The future of both the wastewater network and the wastewater treatment works is
a much more holistic approach bringing the network and the treatment works
together and treating it as a single system. In this way, rather than operating the
wastewater treatment system for process control with the aim of protecting the water
environment, it can also be operated for resource recovery and energy efficiency
with a much wider environmental benefit.
Keywords Biosolid, Burst detection, Mogden formula, Multivariate process
control, Respirometry, Septicity, Thermal hydrolysis, Urban drainage, Wastewater
treatment
1 A Systematic Approach
Wastewater systems can vary in both size and complexity ranging from small and
simple rural catchments to large and complex urban conurbations. In dry weather,
the wastewater collection network receives both domestic wastewater from the
customer and a variety of industrial inputs which can be very mixed in nature. The
network, in the UK alone, is comprised of a variety of sizes and is hundreds of
thousands of miles long, meaning that the residence time in the sewer can vary in
time, depending on the size of the network, from a few hours to a few days. Longer
residence times can create septic conditions and build-up of debris within the sewer
(or within sewage pumping stations), depending upon whether the part of the sewer
is under gravity or part of the pressurised sewer network.
In dry weather there is normally a single output to each wastewater system which
is at the wastewater treatment works (WwTW), barring any problems within the
network which create unplanned discharges. In wet weather this system changes and
there are multiple outputs to the system (for combined systems such as those that
operate in the UK). As flow inputs increase through rainfall runoff from road drains,
the levels of flow in the sewer increase. Designed within the sewer are “relief valves”
in the form of combined sewer (or storm) overflows (CSOs), which provide relief
from the system when the flows are, in principle, dilute enough to have a minimal
impact on the water environment. The only alternative, which can happen when the
sewer is misused, is that the system floods up and into either external public areas or
into the customer’s home.
At the sewage treatment works, the focus has always been to treat the received
flows as efficiently as possible as they are received at works. This has meant
designing works so that they can take flows of up to 300% (the flow to full treatment
is often approximately three times the dry weather flow) and an increase of pollutant
load of up to 40% more. Hence the works are often designed for just treating
wastewater.
112
O. Grievson
a much more holistic approach bringing the network and the treatment works
together and treating it as a single system. In this way, rather than operating the
wastewater treatment system for process control with the aim of protecting the water
environment, it can also be operated for resource recovery and energy efficiency
with a much wider environmental benefit.
Keywords Biosolid, Burst detection, Mogden formula, Multivariate process
control, Respirometry, Septicity, Thermal hydrolysis, Urban drainage, Wastewater
treatment
1 A Systematic Approach
Wastewater systems can vary in both size and complexity ranging from small and
simple rural catchments to large and complex urban conurbations. In dry weather,
the wastewater collection network receives both domestic wastewater from the
customer and a variety of industrial inputs which can be very mixed in nature. The
network, in the UK alone, is comprised of a variety of sizes and is hundreds of
thousands of miles long, meaning that the residence time in the sewer can vary in
time, depending on the size of the network, from a few hours to a few days. Longer
residence times can create septic conditions and build-up of debris within the sewer
(or within sewage pumping stations), depending upon whether the part of the sewer
is under gravity or part of the pressurised sewer network.
In dry weather there is normally a single output to each wastewater system which
is at the wastewater treatment works (WwTW), barring any problems within the
network which create unplanned discharges. In wet weather this system changes and
there are multiple outputs to the system (for combined systems such as those that
operate in the UK). As flow inputs increase through rainfall runoff from road drains,
the levels of flow in the sewer increase. Designed within the sewer are “relief valves”
in the form of combined sewer (or storm) overflows (CSOs), which provide relief
from the system when the flows are, in principle, dilute enough to have a minimal
impact on the water environment. The only alternative, which can happen when the
sewer is misused, is that the system floods up and into either external public areas or
into the customer’s home.
At the sewage treatment works, the focus has always been to treat the received
flows as efficiently as possible as they are received at works. This has meant
designing works so that they can take flows of up to 300% (the flow to full treatment
is often approximately three times the dry weather flow) and an increase of pollutant
load of up to 40% more. Hence the works are often designed for just treating
wastewater.
112
O. Grievson