Environmental Engineering Reference
In-Depth Information
Fig. 5 Combined and separated sewer systems
3.1 What Is the Case?
In Philadelphia, the largest city in Pennsylvania, wastewater and stormwater is
transferred to the city
'
s Water Pollution Control Plants (WPCP) for treatment prior to
final disposal to the nearby waterways via either Combined Sewer Systems (CSS) or
Separated Sewer Systems (PWD
2013
) as displayed in Fig.
5
. All sewer systems as
well as WPCP are owned and managed by the Philadelphia Water Department
(PWD). The CSS, transporting both wastewater and stormwater through the same
pipe, cover approximately 48 % of the total city area. During severe rainfall events,
the
flow may exceed CSS capacity and the over
flow known as Combined Sewer
Over
ow (CSO), is then diverted straight to the rivers or streams without treatment,
causing pollution and threatening the aquatic environment.
3.2 What Was the Way Forward?
The
plan adopted by the city of Philadelphia is a 25-
year plan aimed at reducing pollution from CSO to the extent that 85 % of the water
would be treated in the CSS. The main goals of the plan are summarised below
(PWD
2013
):
'
Green City, Clean Waters
'
Enhancement of river quality, aesthetics and recreation.
Restoration and improvement of aquatic habitats.
Water quality improvement and water quantity decrease
flows into the CSS.
To accomplish these targets, Philadelphia has developed and adopted an inte-
grated
'
Land-Water-Infrastructure
'
approach. This approach includes traditional
'
Stormwater Infrastructure (i.e. sewers, pipes and treatment plants) as well as
Green Infrastructure and projects for natural restoration of aquatic habitats. Green
Stormwater Infrastructure (GSI) applies nature-complying methods to manage run-
off at the source through soil and vegetation absorption and
Grey
'
filtration of water. The
Search WWH ::
Custom Search