Perforating Pipe

8/10/2019 Perforating Pipe

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DESIGN OF PRESSURIZED LIQUID DISTRIBUTION SYSTEM FOR LANDFILL

LIQUIDS ADDITION AND AUGMENTATION

Xianda Zhao, Ph.D., P.E.

CTI and Associates, Inc., Brighton, Michigan USA

Morgan Subbarayan, P.E.CTI and Associates, Inc., Brighton, Michigan USA

Te-Yang Soong, Ph.D., P.E.

CTI and Associates, Inc., Brighton, Michigan USA

ABSTRACT

Whether a landfill facility is conducting a bioreactor operation with large-scale liquid injection

or simply recirculating site-generate leachate, achieving uniform liquid distribution in the waste

mass is always a critical operational goal. Several methods of liquid introduction have been adoptedby the industry. Of these methods, subsurface lateral injection lines (including perforated plastic

pipes) have become standard design for many landfill engineers. The subsurface lateral injection

lines not only provide for safe liquid injection, they also allow for the introduction of a large volume

of liquid even after the waste mass has reached its permitted grade.

Unfortunately, improperly-designed lateral injection lines may result in uneven liquid

distribution. Primary concerns associated with uneven distribution include: leachate outbreaks,

differential settlements, unstable working surfaces, and sometimes even slope instability.

This paper provides methodology for the design of subsurface lateral injection lines,

specifically the design of perforated pipes (pipe sizing, perforation sizing and the selection ofspacing between perforations). Essential design equations, design principle and criteria will be

presented. A design example will also be used to illustrate the step-by-step design procedures.

INTRODUCTION

During the lifespan of a landfill, moisture in the incoming waste as well as liquid entering the

waste mass (in forms of precipitation, snowmelt, surface runoff, and other liquid addition) generates

leachate. Leachate carries the characteristics of the waste constituents and needs to be properly

contained, collected, removed, treated, and ultimately disposed of safely, in order to protect human

health and minimize adverse effects to the environment. Due to the high cost of leachate treatmentand disposal, much research has been performed to find alternative uses for leachate that can reduce

amounts that must be removed from the landfill.

Since as-received waste typically still possesses additional moisture absorptive capacity, re-

introducing leachate back into the waste mass (commonly referred as leachate recirculation) offers

an effective way of reducing leachate treatment costs. The actual moisture absorptive capacity

remains in the waste mass (sometimes referred moisture deficit) varies greatly depending on the


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geographic location, climate, type of waste and other pertinent factors. For landfill sites that are

located in arid or semi-arid areas and for landfills that receive large amount of incoming waste

volume, the remaining moisture absorptive capacity can be very significant. Such large amount of

absorptive capacity represents an immense cost-saving potential for landfill owners and operators

due to the circumvention of leachate disposal and treatment. In fact, reintroducing collected

leachate is widely practiced in the municipal solid waste (MSW) landfills in the United Statesnowadays.

In addition to cost savings, re-introducing leachate offers additional advantages in the

operation of MSW landfills. For example, greater moisture content will increase waste compaction

therefore increasing the filling capacity and consequently, service life of the facility. Furthermore,

increased moisture promotes and accelerates biological decomposition of organic wastes, which will

yield more reusable volume. Ultimately, decomposed wastes are biologically-stabilized which

greatly reduces the long-term adverse impacts to human health and environment.

Recently, bioreactor landfills have been designed, constructed, and operated at a number of

commercial and municipal facilities throughout the United States. In bioreactor landfills, moisturecontent in the waste material is quickly increased to an elevated level to allow for the initiation of

biological decomposition processes at a relatively early stage of waste filling. To achieve this goal,

a large amount of liquid is generally required and in some cases, addition of supplementary liquid is

necessary. Possible sources of supplementary liquids include leachate from other sites, storm water,

wastewater (including biosolid and septage), commercial liquids, animal manure, and others.

