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Wastewater Treatment

Techniques for pumping

sludge

Paul A. Nelsen

ITT Flygt Corporation

Marketing & Business Development

Manager

paul.nelsen@itt.com


Choosing the “right” pump…

….is like choosing the right golf club

at the Augusta National


…is like selecting the correct golf

club to match the conditions!

•Transfer (Driver)

•Metering (Putter)


Pumping Sludge

• Properties or the rheology of sludge

• What type of pump do I use?

• Advantages & Disadvantages

• Progressing Cavity

• Rotary Lobe

• Special Centrifugal

• Practical examples of sludge pumping


What’s your application?

− Return Activated

− Waste Activated

− Primary

− Supernatant

− Scum

− Digester feed

− Imported

− Centrifuge feed

Belt press feed


Sludge video #1


Sludge video #2


Sludge video #3


Sludge video #4


To select a pump, you must know

the following properties:

1. Performance

a. Flow rate

b. Discharge Pressure

c. Suction Pressure (NPSHa)

2. % Dry Solids

3. Solid size

4. Abrasiveness

5. Do you need to Transfer & Meter Sludge?


Viscosity

• Viscosity, property of a fluid that tends to prevent it from

flowing when subjected to an applied force. The tenacity

with which a moving layer of fluid drags adjacent layers of

fluid.

Viscosity is the fluid property responsible for friction.


Viscosity as a function of shear rate

Viscosity is the property of a fluid that prevents it from flowing when

subjected to an applied force.

The tenacity with which a moving layer of fluid drags adjacent layers of fluid


NEWTONIAN

• Viscosity decreases

with the rate of shear.

Non NEWTONIAN

“thixotropic”

NON NEWTONIAN

“dilatant”

• Viscosity increases with

the rate of shear.


Measuring viscosity

Viscosity testing using both a Searle & Hache viscometer


Municipal wastewater sludge

• Municipal wastewater sludge is a Non-Newtonian Fluid.

• Sludge can start out at 300,000 cps and with the addition

of shear can come down to less then 300 cps.

• A centrifugal pump can not pump a viscosity >350 cps

and a sludge density of >6-8 percent.

Beware: water treatment sludge uses ALUM which is dilatant or

shear thickening.


Why do we

need to know

the type of

sludge?


What is the Rheology of the

sludge?

Things we need to know…

DS content?

Are there flocculants/polymers?


We hired a

team of

scientists

and

technicians

to perform

field tests

The test rig consisted of a tank, a dry-mounted pump N-

3127HT and a 4 inch flow loop with a flow meter, two pressure

transmitters and a control valve.


Laboratory & Field test results

• Pump derating:

• Performance curve:

- 1% per % DS (H)

• Power requirement:

Head - [m]

20

15

10

5

1 - 8 %

1 – 8 %

+ 1% per % DS

0

0 50 100 150 200 0

Flow - [m³/h]

5

4

3

2

1

Power - [kW]


Pipe dimension 1%

DS

4”

6”

8”

We charted the results

0.01 1)

1) 44 gpm 2) 132 gpm

0.01 2)

2%

DS

3%

DS

4%

DS

5%

DS

6%

DS

7%

DS

0.0. 0.02 0.05 0.1 0.15 0.25 0.35

0.01 0.01 0.01 0.02 0.04 0.07 0.11 0.17

0.01 0.01 0.01 0.01 0.02 0.04 0.06 0.09

8%

DS

0.01 0.04 0.08 0.15 0.25 0.38 0.54

0.01 0.01 0.01 0.03 0.06 0.11 0.17 0.24

0.01 0.01 0.01 0.02 0.03 0.06 0.1 0.14

Pressure loss estimation (ft/ft pipeline)


Things we learned:

• When designing system

• for DS>4% start-up condition must be considered (Δp>t x 4L/d)

• DS change of 2.5% → 4.5%, yield stress increases by factor of 5

• DS change of 2.5% → 8.5%, yield stress increases by factor of 30

Definition: Yield point, is defined in materials science as the stress at

which a material begins to plastically deform.


