Microfiltration-adsorption hybrid system in organics removal from water

A series of experiments was conducted with a Millipore fiat plate microfilt ration module modified to incorporate in-line powdered activated carbon (PA C) addition. In-line PAC was mixed continuously through a spiral mixing dev ice for a predetermined time prior entering a membrane unit. The results sh owed that this system is excellent in removing fulvic acid (FA). This syste m provides to sufficient contact time for PAC to adsorb organics compared t o the system with in-line adsorbent addition. More than 85% of FA was remov ed from water containing 8 mg/l of FA. To achieve this following conditions were used:.(i) a velocity gradient G (mixing intensity) of 160.4s(-1); (ii ) a hydraulic residence time (mixing time) of 4 minutes; (iii) a PAC dose o f 260 mg/l; and (iv) membrane pore size of 0.22 mu m. In case of low FA con centration (e.g. 1.2 mg/l) in water, the removal efficiency was almost 100% . The removal efficiency also increased with the increase of mixing intensi ty and mixing time. The permeate flux slightly improved when a membrane of pore size 0.22 mu m was used with shorter hydraulic residence time and lowe r PAC concentration. This paper presents a mathematical model developed bas ed on surface diffusion. The model successfully predicted the performance o f this hybrid system.