The experiment of treatment process using UF membrane combin

出　　自： ASIAN WATERQUAL 2001 ― First IWA Asia-Pacific Regional Conference(Proceedings II Poster Presentation), Fukuoka, Japan; September 12-15,2001, p131-135.
发表时间： 2001-9

DONG Bing-zhi, CAO Da-wen, LIU Sui-qing, FANG Jin-chu

（School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China） KUBOTA Hidenobu，ZHU Lie-ping （Toray Enginerring Co., Ltd. Japan）

Abstract: The experiment of UF membrane separation combined with GAC absorption process for production of pure drinking water was conducted. The treatment process fully automated was running steadily. The water quality produced meet standard for pure drinking water （ DB31/197-1997 ） . The UF membrane and process developed by Toray incorporation could remove not only bacterial and turbidity, but also organics effectively.

Keywords: high-quality drinking water, membrane separation, UF membrane, GAC

1 Introduction

　　With the resources being polluted heavily, the drinking water quality produced by traditional process is not satisfactory for citizens in China [1] . Therefore a pure drinking water is booming now in China, becoming a huge market. Although pure drinking water produced by RO membrane treatment is excellent, the influence on health of citizens who drink for a long-time have been concerned. A high-quality drinking water is meant such a drinking water that organics is removed and matters which is good for people‘ health is retained. The high-quality drinking water is getting more and more welcome.School of Environmental Science and Engineering of Tongji University cooperated with Toray Engineering Co., Ltd. to develop GAC-UF treatment process for production of high-quality drinking water.

2. Treatment process description

The flow of treatment system is shown as follows.

The purpose of prefilter is to retain suspended particles and colloids from feed water. GAC absorb organics. The UF membrane developed by Toray incorporation is of hollow fiber type and composed of PAN and has a pore size of 0.01μm and a membrane area of 12m 2 for each module [2] . The purpose of the UF membrane is to reject suspended colloids, bacterium and part of organics. The system had treatment capacity of 12m 3 /d and operated at constant flux. The backwash was performed with hydraulics plus air. The treatment system was operated automatically. The permeate water quality comply with the pure water quality standard （ DB31/197-1997 ） promulgated by Shanghai Technical Supervision Bureau in 1997.


　　As shown in figure 2, the turbidity in feed water was in the range of 0.3 and 0.5 NTU. After treatment, all the turbidity in permeate water was below 0.2 NTU, meeting pure drinking water standard.

3.2 Removal of TOC

　　As shown in figure 3, TOC in permeate water was less than pure drinking water standard of 4 mg/L. The results showed that GAC remove 37.5 percent of TOC and membrane remove 16 percent. Therefore in treatment process studied, both GAC and membrane remove TOC effectively.

3.3 Removal of COD Mn

COD Mn concentration in feed water was higher than pure drinking water standard of 2 mg/L in many cases. The experiment result showed that most of COD Mn was removed by GAC absorption and few were removed by membrane, which can be explanted that COD Mn compose of organics with lower molecular weight.

3.4 Residual chlorine and bacterial number

Figure 5 showed that residual chlorine concentration in feed water was very high, often more than 2 mg/L. So bacterial number in feed water was very few. In this experiment, the pore size of membrane used is 0.01 μm and smallest bacterium in size is about 0.3 μm. Therefore membrane could reject bacterium absolutely. As shown in figure 6, bacterium in permeate was very few or zero, indicating the efficiency of membrane for rejection of bacterium.

3.5 Effect of chemical cleaning

　　After operation of 6 months, the transmembrane pressure increased 2 times compared with the beginning of operation, as shown in figure 7. In this case, the chemical cleaning must be conducted. First oxalic acid and hydrochloric acid was dosed in permeate water tank and circulated for 2 hours to clean inorganics in membrane, then sodium hypochlorite was dosed and circulated for 1 hours to clean organics. Table 1 showed the effect of chemical cleaning on transmembrane pressure. The result indicated that organics in water was responsible for the membrane fouling.

4. Conclusion

　　The experiment of UF membrane separation combined with GAC absorption process for production of pure drinking water was conducted. The treatment process fully automated was running steadily. The water quality produced meet standard for pure drinking water （ DB31/197-1997 ） . The UF membrane and process developed by Toray incorporation could remove not only bacterial and turbidity, but also organics effectively.

5. References

[1] YUE Shun-lin. Municipal water quality problems in China. China Water and Wastewater, 1997, 13(supplement): 35 ～ 38
[2] Hiroyuki Yamamura and Yoshishige Fujii. Advanced feed outside hollow-fiber membrane module for clarification of various waters. Membrane, 1995, 20(5): 309 ～ 315