Wastewater Treatment Plant - Screen bar
Added on 2022-08-11
64 Pages10032 Words28 Views
|
|
|
Contents
Abstract................................................................................................................................................1
1.0 Introduction...................................................................................................................................2
2.0 Aims and Objectives......................................................................................................................2
3.0 Process Flow Diagram...................................................................................................................3
4.0 Mass Balance..................................................................................................................................3
5.0 Mechanical Design.........................................................................................................................5
5.1 Bar Screen..................................................................................................................................5
5.1.1 Screen Selection..................................................................................................................5
5.1.2 Design of Catenary Bar Screen..........................................................................................9
5.2 Grit Removal Tank..................................................................................................................12
5.2.1 Selection of Grit Removal Tank and Oil Removal Tank...................................................12
5.2.2 Design of Aerated Grit Chamber.........................................................................................13
5.3 Sizing of Pipes..............................................................................................................................16
6.0 Piping and Instrumentation Diagram (P&ID)...........................................................................17
6.1 Catenary Screen.......................................................................................................................17
6.2 Aerated Grit Tank...................................................................................................................18
7.0 Start-up and Shutdown and Aerated Grit Chamber................................................................20
8.0 Ancillary Equipment...................................................................................................................21
8.1 Influent Pump..........................................................................................................................21
8.2 Waste Collection Tank............................................................................................................22
Appendix (1): Mass balance Calculations........................................................................................24
1
Abstract................................................................................................................................................1
1.0 Introduction...................................................................................................................................2
2.0 Aims and Objectives......................................................................................................................2
3.0 Process Flow Diagram...................................................................................................................3
4.0 Mass Balance..................................................................................................................................3
5.0 Mechanical Design.........................................................................................................................5
5.1 Bar Screen..................................................................................................................................5
5.1.1 Screen Selection..................................................................................................................5
5.1.2 Design of Catenary Bar Screen..........................................................................................9
5.2 Grit Removal Tank..................................................................................................................12
5.2.1 Selection of Grit Removal Tank and Oil Removal Tank...................................................12
5.2.2 Design of Aerated Grit Chamber.........................................................................................13
5.3 Sizing of Pipes..............................................................................................................................16
6.0 Piping and Instrumentation Diagram (P&ID)...........................................................................17
6.1 Catenary Screen.......................................................................................................................17
6.2 Aerated Grit Tank...................................................................................................................18
7.0 Start-up and Shutdown and Aerated Grit Chamber................................................................20
8.0 Ancillary Equipment...................................................................................................................21
8.1 Influent Pump..........................................................................................................................21
8.2 Waste Collection Tank............................................................................................................22
Appendix (1): Mass balance Calculations........................................................................................24
1
A1.1 Mass balance of Grit Tank (T-102)......................................................................................28
Appendix (2): Mechanical Design calculations................................................................................29
A2.1 Calculations of Catenary bar screen Design............................................................................29
A2.2 Calculations of Aerated Grit Chamber Design...................................................................31
A2.3 Calculations of Oil and Grease Tank..................................................................................33
Appendix (3): Standard Size of carbon Steel Pipe and Calculations....................................................37
Appendix (4): Ancilary Equipment Calculations............................................................................38
A4.1 the Influent Pump....................................................................................................................38
A4.2 Waste Collection Tank (T-111)...............................................................................................39
Reference............................................................................................................................................40
List of figures
