SE4011 (D Herron)

DAN HERRON
DATE 03/04/16
MSc PROFESSIONAL ENGINEERING
CURRENT TECHNOLOGIES & APPLICATIONS
SLUDGE TRANSFER PUMPING APPLICATION
MODULE SE4011

CURRENT TECHNOLOGIES AND APPLICATIONS
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TABLE OF CONTENTS
GLOSSARY................................................................................................ 3
LIST OF FIGURES AND TABLES .................................................................. 3
1. INTRODUCTION .................................................................................... 4
1.1 Selection Motive ..........................................................................................4
1.2 Overview of Process.....................................................................................4
1.3 Key Aims .....................................................................................................5
2. SLUDGE PUMPING PROCESS CONDITIONS ............................................. 6
3. CURRENT PUMPING TECHNOLOGY ANALYSIS......................................... 8
3.1 Positive Displacement - Progressive Cavity Pumps..........................................8
3.2 Pump Specification – MONO Compact C18A................................................ 10
3.3 Investigation Justification........................................................................... 10
4. ALTERNATIVE SLUDGE TRANSFER METHODS........................................ 12
4.1 Positive Displacement Pumps...................................................................... 12
4.2 Centrifugal Pumps ..................................................................................... 13
4.3 UK Utility Companies and NWG Different Opinions/Methods ........................ 14
5. RECOMMENDATIONS .......................................................................... 16
5.1 Grit/Silt Management Techniques ............................................................... 16
5.2 Practical Limitations ................................................................................... 16
5.3 Professional Limitations.............................................................................. 16
5.4 Recommendations for Pump Selection ......................................................... 17
6. CONCLUSION ..................................................................................... 18
7. REFERENCES ...................................................................................... 19
8. BIBLIOGRAPHY.................................................................................... 21
APPENDIX 1 – NWG SCADA REPRESENTATION – SLUDGE PROCESS .......... 22
APPENDIX 2 – WARKWORTH SLUDGE THICKNESS SAMPLES ...................... 23
APPENDIX 3 – SEEPEX SPLIT ROTOR/STATOR DESIGN .............................. 24
APPENDIX 4 – WARKWORTH PSP PERFORMANCE DATA ............................ 25
APPENDIX 5 – NWG JOB HISTORY ON WARKWORTH PSP’S ....................... 26
APPENDIX 6 – QUESTIONNAIRE FOR DIFFERENT UTILITY COMPANIES ...... 27

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GLOSSARY
GAC Gravity Activated Carbon
NWG Northumbrian Water Group
N.D. No Date
PAC Powdered Activated Carbon
PCP Progressive Cavity Pump
Poly Polyelectrolyte (Binding process to thicken sludge)
PS Primary Sludge
PDP Positive Displacement Pump
PSP Primary Sludge Pump
RCM Reliability Centered Maintenance
RGF Rapid Gravity Filters
SCADA Supervision, Control and Data Acquisition – electronic system that demonstrates various
processes throughout the site, system has automated control or manual user desktop
inputs.
VSD Variable Speed Drive
WTW Water Treatment Works
LIST OF FIGURES AND TABLES
Figure 1 Warkworth Site Layout
Figure 2 Warkworth Sludge Treatment Process
Figure 3 Sludge Thickness Calculations
Figure 4 Water Treatment Process Diagram
Figure 5 Worn v New Pump Stator Photos
Figure 6 Progressive Cavity Pump Basics
Figure 7 Rotor/Stator and Abrasive Particles Diagram
Figure 8 Speed v Abrasion Test
Figure 9 Warkworth PSP Drawing
Figure 10 PD v Centrifugal Pump Comparison
Figure 11 Brainstorming Abrasion Measures
Figure 12 Brainstorming Potential Pump Modifications
Table 1 PSPs Overall Cost in 11 year Period
Table 2 Relative Positive Displacement Pump Analysis
Table 3 Strongest Theme Answers from Questionnaire
Table 4 System Recommendations Evaluation