Whether a landfill is conducting a bioreactor operation with large-scale liquid injection or

simply recirculating site-generate leachate, achieving uniform liquid distribution in the waste mass is

always a critical operational goal. Several methods of liquid introduction have been adopted by the

industry: surface spraying, infiltration ponds, subsurface injection via vertical wells, and subsurface

injection via lateral injection lines. Due to concerns such as nuisance, safety, and volume restrictionassociated with some of the methods, subsurface lateral injection lines have become standard

approach for many landfill engineers. The subsurface lateral injection lines not only allow for safe

liquid injection, they also allow for introduction of large volume of liquid even after the waste

mass has reached its permitted grade.

Unfortunately, improperly-designed lateral injection lines can result in uneven liquid

distribution, which will eventually lead to issues such leachate outbreaks, differential settlements,

unstable working surface, or even slope instability.

This paper provides design methodology for the design of subsurface lateral injection lines,

including pipe sizing, perforation sizing and the perforation interval determination. Essential designequations will be presented first, followed by the design principle and criteria and the recommended

design procedures. A design example will also be presented to illustrate the step-by-step design

procedures.

TYPICAL DESIGN AND COMMONLY SEEN ISSUES


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DESIGN METHOLOGY

Design Equations

The unit discharge rate (q) from each of the perforations is governed by the size of the

perforation and the static pressure at its respective location along the pipe:

2/1279.112 PdgPBAq == (1)

Where q = flow rate per perforation (gpm)

B = orifice coefficient, assumed as 0.60

A = area of orifice (in2)

g = gravitational acceleration (32.2 ft/s2)

P = pressure head over orifice (water column in ft.)

d = diameter of perforation (inch)

According to Bernoullis equation, total head at any given point in liquid under motion is the sum of

pressure, velocity and elevation heads:

Zg

VPh ++=

2

2

(2)

Where h = total head (feet)

P = pressure head (feet)

V = velocity (ft/sec)

g = gravitational acceleration (32.2 ft/s2)

Z = elevation head (feet)

Change of total head in pipes is primarily due to friction and other minor losses. Since perforated

pipes are typically constructed with straight sections with limited number of joints, minor losses are

generally considered negligible. Therefore, the friction loss along the pipe will determine thechange in total head. Friction loss in pipes can be calculation using Hazen-Williams equation as:

=

8655.4

85.185.1100002082.0

D

Q

CLhf (3)

Where hf = friction loss head (feet)

L = length of pipe (feet)

C = pipe friction factor (150 for HDPE pipes)

Q = flow rate in pipe (gpm)

D = nominal pipe size (inch)

Due to discharge at perforations, flow in perforated pipes varies along the pipe length (Figure 5).

Flow in perforated pipes can be obtained by summing discharges from all of the downstream holes:

=

=i

j

ji qQ1

(4)

Where Qi = flow in the pipe before perforation i (gpm)

qj = discharge rate at perforation j (downstream of i, gpm)


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n n-1 n-2 n-3 123

q1q2q3qn-3qn-2qn-1qn

LL

Q= Qn

d

D

Q1Q2Q3Qn-3Qn-2Qn-1

Figure 5 Flow Rate along Perforated Pipe

Friction loss in each section between two perforations can be determined as:

=

8655.4

85.185.1100

002082.0D

Q

CLh ifi (5)

Where L is the spacing between two adjacent perforations.

L can be calculated based on totalnumber of perforations (n) as:

1=

n

LL (6)

Based on the conservation of energy, the total head can be calculated as:

ifii

iii

i hzg

VPz

g

VPh +++=++= +

++ 1

2

11

2

22 (7)

For low velocity flow (less than 5 ft/sec), the kinetic head is generally very low (less than 0.4 ft) and

is typically neglected. For horizontal-placed pipes, pressure at an upstream perforation can be

determined as:

ifiihPP +=+1 (8)

The unit discharge rate at an upstream perforation can be calculated as:

+=+=+ 8655.4

85.185.1

22

1

100002082.079.1179.11

D

Q

CLPdhPdq iifii i (9)

The unit discharge rate at the end of the pipe (q1) can be calculated as:

1

2

1 79.11 Pdq = (10)

where P1is the pressure at end of the pipe.