Figure 1: The process flow diagram of the designed part of the wastewater treatment plant (Replace
PFD)......................................................................................................................................................5
Figure 2:The classification of used Screens in wastewater treatment as preliminary stage (Metcalf
& Eddy, 2014).......................................................................................................................................8
Figure 3: four main types of mechanically cleaned coarse screen: Chain-driven screen, reciprocating
rake, catenary screen, and continues belt (Qasim, 2017)....................................................................11
Figure 4: Piping and instrumenting Diagram (P&ID) of Catenary Screen (Replace).........................20
Figure 5: Piping and instrumenting Diagram (P&ID) of aerated grit tank (Replace)......................21
Figure 6: The consumption water per capita per one day in 2018 : (Warner et al., 2019)..................27
List of tables
Table 1: The summary of the mass balance of the first part of wastewater treatment plant...............6
Table 2: The advantages and disadvantages of types of mechanically cleaned coarse screen
(Metcalf & Eddy, 2014)........................................................................................................................8
Table 3: The summary of result of bar screen design........................................................................13
Table 4: The comparison of vortex and aerated grit chambers (Metcalf & Eddy, 2013; EPA, 2003)..14
Table 5: The summary of result of design of aerated grit removal tank............................................17
2
Appendix (2): Mechanical Design calculations................................................................................29
A2.1 Calculations of Catenary bar screen Design............................................................................29
A2.2 Calculations of Aerated Grit Chamber Design...................................................................31
A2.3 Calculations of Oil and Grease Tank..................................................................................33
Appendix (3): Standard Size of carbon Steel Pipe and Calculations....................................................37
Appendix (4): Ancilary Equipment Calculations............................................................................38
A4.1 the Influent Pump....................................................................................................................38
A4.2 Waste Collection Tank (T-111)...............................................................................................39
Reference............................................................................................................................................40
List of figures
Figure 1: The process flow diagram of the designed part of the wastewater treatment plant (Replace
PFD)......................................................................................................................................................5
Figure 2:The classification of used Screens in wastewater treatment as preliminary stage (Metcalf
& Eddy, 2014).......................................................................................................................................8
Figure 3: four main types of mechanically cleaned coarse screen: Chain-driven screen, reciprocating
rake, catenary screen, and continues belt (Qasim, 2017)....................................................................11
Figure 4: Piping and instrumenting Diagram (P&ID) of Catenary Screen (Replace).........................20
Figure 5: Piping and instrumenting Diagram (P&ID) of aerated grit tank (Replace)......................21
Figure 6: The consumption water per capita per one day in 2018 : (Warner et al., 2019)..................27
List of tables
Table 1: The summary of the mass balance of the first part of wastewater treatment plant...............6
Table 2: The advantages and disadvantages of types of mechanically cleaned coarse screen
(Metcalf & Eddy, 2014)........................................................................................................................8
Table 3: The summary of result of bar screen design........................................................................13
Table 4: The comparison of vortex and aerated grit chambers (Metcalf & Eddy, 2013; EPA, 2003)..14
Table 5: The summary of result of design of aerated grit removal tank............................................17
2
Table 6: The common range and typical specification of domestic wastewater (WHO, 2006)............26
Abstract
The primary aim of the project was to full design of screen bar as well as grit and grease removal
tank for wastewater treatment plant that used for more than 200,000 peoples in UK. The most
appropriate type of bar screen was selected as catenary bar screen due it is cost effective than other
types. Additionally, the aerated girt and grease removal tank was selected due to it can handle high
amount of wastewater rather than vortex type. The physical dimensions of catenary bar screen were
estimated where the width, depth, angle, length, and number of bars were found as 1.10m, 1.63m, 75
degree, 1.69 m, and 37 bars respectively. The physical dimensions of grit and oil removal tank were
estimated where number of required tanks, depth of one tank, width, length, and required air were
found as 5 tanks, 4 m, 4.8 m, 3 m, and 1.08 m3/min respectively. The volume of wastewater collecting
tank as well oil collecting tank were found as 75.61 m3 and 32.52 m3 respectively. In addition, the
influent main pump was designed where the type is selected as centrifugal and the required power
was found as 300 kW. Finally, the piping and instrumenting diagram of screen and grit tank was
designed to maintain main variables.
3
Abstract
The primary aim of the project was to full design of screen bar as well as grit and grease removal
tank for wastewater treatment plant that used for more than 200,000 peoples in UK. The most
appropriate type of bar screen was selected as catenary bar screen due it is cost effective than other
types. Additionally, the aerated girt and grease removal tank was selected due to it can handle high
amount of wastewater rather than vortex type. The physical dimensions of catenary bar screen were
estimated where the width, depth, angle, length, and number of bars were found as 1.10m, 1.63m, 75
degree, 1.69 m, and 37 bars respectively. The physical dimensions of grit and oil removal tank were
estimated where number of required tanks, depth of one tank, width, length, and required air were
found as 5 tanks, 4 m, 4.8 m, 3 m, and 1.08 m3/min respectively. The volume of wastewater collecting
tank as well oil collecting tank were found as 75.61 m3 and 32.52 m3 respectively. In addition, the
influent main pump was designed where the type is selected as centrifugal and the required power
was found as 300 kW. Finally, the piping and instrumenting diagram of screen and grit tank was
designed to maintain main variables.