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1. INTRODUCTION
1.1 Selection Motive
After stressing the desire to develop my professional understanding within the ever-changing utilities
business, I opted to analyse systems/processes that are particularly troublesome from a maintenance
and operational perspective. The Primary Sludge transfer system at Warkworth WTW has historically
cost NWG valuable time/money through constant breakdowns. It would appear the abrasive
composition of the sludge is incompatible with the current pumping equipment. This excessive
abrasion in the system is thought to be the key factor causing the significant wearing of rotor/stator
parts in the progressive cavity pumps. Thus wasting valuable maintenance/operational time, and
incurring large capital costs for vital spares. This study was selected to address the issues highlighted
with the two Primary Sludge pumps at Warkworth WTW, intending on producing feasible
solutions/recommendations.
1.2 Overview of Process
Primary Sludge systems are essential for WTW’s; it allows the production plant to transfer the ‘after
product’ of water treatment, to the sludge treatment plant. It is imperative at least one pump in the
system is available; otherwise the sludge tanks would overflow or require emergency tanker removal
at high cost to the business. The Primary Sludge on a WTW is mainly composed of backwash
slurry/debris and sand from the sediment and GAC filters. It is imperative that a steady flow is
delivered from the PSP’s, to allow even mixing during the sludge thickening process.
Figure 1 is a layout drawing of Warkworth WTW; it shows location of the Primary Sludge Pumps and
the distance they pump to the ‘Press Building’ (Highlighted in Red). Estimated linear distance is
around 250m, approximate height difference between Primary pumps and thickener tank is 3.5m.
The basic Key Stages of the Sludge treatment process at Warkworth are as follows; Sludge Holding
Tank, Primary Sludge Pumps, Sludge Thickener (Poly), Buffer Tank, Filter Press and finally taken by
PRIMARY
SLUDGE
PUMPS
Figure 1 - Warkworth Site Layout (Source: NWG Technical Drawings)

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tractor for agricultural spreading. Appendix 1 is a NWG ‘Scada’ flow chart, to represent where the
sludge/wash water comes from, and the subsequent methods of treatment.
The sludge process is only one key stage in the treatment of river water at Warkworth WTW. Figures
2 and 4 demonstrate the key treatment principles in the process, all being essentially critical for
highest quality production. In basic terms, water passes through several filters to remove solids and
bacteria (producing waste by-product of sludge), before finally having the relevant chemicals applied
to correct pH and disinfect water before distribution to the public.
1.3 Key Aims
The key intentions of this investigation is to demonstrate the following:
• Technically broaden knowledge of engineering, scientific and mathematical principles
surrounding sludge pumping techniques.
• Examine technology currently utilised; assess how if functions and performs.
• Analyse all investigation data, providing recommendations for future installations.
Expected benefits of the study are:
• Improve technical understanding of technology available for sludge transfer in the utilities
industry.
• Technical deepening of the scientific principles surrounding sludge pumping techniques.
• Enhance technical knowledge of pumping systems for future installations.
• Understand the practical and professional limitations that apply to sludge pumping techniques.
• Provide Warkworth with several solutions/recommendations for moving forward in the future.
Throughout the main body of this report, I will describe my reflective thoughts and initial actions in
clear segregation of the report facts. They will be highlighted exactly as this passage; this excludes
the ‘Conclusion’ – a reflective passage alone.

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2. SLUDGE PUMPING PROCESS CONDITIONS
My first action for understanding the process conditions: consulting the senior process technician.
His valuable knowledge provided key information surrounding the operating process; I applied this
knowledge and coupled it with literature research to form opinions on the subject.
Figure 2 demonstrates the process arrangement for treating the sludge at Warkworth WTW, ‘arrow
32’ in the diagram is the key focus of this investigation. Primary sludge is typically a very low
percentage of thickness; the value is dependent various different factors including wash-water
volumes and other incoming plant sludge.
Punmia et al (1998, p. 479) state, “Typical solids concentration in raw primary sludge are 6 – 8%”.
The Author selected 3-months of Warkworth samples in attempt to demonstrate average conditions;
please see Appendix 2 for the full sample data. Key statistics to note from the sample data; 3-month
average primary sludge thickness was 4.69%, the 3-month average value of flow was 14.94m!
/H.
Interestingly, the average thickness sample is slightly less than the ‘typical’ primary sludge value
provided by Punmia. After consulting the senior process technician, he suggests it is considerably
thinner because of the sediment and GAC filter backwash-water, and is also arguably the cause of
abrasion within the system.
Sludge density/thickness is continually measured by
automatic instrumentation; the sludge percentage accuracy
is solely dependent on the accuracy of this equipment.
Instrument technicians, to ensure the reliability of their
outputs, continually calibrate them. Figure 3 demonstrates
the manual method of calculating sludge density when
different sludge’s are combined, typically utilised when
instrumentation is out of service. The instrumentation can
quantify the sludge thickness; Sand/Carbon will contribute
to this percentage. Instrumentation cannot demonstrate the
presence of abrasive material within the sludge, the sharp
and hard composition of sand/carbon particles is
undetectable – however are clearly visible when equipment
failure occurs.
Figure 3 - Sludge Thickness Calculation
(Source: Price 1998, p. 108)
Figure 2 - Warkworth Sludge Treatment Process (Source: NWG Technical Drawings)

