sewer is minimised. However, periodic flushing of the sewer in dry weather is also
beneficial in order to minimise the accumulation of debris within the sewer, whether
this can be done in automated control or by manual cleaning of the sewer by jetting.
This is in the operation of the sewer in general, but, in dry weather, there is further
work that can be done. This involves directly detecting debris accumulation or,
by using analysis, detecting and locating areas that are either blocked or partially
blocked that will potentially cause problems when flows increase and possibly
causing overflowing of the network system. The last element of general operation
is detecting where there is infiltration into the sewer. Infiltration simply adds to the
basal flow of the sewer, taking up capacity within the network which will be required
in storm conditions.
The gravity sewer provides the base flow which is transferred to the WTW in dry
weather. Without installing gates within the sewer (which are popular in some
European sewers), there is no method of controlling the gravity sewer. It is on
the pumped sewer, where pumping stations can cause large variations in flow due
to the size of the wet well and the impact that the pumping system can have on the
treatment works. This is particularly the case where pump sizes have been increased
to resolve local flooding issues that have, in turn, caused flooding issues on the
treatment works. This is where the pumping system is larger than the capacity of the
inlet works which as the pumps are oversized causes flooding of the works even in
dry weather. Where there are combined gravity and pumped systems, the situation is
further complicated. However, at their simplest, gravity systems provide the basal
flow, and the pumped systems have the potential to cause problems with overflows
to the environment.
It is when the sewer enters storm conditions that problems in operation can start.
The flow from the gravity network cannot be controlled. The customer input,
whether it is domestic or industrial, will remain the same. The runoff from the
road network will increase, and so will any debris from the road surfaces thereby
increasing the inorganic pollutant load in the sewer. The gravity network is largely
unmonitored as it cannot be controlled. The pumped network is monitored to a
certain extent, and it is here that smart systems can have the greatest potential and
impact.
The philosophy of operation in the pumped wastewater network is to detect where
the underlying flow condition within the sewer is going to increase and to take steps
to increase the capacity of the network by pumping down the sewer to as empty as
possible thus freeing up capacity to manage storm conditions. This is shown in
Fig. 2.
Measuring level within the gravity sewer system, either measuring level in
pumping stations or flow on the pressurised system, can enable a large element of
control of the wastewater network. Where programmes, such as the Duration
Monitoring (EDM) programme in the UK, which measures spills to the environment, exist, they can be used to warn of levels high enough so that wastewater spills
to the environment. Thousands of CSO monitoring installations have been
implemented with many more planned, involving data logging and level measurement to record spill events. Combined with rainfall radar data, online data analysis
116
O. Grievson
beneficial in order to minimise the accumulation of debris within the sewer, whether
this can be done in automated control or by manual cleaning of the sewer by jetting.
This is in the operation of the sewer in general, but, in dry weather, there is further
work that can be done. This involves directly detecting debris accumulation or,
by using analysis, detecting and locating areas that are either blocked or partially
blocked that will potentially cause problems when flows increase and possibly
causing overflowing of the network system. The last element of general operation
is detecting where there is infiltration into the sewer. Infiltration simply adds to the
basal flow of the sewer, taking up capacity within the network which will be required
in storm conditions.
The gravity sewer provides the base flow which is transferred to the WTW in dry
weather. Without installing gates within the sewer (which are popular in some
European sewers), there is no method of controlling the gravity sewer. It is on
the pumped sewer, where pumping stations can cause large variations in flow due
to the size of the wet well and the impact that the pumping system can have on the
treatment works. This is particularly the case where pump sizes have been increased
to resolve local flooding issues that have, in turn, caused flooding issues on the
treatment works. This is where the pumping system is larger than the capacity of the
inlet works which as the pumps are oversized causes flooding of the works even in
dry weather. Where there are combined gravity and pumped systems, the situation is
further complicated. However, at their simplest, gravity systems provide the basal
flow, and the pumped systems have the potential to cause problems with overflows
to the environment.
It is when the sewer enters storm conditions that problems in operation can start.
The flow from the gravity network cannot be controlled. The customer input,
whether it is domestic or industrial, will remain the same. The runoff from the
road network will increase, and so will any debris from the road surfaces thereby
increasing the inorganic pollutant load in the sewer. The gravity network is largely
unmonitored as it cannot be controlled. The pumped network is monitored to a
certain extent, and it is here that smart systems can have the greatest potential and
impact.
The philosophy of operation in the pumped wastewater network is to detect where
the underlying flow condition within the sewer is going to increase and to take steps
to increase the capacity of the network by pumping down the sewer to as empty as
possible thus freeing up capacity to manage storm conditions. This is shown in
Fig. 2.
Measuring level within the gravity sewer system, either measuring level in
pumping stations or flow on the pressurised system, can enable a large element of
control of the wastewater network. Where programmes, such as the Duration
Monitoring (EDM) programme in the UK, which measures spills to the environment, exist, they can be used to warn of levels high enough so that wastewater spills
to the environment. Thousands of CSO monitoring installations have been
implemented with many more planned, involving data logging and level measurement to record spill events. Combined with rainfall radar data, online data analysis
116
O. Grievson