Once the far-end pressure value (P1) and the far-end discharge rate (q1) are determined, unit

discharge rate for all perforations can be obtained using Equations (4) and (9). The entrance

pressure and the total flow rate will be utilized in the pumping system calculations. The above-listed

procedures can be readily incorporated in spreadsheet programs. However, a trial-and-error process

may be required to match the pumping system requirements.

Design Principles


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The ratio of unit discharge rates between the first and the last perforations can be used to

quantify the uniformity of liquid distribution. In other words, if the ratio for a given perforated pipe

design is closer to unity, the liquid is more evenly distributed. As the examples illustrated in Figures

3 and 4, a satisfactory ratio of 1.2 can be found in the pressurized pipe design whereas a ratio

greater than 10,000 (which is clearly inadequate) can be seen in the low pressure design.

Note that the variation in the unit discharge rates is caused by the pressure change in the pipe

and the relative change of the discharge rate can be determined as:

n

n

n

n

P

PP

q

qq 11 =

(11)

Deriving from Equation (11), a correlation between the change in discharge rate and the change in

pressure can be developed as:2

2

=

nnn q

q

q

q

P

P (12)

where q = qn - q1

P = Pn - P1

The correlation between the change in pipe pressure and the change in unit discharge rates can be

established using Equation (12), see Figure 6.

0%

10%

20%

30%

40%

50%

60%

0% 5% 10% 15% 20% 25% 30%

Change in Unit Discharge Rate

ChangeinEntrancePressure

Figure 6 Correlation between Change in Unit Discharge Rate and Change in Entrance Pressure

As previously discussed, pressure change in pipe is primarily due to friction loss:


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=

=1

1

n

i

fihP (13)

The total friction loss in perforated pipes can be estimated using Equation (14):

FPP*= (14)

Note that F is a correction factor and P* is the friction loss calculated for a solid wall pipe

having same diameter, length, and total flow rate. Equations (15) and (16) depict the determinations

for F and P*, respectively. Note that the correlation shown in Equation (15) is established

based on an assumption that the change of unit discharge rate is less than 20%.

( ) 85.1

1

1

85.1

1 nn

i

F

n

i

=

= (15)

=

8655.4

85.185.1

* 100002082.0D

Q

C

LP n (16)

As shown in Equation (15), the correction factor F is a function of the number of

perforations along the pipe. As the number of perforations increases, the correction factor decreases

and ultimately levels off at a value of 0.36 (Figure 7). For most design with more than 100 holes

along the pipe, a correction factor F of 0.36 can be used.

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0 50 100 150 200

Number of Hole on Perforated Pipe (n)

F=hf/hf*

Figure 7 - Friction Loss Correction Factor for Perforated Pipe

Finally, by combining and rearranging Equations (14) and (16), the required pipe diameter can be

determined as:3802.02055.0

6193.1

=

C

Q

P

LFD n (17)

Design Procedures


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Uniform liquid distribution along the perforated liquid injection pipes can be achieved by

proper selection of pipe diameter, size of perforations, and spacing between perforations. A

systematic procedure can be presented in a flowchart format as shown in Figure 8. Individual steps

will be discussed in detail in the following subsections.

Calculation

Total flow rate (Q)

Select

Perforation diameter (d) and unit discharge rate (q)

Calculation

Pressure difference between first and last perforationsEq. 17 and Fig. 7

Calculation

Determine pipe diameter

InputPipe length (L) and linear discharge rate (q*)

InputAllowed variation

for unite discharge rate

DesignPumping system

and entrance pressure

Calculate

Number of perforations (n) and spacing (L)

Satisfied?

YESNo

Satisfied?