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Figure 4 - Water Treatment Process Diagram (Source: Pizzi 2010, p. 107)
The process diagram in Figure 4, demonstrates a basic layout of the water treatment process in
stages. The key outputs to focus on for this investigation are; ‘Wash Water’ and ‘Sludge’. These two
are combined in Warkworth’s sludge holding tank, awaiting transferring to the sludge treatment
plant – by the Primary Sludge Pumps. It is widely assumed that the abrasive nature within the primary
sludge is a result of sand and carbon presence in the wash water. Wash water in this instance is used
to clean the sediment/GAC filters, ensuring bacteria is not present, however the by-product of this
process is thought to considerably hinder the sludge treatment process.
The photographs in Figure 5 are evidence of the abrasive wear apparent in the primary sludge
system. On the left is a ‘Rotor’ removed from one of Warkworth’s PSP’s, on the right is the new
replacement before installation. The abrasive nature of the PS has caused the majority of chrome
finish to wear off, and cut considerable grooves into the steel, thus resulting in the pumps not
performing. Information on configuration of the pump ‘stator’ is available in Chapter 3.
Figure 5 - Worn v New Pump Rotor Photos (Source: Author)
Deep
scores on
Rotor
Chrome
worn off

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3. CURRENT PUMPING TECHNOLOGY ANALYSIS
When analysing the current pumping system, I decided to obtain manufacturers information on
performance under ‘ideal conditions’. It was my objective to compare this information against the
on-site performance, and demonstrate the costs to the business. When discussing the issues with
experienced engineers within NWG, it was clear that this issue has been highlighted before, and
never resolved. This suggests a possible knowledge gap, or lack of interest to take on the challenge
of providing a solution. This possibly reflects a lack of ownership between Maintenance/Operational
teams, suggests a failing in the working system – it is likely an issue between budget allocation.
3.1 Positive Displacement - Progressive Cavity Pumps
Warkworth’s current primary sludge pumping technique is a particular method known as a ‘Positive
Displacement’; Progressive Cavity pumps are a specific type of Positive Displacement pump. Positive
displacement pumps essentially move a fluid by isolating a fixed volume, and forcing/displacing the
trapped liquid into discharge pipework; either by rotating components or linear moving rams. They
are particularly desirable for long pumping distance, high-pressure heads and steady flow delivery.
Figure 6 is a diagram to demonstrate the
basic pumping principles for progressive
cavity application. Continental Ultra Pumps
(2015, pg. 1) state that: “Abrasive fluids can
significantly shorten the life of the stator.”
Huskey (N.D., pg. 9) describes “the big
three” critical influences in the application
of PCPs as being: Abrasion, Temperature
and Viscosity. This investigation focuses on
one of those three key influences; Abrasion.
Huskey (N.D., pg. 10) also continues to
describe the conditions and influences
surrounding abrasive wear:
• Wear is proportional to shaft speed,
reduce the speed to reduce wear.
• Reduce pressure per pump stage (Minimise slippage between rotor and stator).
• Select oversized rotor, increases interference fit and equals longer life span (Less Slippage).
• Select specific abrasion resistant stator material, e.g. RM 100M, RM 103 or Urethane.
• Double chrome rotor for extra base protection.
Vetter and Wirth (1993) conducted a very extensive experiment, investigating characteristics of PCPs
and methods to avoid abrasive wear when designing a system. Their investigation covered a range
of different tests to analyse performance,
power, efficiency and resistance to wear.
Similar to Huskey (N.D.), they
highlighted rotor interference fit as
influential to the amount of abrasive
wear on the moving components.
Examine Figure 7 and note the ‘sealing
line’, this is a fluid gap generated by the
Figure 6 - Progressive Cavity Pump Basics (Source:
Continental Ultra Pumps 2015, pg.1)
Figure 7 - Rotor/Stator and Abrasive Particles Diagram (Source:
Vetter & Wirth, 1993 pg. 55)

