Water Science and Engineering 2008, 1(2) 102-111  DOI:   10.3882/j.issn.1674-2370.2008.02.010   ISSN: 1674-2370 CN: 32-1785/TV

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Keywords
drinking water treatment
particles
size distribution
bacteria attached to carbon fines
inactivation
Authors
Wang Leilei
Chen Wei
Lin Tao
PubMed
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Particle size distribution and property of bacteria attached to carbon fines in drinking water treatment

Wang Leilei, Chen Wei, Lin Tao

College of Environmental Science and Engineering, Hohai University, Nanjing 210098, P. R. China

Abstract

The quantitative change and size distribution of particles in the effluents from a sand filter and a granular activated carbon (GAC) filter in a drinking water treatment plant were investigated. The average total concentration of particles in the sand filter effluent during a filter cycle was 148 particles/mL, 27 of which were larger than 2 μm in size. The concentration in the GAC effluent (561 particles/mL) was significantly greater than that in the sand filter effluent. The concentration of particles larger than 2 μm in the GAC filter effluent reached 201 particles/mL, with the amount of particles with sizes between 2 μm and 15 μm increasing. The most probable number (MPN) of carbon fines reached 43 unit/L after six hours and fines between 0.45 μm and 8.0 μm accounted for more than 50%. The total concentration of outflowing bacteria in the GAC filter effluent, 350 CFU (colony-forming units) /mL, was greater than that in the sand filter effluent, 210 CFU/mL. The desorbed bacteria concentration reached an average of 310 CFU/mg fines. The disinfection efficiency of desorbed bacteria was lower than 40% with 1.5 mg/L of chlorine. The disinfection effect showed that the inactivation rate with 2.0 mg/L of chloramine (90%) was higher than that with chlorine (70%). Experimental results indicated that the high particle concentration in raw water and sedimentation effluent led to high levels of outflowing particles in the sand filter effluent. The activated carbon fines in the effluent accounted for a small proportion of the total particle amount, but the existing bacteria attached to carbon fines may influence the drinking water safety. The disinfection efficiency of desorbed bacteria was lower than that of free bacteria with chlorine, and the disinfection effect on bacteria attached to carbon fines with chloramine was better than that with only chlorine.

Keywords drinking water treatment   particles   size distribution   bacteria attached to carbon fines   inactivation  
Received 2008-03-05 Revised 2008-05-16 Online:  
DOI: 10.3882/j.issn.1674-2370.2008.02.010
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Corresponding Authors: Wang Leilei
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