Surface aeration systems

S U R FA C E A E R AT I O N
S U R FA C E A E R AT I O N
INTRODUCTION
This brochure gives an overview of the activities
of Landustrie Sneek BV in the field of surface
aeration. Landustrie has a long history and broad
experience in this field. For half a century now
Landustrie has designed, manufactured,
supplied, installed and maintained many types of
aeration systems. Since the introduction of a full
scale aeration test tank and the availability of
process know-how, back in the mid eighties,
Landustrie is the market leader in surface
aeration. This scientific approach has resulted in
the successful introduction of the Landy-7, the
fourth generation slow speed surface aerator,
which can easily compete with all other aeration
systems on the market. The Landy-7 is in itself
complete proof of Landustrie’s leading position
on in this market.
LANDY-7
oxygenation capacity [kg 02/kWh]
The Landy-7 is characterized by the following
features:
high and constant efficiency
extremely low reaction forces
wide range of applications
simple and robust construction
low maintenance costs
self cleaning
wide oxygenation range
controlled oxygen input
low total cost of ownership
sustainability
HIGH AND CONSTANT EFFICIENCY
The efficiencies that can be obtained with low speed
surface aerators depend on a number of factors. It is
important to be aware of this, particularly when
comparing low speed aerators with other aeration
systems. An important advantage of the surface
aerator is that the efficiency will be constant over the
full lifetime of the aerator, often up to 30 years. One
important factor is the geometry of the basin in which
the aerator will be installed. For different applications
one can use, as a rule of thumb, the following data:
oxidation ditches
2.2 -2.5 kg O2/kWh
rectangular basins
1.8 – 3.3 kg O2/kWh
lagoons
up to 2.0 kg O2/kWh
The Landy-7 aerator distinguishes from other aerators
by its conical shape. This shape creates a pump
function in the tank, thus pumping up water from the
lower parts of the tank. Water reaching the surface has
a high oxygen deficit, so oxygen transfer is fairly easy.
The integrated conical shape of the Landy-7 has two
main advantages especially when tanks are deeper
than 3 meters:
it creates complete mixing throughout the tank so
the solids are evenly mixed
oxygen enriched water on the surface is mixed with
less oxygenated water from the lower parts of the
tank (secondary aeration). The later explains the
much higer efficiency of the Landy-7 compared to
other brands).
A second consideration is the influence of the α-factor.
For low speed surface aerators this is normally about
0.9 (widely accepted value). Particularly with fine
bubble aeration systems too high α-factors, which can
only be met at laboratory scale, are often assumed .
Moreover, no consideration is given to the composition
of the waste water, which can have a detrimental
influence on the function of the installed aerator.
comparing surface aeration/fine bubble aeration
investments new elements
time
LANDY-7
fine bubble aeration
A general misconception is that low speed
surface aerators create aerosols. This is not the
case as proven by the University of Hannover
(1993). Low speed surface aerators do create
splashing in order to transfer the oxygen into the
water. The strength of a well designed aerator is
achieved with a
controlled splash
pattern. This is another
area in which the
Landy-7 distinguishes
itself over from other
designs. If further
restrictions are in place
regarding splashing or
noise production then
Landustrie can supply
specially designed aero
caps (see photograph
of Stora Enso,
Sweden).
WIDE RANGE OF APPLICATIONS
Naturally, the Landy-7 can be installed in either a
fixed or a floating arrangement. Regarding the
geometry of the basins the options are virtually
unlimited; square or rectangular tanks, round
tanks, shallow or deep tanks (if necessary with
suction tubes) oxidation ditches, MBR- and SBRsystems, lagoons, ponds, mixing or buffer tanks.
The Landy-7 can be applied anywhere and still
maintain its high efficiency.
The floating installation
arrangement has been
newly designed by
Landustrie. It is a more
compact installation
which is not only more
stable under operating
conditions, but also
much easier to trim.
Another advantage is
that the floating unit can
be manufactured locally,
allowing the use of less
expensive local labour
and reduction of
transport cost.