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viscous material being pumped. Theory surrounding this thin film of fluid, suggests it aids with
protecting against abrasive wear; thus rejecting material labeled ‘f’ in Figure 7. However when
increasing speed rate, or introducing abnormal rotation patterns (i.e. bearing/gearbox failure) the
fluid film is eradicated in areas. This allows larger suspended solids within the fluid, to have direct
exposure onto the wearing components, this process is known as slippage. It is also understood that
the protective fluid film, cannot be generated if the gap between rotor-stator is too large. The
hydrodynamic principles of the slippage issues suggest, a differential pressure between cavities
removes the fluid film – particularly occurring in startup, as cavity pressures differ in this situation.
More wear results in a larger gap, proportionally increasing slippage further. Within the investigation
they conducted an experiment directly
analysing wear, using quartz particles at
diameter 15μm. They compared perfect
rotation within the abrasive fluid (B), against
a slightly oscillating rotation (A) (Exactly as a
PCP on site) and measured the wear relative
to speed. Figure 8 depicts the results; it is
evident that the fluid film protects the
perfect rotational components from any
major wear. Looking at data from line ‘A’, it is
would suggest that there is little protection
due to the offset rotation. Moreover it would
appear that speed does proportionally
increase wear to the rotor, thus supporting
Huskeys original statement.
In a more recent study Whittaker (2003) completed more tests surrounding abrasive wear on PCPs.
She believes that for every size of pump, there is one critical particle size range that will create
maximum damage to the pump components. As all other literature stated, rotational speed of the
pump is heavily correlated the amount of abrasive wear on the rotor/stator. Interestingly, she
discovered the coating of the rotor had no relation to the abrasive wear. The main conclusion to
note was: “Reducing the contact pressure between the rotor/stator was found to have a detrimental
effect on both components. It increased the width of, and the amount of particles embedded in, the
type a and b stator wear regimes which consequently increased the width of the wear bands on the
rotor (Whittaker 2003, p. 188).”
After analysing the reviewed evidence, there are several options to consider if PCPs are the
equipment of choice moving forward with Warkworth’s PSPs. Firstly, selecting an oversized PCP
would be advisable, thus reducing the required rotational speed, in turn reducing abrasive wear.
Secondly, a slightly larger PCP, with an oversized rotor, applying literature theory that increasing the
contact pressure – will reduce abrasive wear. This option may also create minor maintenance issues
however.
Progressive Cavity Pumps Analysis
SOURCE ADVANTAGES DISADVANTAGES
PC Pumps (2015) • Low operating costs.
• Can pump very high viscosity fluids.
• Ability to pump high concentrations of solids.
• Limited production rates
• Restricted lift height
• Rotor and Stator Wear
Figure 8 - Speed v Abrasion Test (Source: Vetter & Wirth
1993, pg. 57)
A
B

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PetroWiki (2015) • Moderate Cost
• Low Profile
• Handle sand and viscous fluid well.
• High electrical efficiency.
• Elastomers in stator swell in some fluids.
• Pumps off control is difficult. Lose efficiency
with depth.
• Rotors and stators wear considerably.
Author Opinion
(2016)
• Steady flow rate.
• Can pump very viscous fluids.
• Will pump solids well if correctly designed.
• Cheap operating costs.
• Awkward to overhaul from maintenance
perspective (Working alone).
• Very problematic if designed incorrectly.
• Replacement components are expensive.
Looking objectively from a maintenance perspective, selecting an oversized pump appears a good
option to reduce abrasive wear. It is my opinion however, that abrasive wear can only be minimised
and not eradicated. Therefore I would prefer to recommend installing equipment that is easily
maintained after abrasive damage. Speaking from experience with PCP’s and abrasive sludge, I
would select a ‘Seepex’ PCPs every single time. Why? Their bespoke design is unrivaled in speed
and efficiency during maintenance activities. Reduction of working hours and production downtime is
an imperative aim for this investigation. Appendix 3 contains more expansive diagrams explaining
the concept of a split rotor/stator, Seepex state: “this design makes replacement of rotor/stator up
to 85% faster” (Seepex, 2016 p. 3).
3.2 Pump Specification – MONO Compact C18A
The PSP’s at Warkworth are ‘Mono-bloc
Compact Range’ progressive cavity pumps.
Performance data for the current pumps is
located in Appendix 4. Figure 9 gives a visual
representation of the PCP’s installed at
Warkworth. The key details of the equipment
to note are as follows:
• Linear pumping distance of approximately
250m, a height differential of 3.5m and
outlet pipe size of 100mm.
• Sludge average thickness (from
investigation sample range) is 4.69%, with
an average flow rate of 14.94 m!
/H .
Performance data from the charts in
Appendix 4 suggests the viscosity is
approximately 80strokes – a typically
medium-high abrasion rating (Demonstrated
by RED lines).
• Pump has VSD fitted with a 4KW motor, motor speed ranges from 107-740rpm on 11-77Hz scale.
Shaft speed is reduced by gearbox of ratio 2.94/1, reducing the shaft speed range to 36.4-
251.7rpm.
3.3 Investigation Justification
The PSPs at Warkworth WTW have been constantly problematic from a Maintenance perspective and
are often described as “unfit for purpose”. From a business perspective however, we must
understand the financial and efficiency impact they have on NWG. Appendix 5 represents the
reported jobs on the PSPs between 23/09/2004 to 09/10/2015. Combining the data, it shows that
516.91 hours of work have been completed on the PSPs in that 11+ years period. When analysing
the reported tasks, a very high majority of the issues are caused by the abrasive wear. A cost of
Figure 9 - Warkworth PSP Drawing (Source: Mono,
2014 Section 4 pg. 1)

