Alexander Szabo and Oscar Engle - Svenskt Vatten

Screening
device
The task of the screening device is to separate larger particles from the waste water and protect
the following treatment steps. The treatment ponds today have no screening device and large
floating objects have been seen in the pond. Except from being an unpleasant sight at the pond
(and especially in the receiving river) the larger objects have been observed to clog channels.
According to the Sewerage Services Department (1998) the screening device should have a
maximum clear spacing of 25 mm and be automatically raked, since it serves over 10 000 P.E.
Flow
through
ponds
Design values:
Average temperature for coldest month=26 °C
(TheWeatherChannel)
Qinhe inlet water has a BOD degradation rate (k-value) of 0.24 day -1 at 20 °C (see Table 8.12).
After the first pond the value is
unknown but may be assumed to
be 0.1 day -1 (See Appendix E).
These values must be converted
for actual site conditions of 29
degrees Celsius, using equation 6
from Mara (2003):
57