD, respectively, with no removal in SS. However, with the combination of SnCl4 as a coagulant and 0.9 g/L of JC seed as a flocculant, the SnCl4 dose was reduced to xxiv 8.5 g/L with 99.8 %, 98.5 %, and 74.3 % reductions in SS, colour, and COD, respectively. The sludge and floc characteristics tested showed that JC helped in producing larger flocs, increasing the sludge velocity, and having a higher flocculation index. The treated sample with SnCl4 as coagulant and JC as a flocculant could reduce the toxicity effects to tested Tilapia fish and is safe to be discharged at appropriate dilution concentrations. It can be concluded that JC seeds have the potential to be applied as a natural flocculant with SnCl4 as the main coagulant in the treatment of leachate. This could reduce the dose of the inorganic commercial coagulants currently in use with better sludge properties.