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£1681.92 is incurred each time the pump is worn beyond repair (assuming no gearbox/motor
damage), quotation documents are available but seem irrelevant to include in the report. Table 1
represents the overall financial implications from the PSP in that sample period. Calculated by
charging the relevant technician repair rate to the hours spent, and adding the relevant spares
required to solve the issue.
!
Primary'Sludge'
Pump'1'
Primary'Sludge'
Pump'2' Overall'10'Year'Combined'Cost'(£)'
Maintenance'Labour'Cost'(£)' 8693.03! 6906.74!
!Maintenance'Parts'Cost'(£)' 26798.75! 20103.36!
!Total'Costs'(£)' 35491.78' 27010.1' 62501.88'
Table 1 - PSPs Overall Cost in 11year Period (Source: NWG Internal Job Costing System)
It is very clear that the PSPs are causing significant issues to NWG; incurring £62501.88 over an 11
year period is unacceptable. Considering maintenance efficiency, it could also be argued that 516.91
hours of work would not be required if the equipment was fit for purpose. It was essential to
demonstrate why this issue required addressing; the figures in Table 1 are ‘how’ this issue is
highlighted. The approach intended to quantify cost and time to the business, because they are key
measures of efficiency.
The difference of costs incurred between pump 1 and 2 is significant, there may be several reasons
for this. The most probable reason would be duty rotation from an operational perspective, for
example pump 1 is normal duty with 2 running as a spare for maintenance downtime. This could be
resolved through an auto-duty rotate system. Alternatively it could be a result of inlet pipework
arrangement, causing difference between the volumes of sand/silt able to enter each pipe (Solids
may gather naturally around pump 1’s inlet in the sludge tank). This is however speculation, it would
be interesting to investigate this difference further in the future.
Drawing conclusions from the investigation so far does force questioning the original design. Why
were these theories not considered originally? Depending on the original installer, it could be
argued the system was designed to shorten the lifespan of wearing components, thus requiring
NWG to purchase more from suppliers. Or it could also be complete naivety in the design process.
Regardless of the reason, the issues still require resolving.
After completing this section of the investigation, I was very surprised at my findings. In fact I was
overwhelmed with how much I had learned about Progressive Cavity Pumps. The research and
investigation data has allowed me to be confident in what I would recommend regarding PCPs.
Before I began this study I would state that I knew a considerable amount about PCPs, this
investigation has demonstrated that I knew very little actually. Moreover I was interested to further
deepen my knowledge of Primary Sludge pumping through different methods in the forthcoming
chapter. So far, I have been very pleased with the investigation work – especially regarding the
questions I have raised with the original system. This further enhances my reflective nature as an
engineer.

