Determination of optimum polymeric coagulant in palm oil mill effluent coagulation using multiple-objective optimisation on the basis of ratio analysis (MOORA).

The main limitation of a conventional palm oil mill effluent (POME) ponding system lies in its inability to completely decolourise effluent. Decolourisation of effluent is aesthetically and environmentally crucial. However, determination of the optimum process parameters is becoming more complex with the increase of the number of coagulants and responses. The primary objective of this study is to determine the optimum polymeric coagulant in the coagulation-flocculation process of palm oil mill effluent by considering all output responses, namely lignin-tannin, low molecular mass coloured compounds (LMMCC), chemical oxygen demand (COD), ammonia nitrogen (NH3-N), pH and conductivity. Here, multiple-objective optimisation on the basis of ratio analysis (MOORA) is employed to discretely measure multiple response characteristics of five different types of coagulants as a function of assessment value. The optimum coagulant is determined based on the highest assessment value and was identified as QF25610 (cationic polyacrylamide). On the other hand, the lowest assessment value was represented by AN1800 (anionic polyacrylamide). This study highlights the simplicity of MOORA approach in handling various input and output parameters, and it may be useful in other wastewater treatment processes as well.

Tubular nanofiltration of highly concentrated C.I. Acid Black 210 dye.

Tubular nanofiltration membrane performance to treat water for reuse was carried out by choosing C.I. Acid Black 210 dye as a model dye. It has been shown that increasing pH causes reduction in irreversible fouling factor (IFF) and the dye removal is also affected by solution pH. The total organic carbon removal for pH 4, pH 7, pH 8 and pH 10 is 97.9, 92.3, 94.5 and 94.6%, respectively. The conductivity removal for pH 4, pH 7, pH 8 and pH 10 is 85.1, 88.3, 87.8 and 90.7% respectively. The increase in the initial dye concentration causes rapid increase in fouling until 100 mg/l. Then the fouling increases gradually as it reaches a maximum IFF around 13%. This study also shows that the colour of permeate changes from colourless to light greenish/yellowish (initial concentration of 2,000 and 4,000 mg/l) as the initial dye concentration increases. The conductivity removal was also reduced as the initial dye concentration increased due to screening of the Donnan effect with the presence of salt.

Evaluation of several commercial synthetic polymers as flocculant aids for removal of highly concentrated C.I. Acid Black 210 dye.

The removal of C.I. Acid Black 210 dye from highly concentrated solutions was studied using a coagulation/flocculation process. Aluminium sulphate was used as a primary coagulant and five commercial polymers were used as flocculant aids. The five commercial polymers were ACCEPTA 2058 (poly-diallyl-dimethyl ammonium chloride), ACCEPTA 2047 (high molecular mass (MM) anionic polyacrylamide), ACCEPTA 2111 (high MM cationic polyacrylamide), ACCEPTA 2105 (Low-medium MM cationic polyacrylamide) and ACCEPTA 2037 (Composite of high MM cationic polyacrylamide-inorganic salt(s)). The five polymers behaved differently and they showed maximum colour removal increment in the order: ACCEPTA 2058 > ACCEPTA 2037 > ACCEPTA 2111 approximately = ACCEPTA 2047 > ACCEPTA 2105. Results also showed that the aluminium sulphate is important as primary coagulant and settling time has significant effect on the dye removal.