Note: Descriptions are shown in the official language in which they were submitted.
CA 02789624 2012-09-20
WASTEWATER PUMPING SYSTEM
Field of the Invention
The invention relates to a system and apparatus for pumping of municipal and
industrial wastewaters (sewage) in a safe and efficient manner and in
locations sensitive
to people and local environment.
Background of the Invention
Wastewater (sewage) pumping systems are frequently used in municipal,
industrial, recreational and commercial wastewater collection and disposal
systems. The
pumping systems are either a wetwell type or a wetwell and drywell type.
The wetwell and drywell can be one structure divided by a wall or they can be
separate structures located close to each other.
In the wet well type pumping system, wastewater enters a wet well and is
pumped
out predominantly by submersible wastewater pumps located in the wetwell.
Occasionally, wastewater self priming pumps are located on the top or beside
the
wetwell, on or near the ground level.
In the wetwell and drywell pumping system, wastewater enters a wetwell and
wastewater pumps are located in a drywell with suction lines extended into the
wetwell.
The pumps are dry location type pumps.
- 2 -
CA 02789624 2012-09-20
Usually, minimum two wastewater pumps are installed in a pumping system; but,
a number of pumps used is determined by the pumping system capacity and
reliability
requirements and may vary from one to several pumps in one pumping system.
Both wetwell type and wetwell and drywell type pumping systems can be
underground structures without superstructures or they can be provided with
superstructures above the ground level.
Typical problems encountered in wastewater pumping systems include:
accumulation of solids on the bottom of wetwells and production of
flammable, toxic and corrosive gases which results in complaints and health
and safety hazards, and corrosion of the pumping system components,
need for cleaning of the bottom of wetwells,
lack of provisions for swabbing of forcemains which result in reduction of
pumping capacity of the pumping systems,
lack of retention of large solids at the inlet of wastewater to the wetwells
which results in plugging and damage of the wastewater pumps,
lack of adequate instrumentation for monitoring of the wastewater inlet and
discharge flows and pumping pressure for adequate evaluation of the pumping
system performance, and mainly the pumping capacity, frequency of the
pumps onJoff operation, power consumption and a balance of the wastewater
collected vs the domestic water used in the area serviced by a wastewater
pumping system.
- 3 -
CA 02789624 2012-09-20
,
The invention includes provisions for elimination of the problems associated
with
wastewater pumping systems and which are applicable to small and large wetwell
type
and drywell and wetwell type pumping systems.
The invention provisions eliminate the concerns of gas hazard, safety, health,
corrosion and operation and maintenance, and prolong the pumping system life
span,
pumping capacity and reliability.
Brief Summary of the Invention
The wastewater pumping system of the present invention is a system and
apparatus for pumping of municipal and industrial wastewaters by a wetwell
type or
wetwell and drywell type pumping systems.
The wastewater pumping system is applicable to small and large wastewater
pumping systems, in underground and aboveground installations, in concrete,
steel or
plastic structures and in underground installations with or without
superstructures above
the ground level.
The wastewater pumping system major components include a wetwell,
submersible wastewater pumps and inlet and outlet piping in a wetwell pumping
system,
and wetwell, drywell, non-submersible wastewater pumps and inlet and outlet
piping in a
wetwell & drywell pumping system.
The wastewater pumping system specific additional components comprise the
following:
- 4 -
CA 02789624 2012-09-20
an aeration system for aeration of wastewater in a wetwell and scouring of the
wetwell's bottom sediments,
a removable basket at the inlet of wastewater to a wetwell for retention of
large solids,
a swab launching connection for swabbing of a forcemain which discharges
wastewater from the pumping system,
a water level transmitter for monitoring of the wastewater levels in the wet
well, activation and deactivation of wastewater pumps operation and water
level alarm conditions, and monitoring of the wastewater inflow volumes and
flow rates,
a wastewater pressure transmitter for monitoring of the wastewater pumps
discharge pressure, flow rates and volumes and activation of the discharge
pressure alarm conditions,
a control panel which receives electrical signals from the wastewater level
transmitter and the wastewater pressure transmitter for an automatic and
continuous monitoring of the wetwell wastewater level and the wastewater
pumps discharge pressure, and which parameters are automatically and
continuously transferred to a remote base station, and which parameters are
used by the control panel for an automatic start/stop operation of the
wastewater pumps, start/stop operation of the aeration system, activation of
alarm conditions of the wastewater low and high levels in the wetwell, the
- 5 -
CA 02789624 2012-09-20
wastewater pumps low and high discharge pressure levels, and the wastewater
pumps failure to start.
