1、外文资料Effects of pH on coagulation behavior and floc properties in YellowRiver water treatment using ferric based coagulantsCAO BaiChuan1, GAO BaoYu1*, XU ChunHua1, FU Ying2 & LIU Xin11Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineerin
2、g, Shandong University,Jinan 250100, China;2School of Civil and Architecture, Jinan University, Jinan 250022, ChinaReceived June 13, 2009; accepted October 19, 2009Enhanced coagulation is one of the major methods to control disinfection by-products(DBPs) in water treatment process. Coagulation pH is
3、 an important factor that affects the enhanced coagulation. Recently, many studies focus on the coagulation effects andmechanisms, and few researchers studied the properties of flocs formed under different coagulation pH. Two inorganic polymercoagulants, polyferric silicate sulphate (PFSS) and polyf
4、erric sulphate (PFS), were used in Yellow River water treatment. The influence of pH on coagulation effect was investigated under the optimum dosage, and the results show that both coagulants gave excellent organism removal efficiency when pH was 5.50. According to the variation of zeta potential in
5、 coagulation process, coagulation mechanisms of the coagulants were analyzed. An on-line laser scatter instrument was used to record the development of floc sizes during the coagulation period. For PFSS, pH exerted great influence on floc growth rates but little influence on formed floc sizes. In PF
6、S coagulation process, when pH was 4.00, PFS flocs did not reach the steady-state during the whole coagulation period, while little difference was observed in floc formation when pH was 5.50 and above. The preformed flocs were exposed to strong shear force, and the variation of floc sizes was determ
7、ined to evaluate the influence of pH on floc strength andre-growth capability. In comparison of the two coagulants, PFS flocs had higher floc strength and better recovery capability when pH was 4.00, while PFSS flocs had higher floc strength but weaker recovery capability when pH was 5.50 and above.
8、ferric based inorganic polymer coagulants, pH, coagulation effect, floc formation, floc breakage and re-growthbehavior and floc properties in Yellow River water treatment using ferric based coagulants.Chinese Sci Bull, 2010, 55: 13821387, doi: 10.1007/s11434-010-0087-5Enhanced coagulation is one of
9、the processes recommended by USEPA to remove natural organic matters (NOM) in surface water and to control disinfection by-products (DBPs) 1. The development of new types of coagulants with high coagulation effect is one of the hot topics in the field of enhanced coagulation 2. In the field of drink
10、ing water treatment, many studies focus on ferric based inorganic polymer coagulants, because of their advantages in removing dissolvedorganic compounds, such as high removal efficiency, low bio-toxicity, high coagulation rate and large flocs, excellent sedimentation and dewatering abilities 3. Poly
11、ferric silicate sulphate (PFSS) and polyferric sulphate (PFS) are two kinds of typical coagulants 4,5, which can achieve good removal of natural organic compounds. As the ferric coagulants are dosed, the organic compounds in surfacewater are removed in the following ways 6. The coagulants may react
12、with the functional groups of organic compounds to form complexes or chelates, and part of the organic compounds could be captured by absorption and sweep flocculation. The coagulation pH is one of the main factors that influence the removal effect of enhanced coagulation, and for ferric coagulants
13、the optimum pH range is 5.56.5 7.Floc breakage is accompanied with the growth and transmission of flocs in coagulation process, and the fragCAOBaiChuan, et al. Chinese Sci Bull May (2010) Vol.55 No.14 1383 mentation of flocs influences the efficiency of solid/liquid separation and follow-up treatmen
14、t processes 8. The degree of floc breakage is related to the applied shear force, shear period and floc strength. Under smaller hydrodynamic conditions, the broken flocs have certain capability for re-growth.The extent of re-growth depends on the mechanism of floc formation 9,10.Recently, many studi
15、es focused on the breakage and re-growth capability of flocs formed by traditional inorganic coagulants 11,12, and there have been reports about researcheson the floc properties of organic flocculants and polyaluminum chloride 10,13. For ferric based inorganic polymer coagulants, Wei et al. 14 studi
16、ed the size distributionand fractal of flocs of polyferric chloride and different polyferric-cationic polymer dual-coagulant in humic acid solution. Fu et al. 15 quantitatively studied the sizedistribution of residual particles and the influence of turbulent shear on the flocs in the poly-silicic-ferric coagulation process. There has been no report about the influence of pH on floc formation, floc breakage and re-growth capabi
