Sedimentation tank design for rural communities in the hilly regions of Nepal

  • Emilia Wisniewski


Mathillo Semrang in rural Nepal relies on stream sources to provide drinking water. Erosion and deforestation of local terrain produces turbid water that requires treatment before distribution. The round gravity sedimentation technology currently employed is large in footprint and cannot handle large increases in influent flow rate and silt concentrations resulting from extreme weather events. In partnership with Nepal Water for Health (NEWAH) and Engineers Without Borders Australia (EWB), this project aimed to design a highly simplified, small footprint inclined plate settler (IPS) to treat influent flow-rates ranging from 0.25 to 4 L/s. A 76 % decrease in footprint was achieved by the IPS design for source flow-rates up to 4 L/s. Laboratory analysis revealed that a large inlet area along with a highly sloped floor is essential to the design which may prove problematic in the reduction of footprint in the design. Further research is needed to confirm this finding along with further collaboration with rural Nepalese communities and NEWAH.


Boycott, A. E. 1920. Sedimentation of blood corpuscles. Nature, 104, p. 532.

Culp, G., Hansen, S. & Richardson, G. 1968. High rate sedimentation in water treatment works. Journal of the American Water Works Association, 681-936.

Davis, R. H. & Acrivos, A. 1985. Sedimentation of noncollodial particles at low Reynold’s numbers. Annual Review of Fluid Mechanics, 17, pp. 91-118.

Davis,R.H.,Zhang,X.&Agarwala,J.P.1989.Particle classification for dilute suspensions using an inclined settler. Industrial & Engineering Chemistry Research, 28, pp. 785-793.

Demir, A. 1995. Determination of settling efficiency and optimum plate angle for plated settling tanks. Water Research, 29 (2), pp. 611-616.

Foellmi, S. N. & Bryant, H. H. n.d. Lamella Plate Settlers, Design and Operation: Two Case Histories, from Foellmi_and_Bryant.pdf

Huisman, L. 1986. Discrete Settling in Continuous Horizontal Flow Basins Sedimentation and Flotation: Mechanical Filtration, pp. 38-96. Delft, The Netherlands: Delft University of Technology.

Julien, P. & Shah, S. 2005. Sedimentation Initiatives in Developing Countries. Draft report presented to UNESCO-ISI. Colarado State University, USA.

Leung, W-F & Probstein, R. F. 1983. Lamella and Tube Settlers. 1. Model and Operation. Industrial & Engineering Chemistry Process Design and Development, 22(1), 58-67.

McKean, T., Bourke, B., Mitchell, W., Caplygin, L. & McKeown, R. 2010. Novel application of a lamella clarifier for improved primary treatment of domestic wastewater. Paper presented at the 73rd Annual Victorian Water Industry Engineers and Operators Conference, Exhibition Centre – Bendigo.

Neku, A. & Hillman E.A. 1996. Chapter 16: Sedimentation Tank. In R. Sack & D. Crawford Eds., Rural Gravity Flow Water Systems Design Technique and Standard Structures. Kathmandu, Nepal: UNICEF Nepal.

Nepal Water for Health. 2011a. 2.6 Sedimentation Tank Design Rural Drinking Water Supply System Policy and Procedures (3 ed.). Lothsal, Kathmandu, Nepal.

Nepal Water for Health. 2011b. Rural Drinking Water Supply System Policy and Procedures (3 ed.). Lothsal, Kathmandu, Nepal.

Nepal Water for Health. 2012. Technical drawing of the top view of the current round sedimentation technology. Kathmandu, Nepal: Nepal Water for Health.

Nordic Water Products. 2013a. Lamella Separator – for optimal sedimentation Retrieved 03/05/13, from product-groups/lamella/

Nordic Water Products. 2013b. Lamelle Separator for optimal sedimentation.

Schulz, C. R. & Okun, D. A. 1984. Inclined tube and plate settling Surface Water Treatment of Communities in Developing Countries (pp. 139-144). London: Intermediate Technology Publications.

Shamim, A. & Wais, M. T. 1980. Potential of tube settlers in removing raw water turbidity prior to coagulant. Aqua, 8, pp. 166-169.

Water Resources Management Committee. 2010. Water Use Master Plan – Thumi VDC Gorka. Thumi VDC, Nepal.

Wisniewski, E. 2012. Sedimentation Tank Design for Disadvantaged Rural Communities in the Hilly Regions of Nepal. Engineering Research Report. The Department of Chemical and Biomolecular Engineering. The University of Melbourne.