Because of the excellent
pumping function of the
Landy-7 it can also
ideally be applied with
suction tubes for tanks
with larger depths. Tanks
or oxidation ditches with
depths up to 8 m can in
such way be executed
properly, maintaining the
above mentioned high
efficiencies.
EXTREMELY LOW REACTION
FORCES
The design of the Landy-7 is such that both
radial and axial forces are much lower than with
conventional surface aerators. This has many
advantages. In particular, the forces on the
concrete and on the bearings of the outgoing
shaft of the gearbox will be much lower. Because
of this, in many cases, one can select a gearbox
which will be one size smaller. Also the vibration
characteristics will be reduced enormously, so
that critical vibrations in the gearbox will not
occur.
Square tanks
Floating arrangement
Oxidation ditch
Suction tube
S U R FA C E A E R AT I O N
Forces according FEA
Design criteria for the Landy-7 were not only the
highest possible efficiency but also a simple and
therefore cheaper to manufacture construction.
This is true for both the steel epoxy
coated option and the stainless steel
option in AISI 304 and AISI 316. By using
the Finite Element Analysis Landustrie
guarantees a robust construction with the
least possible material thicknesses. In
this way the forces on the gearbox
bearings are reduced to an absolute
minimum. Also the applied forces in the
Landy-7 are very low due to the shape of
the impeller.
For larger diameter Landy-7 aerators an
intermediate flange can be supplied in
order to reduce transport costs.
LOW MAINTENANCE COSTS
Because the
complete surface
aerator unit is only
built up from
impeller, gearbox
and electric motor,
maintenance is
limited to a yearly
oil check and
periodical checking
of all greasing
points.
EXCELLENT MIXING QUALITIES
In many applications of low speed surface aerators
the function of the aerator is not just limited to introducing oxygen into the water. Also, a part of the
propulsion and mixing has to be provided by the
surface aerator. That is one of the reasons why the
characteristic conical shape is noticeable in the
design of the seven blades. This is the source of
the pump function which is necessary for creating
good mixing conditions inside the basin. For oxidation ditches this results in excellent propulsion.
Also, when suction tubes are installed, for larger
depths between 5.5 and 8 m, this pump function is
very important to ensure a good transfer of oxygen.
WIDE OXYGENATION RANGE
Depending on the specific oxygen demand it is
possible that one single Landy-7 can transfer 1 to
500 kg O2/kWh into the waste water. For any
specific Landy-7 aerator, the range of oxygen
transfer is very large. The efficiency of the surface
aerator is constant over a wide range of both
speed and immersion depth.
Oxygen transfer LANDY-7 surface aerator
OC(10) [kg 02/hr]
SIMPLE AND ROBUST
CONSTRUCTION
diameter LANDY-7 [cm]
CONTROLLED OXYGEN INPUT
SELF CLEANING
The design and the shape of the blades are
configured in such a way that it is impossible for
any rag or other detritus to attach to the impeller.
This is largely due to the virtual cone shape
created by the seven blades.
The selection of the size of the surface aerator is
primary based on the amount of oxygen which has
to be introduced into the water. The oxygen
capacity of the selected Landy-7 can be regulated
in two ways, either by regulating the speed by
means of a variable frequency drive (VFD), or by
variation of the degree of
submergence of the
surface aerator, frequently achieved by changing
the height of the overflow weir. The actual
regulation is nearly
always monitored by
means of an oxygen
probe.
INDUSTRY
An important application for Landy low speed
surface aerators is in the pulp and paper
industry. Whether the Landy-7 is installed in the
classic aeration tank or in conjunction with an
anaerobic bioreactor, in both cases the Landy-7
is up to the job.
SAVINGS WITHOUT INVESTMENT
Low speed surface aerators can often be much
more effective and can save a substantial
amount of energy when the operation of the
aerator is based on the real load and not on the
original design parameters of the treatment plant.
This is very important because 80% of the power
at a waste water treatment plant is consumed by
aeration.