Brief Description of Drawings
Fig. 1 is a vertical section of a wetwell type wastewater pumping system in an
underground installation without a superstructure above the ground level.
Fig. 2 is a horizontal section ¨ plan made below the ground level of the
wastewater pumping system shown on Fig. 1.
Fig. 3 is a vertical section of a wetwell and drywell wastewater pumping
system
in an underground installation with a superstructure above the ground level.
Fig. 4 is a horizontal section ¨ plan made below the ground level of the
wastewater pumping system shown on Fig. 3.
Detailed Description of the Invention
The first preferred embodiment shown on Fig. 1 and Fig. 2 comprises a wetwell
1
with a top cover 2, a bottom floor 3, a gravity wastewater inlet pipe 4, a
pressure
wastewater outlet pipe (forcemain) 5 and a bottom base 8.
The bottom floor 3 is extended outside the wetwell 1 with a lip (flange)
around
the wetwell 1 for fastening of the wetwell 1 to the bottom base 8 with
fasteners 9.
The bottom floor 3 is also connected to the bottom base 8 with a water tight
and a
water resistant compound to eliminate any voids between the bottom floor 3 and
the
- 6 -
CA 02789624 2012-09-20
,
bottom base 8, to prevent any groundwater entry between the bottom floor 3 and
the
bottom base 8, and to prevent a groundwater direct pressure on the bottom
floor 3.
The bottom base 8 is provided to prevent the wetwell 1 buoyancy (uplifting)
due
to the ground water upward pressure on the bottom floor 3.
The wetwell 1, the top cover 2 and the bottom floor 3 can be made of any
material, corrosion resistant and capable of withstanding soil and groundwater
pressure,
and this can include metal, plastic, concrete, brick and wood. In cases, where
the wetwell
1 is made of concrete and preferably reinforced concrete, the bottom base 8
can be
integral with the wetwell 1 without the bottom floor 3 and the fasteners 9.
The top cover 2 provides entries to the wetwell 1 for wastewater pumps 21, a
large solids retention basket 40 and a manway to a ladder or stairs 55, and a
support for
vent pipes 10 and 11; air exhaust pipe 10 and fresh air inlet pipe 11, and for
an air heater-
blower 12 which is preferred in cold climates or an air blower 12 which is
preferred in
warm and moderate climates for an efficient ventilation of the wetwell 1 to
supply large
air flows continuously or intermittently.
The wetwell 1 and the bottom floor 3 are connected with a sloped plate to form
a
cove 7 of which internal surface is at an angle to the wetwell 1 and the
bottom floor 3,
preferably at 45 degrees or smaller angle to the wetwell 1, but preferably not
less than 30
degrees. The wetwell 1 and the bottom floor 3 are also connected horizontally
outside the
cove 7. The cove 7 extends the entire bottom connection of the wetwell 1 and
the bottom
- 7 -
CA 02789624 2012-09-20
floor 3, and it may be filled with air, water or other material of a high
thermal
conductivity and adequate mechanical strength.
The wetwell contains pumps, piping, instruments and controls which comprise:
submersible wastewater pumps 21 with discharge riser pipes 24, a collector
discharge pipe 27, slide away couplings 22, slide guide rails 23 and slide
guide plates 23A,
a swab inlet valve 28 connected to the collector discharge pipe 27,
an aeration system comprising an air aspirator-mixer 20, a wastewater inlet
pipe 29, a wastewater and air discharge pipe 37, wastewater and air
distribution pipes 38 and an air inlet pipe 17,
a large solids retention basket 40 located inside the wetwell 1 at the inlet
pipe
4 entry to the wetwell 1,
a pressure transmitter 30 mounted on the collector discharge pipe 27,
a water level transmitter 46 mounted at the bottom of the wetwell 1,
a control panel 42 which connects electrically with wires 43 to the pumps 21,
the pressure transmitter 30, the water level transmitter 46, automatic on/off
control valves 31 and 34 mounted on the discharge pipe 27 and the aeration
system inlet pipe 29 respectively, and with a wire 45 or through a wireless
communication system to a remote central operation station,
an intermediate operating platform (floor) 51 which is preferred in wetwells
deeper than approximately 3.2 meters,
- 8 -
CA 02789624 2012-09-20
, .
an access ladder or stairs 52 in small wetwells and large wetwells
respectively.
The pumps 21 are connected to the discharge riser pipes 24 with slide away
couplings 22 which allow the pumps 21 removal by lifting from the top cover 2
without
any need for a manual disconnection of the pumps 21 from the discharge riser
pipes 24.
