Response surface methodology applying central composite design with rotatable full factorial (14 non center and 6 center points) was used to discern effect of granular activated carbon (GAC), sand and pH on total trihalomethane (TTHMs) and humic acid (HA) removal from drinking water. Results showed efficient TTHMs and HA removal by GAC while sand column showed little effect for TTHMs but significant for TOC removal. With GAC and sand column of 4 cm, a pH increase from 6 to 8 caused an increase in TTHMs removal from 79.8 to 83.6% while a decrease in HA removal from 26.6 to 6.6% was observed. An increase in GAC column depth from 10 to 20 cm caused a slight increase in TTHMs removal from 99.4 to 99.7%, while TOC removal was increased from an average of 38.85% to 57.4% removal. The developed quadratic model for TTHMs removal (p = 0.048) while linear model for TOC removal (p = 0.039) were significant. GAC column depth (p < 0.0117) and column depth2 (p < 0.039) were most significant factors. A 98% THMs, 30%TOC and 51% residual chlorine removal were optimized at 9 cm GAC and 4 cm sand column depth at pH 8 with desirability factor (D) 0.64.
- drinking water
- humic acid
- residual chlorine
- First received 25 August 2015.
- Accepted in revised form 24 November 2015.
- © IWA Publishing 2015