The aim of this research was to better understand chemical pre-treatment of combined sewer overflows (CSOs) for subsequent ultraviolet (UV) disinfection. Approximately 200 jar tests were completed. Alum (Al2(S04)3·12H2O) resulted in a higher UV light transmission (UVT), and equivalent total suspended solids (TSS) removal, than ferric chloride (FeCl3). An alum dose of 20 mg/L increased the UVT of the raw CSO from 30 to 60% after settling. The addition of 100 mg/L of alum maximized UVT reaching approximately 85%. Flocculation did not increase UVT. However, it did improve the removal of TSS. Cationic polymers worked quickly compared with metal coagulants, but only reached a UVT of 60%. A high positive charge density on the polymer improved the removal of turbidity when compared with low charge, but did not affect UVT. If the goal is to maximise UVT, a very high alum dose may be preferred. If the goal is to minimize coagulant dose with moderate UV performance, cationic polymer at approximately 3 mg/L is recommended.
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Research Article|
September 29 2015
Chemical pretreatment of combined sewer overflows for improved UV disinfection
J. Gibson;
1Environment Canada, Wastewater Technology Centre, Canada Centre for Inland Waters, 867 Lakeshore Road, Burlington, ON, Canada L7R 4A6
3Present Address: Department of Civil Engineering, University of Toronto, 35 St. George St., Toronto, ON, Canada M5S 1A4
E-mail: jgibson@rogers.com
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R. Farnood;
R. Farnood
2Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St., Toronto, ON, Canada M5S 3E5
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P. Seto
P. Seto
1Environment Canada, Wastewater Technology Centre, Canada Centre for Inland Waters, 867 Lakeshore Road, Burlington, ON, Canada L7R 4A6
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Water Sci Technol (2016) 73 (2): 375–381.
Article history
Received:
March 10 2015
Accepted:
August 17 2015
Citation
J. Gibson, R. Farnood, P. Seto; Chemical pretreatment of combined sewer overflows for improved UV disinfection. Water Sci Technol 28 January 2016; 73 (2): 375–381. doi: https://doi.org/10.2166/wst.2015.447
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