The pumps 21 removal is assisted by slide guide rails 23 and slide guide
plates 23A
which guide the pumps 21 lifting from and lowering into the original position
in the
wetwell 1 and precisely into the slide away couplings 22.
The pumps 21 are supported directly on the bottom floor 3 to prevent any
direct
load on the slide away couplings 22, the discharge riser pipes 24 and the
collector
discharge pipe 27, and to prevent jamming, leakage or damage of the slide away
couplings 22 due to a direct load from the wastewater pumps 21 on the slide
away
couplings 22.
The swab inlet valve 28 is preferably of the same diameter as the collector
discharge pipe 27 and it is mounted at the end of the collector discharge pipe
27 with a
straight connecting pipe or on the top of the collector discharge pipe 27 with
preferably a
"y" fitting with the "y" inlet branch declining in the direction of the
wastewater flow
direction in the collector discharge pipe 27. The swab inlet valve 28 allows
for insertion
of a plastic swab into the collector discharge pipe 27 for swabbing of the
pressure
wastewater outlet pipe (forcemain) 5 to remove any sediment and coating from
the outlet
- 9 -
CA 02789624 2012-09-20
, .
pipe (forcemain) 5 to maintain the design wastewater pumping capacity of the
wastewater
pumping system.
The swab is forced downstream the collector discharge pipe 27 and the pressure
wastewater outlet pipe 5 by the wastewater pumped by the wastewater pumps 21.
The aeration system inlet pipe 29 is provided with a manual shut off valve 33,
and
the automatic on/off valve 34.
The aeration system distribution pipes 38 extend vertically from the discharge
pipe 37 to the coves 7 and are terminated with slanted outlets 39 in a
consistent clockwise
or anticlockwise direction along the bottom of the wetwell 1 to scour any
sediment
accumulated on the coves 7 and the bottom floor 3, and to aerate the
wastewater in the
wetwell 1 without a potential of entry of the air supplied with the wastewater
into the
pumps 21.
The sediment scour and the wastewater aeration prevent accumulation and
anaerobic decomposition of organic solids which result in production of
hazardous, toxic
and corrosive gases in the wetwell 1.
The air aspirator-mixer 20 is a venturi type air aspirator with a spiral type
static
mixer, both of non-clog design, with ability to aspire a large quantity of air
and
thoroughly mix the air with the wastewater which enters the air aspirator. The
air
aspirator aspires the air through the air inlet pipe 17. The air aspirator-
mixer 20 is
preferably mounted in the wetwell 1 in a vertical position and above the
intermediate
operating platform 51 for an easy access for maintenance. The air inlet pipe
17 is
- 10 -
CA 02789624 2012-09-20
,
supplied with air from the vent pipe 11 through an air pipe 15 connected to
the bottom of
the vent pipe 11 and an air pipe 16 which is placed in the cove 7 in a spiral
manner to act
as a heat exchanger between the air contained in the air pipe 16 and the air
or water
contained in the cove 7. Such design is preferred in cold climates to increase
the
temperature of the air aspired by the air aspirator-mixer 20 without any
heating of the air
by electrical or other means.
The air inlet pipe 17 is provided, near the air aspirator-mixer 20, with a non-
return
valve 18 and a manual shut off valve 19. The non-return valve 18 prevents an
entry of the
wastewater which flows through the air aspirator-mixer 20 into the air inlet
pipe 17, the
air pipe 16, the air pipe 15 and the vent pipe 11.
The aeration system operation is controlled by a PLC and programmed to suit
the
site conditions, and it is preferred to operate in an intermittent manner of
one to five
minutes "on" (in operation) and one to three hours "off' (idle). The "on" and
"off' time
intervals depend on the wastewater pumping system capacity, location and the
wastewater characteristics such as odor, suspended solids volume, and the
wastewater
flow rate distribution throughout a day, week or season.
When the aeration system is activated the automatic on/off control valves 31
and
34 are activated such that the valve 31 is closed and the valve 34 is open,
and one
wastewater pump 21 is also activated. The wastewater is pumped into the
discharge pipe
27, the inlet pipe 29 and the air aspirator-mixer 20. The wastewater flow
through the air
aspirator develops a vacuum condition which aspires air from the air inlet
pipe 17. The
- 11 -
CA 02789624 2012-09-20
, .
aspired air and the wastewater mix initially in the air aspirator and further
in the spiral
mixer. Thus, wastewater and air mixture flows into the discharge pipe 37 and
further into
the distribution pipes 28, and the slanted outlets 39 which discharge the
wastewater and
air mixture into the cove 7 and into the wastewater contained in the lower
part of the
wetwell 1.