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4. ALTERNATIVE SLUDGE TRANSFER METHODS
In this section of the study, I was very eager to learn what other industries considered best practice
for Primary Sludge Pumping. I was also intrigued to discover what type of Primary Sludge Pumping
systems other UK Utility companies utilise. My intention was to gather wide range of opinions from
different sources and industries, and provide an alternative recommendation to the current system. I
also opted to briefly analyse different WTWs within NWG, to evaluate different PSP styles within the
same organisation.
4.1 Positive Displacement Pumps
PDP PUMP TYPE ADVANTAGES DISADVANTAGES
LOBE • Pass medium solids and abrasives.
• No metal-to-metal contact.
• Positive suction, non-pulsating output.
• Bi-directional.
• Reduced suction capability with thin liquid.
• Requires timing gears and two seals.
• Overhung Load on shafts.
INTERNAL GEAR • Only 2 moving parts, 1 shaft to seal.
• Non-pulsating flow, Bi-Directional.
• Easy to maintain, handles abrasives.
• Flexible design offers application
customization
• Larger pumps usually require reduced
speeds
• One bearing runs in process fluid.
• Overhung load on the rotor shaft.
DIAPHRAGM • No shaft seal required.
• Handles solids and abrasives well.
• Inexpensive.
• Pulsing flow.
• Discharge limited to motor/air supply
capacity.
Table 2 - Relevant Positive Displacement Pump Analysis (Source: Petersen, N.D. p. 2-7)
A positive displacement pump appears the logical selection for Warkworth’s’ PS, due to the long
pumping distance, height differential and steady flow rate required. Which type of Positive
Displacement Pump? And Why? Are key questions to ask.
Table 2 represents information collated in a research project on the selection of Positive
Displacement pumps; all advantages/disadvantages are relative to the equipment type. However in
an ever-changing environment with new technology, manufacturers are very competitive in terms of
marketing their products. Which evidently, makes it very hard to select the correct equipment for
application.
Extensive research of different PD pump manufacturers resulted as expected. Different Progressive
Cavity, Diaphragm and internal gear pumps were all very capable in the application of pumping
abrasive sludge.
Grzina et al (2002, Section 9 p. 2) state, “The final textbook for optimum slurry pump design is yet to
be written and even powerful computer programs are just beginning to approach this goal. Personal
knowledge and past experience is much more important in the design of slurry than of water
pumps.” I concur; gathering past experience and advice appears to be the best method of obtaining
‘best practice’ for Primary Sludge Pumping.
Evidence would suggest that there are many capable products available to pump abrasive sludge,
however gathering opinions/recommendations from experience appear to aid in their selection.

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4.2 Centrifugal Pumps
It is important to consider Centrifugal pumps in the investigation, even if they aren’t typical practice
for Warkworth’s particular sludge system. Although centrifugal pumps would not be labeled useless
in this application, they could compromise efficiency. It is also feared that flow rate could be
inconsistent over that distance, thus affecting the thickening process.
Figure 10 represents the comparison between PD and centrifugal pumps, and demonstrates why PD
pumps are the preferred method at Warkworth. The ‘Performance’ graph compares the flow capacity
with change in head, clearly showing PD pumps maintain the imperative steady flow rate. Flow rates
and viscosity are also considered, again demonstrating superiority of PD pumps with any viscous
materials. Comparing efficiency and head height, the centrifugal pump begins to deteriorate when
the head is too large; PD pumps are also stronger in this comparison.
Although Centrifugal pumps aren’t the key selection for Warkworth WTW, there are some excellent
designs that are very capable to pump abrasive material. These designs are worth considering, as
the option could be available in the future, depending on extensive system alterations.
An interesting article produced by Water and Wastewater Treatment Magazine (2013) reviewed
United Utilities success on overcoming pumping grit/solids at one of their particular sites. Albeit a
sewage pump, the principles of transferring abrasive material remains similar. It states: “the only
maintenance that these grit pumps require is the occasional replacement of the mechanical seals.”
The article focused on a particular pump model ‘WEMCO’ – designed by Weir Pumps. According to
the literature, they appear to have various methods to solve abrasive pumping issues.
Goulds SRL centrifugal pumps are another adapted design; they also claim to provide equipment
that handles the pumping of ‘sand and gravels’. A key design benefit is a larger diameter semi-open
impeller, running at slower speeds to reduce abrasive wear. “The SRL is built to stand up to the
toughest services, while providing maximum reliability and extreme ease of maintenance.” Goulds
Pumps (2015, pp. 2,5).
Centrifugal pumps are clearly available to handle heavily abrasive fluids; however a tentative
approach should be taken when selecting products from manufacturers sales brochures. If the
Centrifugal option were more feasible for Warkworth, more in-depth research would be completed.
Figure 10 - PD v Centrifugal Pump Comparison (Source: Pump School, p. 1)

