Optimization of coagulation-flocculation process for colour removal from Azo dye using natural polymers: response surface methodological approach

The ability of organic polymer rich coagulants for colour removal from acid dye was studied. An improved method for the extraction of the active coagulant agent from the seeds was employed. The effects of four variables including pH, coagulant dosage, dye concentration and time were analyzed. Response surface methodology (RSM) using face-centered central composite design (FCCD) was used to optimize the four variables. Increase in the colour removal efficiency was higher in acidic solution pH. Accurate control of coagulant dosages gave optimum destabilization of charged particles and re-stabilization occurred at above 800mg/L dosages. Polymer performances were measured through time-dependent decrease in particle concentrations following aggregates growth. The verification experiment agreed with the predicted values having less than 4% standard error. Overlay contour plot was used to establish an optimum condition for the multiple responses studied. The response surface approach was appropriate for optimizing the coagulation-flocculation process while minimizing the number of experiments. Coagulants studied should be considered as an alternative for conventional coagulants that are widely used in dye wastewater treatment plants.Keywords: Coagulation-flocculation, Azocarmine G, multiple response optimization, response surface design, colour removal, natural organic polymers

Performance of polymer coagulants for colour removal from dye simulated medium: Polymer adsorption studies

205-215Evaluation of natural coagulants for colour removal from dye simulated wastewater has been studied. The proximate compositions and surface morphologies of the organic polymers are investigated. The effects of operational parameters including pH, coagulant dosage, dye concentration, settling time and temperature are tested and their optimum operating ranges determined. Acidic solution pH increased the colour removal efficiency. Accurate control of coagulant dosages is required for optimum destabilization of charged particles. Dye concentration is a driving force that shows the extent of particle transfer. Polymer performances on the flocculation process are measured through time-dependent decrease in particle concentrations and consequently, promoting flocs growth. Charge neutralization, polymer adsorption, inter-particle bridging and sweep-flocculation are the active mechanisms in the removal process. Adsorption of particles on the polymer surfaces occur mostly as a monomolecular layer and according to chemisorption mechanism. The agreement of pseudo-second order and Elovich model with high correlation (R2>0.926) confirms the coagulation-flocculation/adsorption kinetics behaving more as a second-order rate process

Optimization of coagulation-flocculation process for colour removal from Azo dye using natural polymers: response surface methodological approach

The ability of organic polymer rich coagulants for colour removal from acid dye was studied. An improved method for the extraction of the active coagulant agent from the seeds was employed. The effects of four variables including pH, coagulant dosage, dye concentration and time were analyzed. Response surface methodology (RSM) using face-centered central composite design (FCCD) was used to optimize the four variables. Increase in the colour removal efficiency was higher in acidic solution pH. Accurate control of coagulant dosages gave optimum destabilization of charged particles and re-stabilization occurred at above 800mg/L dosages. Polymer performances were measured through time-dependent decrease in particle concentrations following aggregates growth. The verification experiment agreed with the predicted values having less than 4% standard error. Overlay contour plot was used to establish an optimum condition for the multiple responses studied. The response surface approach was appropriate for optimizing the coagulation-flocculation process while minimizing the number of experiments. Coagulants studied should be considered as an alternative for conventional coagulants that are widely used in dye wastewater treatment plants.Keywords: Coagulation-flocculation, Azocarmine G, multiple response optimization, response surface design, colour removal, natural organic polymers

Kinetics of the Valorization of Food Waste for Medium Chain Carboxylates Production; Effect of Ensiling and Inoculum source.

Higher yields of medium chain carboxylates (MCC) can be obtained from the anaerobic fermentation of complex feedstocks like food waste if pretreatment preceeds fermentation. However, many conventional pretreatment processes produce inhibitors that could affect downstream processing in addition to increasing the cost of the overall process. In this study, ensiling was used as a cost effective and sustainable pretreatment method to instigate the formation of electron donors like lactic acid and ethanol in food waste for MCC production. Food waste was ensiled for 120 days and thereafter subjected to batch anaerobic fermentation using two different inocula including leachate and rumen fluid. Results show that ensiling degraded the cellulose and hemicellulose component of food waste and converted the water soluble carbohydrate content to lactic acid, acetic acid and ethanol. Ensiled substrates had a total MCC yield of 990.44 g/kgVS and 878.68 g/kg VS when leachate and rumen fluid was used as inoculum respectively, while the unensiled food waste had a total MCC yield of 522.80 g/kgVS and 430.88 g/kgVS when leachate and rumen fluid was respectively used as inoculum. In order to predict the MCC production, two kinetic models were used including the first-order model and the modified Gompertz model. Statistical indicators including the coefficient of determination, R2, the root-mean-square-error and the Akaike Information Criterion show that the first-order model predicted the experimental MCC better than the modified Gompertz model. &nbsp