The aeration system can be activated at any time when the wastewater pumps are
switched off at a low wastewater level 47 and before the wastewater pumps are
switched
on at a high water level 48 in the wetwell structure 1. The aeration system is
usually
switched on and off automatically but a manual operation is also provided for
testing and
inspections.
The aeration system can also efficiently operate when the wastewater pumps 21
are started at the high wastewater level 48 or a higher level and the
wastewater pumps 21
discharge pressure is 15 psi (1 Bar) or higher. In such cases the automatic
valves 31 and
34 are open for the duration of the aeration system operation and the valve 34
is closed
after the aeration is completed, but the valve 31 remains open or it can be
removed if the
wastewater pumps 21 discharge pressure is consistently 15 psi (1 Bar) or
higher. In a
wastewater pumping system with a consistent discharge pressure between 10 and
15 psi
(0.67 to 1 Bar) the control valve can be eliminated, but the second pump 21
should be
activated when the aeration system is activated.
-12-
CA 02789624 2012-09-20
, .
The wastewater pumps 21 operation is automatically controlled by a PLC located
in the control panel 42 and the water level transmitter 46 which detects
wastewater levels
47, 47A, 48, 49 and 50 in the wetwell 1.
The wastewater pumps 21 operate predominantly as a single pump at a time,
activated at the wastewater level 47 and the pumps 21 operation is
automatically
alternated, but, the second pump 21 will be activated at the wastewater level
49, and both
pumps will be switched off at the wastewater level 47.
The water level transmitter 46 provides a continuous output of 4-20 mA or
other
electronic output to the PLC located in the control panel 42. The electronic
output is used
for a continuous display of the wastewater levels, detection of the pumps 21
operating
levels 47, 48, 49, detection of a high wastewater level alarm 50, detection of
a low
wastewater level alarm 47A and calculation of the wastewater inflow rates and
volumes
when the wastewater pumps 21 are not in operation.
The wastewater inflow rates and volumes are useful for analyses of the
wastewater flow pattern throughout a day, week or other periods of time which
can be
used as design parameters for wastewater collection and pumping systems in
similar
developments.
The high wastewater level alarm 50 is an indication of an inadequate
wastewater
pumping system capacity which can be related to the pumps 21 wearout, reduced
flow
capacity of the pressure wastewater outlet pipe 5, high wastewater inflow
rates or
breakdown of one pump 21.
- 13 -
CA 02789624 2012-09-20
, .
The low wastewater level alarm 47A is an indication of a malfunction of the
pumps 21 on/off operation control system and a failure to switch off the pumps
21 at the
low wastewater level 47.
The pressure transmitter 30 provides a continuous output of 4-20 mA or other
electronic output to the PLC located in the control panel 42. The electronic
output is used
for a continuous display of the wastewater pumps 21 discharge pressure and
on/off
operation status, and calculations of the wastewater pumping flow rates and
volumes by
means of an algorithm and the wastewater pumps 21 capacity curves (flow rate
vs
discharge pressure curve).
The pumps 21 discharge pressure information is used for analyses of the pumps
21 performance which may be affected by the pumps wearout or the pressure
wastewater
outlet pipe 5 flow capacity reduction which can be caused by sediments,
coating,
squeezing or kinking of the outlet pipe 5.
The pumps 21 wearout can be checked by observing the pumps discharge
pressure at the "shut off condition" by closing the automatic control valve 31
or the
manual shut off valve 32 when one pump 21 is in operation and the aeration
system is not
in operation.
The pumps 21 discharge riser pipes 24 are provided with non-return valves 25
and
shut off manual valves 26. The non-return valves 25 are non-clog type and the
shut off
valves 26 are either gate valves, knife gate valves, plug valves or ball
valves preferably a
full port design. The non-return valves 25 and the shut off valves 26 are
preferably
- 14 -
CA 02789624 2012-09-20
. .
mounted above the intermediate platform 51 for an easy access for operation
and
maintenance.
The vent pipe 11 provides fresh air inlet into the wetwell 1 and the aeration
system air aspirator-mixer 20. The vent pipe 11 extends into the lower part of
the wetwell
1, preferably below the intermediate floor 51.
The vent pipe 11 bottom end is provided with a side outlet and a non-return
valve
14 which admits fresh air into the wetwell 1 and a bottom outlet which
connects to the air
pipe 15, and which supplies fresh air to the air aspirator-mixer 20 through
air pipes 16
and 17.