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4.3 UK Utility Companies and NWG Different Opinions/Methods
In this section, I composed a selection of questions surrounding PS pumping techniques. I sent a
blanket email to all other UK Utilities companies, requesting answers to my investigation questions.
This was an attempt to gain insight into how other Water companies operate relative to Primary
Sludge Pumping. I also asked the same questions of different WTW managers within NWG. Taking
Ethics into consideration, all persons questioned were specifically asked if their information could be
documented in this report.
The questions I composed for the UK’s other Utility Companies and NWG’s other site managers are
as follows:
1. What type of pumps do you use for Primary Sludge Pumping on your Water Treatment Works?
2. Do you suffer with abrasive wear on your equipment?
3. Can your provide me with details of your primary sludge system and pump specification?
4. Does your sludge system incorporate wash water from sediment filters?
5. Do you have any special measures to counteract abrasion within your Primary Sludge Pumps?
Appendix 6 contains a detailed information table, consisting of answers received from the other UK
water providers and two separate NWG sites. All companies were asked the same matrix of
questions, in attempt to keep the data range as accurate as possible.
The data clearly shows a trend in most popular PSP types; Progressive Cavity pumps are by far the
most common between the evidence collected, second were hydraulic RAM pumps. Centrifugal and
diaphragm pumps are apparent, obviously depending on their bespoke system arrangements –
significant modifications are required to install at Warkworth. All specifications appear different also,
resulting in more ambiguous further recommendations. Selecting ‘best practice’ from this data is
onerous; it is advisable to apply the equipment that best suits the current system arrangement.
Measuring the amount of abrasive wear is difficult; it is all relative to normal operation and
experience. Evidence suggests that having grit measures could be beneficial, although this would
require considerable capital investment from NWG. Evidently it appears dosing powdered carbon
significantly increases wear at Broken Scar, clearly supported by the issues apparent at Warkworth.
Most interesting of all the evidence is the counteraction to abrasion, RCM and Lean methodologies,
grit removal, different materials selection and filter backwash monitoring. All methods appear
feasible to apply without major constraint; these could be incorporated with recommendations for
equipment replacement/upgrade.
In reflection of this evidence gathering process; the results are interesting, although some not
entirely conclusive. Exceptions are: PCP’s appear the most popular method for Primary sludge
transfer, and GAC/PAC significantly increases equipment wear. The majority of data incorporates
sediment filter backwash in the sludge system, this however correlates inconclusively with the relative
diagnosis of ‘excessive wear’. Why? It would appear the opinions of ‘excessive wear’ seem to differ;
predictably this will always be the case with human nature. Methods to minimise abrasion, are strong
testament to the importance of gathering different opinions. This provides a wider scope on the
consideration of ‘best practice’, thus strengthening future recommendations. Summary Table 4
represents the key answer themes across the questionnaire matrix.

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Common Themed Answers
1. Primarily Progressive cavity pumps and secondly RAM pumps.
2. Very mixed responses as discussed, ‘excessive wear’ is open to personal interpretation.
3. Hard to provide particular specifics, ones provided described ‘Mono’ progressive cavity pumps.
4. Every returned questionnaire incorporated sediment filter backwash-water.
5. The majority of companies have implemented a various range of methods to reduce the amount
of abrasive wear in their equipment.
Table 3 - Strongest Theme Answers from Questionnaire
I was very pleased with the positive input I received from the UK’s other utility companies and other
NWG sites. I was pleased that ‘Welsh Water’ shared my preference for Seepex PCP’s. I suspect the
preference will particularly apply to maintenance personnel, rather than on a managerial level. It
would be interesting to compare the initial capital cost of Mono and Seepex, and their operational
efficiency – perhaps future work for this investigation.