Output

Perforation diameter (d), spacing (L),pipe diameter (D) and entrance pressure (Pn)

YESNo

Changelineardischargerate(q*)

Figure 8 Design Procedure Flowchart

1. Selecting input parameters

Length of the perforated pipe (L) is generally determined by the dimensions of the waste lift

where the injection line is to be installed. To avoid leachate outbreaks on refuse slopes, the

injection lines should not be located within 50 ft of the exterior waste slope. The injection lines

are typically spaced horizontally 50- to 150 ft with a vertical interval of 20 ft.

The linear discharge rate (q*) should also be pre-selected. The actual value is controlled by the

infiltration capacity of the waste. Reinhart and Townsend (1998) suggested that injection rates

between 25- to 50 gpd/ft are adequate. To further promote lateral distribution and minimize

biological clogging, intermittent liquid injection should also be considered (Reinhart and

Townsend, 1998). Generally speaking, selecting linear discharge rate between 0.2- to 0.4 gpm/ft

seems appropriate.

2. Determining total flow rate


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The total flow rate (Q) can be calculated as:

*LqQ= (18)

Note that this total flow rate is identical to the entrance flow rate (Qn).

3.

Determining the entrance pressure

Based on the required flow rate, the pumping and forcemain analyses can be conducted and

subsequently, the entrance pressure can be determined. Since the procedure is a common

practice for hydraulic engineers, no detailed discussed will be provided herein. Note that,

however, the entrance pressure should be less than 5 psi (11.5 ft of water column) to avoid

excessive increase in pore pressure which may adversely impact the slope stability (Bachus, et

al., 2004).

4. Selecting size of perforations and calculating the unit discharge rate

As long as the clogging potential is avoided, smaller perforation sizes are preferred for better

liquid distribution. Unit discharge rate can be determined based on the entrance pressure and theperforation size using Equation (1). See Figure 9 for typical correlations.

0

2

4

6

8

10

12

14

16

18

20

0 2 4 6 8 10 12

Unit Discharge Rate (gpm)

Pressure(ft)

d=1/8 in

d=3/16 in

d=1/4 in

d=5/16 in

d=3/8 in

d=7/16 in

d=1/2 in

Maximum Recommended Entrance Pressure 11.5 ft

Figure 9 Unit Discharge Rate vs. Entrance Pressure for Different Sizes of Perforation


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5. Calculating number and spacing of perforations

Number of perforations (n) can be calculated as:

q

Qn= (19)

Spacing between perforations (L) can be calculated as:

1=

n

LL (20)

In most cases, the number of perforations (n) should be greater than 50 (i.e., q/Q< 2%) and

spacing between perforations (L) should be less than 2% of the length of perforated section (L).

If these requirements are met, the design procedure can continue. Otherwise, a new perforation

size shall be selected and Step 4 shall be repeated until all design requirements are met.

6. Selecting the allowable variation for unit discharge rate and calculating the corresponding

allowable pressure difference

Friction loss along the perforated pipe can be minimized but can not be completely eliminated.

In other words, some differences in the unit discharge rate will always exist. A tolerable

variation should be pre-determined for each project. To maintain a reasonable pipe size, the

tolerance (q/qn) can be set between 10% and 20%. The corresponding variance in pressure

between the two extreme ends of the perforated pipe can be calculated using Equation (12) or

Figure 6. Subsequently, the allowable pressure drop (P) in the perforated pipe can be

calculated based on the entrance pressure.

7. Determining pipe size

Size of the perforated pipe can be determined using Equation (17), or Figure 10, based on the

unit friction loss and total flow rate. Unit friction loss can be calculated by dividing the

allowable pressure drop (P) by the length of perforated pipe (L). Note that the correction factor

(F) can be obtained from Figure 7. If the number of perforation is greater than 100, the value of

F can be assumed as 0.36.

The diameter of the perforated pipe should be rounded to higher standard size. If the result is not

satisfactory, a new linear discharge rate can be selected and the entire design procedure can be

repeated. The following example illustrates the use of the above-mentioned design procedures.