Stora Enso, Sweden
AFTERSALES
Landustrie’s after sales service is the customers
connection to Landustrie for not only supply of
spare parts but also for training and supervision.
Worth mentioning are installation upgrades,
some of which have amazingly short payback
times through savings in energy and
maintenance.
[email protected]
+31 6 515 486 888
AERATION SCAN/RETROFIT
Landustrie has developed a toolbox for checking
the functioning of the surface aerators in relation
to the actual load. The goal of this aeration scan
is to optimise the aeration, thus improving the
efficiency and durability. The savings can be as
much as 30%.
If larger deviations are found it might be
necessary to retrofit the existing installation.
Also for those type of installations (projects)
Landustrie is the ideal partner to give the client
the most
economical
advice based
on existing
parameters.
Adapt to praxis
Surface aerators can be much more effective
and efficient. At the design stage of a waste
water treatment plant the calculations are based
on the maximum load of the plant, including a
projection of growth for the lifetime of the plant.
(The number of aerators and sizing is based on
those parameters.) But what happens when the
load is much less than anticipated and the
circumstances are quite different than originally
assumed? By adapting the installation to the
actual loading one can improve the efficiency
and the process considerably and thus save a
substantial amount of energy.
LOW TOTAL COST OF OWNERSHIP/
SUSTAINABILITY
By supplying equipment with a life time of 25
years or more, with the highest possible system
efficiency, Landustrie offers highly sustainable
solutions. Relative low investment, constant high
efficiency with low maintenance cost result in the
lowest possible Total Cost of Ownership (TCO).
REFERENCES
For half a century Landustrie has been involved
in aeration projects, and many prestigious
references have been achieved. In this brochure
we restrict ourselves to some more recent examples of the over 8000 units supplied world-wide.
Snydersville, USA
Harvey Ave, USA
Papier industry Taipei, Taiwan
Amersfoort, The Netherlands
Hartbeesfontein, South Africa
Barcelona, Spain
LANDUSTRIE TEST FACILITIES
Since the middle of the eighties Landustrie has
had the necessary facilities to undertake aerator
testing in their own full scale test tank. This tank
is unique in Europe, and probably in the world, in
terms of size and testing possibilities. The
dimensions are 20 * 20 * 6 m, creating an
effective volume of 2200 m3, at a water depth of
5.5 m. In the tank a height adjustable bridge is
installed in order to be able to simulate lower
water depths.
There is also the option of inserting extra walls
in the tank to reduce the volume.
Landustrie test tank
The standard drive-unit of the test installation is
a 90 kW drive-unit provided with a variable
frequency drive (VFD). The foundation plate is
flexibly mounted and provided with 4
measurement probes using strain gauges, to
measure the radial and axial forces. The rise in
oxygen content is measured by 4 oxygen
probes. The measured value of the axial and
radial forces, the torque and the oxygen content is
monitored by data loggers. In short, the monitoring
is fully automatic.
Apart from oxygen measurements, vibration, noise
level and water flows can be measured. Oxygen
measurements are undertaken in
potable water, corrected to standard conditions
(T= 200C en P0 = 1013 hPa). In compliance with
EN 12255-15.
In this tank nearly all Landy-7 aerators are
tested under different conditions. Landustrie is
therefore capable of predicting the efficiency which
can be expected under the given conditions.
Besides measurements for Landustrie’s own use,
measurements for third parties can be carried out
in the presence of the client.
A E R AT I O N R O T O R S
LANDY-700
Pasveer oxidation ditch
LANDY AERATION ROTORS
For more than 50 years Landustrie has designed,
manufactured, supplied and installed several
types of aeration rotors. Initially, the aerators were
installed in the classical Pasveer oxidation ditch,
but later they were also applied in several other
configurations. Every Landy aeration rotor
consists of the following components;
rotor
bearings
drive-unit
splash plates
baffles
Optionally, Landy aeration rotors can be supplied
with heated bearings, in order to avoid freezing
during cold weather, and splash covers for the
avoidance of aerosols.