“TR185”

and

“Frost”


• Hydraulic gradient

• Pressure gradient

dP

dl

i

TR 185



2

V

g D

2

2


V

D

f

2

f

where,

i= hydraulic gradient (m/m)

V= average velocity (m/s)

g= gravity acc. (m/s 2 )

D= pipe diam. (m)

ρ= density (kg/m 3 )

f= Fanning friction factor

dP/dl= pressure gradient


TR 185

Reynolds number

R


Flow parameters:


V

D 8 V




e L

D

L – laminar viscosity (Nsn/m2)

n – power law index

( 1n

)

where,

ρ= density (kg/m 3 )

V= av. velocity (m/s)

D= diameter (m)

L= laminar viscosity

(Ns n /m 2 )

n= power law index


TR 185

h


where,

2

V

F

K

2

g

K= point loss factor

Fittings-loss factor

1000

Empirical relation between fitting-loss factor and

100

10

1

0,1

Reynolds number

F

1

1 10 100 1000 10000 100000

Reynolds number

2000

Re


Pump de-rating

• Performance curve: -

1% per % DS (H)

• Power requirement: +

1% per % DS (kW)

Head - [m]

20

15

10

5

1 - 8 %

1 – 8 %

0

0 50 100 150 200 0

Flow - [m³/h]

5

4

3

2

1

Power - [kW]


Flygt’s Sludge Module within FLYPS.

Flyps pump selection program to derate

pump curves.

Also, FLYPS can help you evaluate the

added losses experienced through

pipe work and fittings when pumping

sludge, as well as correct the motor

power data.


Enough about the fluids!

Let’s talk pumps!!!


Types of pumps used for “Thickened

sludge”

Diaphragm

Progressing

Cavity

Pumping

sludge

Rotary

Lobe

Special

Centrifugal


WEAR & TEAR!!!!!!!!!!!!!


What’s really important to WWTP?

• Reducing Operations Budget

Increase reliability (solve clogging issues)

Increase resistance to wear

• Reduce Energy Costs

• Flood-proof Protection

(i.e. recent floods in Nashville & Atlanta)


Positive displacement pumps are..

• Those in which energy is imparted to the liquid in a fixed

displacement volume.

Dynamic pumps are…

Dynamic pumps impart energy to the liquid by means of

an impeller or propeller.

This force is converted to pressure as the fluid is pushed

against the pump casing.


PD versus Centrifugal pumps

• Positive displacement or “PD” pumps

PD pumps are good metering devices.

PD pumps self-prime themselves.

• will supply as much pressure as needed until

the rated motor horsepower is exceeded.

• Centrifugal pumps

Centrifugal pumps do not meter.

Centrifugal pumps will not self-prime

• Need flooded suction

Flow rate will change as head pressure changes

(variations in suction or discharge pressure will

change flow rate).


Why use a Centrifugal pump?

• Low initial cost (< $$$’s)

• Lower cost of operation (< $$$’s)

• Less maintenance

• Easy maintenance

• Less energy consumption

• Reliable Operation

• Less chance of clogging

• More durable materials

• Less components to break

• No gear box required


Progressing Cavity Pumps


Manufacturers of “PC” pumps

• Moyno

• Monoflo (Mono)

• Netzsch

• Allweiler

• Seepex

• Tarby


Progressive Cavity Pumps

A single helix rotor turning in a double helix stator creating a

progressive cavity as the rotor turns


Advantages

•Pressures to 400 psig

•Pulls suction to 28 in-Hg V

•Metered flow

•Low shear

Disadvantages

•Will not run dry

•High starting torque

•Must run 180 rpm or less

•Requires a macerator

•Costly repairs & difficult to rebuild in place

•Liquid wants to be 200-300 cps viscosity or greater

Progressing Cavity

•Wears 3-4 times faster than a centrifugal pump in hard iron

•Typical WWTP application exposes mechanical seal to full discharge pressure


Failure points…


Rotary Lobe Pumps


Manufacturer’s of Rotary Lobe pumps…

•Vogelsang

•Boerger

•LobePro

•Alfa Laval

•Swaby Lobeline

•Netzsch


ROTARY LOBE Advantages

•Metered flow rate

•Pressures to 90 psig (really 40-50 psig)

•Runs dry for 5-10 minutes

•Compact

•Low shear pumping

•Low pulsations with screw rotor design

•Runs in either direction

Disadvantages

•High maintenance (3-4 times Npump)

