Chapter 3 Decision Support Model (IUWS-DSM) - Tubdok

Chapter 3 · Decision Support Model (IUWS-DSM) 77
based only on pipe diameter and length. Thereby, the IUWS-DSM excludes the factor of
population density, too.
Pump stations are the essential parts of the conveying system, so the empirical cost
functions are developed in general. Other ancillary works such as storages, valves and
hydrants, etc., are often estimated approximately as the percentage of the pipe costs.
Certainly, the costs of those ancillary works can be estimated by empirical cost function, as
well (e.g. USEPA 1999 and Burnside 2005).
The same methods are used to estimating O&M costs of conveying system, i.e. with cost
functions or as percentage of construction cost. Oron (1996) states that annually O&M costs
of distribution system are usually up to 3,0% of the overall capital investment over the lifetime
of the asset, and Tang et al. (2006) calculated O&M costs of the water reuse system in Hong
Kong to be 1,03% of the capital cost. The general O&M cost is thereby suggested as 2,0% of
the capital cost (Chugg 2007).
3.4.3 Energy assessment
Nowadays the energy gains more and more attention worldwide. As an objective criterion,
the assessment of energy consumption can help to compare not only different equipments
and techniques, but also operational and management levels of water facilities between
regions/countries. However, the research and information about the energy consumption in
urban WIS are universally inadequate. So there are no existing simple tools to estimate the
energy consumption in WIS. Against this background, a sketchy method for assess energy
consumption is proposed.
Energy Consumption in a Waterworks
raw water pumping
alum & polymer feed
rapid mix
flocculation
clarification
gravity filtration
filtration media
hydraulic surface wash
backwash pumping
in-plant pumping
Cl2 feed
clearwell storage
finished water pumping
admin. labor. mainten.
0,6
1,4
0,3
0,0
0,3
0,5
0,4
0,0
4,7
3,0
2,1
11,1
8,6
67,0
0 10 20 30 40 50 60 70
energy consumption (%)
Energy Consumption in a WWTP
influent pump station
headworks
1st clarifier & sldg.pmp.
AS aeration
2nd clarifier & RAS
thickener & sldg.pmp.
effluent filters
process water
solids dewatering
heating
lighting
post-aeration / Cl2 mix
0,4
3,7
1,6
0,9
4,5
3,6
2,2
3,1
7,0
7,1
10,3
Figure 32: Distribution of energy consumption in
a waterworks (HDR 2001) and a WWTP (Metcalf & Eddy 2003)
55,6
0 10 20 30 40 50 60 70
energy consumption (%)
In WIS, energy is mainly used to drive motors, and it occurs mostly in two places, i.e.
treatment plant and pump station. Figure 32 depict the distribution of energy consumption in