Feasibility Report - Busia Nzoia Cluster – Feasibility Study
Phase II Towns – Kakamega, Busia and Nambale
APPENDIX A.3
DESIGN CAPACITY CHECKS FOR EXISTING TREATED WATER PUMPING MAINS
Treatment Works design capacity= 2700m3/d
=31.25l/s
The Water Supply is divided into three main areas with the following demands
- BusiaTownship and Angoromo – 795m3/d
- Busia Mundika High Level Zone – 645m3/d
- Funyala Bumala Water Supply Scheme – 1260m3/d
The discharge in the rising main is as follows
Table 2.8 Treated Water Rising Main Sizes and Discharges
Pipe Size (mm) / Discharge (m3/d) / Discharge (l/s)250 / 1440 / 16.7
200 / 1440 / 16.7
150 / 795 / 9.2
The flow velocities and head losses in the mains at the above flow rates are obtained from a flow nomograph for Hazen Williams formula.
a)For the 250mm Dia main:
Head Loss =0.8m/1000m
Flow Velocity=0.32m/s
Total head loss in pipe= 0.8 x 2000/1000
=1.6m
Static Head =23.8m
Total pumping head required=23.8 + 1.6
=25.4m
Total pumping head available=114m {Pump Rating}
Allowable head loss in pipe=114 – 25.4m
=88.6m
The flow velocity, 0.32m/s, and head loss, 1.6m, in the 250mm dia Raw Water Pumping Main are within allowable limits; 2m/s and 88.6m respectively.
b)For the 200mm Dia main:
Head Loss =3.3m/1000m
Flow Velocity=0.53m/s
Total head loss in pipe= 3.3 x 2000/1000
=6.6m
Static Head =15.6m
Total pumping head required=15.6 + 6.6
=22.2m
Total pumping head available=114m {Pump Rating}
Allowable head loss in pipe=114 – 22.2m
=91.8m
The flow velocity, 0.53m/s, and head loss, 6.6m, in the 250mm dia Raw Water Pumping Main are within allowable limits; 2m/s and 91.8m respectively.
c)For the 150mm Dia main (To Busia):
Head Loss =3.5m/1000m
Flow Velocity=0.5m/s
Total head loss in pipe= 3.5 x 8000/1000
=28.0m
Static Head =19.2m
Total pumping head required=19.2 + 28.0
=47.2m
Total pumping head available=114m {Pump Rating}
Allowable head loss in pipe=114 – 47.2m
=66.8m
The flow velocity, 0.5m/s, and head loss, 28m, in the 150mm dia Raw Water Pumping Main are within allowable limits; 2m/s and 66.8m respectively.
d)For the 150mm Dia main ( To Bugengi):
Design Capacity = 695m3/d
= 8.0 l/s
Head Loss =3.0m/1000m
Flow Velocity=0.44m/s
Total head loss in pipe= 3.0 x 7200/1000
=21.6m
Static Head =11.8m
Total pumping head required=21.6 + 11.8
=33.4m
Total pumping head available=114m {Pump Rating}
Allowable head loss in pipe=114 – 33.4m
=80.6m
The flow velocity, 0.44m/s, and head loss, 21.6m, in the 150mm dia Raw Water Pumping Main are within allowable limits; 2m/s and 80.6m respectively.
e)Conclusion on the Design Capacity of the Treated Water Pumping Mains
The 4nr Treated Water Pumping Mains have an adequate capacity to transmit water from the Treatment Works to the Storage Tanks to enable the Treatment Works operate at full design capacity (2700m3/d).
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