Variability of Settling Characteristics of Solids in Dry and Wet Weather Flows in Combined Sewers: Implications for CSO Treatment
Rent the article at a discountRent now
* Final gross prices may vary according to local VAT.Get Access
Four devices developed for measuring settling velocity distributions of combined sewer overflow (CSO) solids were applied to dry and wet weather flow samples from an urban area serviced by combined sewers (Welland, ON, Canada). The settling column-based methods (the Aston, Brombach and US Environmental Protection Agency columns) produced comparable results indicating minimal differences in settleability of dry and wet weather samples. The elutriation apparatus, which assessed settling velocities in a flowing medium, indicated higher settleabilities than the column methods. This was attributed to enhanced opportunities for particle coalescence in the flowing medium, which should better approximate actual sedimentation conditions. While the elutriation apparatus also indicated larger differences in settleabilities between dry and wet weather samples than the column methods, this difference was not statistically significant. Experimental distributions of particle settling velocities were approximated by a mathematical function, which was then used to estimate partial settling of total suspended solids (TSS) with settling velocities smaller than the clarifier overflow rate. The TSS removal target of 50%, which is applicable to CSOs in Ontario, could be met for overflow rates ranging from 4.7 to 6.8 m/h, for dry and wet weather flows, respectively, based on the average settling velocities measured. Experimental data collected in the study indicate that the design of CSO storage and settling facilities is affected, among other factors, by both the apparatus used to assess CSO settleability and the inter-event variability of CSO settling characteristics.
- Aiguier, E, Chebbo, G, Bertrand-Krajewski, J-L, Hedges, P, Tyack, N (1996) Methods for determining the settling velocity profiles of solids in storm sewage. Water Science and Technology 33: pp. 117-125 CrossRef
- Chancelier, JPh, Chebbo, G, Lucas-Aiguier, E (1998) Estimation of settling velocities. Water Research 32: pp. 3461-3471 CrossRef
- Dobbins, WE (1944) Effect of turbulence on sedimentation. Trans. ASCE 109: pp. 629-678
- Exall, K., Krishnappan, B.G., Marsalek, J., Rochfort, Q., Seto, P. and Baker, M. (2005). Evaluation of CSO treatability for the City of Welland—Final report. NWRI Publication No. AEMRB TN05-001, Environment Canada, Burlington, ON, Canada.
- Gromaire, MC, Kafi-Benyahia, M, Gasperi, J, Saad, M, Chebbo, G (2008) Settling velocity of particulate pollutants from combined sewer wet weather discharges. Water Science and Technology 58: pp. 2453-2465 CrossRef
- He, C, Marsalek, J, Rochfort, Q, Krishnappan, BG (2006) Case study: refinement of hydraulic operation of a complex CSO storage/treatment facility by numerical and physical modeling. Journal of Hydraulic Engineering, ASCE 312: pp. 131-139 CrossRef
- Krishnappan, BG, Marsalek, J, Exall, K, Stephens, RP, Rochfort, Q, Seto, P (2004) A water elutriation system for measuring settling velocity distribution of suspended solids in combined sewer overflows. Water Quality Research Journal of Canada 39: pp. 432-438
- Marsalek, J, Krishnappan, BG, Exall, K, Rochfort, Q, Stephens, RP (2006) An elutriation apparatus for assessing settleability of combined sewer overflows (CSOs). Water Science and Technology 54: pp. 223-230 CrossRef
- Wastewater engineering: Treatment and reuse. McGraw Hill, Toronto
- Michelbach, S, Wöhrle, C (1993) Settleable solids in a combined sewer system, settling characteristics, heavy metals, efficiency of storm water tanks. Water Science and Technology 27: pp. 153-164
- Ministry of the Environment (undated). Determination of treatment requirements for municipal and private combined and partially separated sewer systems. Procedure F-5-5, Ontario Ministry of the Environment, Toronto, ON. http://www.ene.gov.on.ca/environment/en/resources/STD01_076048.html. Accessed 28 July 2011).
- O’Connor, T.P., Fischer, D., Field, R., Cigana, J., Gagné, B. and Couture, M. (2002). Testing solids settling apparatuses for design and operation of wet-weather flow solids-liquid separation processes. US EPA report no. EPA/600/R-02/090. October 2002. CRADA # 136-96. National Risk Management Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Cincinnati, OH, USA.
- Piro, P, Carbone, M, Tomei, G (2011) Assessing settleability of dry and wet weather flows in an urban area serviced by combined sewers. Water Air Soil Pollution 214: pp. 107-117 CrossRef
- Pisano, WC, Brombach, H (1996) Solids settling curves—Wastewater solids data can aid design of urban runoff controls. Water Environment Technology 8: pp. 27-33
- Rasmussen, MR, Larsen, T (1996) A method for measuring sludge settling characteristics in turbulent flows. Water Research 30: pp. 2363-2370 CrossRef
- Rauch, W, Thurner, N, Harremoës, P (1998) Required accuracy of rainfall data for integrated urban drainage modelling. Water Science and Technology 37: pp. 81-89 CrossRef
- Tyack, J.N., Hedges, P.D. and Smisson, R.P.M. (1993). A device for determining the settling velocity grading of storm sewage. 6th Int. Conf. on Urban Storm Drainage. Niagara Falls, Ontario, Canada, pp 1805-1810.
- Walling, DE, Woodward, JC (1993) Use of a field-based water elutriation system for monitoring the in-situ particle size characteristics of fluvial suspended sediment. Water Research 27: pp. 1413-1421 CrossRef
- Zabel, T, Milne, I, McKay, G (2001) Approaches adopted by the European Union and Selected Member States for the control of urban pollution. Urban Water 3: pp. 25-32 CrossRef
- Zukovs, G, Desilets, N, Szustka, H (2005) Wet weather treatment and disinfection in the City of Welland. Proceedings of the Water Environment Federation, Disinfection 2005: pp. 748-763
- Zukovs, G, Marsalek, J (2004) Planning and design of combined sewer overflow treatment. Water Quality Research Journal of Canada 39: pp. 439-448
- Variability of Settling Characteristics of Solids in Dry and Wet Weather Flows in Combined Sewers: Implications for CSO Treatment
Water, Air, & Soil Pollution
Volume 223, Issue 6 , pp 3021-3032
- Cover Date
- Print ISSN
- Online ISSN
- Springer Netherlands
- Additional Links
- Combined sewer overflow (CSO)
- Suspended solids
- Settling column
- Elutriation apparatus
- Settling velocity distribution
- Industry Sectors