DESIGN EXAMPLE

A landfill plans to install several leachate recirculation lines on the active surface. Based on

the geometry of the lift boundary, three subsurface leachate injection lines will be installed (Figure

11). Leachate will be pumped from the storage facility, through a forcemain, into a control vault

located at the base of the northeastern slope. Designated transmission lines will direct leachate from

the vault into the perforated pipes. Only one line will be used during each injection event.


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Using the recommended procedures discussed earlier, the following design can be formulated:

1. Selecting input parameters

Line Length

(ft)

Linear Discharge Rate

(gpm/ft)

1 600 0.15

2 300 0.30

3 150 0.60

Note that the selected linear discharge rates will result in similar total discharge rate for each

of the 3 injection lines.

2. Determining total flow rate using Equation (18)

Line Linear Discharge Rate

(gpm/ft)

Total Flow Rate

(gpm)

1 0.15 90

2 0.30 903 0.60 90

3. Determining the entrance pressure

To avoid excessive velocity and friction the loss, flow rate will be controlled below 100

gpm. Note that the entrance (immediately before the first perforation) pressures listed below

were determined via separate forcemain analyses. Differences in the calculated entrance

pressures are results of the different lengths in the transmission pipes between the control

vault and the perforated pipes.

Line Entrance Pressure(Water column in ft.)

1 2.5

2 3.4

3 4.3

4. Selecting size of perforations and calculating the unit discharge rate

A perforation size is pre-selected as 3/16 inches in diameter. With that, the unit discharge

rates can be calculated using Equation (1). Results of the unit discharge rates are listed

below:

Line Entrance Pressure

(Water column in ft.)

Diameter of

Perforation (inch)

Unit Discharge Rate

(gpm)

1 2.5 3/16 0.66

2 3.4 3/16 0.76

3 4.3 3/16 0.86

5. Calculating number and spacing of perforations

For Line 1, the number of perforations can be calculated as:


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13766.0

90==

q

Qn

Subsequently, the spacing between perforations (L) can be determined as:

ftn

L

L 40.41137

600

1 ==

For ease of construction, the spacing is set to 4.5 ft, which will result in a total of 134

perforations. Same procedures can be repeated for Lines 2 and 3. Results for all three lines

are listed below.

Line Length

(ft)

Total Flow Rate

(gpm)

Unit Discharge Rate

(gpm)

No. of

Perforations

Spacing

(ft)

1 600 90 0.66 135* 4.5

2 300 90 0.76 121 2.5

3 150 90 0.86 101 1.5

Note: *Spacing for the last two perforations at end of the pipe is 1.5 ft.

6. Selecting the allowable variation for unit discharge rate and calculating the corresponding

allowable pressure difference

The allowable variation in the unit discharge rate is pre-selected as 20%. With that, the

allowable pressure drop can be calculated using Equation (12).

Line Variation in Unit

Discharge Rate

Entrance Pressure

(Water column in ft.)

Allowed Pressure Drop

(ft)

1 20% 2.5 0.90

2 20% 3.4 1.22

3 20% 4.3 1.55

7. Determine pipe size

Diameter of the pipe can be calculated using Equation (17). The correction factor F can be

selected using Figure 6. Since the numbers of perforations are greater than 100 for all three

lines, an F-value of 0.36 will be used for the pipe sizing calculations for all lines.

Line Length

(ft)

Total Flow

Rate

(gpm)

Allowed

Pressure Drop

(ft)

No. of

Perforations

Pipe Diameter

- Calculated

(inch)

Pipe Diameter

- Selected

(inch)

1 600 90 0.90 135 4.11 4

2 300 90 1.22 121 3.35 4

3 150 90 1.55 101 2.77 3

Note that the pipe diameter can also be selected based on the unit friction loss and the total

flow rate using Figure 10.

