Note: Descriptions are shown in the official language in which they were submitted.
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Field of the Invention
The invention relates to a process and apparatus for biological wastewater
treatment as a secondary or a tertiary treatment process.
Background of the Invention
Biological, activated sludge wastewater treatment process usually operates as
a
secondary treatment system or a tertiary treatment system for removal of
Suspended
Solids, Biochemical Oxygen Demand, Nitrogen and/or Phosphorous.
The treatment systems involve wastewater aeration, sludge recirculation and
disposal (waste) and aerated wastewater recirculation. The aeration system can
be
continuous or cyclic. The aeration system usually requires air blowers and air
diffusers
located in aeration tanks or proprietary air aspirators are used in
conjunction with a pump
which pumps wastewater and air in an aeration chamber.
Simple one-pump aeration system usually operates as a secondary treatment
process with a sludge recirculation or extended aeration secondary treatment
process
without a sludge recirculation. These processes do not provide a tertiary
treatment and
the secondary treatment which they provide is not well controlled and
efficient. These
systems usually require large tanks to provide adequate secondary treatment
due to a lack
of an adequate treatment process and controls in regard to sludge
recirculation and
disposal of excess sludge, and aeration and mixing in the aeration chamber,
and
recirculation of aerated wastewater.
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Also, the aeration systems used are not efficient in regard to the oxygen
transfer
to the wastewater.
This invention is based on the wastewater aeration by means of a pump and an
efficient air aspirator-mixer. The pump also recirculates and wastes the
sludge produced
by the biological treatment process, and recirculates the aerated wastewater
to accomplish
a tertiary treatment. The air aspirator-mixer is highly efficient in regard to
the oxygen
transfer to the wastewater.
The objectives of this invention include the following:
= To provide wastewater aeration, sludge recirculation and waste and
wastewater
recirculation by means of the same pump.
= To supply air to the wastewater and sludge and to mix the air and the
wastewater and sludge by an efficient air aspirator-mixer.
= To provide a tertiary biological wastewater treatment process for removal of
Suspended Solids, Biochemical Oxygen Demand, Nitrogen and Phosphorous
and which can also be used as a secondary biological wastewater treatment for
removal of Suspended Solids and Biochemical Oxygen Demand.
= To provide flexibility and control of the time and rates of the wastewater
and
sludge aeration, sludge recirculation and waste, and the aerated wastewater
recirculation.
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= To provide wastewater treatment system which can be used for small, shop
fabricated treatment plants for installation above or under ground, and large,
site
assembled treatment plants.
= To provide wastewater treatment system which is compact and has a small foot
print.
= To provide a system of low operation and maintenance requirements.
Summary of the Invention
The treatment system of the present invention is a process and apparatus for
biological, activated sludge treatment of municipal and industrial
wastewaters.
The treatment system provides a tertiary treatment for removal of Suspended
Solids, Biochemical Oxygen Demand, Nitrogen and Phosphorous. Also, the
treatment
system can operate as a secondary treatment for removal only of Suspended
Solids and
Biochemical Oxygen Demand.
The treatment system comprises primary suspended solids and excess (waste)
activated sludge retention chamber, anoxic chamber, aeration chamber,
clarifier chamber,
wastewater aeration and recirculation, activated sludge recirculation,
aeration and waste
system, and instrumentation as shown on Fig. 1& 2.
A wastewater pump and an efficient air aspirator-mixer are used to provide the
wastewater aeration and recirculation, and the activated sludge recirculation,
aeration and
waste. The wastewater pump can be a submersible pump located in the aeration
chamber
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or a dry pit pump located beside the aeration chamber. The air aspirator-mixer
is located
either above or beside the aeration chamber. Single or multiple pumps and air
aspirator-
mixers can be used, depending on the size and capacity of the treatment
system.
A wastewater effluent pump can be used instead of a non-clog wastewater pump
for a better efficiency of the pumping and aeration process.
The patented J.K. air aspirator-mixer (Patent No. US 6,969,052 B2) is
preferred,
but other air aspirators and mixers can be used as well, if adequate air
supply and the air
and wastewater mixing are provided.
The primary suspended solids and the excess activated sludge retention chamber
is sized either to retain the sludge for a longer period of time of several
months or weeks,
which may be preferred in small treatment systems, such as domestic or
institutional
systems, or for a much shorter period of time of several hours or days which
is preferred
in large treatment systems such as municipal or large industrial systems, in
which case,
the sludge is removed from the chamber continuously or intermittently daily
for further
treatment or disposal.
The aeration process can be continuous or intermittent depending on the
wastewater supply pattern throughout a day or other period of time.
In the continuous aeration mode, it is preferred to control the air supply
flow rate
such to develop horizontal stratification zones in the aeration chamber, from
the bottom
to the top, of a high aeration zone, a moderate aeration zone, a light
aeration zone and a
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mixed anoxic zone, in order to continuously provide Biochemical Oxygen Demand
removal, nitrification and denitrification in the aeration chamber.
