Improving Sewer Systems: A Report on Self-Cleansing Design

This report from the Urban Water Journal investigates the self-cleansing design of sewer systems, addressing the inefficiencies of traditional designs that rely on fixed minimum flow criteria. The research focuses on developing a non-deposition design criteria using scientific experiments, considering parameters such as bed shear stress and minimum velocity to enhance sewer performance and reduce maintenance costs. The methodology involves observations, hypothesis formation, and data collection through experiments using PVC pipes, non-cohesive sands, and flumes. The results derive non-deposition design criteria for bed and suspended load, comparing minimum and required velocities and validating accuracy against existing criteria. The report concludes by highlighting the development of improved self-cleansing formulas, while acknowledging the need for further research to ensure practical applicability and successful real-world results. Desklib offers a platform for students to access similar solved assignments and research papers.

Running head: URBAN WATER JOURNAL
Urban Water Journal
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Table of Contents
Introduction......................................................................................................................................2
Statement of problem...................................................................................................................2
Background of work....................................................................................................................2
Objectives....................................................................................................................................3
Methodology....................................................................................................................................3
Results and Discussions...................................................................................................................3
Conclusions......................................................................................................................................4
References:......................................................................................................................................5

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Introduction
Statement of problem
The paper contains research on the self-cleansing design of sewers, that is, on the basis of
bed shear stress and minimum velocity. The problem that has been referred to, is the inefficiency
of traditional sewer sytems where the criterion of low flow is kept minimum and fixed. This is
inadequate as it does not suit itself to the changing conditions. There is also need of high
maintenance cost. The design of sewer systems should have adequate velocity of self-cleansing
on an average flow. The design for self-cleansing needs to be developed to perform more
efficiently. After making some experiments, the study developed non-deposition design criteria
that is new process with part-full flow
Background of work
The topic is of concern and there are related works on the design of sewer systems.
Scientific experiment has been conducted which provided details about the bed-load transport.
Few parameters that are taken into account, have provided accuracy to a great extent. These
parameters included relative size of grain, Froude number, sediment’s volumetric concentration.
These parameters were used in the design for transport but the new design that was applied
consisted ofanother extra parameter along with these, that is thickness of the sedimentation.
(Ebtehaj, Bonakdari and Sharifi 2014) . Another paper discusses that a comprehensive approach
should be taken to serve a proper design practice keeping into account all climate change
sensitivity and uncertainities. This paper has focused only on design storms and rainfall
intensities (Watt and Marsalek 2013).

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Objectives
The research aims to focus on the following :
 To improve the sewer system by making changes in the high flow criteria and low flow
 To design in such a way as to lessen the maintenance cost of the sewer sytem
 To develop a design that eliminates the problems of the traditional sewer systems.
Methodology
The methodology used in this research is scientific experiments. For this purpose,
observations are made and hypothesis is formed. On the basis of this hypothesis, experiments
have been conducted, data collected and conclusions have been drawn (Lewis 2015). The
scientific experiment done has developed how the sewer system can be improved in terms of
velocity and changing weather. Secondary data has also been taken into account while doing the
research. The secondary data involves the studies by Macke and May who have laid formulas for
the design earlier. Other several studies of researchers have also been taken into consideration
for determining the incipient motion and the equation ( Ebtehaj and Bonakdari 2013).
For the purpose of this research, theorem of Buckingham Pi has been used to perform
dimensional analysis. The experiments involved the use of PVC pipes, three non-cohesive sands,
telescope and flume. The paper has illustrated the process and apparatus of experiment which
show part-full flow.
Results and Discussions
The scientific experiment has laid down the results and derivation of non-deposition
design criteria regarding bed and suspended load. The criteria has been set in the form of relative

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size of grain, sediment concentration and semi-empirical relationships. Comparison of minimum
velocity with that of required velocity has been done just like Camp has laid down. Accuracy
has been checked by comparing it with the criteria set by Macke and May.
Conclusions
The report hence concludes how to develop formulae for self-cleansing for designing
sewers on the basis of laboratory experiments. The earlier criteria that was single-parameter did
not provide proper estimates unlike the developed design criteria. The equations for suspended as
well as bed load did agree adequately with Macke’s and May’s equations. However, further
research is still required as no scientific research can give the exact result and there can be
changes in each result. And it has to be checked whether this equation can be applied practically
for successful results.

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References:
Ebtehaj, I. and Bonakdari, H., 2013. Evaluation of sediment transport in sewer using artificial
neural network. Engineering Applications of Computational Fluid Mechanics, 7(3), pp.382-392.
Ebtehaj, I., Bonakdari, H. and Sharifi, A., 2014. Design criteria for sediment transport in sewers
based on self-cleansing concept. Journal of Zhejiang University Science A, 15(11), pp.914-924.
Lewis, S., 2015. Qualitative inquiry and research design: Choosing among five approaches.
Health promotion practice, 16(4), pp.473-475.
Watt, E. and Marsalek, J., 2013. Critical review of the evolution of the design storm event
concept. Canadian Journal of Civil Engineering, 40(2), pp.105-113.