3
1.0 Introduction
The screening is utilized in the first stage of wastewater treatment as preliminary stage. The
main purpose of the screen is to eliminate large objects (e.g. logs of woods, tires, and concrete blocks)
in order to protect the pump and the mechanical equipment from damage, thus the selected type
should be coarse screen (Qasim, 2017). The elements of screening consist of wires or rods, gratings,
parallel bars, perforated plate, or wire mesh where the shape of the openings can be rectangular or
circular slots. The coarse screen or bar rack composed of parallel rods or bars, coarse screen is utilized
for just eliminating coarse solids (Metcalf & Eddy, 2014).
The grit removal tank is used to remove grit by settlement force where the grit consist of many
materials such as: seed, coffee ground, bone chips, eggshells, glass fragment, soil, stone, sand, gravel,
and cinder. In addition, the same tank removes oil and grease by introducing air into the wastewater,
which enhances the separation of oil from water, then oil and grease floats to the surface of the water
and removed by skimming (EPA, 1995).
2.0 Aims and Objectives
The aim of the project is to design a screen bar for wastewater treatment plant that serves a city in
south wales that has 200,000-population size, as well as a grit removal tank and its oil and grease tank
which the skimmed oil and grease is stored in. The objectives of the project are demonstrated in the
following points:
1) Process Flow Diagram (PFD) of the assigned part of wastewater treatment plant (Screening
and Grit Removal).
2) Mass balance of the assigned part of wastewater treatment plant.
3) Energy balance for the assigned part of wastewater treatment plant.
4) Mechanical design of screen bar in order to define and calculate the required physical
dimensions of screen bar based on the inlet flowrate.
5) Mechanical design of grit removal tank in order to define and calculate the required physical
dimensions of grit tank based on the inlet flowrate.
6) Design piping and instrumenting (P&ID) of screen bar and grit removal tank.
7) Create a 3D design of the selected screen and grit removal tank.
8) Simple design of influent pump, air compressor and waste collection tank (T-111).
4
The screening is utilized in the first stage of wastewater treatment as preliminary stage. The
main purpose of the screen is to eliminate large objects (e.g. logs of woods, tires, and concrete blocks)
in order to protect the pump and the mechanical equipment from damage, thus the selected type
should be coarse screen (Qasim, 2017). The elements of screening consist of wires or rods, gratings,
parallel bars, perforated plate, or wire mesh where the shape of the openings can be rectangular or
circular slots. The coarse screen or bar rack composed of parallel rods or bars, coarse screen is utilized
for just eliminating coarse solids (Metcalf & Eddy, 2014).
The grit removal tank is used to remove grit by settlement force where the grit consist of many
materials such as: seed, coffee ground, bone chips, eggshells, glass fragment, soil, stone, sand, gravel,
and cinder. In addition, the same tank removes oil and grease by introducing air into the wastewater,
which enhances the separation of oil from water, then oil and grease floats to the surface of the water
and removed by skimming (EPA, 1995).
2.0 Aims and Objectives
The aim of the project is to design a screen bar for wastewater treatment plant that serves a city in
south wales that has 200,000-population size, as well as a grit removal tank and its oil and grease tank
which the skimmed oil and grease is stored in. The objectives of the project are demonstrated in the
following points:
1) Process Flow Diagram (PFD) of the assigned part of wastewater treatment plant (Screening
and Grit Removal).
2) Mass balance of the assigned part of wastewater treatment plant.
3) Energy balance for the assigned part of wastewater treatment plant.
4) Mechanical design of screen bar in order to define and calculate the required physical
dimensions of screen bar based on the inlet flowrate.
5) Mechanical design of grit removal tank in order to define and calculate the required physical
dimensions of grit tank based on the inlet flowrate.
