Application of Response Surface Methodology (RSM) for Optimizing Turbidity of Paper Recycling Wastewater Using Microwave Technology

Aims: The aim of the study was to use Response Surface Methodology (RSM) to find optimal experimental design for wastewater treatments from office paper recycling. In this way, interactive effects of treatment factors were evaluated, including microwave power (MW) and durations with centrifuge time while turbidity of wastewater was chosen as the dependent output variable or an optimal response.

Methodology: The RSM approach was utilized for optimization of the process parameters and identifying the optimal conditions for the removal of turbidity in paper recycling wastewater. In this regard, a three-factor RSM were selected, using MW irradiation power (Watts), durations (seconds) and centrifuge time (min). Statistical analysis of variance (ANOVA) was carried out to identify the adequacy of the developed model. In this case, specially prepared office papers (one-side laser printed) were subjected to standard paper recycling procedure for obtaining wastewater at laboratory conditions. The experimentally derived RSM model was validated using range of statistical parameters.

Conclusions: The study revealed that under the RSM optimized conditions, a marked reduction in the turbidity of wastewater was observed for both groups studied. The R2, R2(adj) and R2(pred) values were indicates, the developed model was significant which revealed a well agreement between the experimental data and proposed model. In this approach, the R2=99.710% and lack-of-fit value were found to be 0.111 (p>0.05), which shows the model and the data consisted to each other. The lowest turbidity value was found with 150.000 Watts and 60.000 seconds in MW conditions with 15.000 minutes of centrifugation time, experimentally. With employing these variables, the turbidity value of 6.65 NTU was determined. However, the highest turbidity value of 18.013 NTU was found with MW power of 200.00 Watts with 40.000 seconds of durations and 1.591 minute of centrifugation time. It is important to note that with using optimized parameters, the turbidity value of 1.43 NTU was calculated while 1.47 NTU was found with experimentally.