8. Results verification

Based on output of the design procedures (i.e., pipe size, perforation size and spacing,


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entrance pressure, etc.), three simulations were executed using a spreadsheet program that

incorporates Equations (4), (9) and (10). Results of the simulation illustrate the predicted

discharge rate at each of the perforations along the entire perforated sections, see Figure 12.

Further examining the results shown in Figure 12 reveals that the actual variations of unit

discharge flow rates (changes between the first and the last perforations) are 18%, 7% and10% for Lines 1, 2 and 3, respectively. All of which are less than the pre-selected maximum

allowable variation (20%, see Step 6 in the previous section). Therefore the design is

verified as appropriate. Otherwise different pipe sizing may be considered and the

procedures can be repeated until the result is successfully verified.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 100 200 300 400 500 600

Length from distal (ft)

Flow

perHo

le(gpm)

Line 1 Line 2 Line 3

Distance from the end of pipe (ft)

UnitDischargeFlo

w

Rate(gpm)

Figure 12 Predicted Discharge Flow Rate along the Perforated Pipes (Example Problem)

MAXIMUM PERFORATION LENGTH

There is a theoretical length limitation to the perforated section of any liquid injection pipe. In

other words, one set of design parameters (i.e., pipe size, perforation size and spacing, allowable

variation in unit discharge rate and entrance pressure, etc.) will not offer same performance when

different perforated lengths are used.

To demonstrate this fact, two design charts were developed and shown in Figures 13 and 14.

Both charts assumed a 5-ft spacing between perforations and an entrance pressure of 5-ft of water

column. Additionally, both charts correlate the perforation size with the maximum pipe length and

the corresponding discharge flow rates for different pipe sizes. The only difference between Figures

13 and 14 is the allowable variation among the unit discharge rates a maximum variation of 10%

and 20% were assigned in Figures 13 and 14, respectively.


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0

200

400

600

800

1000

1200

1400

1600

1800

2000

1/8 3/16 1/4 5/16 3/8 7/16 1/2

Orifice Diameter (in)

MaxPipeLength(ft)

D=6 in

D=5 in

D=4 in

D=3 in

D=2 in

0

50

100

150

200

250

300

350

400

1/8 3/16 1/4 5/16 3/8 7/16 1/2


TotalFlowrate(gpm)

D=6 in

D=5 in

D=4 in

D=3 in

D=2 in

Figure 13 Correlation between Size of Perforation, Maximum Pipe Length and Discharge Flow

Rates for Different Pipe Sizes (maximum allowable difference on unit discharge rate = 10%)


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0

500

1000

1500

2000

2500

1/8 3/16 1/4 5/16 3/8 7/16 1/2


MaxPipeLength(

ft)

D=6 in

D=5 in

D=4 in

D=3 in

D=2 in

0

50

100

150

200

250

300

350

400

450

500

1/8 3/16 1/4 5/16 3/8 7/16 1/2


TotalFlowrate(gpm)

D=6 in

D=5 in

D=4 in

D=3 in

D=2 in

Figure 14 Correlation between Size of Perforation, Maximum Pipe Length and Discharge Flow

Rates for Different Pipe Sizes (maximum allowable difference on unit discharge rate = 20%)

As clearly indicated in Figures 13 and 14, all of the design parameters are interrelated and notypical perforated pipe design is universally applicable. Design engineers should have a thorough

understanding of both the project requirements and the design mechanism in order to provide an

effective design of liquid injection system.


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PARAMETRIC ANALYSES AND OBSERVATIONS

This section presents the results of a series of parametric analyses. The parametric analyses

were designed to demonstrate the sensitivity embedded in various design parameters in the design of

perforated liquid injection pipes. Four critical design parameters including size of perforation, size

of pipe, spacing between perforations, and the entrance pressure were evaluated. Table 1

summarizes the results of the parametric analyses and the authors observations and comments.

Table 1 Results of the Parametric Analyses with Observations

Design

Parameter

Range of

Variation

Graphical

ResultsObservations/Comments

Perforation size 1/8- to 1/2

in diameter

Figure 15 Smaller perforations allow for longer liquidinjection distances.

