Emissions of pollutant loads from combined sewer systems and ...

140000
120000
100000
80000
60000
40000
20000
11 th International Conference on Urban Drainage, Edinburgh, Scotland, UK, 2008
0
WWTP dw
WWTP ww
CSO or SSO
Cu CSS Cu SSS carb CSS carb SSS E2 CSS E2 SSS
Figure 3. Emitted loads of copper (Cu) [g/year], carbamazepine (carb) [mg/10/year] and
estradiol (E2) [mg*10/year] calculated by pollution load simulations
WWTP (dw): effluent WWTP dry weather; WWTP (ww): effluent WWTP wet weather; CSO: combined sewer overflow; SSO: storm sewer outlets; CSS:
combined sewer system; SSS: separate sewer system
Disconnection of paved areas
A common measure to reduce emissions from urban drainage systems is the disconnection of
paved areas from the drainage system. This is especially true for low contaminated flow types
like roof runoff and runoffs from street areas with a low traffic density. These flow types are
often infiltrated to the groundwater by several devices (e.g. trenches).
Exclusively by the example of the chosen hypothetical separate sewer system 25 % of the
paved areas were disconnected, demonstrated in Figure 4 for the surface runoff derived
parameters COD and copper. This value certainly represents an upper limit in existing
systems. Within, the annual pollution loads infiltrated into the soil groundwater system are
illustrated as white bars.
Results for COD and copper clearly show, that even a significant disconnection of paved
areas leads to dominant total emissions resulted from the separate sewer system. Therefore,
also under these conditions, total emissions to the receiving waters from the combined sewer
system are significant lower in relation to a separate sewer system.
6 Welker