The wastewater and activated sludge are also recirculated to the anoxic
chamber,
located between the primary sludge holding chamber and the aeration chamber,
in order
to provide for phosphorous and nitrogen removal in the anoxic chamber.
In the anoxic chamber, the aerated wastewater and activated sludge are mixed
with the fresh unaerated wastewater which quickly depletes the oxygen
contained in the
aerated wastewater, thus phosphorous and nitrogen removal processes are
accomplished.
In the intermittent aeration mode, the wastewater is subjected to aeration and
no
aeration (anoxic) with mixing periods of approximately 1 hour to 2 hours each
period.
The wastewater is recirculated to the anoxic chamber during the aeration
period or both
during the aeration and no-aeration periods. The intermittent aeration mode is
preferred
during low wastewater flow periods and no flow periods which may appear in
small
systems or industrial systems operated on shift basis, and low strength
wastewater
systems.
The use of the highly efficient air aspirator-mixer, patented by the inventor,
ensures a high level of oxygen transfer to the wastewater immediately after
the air is
aspired into and mixed with the wastewater, and which takes place before the
aerated
waste water enters the aeration chamber. The oxygen transfer into the
wastewater
continues in the aeration chamber but it diminishes from the bottom to the top
of the
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chamber, thus the level of aeration (oxygen transfer) is reduced from the
bottom to the
top and the horizontal aeration stratification zones are developed in the
aeration chamber.
The other advantage is derived from the aeration stratification, that the
inlet
unaerated wastewater and the activated sludge return from the clarifier are
mixed with the
highly aerated wastewater and the mixture is further immediately re-aerated
and mixed in
the air aspirator-mixer and returned to the highly aerated wastewater zone.
The aeration and recirculation pump provides the aeration and recirculation of
the
wastewater, and the activated sludge at a flow rate of up to twelve times
higher than the
inlet wastewater design flow rate. The activated sludge recirculation flow
rate and the
aerated wastewater flow rate are several times higher than the inlet
wastewater flow rate
and up to 70% of the aeration/recirculation pump flow rate. The flow rates are
related to
the inlet wastewater quality and the required treated effluent quality.
The aerated wastewater flows into the clarifier at a flow rate of up to 100%
higher
than the inlet wastewater design flow rate. The biomass developed in the
aeration
process settles at the bottom of the clarifier and is recirculated to the
aeration chamber
along with a portion of the treated wastewater which entered the clarifier.
The portion of
the treated and clarified wastewater, equal to the inlet wastewater flow rate,
is discharged
from the clarifier to a disposal.
The activated sludge is intermittently or continuously wasted into the primary
suspended solids and excess activated sludge retention chamber by intermittent
or
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continuous discharges of the recirculated wastewater and activated sludge into
the sludge
retention chamber.
A portion of the wastewater and activated sludge recirculated by the aeration
and
recirculation pump is discharged to the upper zone in the aeration chamber,
before the
wastewater and activated sludge are re-aerated, to provide nutrients for the
denitrification
process which takes place in the upper part of the aeration chamber.
A suspended solids meter is preferred to monitor the suspended solids (mixed
licquir suspended solids) density in the aeration chamber lower, high aeration
zone and
dissolved oxygen meters are preferred to monitor the dissolved oxygen in the
aeration
chamber lower, high aeration zone and the upper, low aeration/anoxic zone
boundary.
A flow meter is preferred on the inlet wastewater line to monitor the inlet
wastewater flow rates and volumes.
The above instrumentation is not mandatory, but it is preferred to facilitate
setting
up of the system operating parameters for a high efficiency performance,
reliability and
consistency in applications of varying inlet wastewater flow rates and
quality.
Brief Descriptions of the Drawings
Having thus generally described the invention, it will be referred to more
specifically by reference to the accompanying drawings illustrating preferred
embodiments, and in which:
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Fig. 1 is a diagrammatic illustration in vertical cross-section of the
treatment
process and apparatus with the aeration and recirculation pump located inside
the aeration
chamber.
Fig. 2 is a diagrammatic illustration in horizontal cross-section of the
treatment
process and apparatus with the aeration and recirculation pump located inside
the aeration
chamber.
Detailed Description of the Invention
According to the embodiment of the invention, as shown on Fig. 1& 2, the
treatment system comprises the following major components: a primary suspended
solids
and activated sludge waste retention chamber 1, further referred to as
retention chamber,
an anoxic chamber 2, an aeration chamber 3, a clarifier chamber 4, access
manholes 5, an
inlet wastewater pipe 7, an inlet wastewater flow meter 8, an aeration and
recirculation
pump 28, an air aspirator-mixer 34, and an effluent wastewater pipe 47.
Inlet wastewater enters the retention chamber 1 through the inlet pipe 7, the
flow
meter 8 and a discharge pipe 9. The flow meter 8 is vented on the inlet and
outlet sides
with vent pipes 10. The discharge pipe 9 is preferably directed toward the
front end of
the retention chamber 1.
The inlet wastewater suspended solids and the activated waste sludge settle in
the
retention chamber 1 and a clarified wastewater flows toward the anoxic chamber
2, as
shown by a flow direction arrow 11.