•Expensive initial & repair costs

•High wear due to slip

•Not rag friendly, requires a macerator

•Requires gearbox running 180 rpm or less

•High starting torque


Failures…


FLYGT A-C Series

NS Non-clog Pumps


NON-CLOG PRODUCT

FEATURES

Tangential Discharge for ease of

Solid passing Capability. Discharge

Nozzle can be rotated to suit any one

of 8 discharge positions

Packing, Single , Double

Mechanical seal, or

Dynamic seal available

Back pull-out design eliminates

need to remove casing from piping

Horizontal and vertical mounting

arrangements available

Handhole or Clean-out port is standard on

casing (and suction nozzle when applicable)

Standard Gauge Connections

Standard 2-vane impellers.

Available in either CW or

CCW rotation

Close tolerance stainless steel

impeller wear ring and suction

cover wear plate combination to

provide high and easily renewable

operating efficiencies

Tapered shaft/impeller fit (will

not loosen and hence reduces

vibration)

Standard Casing Drain & Vent


Non-clog impeller


Non-clog Pumps


•Advantages

Centrifugal Recessed Impeller

•Slurry design

•Handles large solids

•Minimal contact with solids

•Quiet operation

•Semi-clog resistant

•Disadvantages

•Does not meter flow

•Very low efficiency

•Requires special materials


RECESSED IMPELLER or Vortex

Spherical

Solid Size…


Recessed

Impeller

Grit Pumps


Centrifugal Screw Pump

Vertical leading edge which grabs rags

Advantages

•Solids handling

•Smooth flow

•Efficient to 80 percent

Disadvantages

•High initial cost

•Requires special materials

•Not a metering pump

•Tough to manufacture & balance

•Clogs at vertical leading edge

•Very long shaft overhang causing shaft

deflection

•premature bearing failure and

contact/interference to suction cover


Flygt N-Pump

•Advantages

•Solids Handling to 6-8 percent

•Clog resistant (Back swept leading edge)

•Cutter grove in volute “Insert ring” tears

solids

•Efficient operation

•Small, compact design

•Center-line discharge

•Disadvantages

• will not become air bound

•Does not meter (without FMC & VFD)

•Requires special materials

•Must be installed in the NZ configuration


WEAR: Cast iron impeller & insert ring


Advantages

Centrifugal CHOPPERS

• Heavy duty design

• Chops solids to small sizes

• Reliable operation until cut bar wears

Disadvantages

Inefficient design

• High wear on cutter bar

• Clogs with minimal wear on cutter bar


FLYGT “Chopper” pumps

Advantages

• Heavy duty design

• Chops solids to small sizes

• Modular design

• Hard iron 25% Cr

• Guide pin

Cast Iron Impeller

Disadvantages

• Efficiency drops 15-20 percent over Npump

• Does not meter

• Requires special materials

Cast Iron Insert ring Hard-Iron Insert ring

Hard-Iron Chopper ring

Pump housing

Hard-Iron Impeller


Pump selection recommendations

Flow (gpm)

30

Primary

sludge

removal

RAS

WAS

Digested

sludge

N-pump, first choice

PC-pump, first choice

Thickened

sludge

Dewatered

sludge

PC-pump,

first choice

Global market (MUSD/Year)


Let’s talk clogging…


Must handle rags!


…or these modern day clogging headaches


What is the efficiency of a clogged pump?

•NP 3127 impeller 488

•Pump after 5 years of operation

•Never Clogged !


JEA – Jacksonville, Florida


Practical examples of pumping

sludge

•Oak Ridge, TN.

•Tybee Island, GA.


Oak Ridge, TN


Tybee Island, GA

Flygt replaced two 25 hp PC pumps with two 5hp

NT3102-465 pump!

Application = RAS


Summary

If it flows, use gravity.

If gravity does not work… use a centrifugal pump.

Lower Life Cycle Cost (LCC)

A centrifugal pump can not pump a viscosity

>350 cps and a sludge density of >8 percent.

Keep pipe work simple with short suction line

constant diameter

no bends or elbows


Paul A. Nelsen

Marketing & Business Development Mgr

FLYGT Products

paul.nelsen@itt.com


• What’s really important to this market?

