Air Bio Control (ABC)
Efficient and reliable control of air-supply systems
Answers for energy.
Thinking in systems
– the multiplier effect …
Siemens has decades of experience in turbocompressor
technology and aeration know-how, with more than
6,000 units now in operation worldwide.
Siemens provides complete air-supply
systems for wastewater-treatment plants,
thus ensuring effective integration of
the aeration process with the other
downstream processes in the plant.
This makes it possible to achieve full
end-to-end control, avoiding bottlenecks
and boosting efficiency at every stage.
The prime advantages of the system
solutions include:
The three integrated
control loops
The aeration process consists
of three central control loops
that – when fully integrated
and fine-tuned – ensure
smooth, efficient operation
of the aeration system:
Single-source responsibility
System integration
Greater overall efficiency
Better control and smoother operation
Avoiding interface issues
Start-up and fine tuning
Greater system reliability
On-line support via modem
(wireless or PSTN)
Dissolved
oxygen /ammonium
flowcontrol
Automatic
pressure set-point control
(based on the “most open valve” principle)
Main-header
pressure control
Dissolved oxygen/
ammonium flowcontrol
Most aeration systems are controlled
on the basis of measurements of the
dissolved oxygen in the aeration tanks.
The settings of the air-flowcontrol
valves are based on these measurements.
It is possible to achieve considerable
additional improvements in control of
the aeration system by also including
such parameters as ammonium control
to determine the oxygen set-point.
This results in a lower average air-flow
and makes it possible to comply with
both current and future environmental
requirements worldwide.
Automatic pressure set-point control
To minimize power consumption, the
header pressure is kept as low as possible
by monitoring the control-valve positions.
During peak loads, the header pressure is
increased in order to provide maximum
air-flow. Under part-load conditions, it is
reduced to keep power consumption to
a minimum. This enables continuous
adjustment of the total delivered air-flow
to match requirements exactly.
An unlimited range of different processes
can also be linked to the main air header,
thus facilitating control of many additional
sub-processes.
Main-header pressure control
The aeration tanks are supplied with airflow through a main-air header. This is
kept at a constant pressure by regulating
the compressors between 40–100 %
capacity.
The system is designed to match different
types of aeration processes to comply with
client requirements.
The right choices
Increasing demands for quality and tougher
legislation on environmental issues create
needs for the best possible control of the
aeration process.
Experience from a large number of
wastewater-treatment plants has shown
that the right choices for control systems
and solutions rapidly give full pay-back
in terms of energy savings and ensure
full compliance with legal requirements
regarding the effluent.
With the rapidly accelerating automation of
wastewater-treatment plants, choosing the
most appropriate technology is no longer
sufficient. It is now increasingly important
to identify the overall configuration that
provides maximum efficiency, via integrated
system design.
ABC Panel
The Siemens ABC Panel is designed to ensure the efficient,
reliable control and monitoring of the complete air supply
system – automatically and/or remotely, if required. The ABC
system uses a standard Programmable Logic Controller (PLC),
running customized, job-specific software, to monitor and
control the complete air-supply system for aeration and
compressors as one highly efficient, integrated system.
A standardized Profibus DP master interface is fitted for
communicating with multiple Local Control Panels (LCPs).
Control
Control
Where several aeration cells are automated
to provide varying air-flow, flowcontrollers
can be added to control each air-flow
control valve with a fine-tuning sub-loop,
enabling set-point adjustment via the
dissolved oxygen level.
FLOW
The most basic solution involves
control of the air-flowcontrol valve
directly via the oxygen levels, using
a controller. This ensures that the
biological processes have a constant
level of dissolved oxygen.
Control
Another option is to add a flowcontroller to the conventional
oxygen-control loop. The flowcontroller can also be used to
limit the maximum and minimum
air-flow.
Control
Control
A system that monitors multiple process
variables must be designed and implemented
to ensure reliable, long-term operation.
Control
Control
FLOW
Cascade control
The graph illustrates the optimized air-flow, with
three on-line Siemens compressors. Together,
these provide a seamless, consistent air-flow,
ranging from one unit at minimum capacity to all
three compressors at maximum capacity, meeting needs for a wide variety of plant air-flows and
wide-ranging system oxygen demands.
The basic oxygen control can be
improved by adding an ammonium
controller. This increases and
decreases the oxygen set-point
when needed, reduces the average
air-flow (and energy consumption),
and ensures optimum nitrogen
removal.
Power consumption
400
300
200
100
0
0
100
200
Capacity
300
Control
The ideal air-supply system features
full ammonium and dissolved-oxygen
control in order to give precise and
stable operation.
Analysis prior to design
Each wastewater treatment plant operates differently,
with individual characteristics and requirements that
result in widely differing operating cycles.
Prior to any design work, Siemens
experts therefore carefully investigate
and analyse the overall operating
philosophy behind the hourly, weekly
and monthly running of the existing
plant. Together with an evaluation of
aeration efficiency, this enables Siemens
to provide the system designs best suited
to system requirements. This covers
such parameters as the opening times
of flowcontrol valves, and all items that
play a crucial role in ensuring minimum
downtime and highest efficiency.
Siemens is uniquely capable of designing
aeration systems that exactly match your
present needs, while also taking future
requirements into consideration. We
spend time with your consultants and
plant operators to understand your needs
in full and to integrate our know-how
with yours in order to find the most
effective form of control.
The right solution yields considerable
savings up front, as well as greater
efficiency in all the other processes that
interface with aeration.
Experience in action
When Siemens deals with your air
flow requirements – both current and
future – you benefit from the total
sum of our experience from more than
6,000 single-stage turbocompressors
throughout the world. We know that
it is essential to focus on the correct
dimensioning of the aeration system
as a whole in order to avoid inefficient
operation and unnecessary costs.
Benefits and features
An automated air-supply system assures
the lowest system-operating pressure,
thereby keeping power consumption to
the minimum.
Continuous monitoring of process
variables such as dissolved oxygen or
ammonium ensures the lowest airflow delivery, optimizing the aeration
process and minimizing power consumption. Precise, continuous airflowcontrol enables maximization
of the more complex nitrification /
denitrification process, as required in
the most modern aeration processes.
Air-supply system automation eliminates
the need for direct operator intervention
and optimizes process control, ensuring
superior effluent quality.
Published by and copyright 2009:
Siemens AG
Energy Sector
Freyeslebenstrasse 1
91058 Erlangen, Germany
Siemens AG
Energy Sector
Oil & Gas Division
Wolfgang-Reuter-Platz
47053 Duisburg, Germany
Siemens Energy Inc.
10730 Telge Road
Houston, Texas 77095, USA
Siemens Turbomachinery Equipment A/S
Allégade 2
3000 Helsingør, Denmark
Phone +45 49 21 14 00
For more information, please contact
our Customer Support Center.
Phone:+49 180 524 70 00
Fax: +49 180 524 24 71
(Charges depending on provider)
E-mail: support.energy@siemens.com
Oil & Gas Division
Order No. E50001-G420-A115-X-4A00
Printed in Germany
Dispo 34806, c4bs No. 7423 WS 07092.
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bleached paper.
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Trademarks mentioned in this document
are the property of Siemens AG, its affiliates,
or their respective owners.
Subject to change without prior notice.
The information in this document contains
general descriptions of the technical options
available, which may not apply in all cases.
The required technical options should therefore
be specified in the contract.
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