Characterization of re-grown floc size and structure: effect of mixing conditions during floc growth, breakage and re-growth process.
The impact of mixing speed in three stages-before breakage, during breakage, and after breakage-on re-grown floc properties was investigated by using a non-intrusive optical sampling and digital image analysis technique, respectively. And then, on the basis of different influence extent of mixing speed during each stage on size and structure of re-grown flocs, coagulation performance with varying mixing speed was analyzed. The results indicated that the broken flocs could not re-grow to the size before breakage in all cases. Furthermore, increasing mixing intensity contributed to the re-formation of smaller flocs with higher degree of compactness. For slow mixing before breakage, an increase in mixing speed had less influence on re-grown floc properties due to the same breakage strength during breakage, resulting in inconspicuous variation of coagulation efficiency. For rapid mixing during breakage, larger mixing speed markedly decreased the coagulation efficiency. This could be attributed that mixing speed during breakage generated greater influence on re-grown floc size. However, as slow mixing after breakage was elevated, the coagulation efficiency presented significant rise, indicating that slow mixing after breakage had more influence on re-grown floc structure upon re-structuring and re-arrangement mechanism.
Skate Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China. nanjun119@163.com.
Jun
J
Nan
Skate Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China.
Zhenbei
Z
Wang
Skate Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China.
Meng
M
Yao
Skate Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China.
Yueming
Y
Yang
Skate Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China.
Xiaofei
X
Zhang
D000536:Aluminum Hydroxide / Q000737:chemistry*; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D010316:Particle Size; D018508:Water Purification / Q000379:methods*
C016213:aluminum oxychloride; D000536:Aluminum Hydroxide
Breakage; Coagulation; Floc properties; Mixing speed; Re-growth