Utilisation of natural plant-based fenugreek (Trigonella foenum-graecum) coagulant and okra (Abelmoschus escluentus) flocculant for palm oil mill effluent (POME) treatment

[Display omitted] •Fenugreek and okra can be utilised as natural coagulants and flocculants respectively for the treatment of palm oil mill effluent (POME).•Removal efficiencies of turbidity, total suspended solids and chemical oxygen demand were 94.97, 92.70 and 63.11 % respectively.•Sludge produced from the treatment process was high in its calorific value and can be used as solid fuel briquettes.•Experimental data has been modeled using Response Surface Methodology (RSM). Fenugreek (Trigonella foenum-graecum) and okra (Abelmoschus esculentus) were utilised as natural coagulants and flocculants respectively for the treatment of palm oil mill effluent (POME). Optimisation and modeling of the coagulant and flocculant dosages, pH and rapid mixing speed were carried out using Response Surface Methodology (RSM) method by applying the Analysis of Variance (ANOVA). ANOVA studies the relationship between the four independent variables to obtain maximum removal of pollutants. Experimental results showed a removal of 94.97, 92.70 and 63.11 % in turbidity, TSS and COD, respectively. The particle bridging mechanism was found to be pre-dominant in the treatment process. Sludge generated was non-toxic and high in calorific value, indicating potential to be made into clean solid fuel briquettes. Treatment of POME using natural material proved to be cost effective and environmentally friendly, with zero generation of waste, thus providing a more circular waste management approach for the industry.