Where the vent pipe 11 is provided with the air heater-blower or air blower 12
and the air heater-blower or the air blower 12 operates in an intermittent
manner, it is
preferred that the air heater-blower or the air blower 12 is also activated
when the
aeration system is activated for an efficient air and gases exhaustion from
the wetwell 1.
When the aeration system is activated the non-return valve 14 prevents air
entry
from the lower part of the wetwell 1 into the air pipe 15 and the air
aspirator-mixer 20.
Thus, only fresh air from the atmosphere is used for the wastewater aeration.
The large solids retention basket 40 is provided to retain large solids
preferably
larger than 32 mm diameter or smallest dimension in any direction, to prevent
plugging
of the pumps 21 and the discharge riser pipes 24, the collector discharge pipe
27 and the
pressure wastewater outlet pipe 5, and the aeration system wastewater inlet
pipe 29, air
- 15 -
CA 02789624 2012-09-20
. ,
aspirator-mixer 20, wastewater and air discharge pipe 31, wastewater and air
distribution
pipes 38 and the slanted outlets 39.
The basket 40 is made preferably of a non-corrosive material such as wire or
perforated plate of stainless steel, aluminum, brass or plastics with openings
preferably
32 mm diameter or square, and is circular, square, rectangular or other shape
in its
horizontal cross section, and which is preferably equal to or larger than the
diameter of
the inlet pipe 4, and its length is preferably two times or larger than the
inlet pipe 4
diameter, and it extends at least 100 mm above and 300 mm below the gravity
wastewater inlet pipe 4.
The basket 40 is mounted inside the wetwell 1, at the inlet pipe 4 entry into
the
wetwell 1 on slide rails 41 which allow removal of the basket 40 to the top of
the wetwell
1 from the top cover 2 for removal and inspections of the solids retained in
the basket 40.
The top cover 2 and the intermediate platform 51 are provided with openings
and
hinged covers for passing of the pipes 10, 11, 17, 24, 27 & 38, the basket 40,
the pumps
21 and the ladder or stairs 55.
The air vent pipe 10 is provided for exhausting of air and gases from the
wetwell
1 and it protrudes into the wetwell 1 below the top cover 2 preferably not
more than 150
mm.
The vent pipe 11 is provided for a fresh air entry into the wetwell 1 and for
the air
aspirator-mixer 20.
- 16 -
CA 02789624 2012-09-20
. .
The air vent pipes 10 and 11 may enter the wetwell 1 through the top cover 1
or
on a side through the upper part of the wetwell 1.
The second embodiment of the invention is shown on Fig. 3 and Fig. 4. For the
embodiments disclosed herein, the same reference numerals are used for the
same or
substantially similar features. The essential difference between the first and
the second
embodiments is in the wastewater pumping system structure which in the second
embodiment comprise a wetwell 1 and a drywell lA and which are separated by a
solid
wall 57.
The wetwell 1 and the drywell lA may be covered by a superstructure 56 with a
dividing solid wall 58.
The walls 57 and 58 are provided to prevent a direct movement of air and gases
which may be contained in the air between the wetwell 1 and the drywall 1A.
The wetwell 1 and the drywell lA may be installed without the superstructure
56
over one or both wells 1 and 1A. The wetwell 1 and the drywell 1A may be
installed as
directly connected or separate structures located close to each other.
The wetwell 1 comprises the inlet gravity pipe 4, the large solids retention
basket
40 with the slide rails 41, the ventilation pipes 10 and 11, the access ladder
or stairs 55,
the aeration system discharge pipe 37 and the distribution pipes 38 with the
slanted
outlets 39, suction pipes 53 with inlet bells 54 for the wastewater pumps 21,
and the
water level transmitter 46.
-17-
CA 02789624 2012-09-20
The drywell 1 A comprises the wastewater pumps 21 with the discharge riser
pipes
24, the collector discharge pipe 27, the outlet pressure pipe 5, the aeration
system with
the inlet pipe 29, the air aspirator-mixer 20, the air inlet pipe 17 to the
air aspirator-mixer
20, the pressure transmitter 30, the ventilation pipes 10 and 11, the access
ladder or stairs
55 and the control panel 42 which can also be located in the superstructure 56
above the
drywell 1A.
The swab inlet valve 28 is located on a "y" fitting mounted on the collector
discharge pipe 27.
The air inlet pipe 17 to the air aspirator-mixer 20 receives air directly from
the
drywell 1A or from the superstructure 56 located above the drywell 1A.
The wastewater pumps 21 are provided with shut off valves 52 on the suction
pipes 53 for disconnection of the pumps 21 for a service or replacement.
The wastewater pumping system operation of the second embodiment is identical
to the system operation of the first embodiment.
20
- 18 -