6) Design piping and instrumenting (P&ID) of screen bar and grit removal tank.
7) Create a 3D design of the selected screen and grit removal tank.
8) Simple design of influent pump, air compressor and waste collection tank (T-111).
4
3.0 Process Flow Diagram
The process flow diagram of the designed part of the wastewater treatment plant can be shown in the
following Figure 1:
Figure 1: The process flow diagram of the designed part of the wastewater treatment plant (Replace
PFD)
The process flow diagram of the wastewater treatment plant is shown in Appendix (A3).
Stream 1, which consists of untreated wastewater, enters the first treatment unit (Screen F-101), which
is used to eliminate large debris and coarse solids such as rags, plastics, and rocks. The opening size
of the coarse screen is 6mm. In rare instances, where the influent flow exceeds the value of ‘Formula
A’ (approx. 380,000 m3/d, see Appendix 4) the bypass will be opened and will release untreated
sewage, in order to prevent flooding of the plant. After screening, wastewater is pumped to the second
treatment unit (Grit tank T-102) which is used to eliminate grit, sand, and silt from water by
settlement as well as oil and fat by skimming (Qasim, 2017). Usually, the required residence time for
grit removal is 2-5mins (Scholz, 2015). The oil and grease is skimmed and exits from the top to a
collection tank (T-104) as stream 6; the wastewater without grit and oil exits from the middle of the
grit tank to the next unit as stream 4.
4.0 Mass Balance
There are also same parameters should be estimated based on the following Equations, where the
mass the sludge can be estimated as the following Equation 1 (ÇANKAYA, 2013):
Mass of sludge=TSS∗Q
100 (1)
5
The process flow diagram of the designed part of the wastewater treatment plant can be shown in the
following Figure 1:
Figure 1: The process flow diagram of the designed part of the wastewater treatment plant (Replace
PFD)
The process flow diagram of the wastewater treatment plant is shown in Appendix (A3).
Stream 1, which consists of untreated wastewater, enters the first treatment unit (Screen F-101), which
is used to eliminate large debris and coarse solids such as rags, plastics, and rocks. The opening size
of the coarse screen is 6mm. In rare instances, where the influent flow exceeds the value of ‘Formula
A’ (approx. 380,000 m3/d, see Appendix 4) the bypass will be opened and will release untreated
sewage, in order to prevent flooding of the plant. After screening, wastewater is pumped to the second
treatment unit (Grit tank T-102) which is used to eliminate grit, sand, and silt from water by
settlement as well as oil and fat by skimming (Qasim, 2017). Usually, the required residence time for
grit removal is 2-5mins (Scholz, 2015). The oil and grease is skimmed and exits from the top to a
collection tank (T-104) as stream 6; the wastewater without grit and oil exits from the middle of the
grit tank to the next unit as stream 4.
4.0 Mass Balance
There are also same parameters should be estimated based on the following Equations, where the
mass the sludge can be estimated as the following Equation 1 (ÇANKAYA, 2013):
Mass of sludge=TSS∗Q
100 (1)
5
Where: (TSS : total suspended solid in mg/L (PPM), and Q : the volumetric flowrate of inlet
wastewater). The mass of volatile suspended solid can be estimated based on the following Equation 2
(ÇANKAYA, 2013):
Mass of VSS= VSS∗Q
100 (2)
Where: (VSS : volatile suspended solid in mg/L (PPM), and Q : the volumetric flowrate of inlet
wastewater). The mass of BOD (biochemical oxygen demand) which refers to the required amount of
oxygen that would be consumed if all the organic materials, so it is an indicator for the amount of
organic matters in water. It is can be estimated based on the following Equation 3 (ÇANKAYA,
2013):
Mass of BOD= BOD∗Q
100 (3)
Where: (BOD : biochemical oxygen demand in mg/L (PPM), and Q : the volumetric flowrate of inlet
wastewater). The oil and grace can be estimated based on the following Equation 4:
Mass of OIL=oil conentration∗Q
100 (4)