• Selling against competing technologies:

• Sludge Pumps

• Reciprocating

• Progressing Cavity

• Rotary Lobe

Influent Pumps

• Archimedes Screw Pumps

• Miscellaneous

• Cutter pumps

Agenda

• Presenting ITT’s Sludge Handbook


What’s really important to this customer?

• Reducing his Operations Budget

Increase reliability (solve clogging issues)

Increase resistance to wear (3-4 times the life)

• Reduce Energy Costs

• Flood-proof Protection

(i.e. recent floods in Nashville & Atlanta)


But to properly select a pump,

you must know the following properties:

Performance expectations

a. Flow rate

b. Discharge Pressure

c. Suction Pressure (NPSHa)

d. % Dry Solids

e. Does customer need to Transfer & Meter Sludge?


It’s like choosing the right golf club….

•Transfer (Driver)

•Metering (Putter)


Types of pumps used for sludge

Plunger,

Double Disc,

&

Diaphragm

Progressing

Cavity

Pumping

sludge

Rotary

Lobe

Centrifugal


Positive displacement pumps are..

• Those in which energy is imparted to the liquid in a fixed

displacement volume.

• Such as a casing or a cylinder, by the rotary motion of gears,

screws or vanes, or by reciprocating pistons or plungers.

Dynamic pumps are…

Dynamic pumps impart energy to the liquid by means of

an impeller or propeller.

This force is converted to pressure as the fluid is pushed

against the pump casing.


PD vs. Centrifugal pumps

• Positive displacement or “PD” pumps

PD pumps are good metering devices.

PD pumps self-prime themselves.

PD pumps will supply as much pressure as needed until

the rated motor horsepower is exceeded

• Centrifugal pumps

× Centrifugal pumps do not meter.

× Centrifugal pumps will not self-prime

× Need flooded suction

× Flow rate will change as head pressure changes

(variations in suction or discharge pressure will change flow rate)


Why use an Npump?

• Lower initial cost (< $$$’s)

• Lower cost of operation (< $$$’s)

• Less maintenance

• Easy maintenance

• Less energy consumption

• No Macerator required

• Reliable Operation

• Eliminates potential for clogging

• More durable materials

• Less components to break

• No gear box required


Competing Technologies


Plunger Pumps


How does a Plunger pump work?


Manufacturers of Plunger pumps

•WASTECORP.

•Komline-Sanderson

•Carter Pumps Inc.


Easy to Maintain????


Here’s a “typical” parts list…


Advantages

• Positive displacement

• Self priming

• Meters flow

• Flow rate is not system head

dependent

• Flow rate is not sludge

concentration dependent

• Easy clean out capability

• Low cost of maintenance???

Plunger Pumps

Disadvantages

• High Capital Cost

• High Maintenance

• Lots &Lots of Parts

• Packing Leaks

• Must lubricate Babbit that

drives plungers

(2-3 drops/min = 1 quart/day)

• Very Messy


Existing TWAS Pump


New TWAS Pump

• NT3102 – 5hp was installed in 2002.

• Empties tank in less than a third of the time it took the previous pump.


Double Disc & Diaphragm Pumps


Manufacturers of Disk or Diaphragm pumps

• Penn Valley

• SSP Alfa Laval

• Dorr Oliver ODS

• Carter Pumps

• Gorman-Rupp


Operating Principle

The Double Disc is based on a “Free Diaphragm”

technology, the pump utilizes a unique principle of

operation where the discs perform the duties of both

diaphragm and valve.

Suction Cycle Discharge Cycle


Operation sequence of Diaphragm pumps


Features & Benefits

Repair-in-Place design w/ hinged housings

Only 5 wetted components

Self-priming with high suction lifts

Seal-less design, no packing or mechanical seals

No seal water required

Runs dry without damage

No check valves, no fouling problems

Handles up to 3/4” solids

Two (2) year warranty


Do It Yourself with genuine Double Disc parts.


Double Disc & Diaphragm Pumps

Advantages

• Simple, rugged design

• Easy maintenance

Disadvantages

• High purchase price

• Frequent maintenance

• Flexure life = 400,000 cycles

• large pulsations w/o dampeners

• Do not handle bottle caps


Midland, Texas – Diaphragm pump

• Eight Gorman-Rupp pumps being powered by six – 7.5 to 10hp compressors

• Efficiency goes from 100% theoretical to 20-22% because of high cost for making air.


