there is potentially a blockage within the system as a raised level at one particular
point, and a significantly lower downstream would indicate this. The problem of this
is twofold:
1. How many sewer level monitors are needed to provide a resolution good enough
to provide situational awareness and where within the network should they be
located, as it is not financially viable to monitor everywhere?
2. How can sewer level monitors be installed at a reasonable cost?
Moving on from just using simple level measurements, the rate of change can also
be used in a number of situations. The simplest of these methods is to measure the
rate of change within a pumping station wet well. Some of the simpler control
techniques use the rate of change to predict the flow rate within the wet well to imply
flow by conducting a smaller version of a drop test. This requires an outflow pump
rate (or flow measurement) to provide a measure of what is leaving the system and
the rate of change within the wet well to measure the increase of volume over time
(i.e. the flow rate).
Within the gravity network, any unusual change of level can be used to predict
where there is a blockage (i.e. where a downstream level is lower than an upstream
level there is a good indication that an unusual situation is occurring that needs
further investigation).
When flow monitoring of the gravity network is brought into the equation, what
benefit does it bring over level monitoring in isolation? Looking at flow monitoring,
it is even more difficult to install than level monitoring and, unless it is used to
control aspects of the network, or measure particular inputs into the network with an
approach similar to the potable water networks DMA approach, then it could be used
to indicate particular areas of risk of infiltration within the gravity network.
Wastewater networks require regular inspection in order to prioritise and perform
effective maintenance. Currently wastewater networks are generally inspected using
CCTV, taking one of two approaches. The first requires a camera, attached to a semirigid wire, to be pushed through the network. In doing so the collected footage is left
to be analysed later by a trained engineer. Although quick to collect, the footage
gathered is often of lower quality as the camera does not travel smoothly through the
pipe. Alternatively a camera can be attached to a remote-controlled pig which is
driven through the network. A skilled operator can often identify and record faults
whilst operating the device. In doing so footage takes longer to collect, but does not
require further analysis and is often of higher quality. CCTV (along with GPS) is the
most commonly used technique for locating pipes and internal inspection [16]. The
Water Research Centre (WRC) in UK devised the first condition grading scheme
that provides protocols and guidelines for formally assessing current condition of
individual pipes using CCTV inspection [17]. These can be somewhat subjective if
performed by a human, and the latest research has been exploring the automation of
CCTV footage.
With infiltration there are a number of passive technologies that have been
developed to look into the state of the gravity wastewater network as well as, in
some cases, the pressurised network. These range from looking at the thermal
Monitoring and Controlling a Smarter Wastewater Treatment System: A UK. . .
123
point, and a significantly lower downstream would indicate this. The problem of this
is twofold:
1. How many sewer level monitors are needed to provide a resolution good enough
to provide situational awareness and where within the network should they be
located, as it is not financially viable to monitor everywhere?
2. How can sewer level monitors be installed at a reasonable cost?
Moving on from just using simple level measurements, the rate of change can also
be used in a number of situations. The simplest of these methods is to measure the
rate of change within a pumping station wet well. Some of the simpler control
techniques use the rate of change to predict the flow rate within the wet well to imply
flow by conducting a smaller version of a drop test. This requires an outflow pump
rate (or flow measurement) to provide a measure of what is leaving the system and
the rate of change within the wet well to measure the increase of volume over time
(i.e. the flow rate).
Within the gravity network, any unusual change of level can be used to predict
where there is a blockage (i.e. where a downstream level is lower than an upstream
level there is a good indication that an unusual situation is occurring that needs
further investigation).
When flow monitoring of the gravity network is brought into the equation, what
benefit does it bring over level monitoring in isolation? Looking at flow monitoring,
it is even more difficult to install than level monitoring and, unless it is used to
control aspects of the network, or measure particular inputs into the network with an
approach similar to the potable water networks DMA approach, then it could be used
to indicate particular areas of risk of infiltration within the gravity network.
Wastewater networks require regular inspection in order to prioritise and perform
effective maintenance. Currently wastewater networks are generally inspected using
CCTV, taking one of two approaches. The first requires a camera, attached to a semirigid wire, to be pushed through the network. In doing so the collected footage is left
to be analysed later by a trained engineer. Although quick to collect, the footage
gathered is often of lower quality as the camera does not travel smoothly through the
pipe. Alternatively a camera can be attached to a remote-controlled pig which is
driven through the network. A skilled operator can often identify and record faults
whilst operating the device. In doing so footage takes longer to collect, but does not
require further analysis and is often of higher quality. CCTV (along with GPS) is the
most commonly used technique for locating pipes and internal inspection [16]. The
Water Research Centre (WRC) in UK devised the first condition grading scheme
that provides protocols and guidelines for formally assessing current condition of
individual pipes using CCTV inspection [17]. These can be somewhat subjective if
performed by a human, and the latest research has been exploring the automation of
CCTV footage.
With infiltration there are a number of passive technologies that have been
developed to look into the state of the gravity wastewater network as well as, in
some cases, the pressurised network. These range from looking at the thermal
Monitoring and Controlling a Smarter Wastewater Treatment System: A UK. . .
123