Based on pervious equations and the calculations, the summary of the results of mass balance for the
assigned part of wastewater treatment plant is shown in the following Table 1:
Table 1: The summary of the mass balance of the first part of wastewater treatment plant
Components 1 (mg/L) 1 2 3 4 5 6
TSS 195 0.1513 0.1362 0.0151 0.0953 0.0409
VSS 150 0.1164 0.1048 0.0116 0.0733 0.0314
BOD 200 0.1552 0.1552 0.1552
COD 508 0.3942 0.3942 0.3942
Oil & Grease 76 0.0590 0.0590 0.0206 0.0383
Phosphorus 5.6 0.0043 0.0043 0.0043
Nitrogen 35 0.0272 0.0272 0.0272
6
wastewater). The mass of volatile suspended solid can be estimated based on the following Equation 2
(ÇANKAYA, 2013):
Mass of VSS= VSS∗Q
100 (2)
Where: (VSS : volatile suspended solid in mg/L (PPM), and Q : the volumetric flowrate of inlet
wastewater). The mass of BOD (biochemical oxygen demand) which refers to the required amount of
oxygen that would be consumed if all the organic materials, so it is an indicator for the amount of
organic matters in water. It is can be estimated based on the following Equation 3 (ÇANKAYA,
2013):
Mass of BOD= BOD∗Q
100 (3)
Where: (BOD : biochemical oxygen demand in mg/L (PPM), and Q : the volumetric flowrate of inlet
wastewater). The oil and grace can be estimated based on the following Equation 4:
Mass of OIL=oil conentration∗Q
100 (4)
Based on pervious equations and the calculations, the summary of the results of mass balance for the
assigned part of wastewater treatment plant is shown in the following Table 1:
Table 1: The summary of the mass balance of the first part of wastewater treatment plant
Components 1 (mg/L) 1 2 3 4 5 6
TSS 195 0.1513 0.1362 0.0151 0.0953 0.0409
VSS 150 0.1164 0.1048 0.0116 0.0733 0.0314
BOD 200 0.1552 0.1552 0.1552
COD 508 0.3942 0.3942 0.3942
Oil & Grease 76 0.0590 0.0590 0.0206 0.0383
Phosphorus 5.6 0.0043 0.0043 0.0043
Nitrogen 35 0.0272 0.0272 0.0272
6
Ferric Chloride
Polymer
Biogas
Total solids 806 0.6255 0.6103 0.6103
Water 774.734 774.7347 774.7347
Overall Flow (kg/s) 776
776.000
0 775.9849 0.0151 775.9465 0.0409 0.0383
5.0 Mechanical Design
The aim of this section is to select the suitable type of screen bar based on many factors as
well as design screen bar in order to find the physical dimension of it. Additionally, it is required to
select the suitable type of grit removal tank based on many factors as well as design screen bar in
order to find the physical dimension of it.
5.1 Bar Screen
The main purpose of the screen is to eliminate large object (e.g. logs of woods, tires, and
concrete blocks) in order to protect the pump and the mechanical equipment from damage, thus the
selected type should be coarse screen (Qasim, 2017).
5.1.1 Screen Selection
The elements of screening consist of wires or rods, gratings, parallel bars, perforated plate, or
wire mesh where the shape of the openings can be rectangular or circular slots. The two most
commonly used types of screens in wastewater treatment are shown in Figure 2, these types are fine
and coarse screens. They are utilized in the first stage of wastewater treatment as preliminary stage.
The coarse screen (also known as bar rack) are composed of parallel rods or bars, coarse screen
functions. Due to a large opening of usually 6mm to 150mm (as shown in figure 2) anything smaller
than this opening will pass through. Fine screen on the other hand employ perforated plate or wire
mesh, the use of this allows fine screens to prevent any solids larger than 6mm to pass through.
Finally micro-screens, operate on a microscopic level, only particulate matter smaller than 0.5
micrometers can pass through. (Metcalf and Eddy, 2014).
7
Polymer
Biogas
Total solids 806 0.6255 0.6103 0.6103
Water 774.734 774.7347 774.7347
Overall Flow (kg/s) 776
776.000
0 775.9849 0.0151 775.9465 0.0409 0.0383
5.0 Mechanical Design
The aim of this section is to select the suitable type of screen bar based on many factors as
well as design screen bar in order to find the physical dimension of it. Additionally, it is required to
select the suitable type of grit removal tank based on many factors as well as design screen bar in
order to find the physical dimension of it.