Progressing Cavity Pumps


Manufacturers of “PC” pumps

• Moyno

• Monoflo (Mono)

• Netzsch

• Allweiler

• Seepex

• Tarby


Progressive Cavity Pumps

A single helix rotor turning in a double helix stator creating a

progressive cavity as the rotor turns


Advantages

•Pressures to 400 psig

•Pulls suction to 28 in-Hg V

•Metered flow

•Low shear

Disadvantages

•Will not run dry

•High starting torque

•Must run 180 rpm or less

•Requires a macerator

•Costly repairs & difficult to rebuild in place

•Liquid wants to be 200-300 cps viscosity or greater

Progressing Cavity

•Wears 3-4 times faster than a centrifugal pump in hard iron

•Typical WWTP application exposes mechanical seal to full discharge pressure


Failure points…


6,000

5,000

4,000

3,000

2,000

1,000

0

Primary Sludge

• 3-5% Dry Solids

• Transfer 360 ft, 30ft Static

• Pumps Start with Flooded Suction

• Then Run on Suction Lift

• $4000 Savings – per pump/yr.

Capex Energy Spares Labor Total

P C Pump

N Pump

Saving


Digester Recirculation

• Replaced existing “PC” pumps

• Pumps run 24/7 with minimal spare parts usage

• 8-9 degF rise in digester temperature (82 to 91 degF)

(Less energy input into heat exchanger)

• Reduced cost of ownership


Digester Recirculation

• Digester Recirculation Sludge ~ 5% DS

• Very Raggy, existing pumps block daily

• Expensive to Repair ~ $9500

• Digester Temp. 9 o F Higher

• Three Pumps Installed in Total

• Process down-time eliminated!


Replaced 25 hp PC pumps with 5hp Npumps

•Trial Pump for RAS Application

(immediately purchased a 2 nd pump)

•Repaired PC pumps 2-3 times/yr.

•3 yrs - never touched their Npump


Rotary Lobe Pumps


Manufacturer’s of Rotary Lobe pumps…

•Vogelsang

•Boerger

•LobePro

•Alfa Laval

•Swaby Lobeline

•Netzsch


ROTARY LOBE Advantages

•Metered flow rate

•Pressures to 90 psig (really 40-50 psig)

•Runs dry for 5-10 minutes

•Compact

•Low shear pumping

•Low pulsations with screw rotor design

•Runs in either direction

Disadvantages

•High maintenance (3-4 times Npump)

•Expensive initial & repair costs

•High wear due to slip

•Not rag friendly, requires a macerator

•Requires gearbox running 180 rpm or less

•High starting torque


Failures…


Replace RLP with Npumps

• Customer was spending $8k

per month to repair the Boerger

pumps (nine total)

Boerger pump

Replaced RLP with Npump on 6 month

trial and customer immediately

purchased a second pump (before trial

was completed)

Flygt N-pump


Economics (Life Cycle Costs)

Life Cycle Cost

Initial Purchase

Planned maintenance

*Cost of rebuild

10 year cost

PC

$21,000

$0

$7,000

$42,000

Lobe

$19,000

$0

$6,000

$37,000

DISC

$23,000

$0

$2,000

$33,000

* Considers three rebuilds for both PC & RL pumps, 5 rebuilds for DISC and no

rebuilds for Npump

(N pump must have Hard iron impeller & Insert Ring)

N pump

$11,000

$4,000

$0

$15,000


Screw Conveyor Pumps


Why Use a Screw Pump?

The Archimedes Screw Pump

• Efficient in handling large volumes of liquid at relatively low lifts.

• Ability to handle variable capacity with a simple constant speed drive.

• Operates at or above 70% efficiency for 2/3 of its operating capacity.

• No increase in pumping head caused by deep influent as required for centrifugal pumps.

• Less head required because there are no friction losses created by pipe, valves, and fittings.

• Non-clog


Screw Conveyor Pump Manufacturers

• Siemens (US Filter)

• Lakeside Equipment Company

• Spaans Babcock

• BioSec Enviro

• Martin Sprocket & Gear, Inc.

