Frequent Chemical Cleaning Research Articles

Intermittent crossflushing of hollow fiber ultrafiltration systems

The successful operation of dead-end ultrafiltration systems depends on the effectiveness of cleaning (hydraulic and/or chemical cleaning). In this study, backwashing conditions such as pressure and duration were studied in order to maximize the net flux per cycle. Monitoring the backwash flux and turbidity of the backwash water showed that the efficiency of backwashing was more dependent on backwashing time than pressure. The effectiveness of backwashing was significantly improved by the use of crossflushing. In general, 99.9±1% flux restoration could be achieved when backwashing was preceded by crossflushing while 94.5±1% could be achieved by backwashing alone. Crossflushing was more effective when the crossflush velocity in the fiber was in the turbulent regime (v ≅ 1.6 m/s). Crossflushing and pressure pulsing can be employed to increase the efficiency of dead-end, hollow fiber ultrafiltration systems because the frequency of backwashing and chemical cleaning, permeate consumption and system down time are reduced.

Control and modeling of membrane fouling due to microorganism growth by UV pretreatment

Control of membrane-fouling is an important topic for extending continuous running time and reducing the frequency of chemical cleaning in membrane processes. Since the microorganism contribution to membrane fouling was considered to be significant, UV was thought to be effective to control membrane fouling. In this study, a pilot plant scale MF-membrane system (flow rate = 5 m3d−1) was operated in order to investigate the effect of UV pretreatment. As the experimental results, it was found that UV irradiation prevented the membrane fouling by control the microorganism concentration in the feed. And the continuous running time of membrane was extended 6 times longer than that of a process without UV pretreatment. In order to know how UV pretreatment prevented fouling, we also investigated the residual bactericidal effect which persists in water even after UV irradiation. However, the residual bactericidal effect wasn't observed in our experiment, therefore inhibition of microorganism growth by the residual effect in the membrane module could be ignored. We developed the theoretical model of microorganism growth on membrane as a membrane fouling material. This model can explain the observed membrane fouling due to microorganism growth.

Control and modeling of membrane fouling due to microorganism growth by UV pretreatment

Control of membrane-fouling is in important topic for extending continuous running time and reducing the frequency of chemical cleaning in membrane processes. Since the microorganism contribution to membrane fouling wis considered to be significant, UV was thought to be effective to control membrane fouling. In this study, a pilot plant scale MF-membrane system (flow rate = 5 m3d−1) was operated in order to investigate the effect of UV pretreatment As the experimental results, it was found that UV irradiation prevented the membrane fouling by control the microorganism concentration in the feed. And the continuous running time of membrane was extended 6 times longer than that of a process without UV pretreatment In order to know how UV pretreatment prevented fouling, we also investigated the residual bactericidal effect which persists in water even after UV irradiation. However, the residual bactericidal effect wasnt observed in our experiment, therefore inhibition of microorganism growth by the residual effect in the membrane module could be ignored. We developed the theoretical model of microorganism growth on membrane as a membrane fouling material. This model can explain the observed membrane fouling due to microorganism growth.