DIFFERENT TYPES
Landustrie has developed two standard types,
the Landy-700 and the Landy-1000, both of
which have the following features;
high efficiency
robust and reliable construction
wide oxygenation capacity range
low maintenance costs
long life
low exploitation costs
Depending on specific requirements, it is
possible to supply other sizes of aeration rotors.
The Landy-700 is an upgrade of the well-known
cage rotor. The construction of the Landy-700 is
similar to the Landy-1000 type, however the
diameter of the brush aerator is limited to
700 mm.
Normally the Landy aeration rotor is supplied as
a package unit, complete with bridge rotor,
bearings, drive-unit, splash guards and a bridge.
This compact unit not only allows for a simple
civil engineering construction but also facilitates
a very simple installation procedure. When no
bridge is supplied, the bearings are located
directly onto the civil construction.
The Landy-700 has a diameter of 700 mm and is
available up to a length of 9 m. The oxygenation
capacity is, under standard conditions,
54 kg O2/h, at a rotor length of 9 m and an
efficiency of 1.8 kg O2/kWh.
Landy-700 prefab
REGULATION OF OXYGENATION
For regulation of the oxygenation capacity there
are two options:
Variation of the rotational speed, effected
by a variable frequency drive (VFD) or a
pole-changeable electric motor.
Variation of the immersion depth of the
aerator, effected by overflow weirs.
LANDY-1000
The Landy-1000 aeration rotor is the result of
recent research and extensive testing.
The Landy-1000 consists of a hollow seamless
steel tube. Around the tube twelve blades are
clamped in a star-shaped configuration. This is
done by means of bolted connections (not
welded). The width of the blades is 75 mm and
the star-shaped blades are slightly staggered
from one another. Thus, when rotating, not all the
blades will hit the water simultaneously, in order
to reduce the load on the bearings. On both ends
of the tube splash plates are mounted to avoid
splashing of the water onto the bearings. The
Landy-1000 can also be supplied with a
prefabricated bridge construction.
Landy-1000
The Landy-1000 has a diameter of 1000 mm
and is available up to a length of 9 m.
The oxygenation capacity under standard
conditions is 85 kgO2/h, at a rotor length of 9 m
and an efficiency of 2.0 kg O2/kWh.
APPLICATIONS
Landy aeration rotors can be installed in both
municipal and industrial waste water treatment
plants. Landustrie has also supplied Landy
aeration rotors for use in potable water
installations.
LANDY aeration rotor
100
Landy-1000 without bridge
120
140
160
180
200
220
240
Landy-700 with bridge
260
280
300
R E N TA L A E R AT O R S
RENTAL OF SURFACE AERATORS
In order to fulfill the growing demand for
temporary aeration installations, Landustrie offers
the hire of a floating Landy-7 slow
speed surface aerator. If requested the unit
can also be hired without the floating
construction.
These rental aerators can be used during the
rebuild or renovation of existing waste water
treatment plant. Of course it is also possible to
apply these units for additional aeration, for use
in lagoons or pond aeration or for tests in which
one wants to compare different aeration systems.
PRICING
The rental price comprises a weekly rental price,
with separate costs for transport, assembling,
dismantling and other options.
New Landy floating construction
RENTAL SUPPLY
a Landy-7 high efficiency slow speed surface
aerator
quick delivery
assembling and dismantling of both the
existing and rental unit(s)
optional supply of variable frequency drive
(VFD)
minimum rental period is one week
TECHNICAL DATA ON RENTAL
AERATORS*
Motor power
Oxygenation capacity
Diameter (Landy-7)
Peripheral speed
* On request other units might be available.
Landustrie Sneek BV
Watertechnology
P.O. Box 199
NL-8600 AD Sneek
The Netherlands
Tel. +31 515 - 48 68 88
Fax +31 515 - 41 23 98
e-mail [email protected]
website www.landustrie.nl
Office address Pieter Zeemanstraat 6, Sneek
09-2013 1500 ENG
New Landy floating construction
37 kW
± 80 kg O2/h
1800 mm
max. 5 m/s