5.1 Bar Screen
The main purpose of the screen is to eliminate large object (e.g. logs of woods, tires, and
concrete blocks) in order to protect the pump and the mechanical equipment from damage, thus the
selected type should be coarse screen (Qasim, 2017).
5.1.1 Screen Selection
The elements of screening consist of wires or rods, gratings, parallel bars, perforated plate, or
wire mesh where the shape of the openings can be rectangular or circular slots. The two most
commonly used types of screens in wastewater treatment are shown in Figure 2, these types are fine
and coarse screens. They are utilized in the first stage of wastewater treatment as preliminary stage.
The coarse screen (also known as bar rack) are composed of parallel rods or bars, coarse screen
functions. Due to a large opening of usually 6mm to 150mm (as shown in figure 2) anything smaller
than this opening will pass through. Fine screen on the other hand employ perforated plate or wire
mesh, the use of this allows fine screens to prevent any solids larger than 6mm to pass through.
Finally micro-screens, operate on a microscopic level, only particulate matter smaller than 0.5
micrometers can pass through. (Metcalf and Eddy, 2014).
7
Figure 2:The classification of used Screens in wastewater treatment as preliminary stage (Metcalf
& Eddy, 2014)
Since the main purpose of the screen is to eliminate large object (e.g. logs of woods, tires, and
concrete blocks) in order to protect the pump and the mechanical equipment from damage, thus the
selected type should be coarse screen (Qasim, 2017). Since the number of population is over 20,000
(i.e. large wastewater treatment plant) and the wastewater has sludge, so the used type is coarse screen
(i.e. bar screen) is used (EPA, 1995). The hand cleaned coarse screen can only be used for small
wastewater pumping stations (Qasim, 2017); therefore, the mechanically cleaned coarse screen is
used.
As shown in Figure 2, there are four main types of mechanically cleaned coarse screen:
Chain-driven screen, reciprocating rake, catenary screen, and continues belt. To select the suitable
type of screen, it has to study the advantages and disadvantages of each types where it can be
demonstrated as following Table 2 (Metcalf & Eddy, 2014):
Table 2: The advantages and disadvantages of types of mechanically cleaned coarse screen
(Metcalf & Eddy, 2014)
Types of Screen Advantages Disadvantages
Chain-driven screen Short cleaning cycle.
Utilized to application with
heavy duty.
The moving parts are
submerged, so the
maintenance requires for
shut down the process and
8
& Eddy, 2014)
Since the main purpose of the screen is to eliminate large object (e.g. logs of woods, tires, and
concrete blocks) in order to protect the pump and the mechanical equipment from damage, thus the
selected type should be coarse screen (Qasim, 2017). Since the number of population is over 20,000
(i.e. large wastewater treatment plant) and the wastewater has sludge, so the used type is coarse screen
(i.e. bar screen) is used (EPA, 1995). The hand cleaned coarse screen can only be used for small
wastewater pumping stations (Qasim, 2017); therefore, the mechanically cleaned coarse screen is
used.
As shown in Figure 2, there are four main types of mechanically cleaned coarse screen:
Chain-driven screen, reciprocating rake, catenary screen, and continues belt. To select the suitable
type of screen, it has to study the advantages and disadvantages of each types where it can be
demonstrated as following Table 2 (Metcalf & Eddy, 2014):
Table 2: The advantages and disadvantages of types of mechanically cleaned coarse screen
(Metcalf & Eddy, 2014)
Types of Screen Advantages Disadvantages
Chain-driven screen Short cleaning cycle.
Utilized to application with
heavy duty.
The moving parts are
submerged, so the
maintenance requires for
shut down the process and
8
End of preview
Want to access all the pages? Upload your documents or become a member.
Related Documents
Waste Water Treatment: State-of-the-Art System for Efficient Contaminant Removallg...
|5
|1162
|153
Odor in Wastewater Management Systemlg...
|7
|549
|19