• Torqueflow Sydex

• Schreiber LLC.

• Arlat Technology - A Div. of Price Schonstrom Inc.

• Landustrie Sneek BV (Landy Screw Pumps)

• EPIC International

• Ritz-Atro GmbH

• SPECO Division of WAM S.p.A.


Advantages

• Rugged, Heavy-duty

• Non-Clogging design

• Lower cost concrete trough

• Low speed

• Low noise

Screw Conveyor Pumps

Disadvantages

• Huge Capital cost

• Purchase price (3-5 x’s)

Installation cost (3-5 x’s)

• Requires a lot of space

• Huge grease lubrication costs

(Upwards of $70,000/ yr.)

• 3-4 days to remove & service

• Highly inefficient when flighting to

concrete trough wears


Screw

Conveyor

Pumps


Screw Pump Replacement

Delta Township, MI


Screw Pump Replacement

O’Fallon, MO


JCH replaced these 10 mgd @ 50 feet CPC Screw Pumps

•CP pump ran from 1992-2007 (15 years)

•N pumps have since replaced C pumps (1997-today)


Cutter Pumps

• Vaughan

• Landia

• Tsurumi

• Barnes

• BJM


Their Sales Pitch…


Competitor’s pump


Competitor’s pump


Weakness as perceived by the competition


Tsurumi selling points


Advantages

• Heavy duty design

• Cuts solids to small sizes

• Reliable operation

(until cut bar wears)

Disadvantages

Inefficient

Inferior cutter bar material

• Clogs with minimal wear

CHOPPER/ CUTTER


FLYGT “Chopper” pumps

Advantages

• Heavy duty design

• Chops solids to small sizes

• Modular design

• Superior Hard iron material

• Guide pin

Disadvantages

• Efficiency drops 15-20%

over Npump

• Does not meter

Cast Iron Impeller

Cast Iron Insert ring Hard-Iron Insert ring

Hard-Iron Chopper ring

Pump housing

Hard-Iron Impeller


Flygt N-Pump Advantages

•Solids Handling to 6-8 percent

•Clog resistant (Back swept leading edge)

•Cutter grove in volute “Insert ring” tears solids

•Efficient operation

•Small, compact design

•Center-line discharge

• will not become air bound

•Complete ownership for pump & motor

Disadvantages

•Does not meter

•Does not self-prime

•Not a “PD” pump


High chrome gives…

4 x life vs. cast iron

2 x life vs. hardened tool steel


Vaughan Chopper Replacement

• Requirement: Flygt Cutter had to Work on Vaughan RotoMix System

Installed Since March 2010 w/ no sign of wear

• Higher Flow than Vaughan Unit (870 vs. 443 gpm)

Indications of Better Mixing

• Surface Crust Appears to be Breaking


Npump replaces competitors Chopper

Lift station pump which clogged weekly due to worn cutter

bar was replaced with Npump and has not clogged since!

* City now has flood-proof protection!


MACERATORS


MACERATORS

These types of pumps require a Macerator:

•Piston Plunger

•Diaphragm

•Double Disc

•Progressing Cavity

•Rotary Lobe


…because they cannot handle rags!


…or these modern day clogging headaches


Npumps do not require a Macerator!

• No Muffin Monster!

• No Franklin Miller!

• No Seepex!

• No Vogelsang!

• No Boerger!

• No Allweiler!

• No Monoflo!


Summary: Rule of thumb

If it flows, use an Npump!

Lower Life Cycle Cost (LCC)

A centrifugal pump can not pump a viscosity

>350 cps and a sludge density of >6-8 percent.

Keep pipe work simple with short suction line

constant diameter

no bends or elbows

no constrictions


For ALL Treatment Plant Pump Activities…

Applications

− RAS, WAS, TWAS & Primary

− Scum pits

− Digester feed

− Imported

Influent/ Final Effluent

Competing technologies

− Plunger

− Diaphragm

− Double Disc

− Progressing Cavity

− Rotary Lobe

Please call or Email me for help &

guidance:

Paul Nelsen

(203) 610-0853


To be released

soon!


THANK

YOU!

Paul A. Nelsen

Market Manager

Industrial & Treatment Plant Pumping

paul.nelsen@itt.com

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