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The clarified wastewater flows to an overflow trough 13 and further to the
anoxic
chamber 2, through a pipe 14 which connects to a wastewater and activated
sludge return
pipe 38, inside the anoxic chamber 2.
The clarified wastewater and recirculated wastewater and activated sludge mix
together in the anoxic chamber 2 and the mixture of the wastewater and the
activated
sludge flows to the aeration and recirculation pump 28 through a perforated
pipe 16
located in the anoxic chamber 2 and a perforated pipe 17 (single or multiple)
located in
the aeration chamber 3.
The aeration and recirculation pump 28 receives wastewater and activated
sludge
from the anoxic chamber 2, aerated wastewater from the bottom of the aeration
chamber
3 and nitrified and partially denitrified wastewater from the top of the
aeration chamber
3, and activated sludge from the clarifier chamber 4.
The mixture of wastewater and activated sludge is pumped into two streams;
one,
an aeration stream through a pipe 33 and the air aspirator-mixer 34 where it
mixes with
air and the aerated mixture is discharged into the aeration chamber 3 through
solid
discharge pipe 35 and bottom perforated pipe 36, and the second, a
recirculation stream,
through a pipe 37, is not aerated and it is occasionally or continuously
discharged to the
retention chamber 1 through a control valve 41 and a discharge pipe 39 and to
the anoxic
chamber 2 through a control valve 40 and a discharge pipe 38, and to the upper
part of
the clarifier 3 through a control valve 55 and a discharge pipe 54.
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Treated wastewater and activated sludge overflow from the aeration chamber 3
into the clarifier chamber 4 through horizontal troughs 27 and discharge pipes
26 & 25.
The discharge pipe 25 is provided with a non-return valve to prevent flow of
the treated
wastewater from the upper part of the clarifier chamber 4 to the aeration and
recirculation
pump 28.
The treated wastewater and the activated sludge separate in the clarifier
chamber
4 and a clarified treated wastewater overflows to a trough 46 and further to
the effluent
pipe 47, and the activated sludge settles to the bottom of the clarifier
chamber 4, and it is
returned by the aeration and recirculation pump 28 partially to the aeration
chamber 3,
anoxic chamber 2 and the retention chamber 1 where the activated sludge is
wasted.
The treatment processes which take place in the aeration chamber 3 comprise
four
horizontal zones which from the bottom to the top are high aeration, moderate
aeration,
low aeration and anoxic zone.
The Biochemical Oxygen Demand (BOD) removal and the nitrification of
ammonia to nitrate take place in the high, moderate and low aeration zones
while the
denitrification process takes place in the anoxic zone.
The nitrified and partially denitrified wastewater which is returned to the
anoxic
chamber 2 undergoes a phosphorous removal process and further denitrification
process.
A suspended solids removal is accomplished in the retention chamber 1 and in
the
clarifier chamber 4.
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The aeration system which comprises the aeration and recirculation pump 28 and
the air aspirator-mixer 34 also includes an open/close control valve 44, a
rotometer 43
and an air inlet pipe 42. The rotometer 43 measures the air flow rate and the
control
valve 44 permits to operate the aeration chamber 3 in intermittent modes of
aeration and
no aeration (anoxic) while maintaining mixing of the wastewater in the
aeration chamber
3 by the aeration and recirculation pump 28. This mode of operation is
preferred during
low flow or no flow of the inlet wastewater periods, and low strength
wastewater
systems.
Wastewater & activated sludge mixture flow rates into the aeration stream 33
and
the recirculation stream 37, can be adjusted by manually operated valves 31 &
32.
The density of the suspended solids in the aeration chamber 3 is monitored by
a
suspended solids meter 52 and the desired density of the suspended solids in
the aeration
chamber 3 is maintained by periodical discharges of the mixture of the
wastewater and
the activated sludge which enter the aeration & recirculation pump 28 into the
retention
chamber 1, through the control valve 41 and the discharge pipe 39.
Oxygen levels in the aeration chamber are monitored at two levels; at a low
level
in the high aeration zone and at an upper level at the low aeration and anoxic
zones
boundary, by oxygen sensors 48 & 49 respectively and an oxygen monitor 50. The
oxygen levels in the aeration chamber 3 can be adjusted, to desired levels, by
a manually
operated air supply rate of flow control valve 53 or by the automatic air
supply on/off
control valve 44, by an intermittent supply of air to the aeration chamber 3.
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The primary suspended solids and the activated sludge waste can be removed
from the retention chamber 1 periodically or more frequently either by pumping
out the
sludge waste or discharging it through a control valve 15 to a designated
sludge
processing facility or disposal site.
The invention is not limited to the embodiment shown on Fig. 1& 2 and as
outlined above, and it encompasses all the variations thereof which include
installation of
the aeration and recirculation pump 28 outside the aeration chamber 3,
multiple aeration
& recirculation pumps and air aspirator-mixers, separate aeration and
recirculation
pumps, open chambers without access manholes, underground and above ground
chambers, separate chambers connected with pipes or channels, inlet wastewater
flow
meter located in a separate chamber etc.
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