Geography Reference
In-Depth Information
characteristics that are typical of the area they
represent. DCM managers must appreciate the
dynamic characteristics of urban populations and
take positive steps to maintain the DCM. A
properly maintained and analysed DCM will yield
detailed information about water use. Such
information can then be used with small-area
population forecasts to forecast water demand.
Because the UK system is combined, a
rainstorm of moderate size in an urban area,
concentrated through the system, could easily
flood the water treatment works, so sewer
overflows exist to divert the high flows away from
the works and directly into the river. This occurs,
in theory, at about six times the dry weather flow,
but changes in rain characteristics, in the density
and extent of the network, in the condition of the
network, etc. has resulted in combined sewer
overflows (CSOs) occurring too frequently and
over an excessively prolonged period. The sewer
system, like the potable water supply system, is out
of sight and was built by predecessor organisations
from which records of type, location and
characteristics have not always been available. The
resulting ignorance of the basic system raises a
number of important and apparently simple
research questions, which are listed below. They
are questions of great importance since
replacement of the underground sewer assets is
(gu)estimated to cost in excess of £100billion.
WASTE WATER MANAGEMENT
Waste water management concerns the
management of water after use by the customer
prior to return to the environment. It is
considered within this section because waste
waters are the financial responsibility of the water
companies. A fuller treatment of water quality
issues is given in Chapter 11.
Sewer networks remove organic wastes from
houses and wastes from factories. Sewerage
networks remove street waters after rainfall and
as such are a replacement for the hydrological
network disrupted in urban development. In the
United Kingdom sewage and sewerage
networks are mainly combined. They have
developed piecemeal and for the most part are
long-established under a variety of regulatory
regimes. Such regimes were initially local and
have relatively recently become national. The
networks usually lead to a treatment works, the
effluent from which discharges into the natural
environment. Treatment works are designed
primarily to remove organic wastes, and these
works cannot remove exotic chemicals.
Therefore the operators of the works have a
right to choose which discharges, other than
domestic discharges, they will accept into the
network. This choice is exercised through a
Trade Effluent Permit. The control of effluents
from the treatment works to the natural
environment is controlled by a Consent to
Discharge, which is set by the Environment
Agency in the UK. Both consents and permits
set conditions on the nature and concentration
of the effluents, and both set financial
requirements on the holder.
1
Where is the pipe network?
2
What are its characteristics and condition?
3
Which section will fail next?
4
How can repair, maintenance and
replacement be carried out without above-
ground disruption?
All of these questions will prompt the development
of remote, preferably non-invasive, monitoring
technologies, probably deriving as much from the
geophysical as the engineering domain. Assessments
of condition and such things as sewage exfiltration
will be required while operational use continues
and will preferably be made through external
surrogate data. The water manager will increasingly
use intelligent technologies to monitor and repair
the network, particularly to ensure that problems
such as blockages are removed and not simply
displaced. A greater use of modelling will be
required to predict and prioritise maintenance and
replacement. This modelling will need to be highly
integrated with the forecasts for other elements of
the water system, such that the effects of water
conservation, grey water reuse and roof rain
retention on the sewer flows can be determined.
