A pilot-scale study of the integrated floc-ultrafiltration membrane-based drinking water treatment process

Although applications of the integrated ultrafiltration (UF) membrane have been investigated for years, most studies have been conducted at the lab scale. Here, a case study on the integrated Fe-based floc-UF process was presented. To enhance membrane performance, both pre-filtration (bag filter) and pre-oxidation were used as pretreatments to re-move particles and inhibit the development of microorganisms. Results showed that the integrated process operated stably with pre-treatments, and the UF membrane fouling behavior could be divided into three different phases: slow increase rate (phase I), medium increase rate (phase II), and fast increase rate (phase III). In comparison to those in phases II and III, both natural organic matters and colloids were the main membrane fouling mechanisms dur -ing phase I, as the pollutants were not successfully removed by flocs initially. With the continuous injection of flocs, a loose cake layer became the main fouling mechanism during phase II, resulting in the deterioration of membrane foul -ing. During phase III, however, microorganisms (e.g., Proteobacteria) were inevitably nourished within the cake layer and played an important role in aggravating the degree of membrane fouling. During this integrated membrane-based process, several operating factors, including floc concentration, sludge discharge frequency, and the aeration rate dur -ing backwashing, played important roles in determining membrane performance. In addition, except for oxygen con-sumption, all the effluent quality parameters met the drinking water criteria followed in China (GB5749-2006).

Automated summary

This study presented a case study on the integrated Fe-based floc-UF process and investigated the fouling behavior of the UF membrane in different phases. The results showed that microorganisms played an important role in aggravating membrane fouling during the third phase. Several operating factors were found to be important for determining membrane performance in this integrated membrane-based process.