However, total flow rate will decrease when smallerperforations are used, which implies a longer

injection period during each injection event.

Maximum injection distance varies between 80- to540 ft within the range of analyses.

Pipe size 2- to 6 inch

in diameter

Figure 16 Larger pipes allow for longer injection distances.Maximum injection distance varies between 100- to

710 ft within the range of analyses.

Perforation

spacing

1- to 10 ft. Figure 17 Maximum injection length can be increased by usinglarger perforation spacing.

Due to potential clogging of perforations, theauthors recommend a maximum of 10-ft spacing

between perforations.

Entrance

pressure

1 to 10 ft ofwater

column

Figure 18 Entrance pressure has only slightly influence on themaximum injection length.

However, flow rate does increase with higherpressure, which implies a shorter injection period

during each injection event.

CONCLUSIONS

One of the essential goals when designing liquid injection lines is to uniformly distribute liquid

into the waste mass. According to the information documented in literature and the authors past

project experiences, the most effective injection method is the use of lateral injection lines (trenchesor mounds). However, an improperly-designed lateral injection line can still result in an uneven

liquid distribution, which may eventually lead to issues such leachate outbreaks, differential

settlements, unstable working surface, or even slope instability.

A systematic design procedure is recommended and presented in this paper, following which

will allow the engineers to properly select system parameters (e.g., pipe size, perforation size,

perforation spacing, and entrance pressure) and meet their project-specific requirements.


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0

100

200

300

400

500

600

1/8 3/16 1/4 5/16 3/8 7/16 1/2

Hole Size (inch)

MaximumL

ength(

ft

0

20

40

60

80

100

120

TotalFlowrate(gpm

Max Pipe Length Flowrate

Entrance Pressure = 5 ft W.C.

Pipe ID = 3 inches

Perforation: 1 hole every 5 ft

Figure 15 - Effect of Perforation Sizes (q/q =10%)

0

100

200

300

400

500

600

700

800

2 3 4 5 6

Pipe ID (inch)

MaximumL

ength

(ft

0

30

60

90

120

150

180

210

240

TotalFlowrate(g

pm)

Max Pipe Length Flowrate


Perforation: 1 hole every 5 ft

Hole size = inch

Figure 16 - Effect of Pipe Sizes (q/q =10%)


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0

50

100

150

200

250

300

350

400

450

1 2 3 4 5 6 7 8 9 10

Spacing between Holes (ft)

Maximum

PipeLength(ft)

dq/q=10% dq/q=20%


Hole size = inchPipe ID = 3 inch

0

20

40

60

80

100

120

140

160

1 2 3 4 5 6 7 8 9 10

Spacing between Holes (ft)

TotalFlowrate(gpm)

dq/q=10% dq/q=20%

Figure 17 - Effect of Perforation Spacing

0

50

100

150

200

250

300

350

400

450

1 2 3 4 5 6 7 8 9 10

Entrance Pressure (ft W.C.)

MaximumP

ip

eLength(ft)

dq/q=10% dq/q=20%

Hole size = inch

Spacing = 5 ft

Pipe ID = 3 inch

0

20

40

60

80

100

120

140

160

1 2 3 4 5 6 7 8 9 10

Entrance Pressure (ft W.C.)

TotalFlowrate(gpm)

dq/q=10% dq/q=20%

Figure 18 - Effect of Entrance Pressure


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REFERNCES

Reinhart, D.R. and T.G. Townsend (1998). Landfill Bioreactor Design and Operation, published

by Lewis Publishers, New York

Bachus, R.C., M.F. Houlihan, E. Kavazanjian, R. Isenberg, and J.F. Beech (2004). Bioreactor

landfill stability: key considerations, in MSW Management, September/October,

http://www.mswmanagement.com/mw_0409_biostability.html

Documents

Perforating Pipe