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5. RECOMMENDATIONS
When providing recommendations, I had to be very considerate of several limitations surrounding
the current system and business constraints. In reflection, I have collected a lot of important
information to provide strong recommendations, also developing my own skills and knowledge
throughout this investigation process.
After evaluating the evidence gathered throughout the investigation, there are several options to
consider for improving Warkworth’s Primary Sludge system. Each option would require different a
modification in unique ways – some are cheaper/easier, some expensive and complicated. It is
important to think logically in terms of cost versus benefit to the business, the thought rationale (Of
the Author) for evaluating these choices can be seen in Figures 11 and 12.
5.1 Grit/Silt Management Techniques
The evidence taken from the grit-management brainstorming task (Figure 11) was incorporated from
other utility companies – essentially consisting of their best practice. Raising awareness for reducing
amounts of sand/GAC being washed into the sludge system would be very beneficial, could also
highlight any methods/ideas within the team for reducing the magnitude of abrasion. Application of
RCM techniques for the equipment would also be beneficial when considering breakdown costs. A
bespoke brief and procedure would be required; this would be modeled against the pump during
planned maintenance – providing indication of abrasive wear on the equipment. Installing grit
removal equipment would significantly reduce abrasive wear, however the capital installation cost
would require comparison to PSP costing – to assess the feasibility of an extra system to protect the
PSP’s.
5.2 Practical Limitations
• Pipework and panel modifications.
• Process arrangements for thickening.
• Plant downtime during upgrades.
• Installation of grit removal equipment, physical dimensions of space.
5.3 Professional Limitations
• Limited to companies/equipment to be installed off NWG’s contractor framework.
• Presenting the justification for changes, persuading decision makers on improvements.
• Obtaining funds to complete recommendations.
• Considering social factors, reducing workload – potentially affecting job security.
• Demonstrating the importance of abrasive sludge monitoring to field teams.
Figure 12 - Brainstorming Abrasion Measures (Source:
Author)
Figure 12 - Brainstorming Potential Pump Modifications
(Source: Author)

17
5.4 Recommendations for Pump Selection
A comprehensive range of research and investigation data was completed, to analyse primary sludge
pumping methods. All methods were essential in evaluating ‘best practice’ for pumping abrasive
sludge; this information narrowed the recommendations to three feasible options when considering
the process conditions:
• Progressive Cavity Pumps
• Diaphragm Pumps
• Centrifugal Pumps
All three methods will require bespoke modifications, and all incurring different cost to the business.
Advantages and disadvantages of each method have been evaluated; they are available in Table 3.
Potential System Modifications
SUGGESTION ADVANTAGES DISADVANTAGES
Install larger Progressive Cavity Pumps
(Preferably Seepex with split Rotors/stators),
reducing the running speed and
proportionally reducing wear.
Small pipework modifications required to
install.
Very efficient pumping method, less wear at
a slower speed – theoretically.
Constant flow rate, good for current
thickening mix process.
Are susceptible to slippage wear when
starting up.
Install diaphragm pumps, best equipment
for minimal abrasive wearing.
Excellent at pumping abrasive material.
Cheaper replacement parts, less wearing
components.
Give a pulsating flow when pumping,
affecting the thickening process.
Would require altering the poly, thickening
and mixing process.
Considerable pipework modifications.
Install centrifugal pumps, very capable at
pumping abrasive material for limited
distances/heads.
Reliable equipment, handle abrasive sludge
very well.
Would require extensive modification to
sludge holding tanks, or sludge press
location.
Table 4 - System Recommendations Evaluation
Considering the Diaphragm pump proposal, this would be a very sensible option in terms of
reducing abrasive wear. This system however, would require considerable modification to the
thickening process. Pulsating flows from the pumps would cause the sludge flocculation mix to be
inconsistent, affecting the process – therefore the mixing arrangement with the poly would require
modifying for this proposal.
The proposal for installing Centrifugal pumps is arguably the least feasible of the three. It is
important to consider the effectiveness of this pump for abrasive sludge, however the civil,
mechanical and electrical modifications appear large/complicated. Modifications would require re-
location of sludge holding tanks, or sludge treatment press equipment. The injection of initial funds,
would far outweigh the benefit for this study, estimated figures could potentially escalate into the
millions – rendering the proposal, somewhat unrealistic.
Looking objectively at the three proposals, installing larger Progressive Cavity Pumps appears the
most sensible solution to the issue. Reasons why: As mentioned earlier, speed is proportional to
wear with PCP’s. Installing larger pumps would considerably reduce the wear of moving
components. Very minimal pipework modifications would be required for this installation; the main
capital investment would be the new pumps and VSD’s. No extra modification would be required to
accommodate the pumps within the process, only configuring flow rates to ensure the correct sludge
thickening mixture. The abrasive nature of sludge will always be apparent, but hopefully reduced;
therefore from a maintenance perspective it is important to consider the simplest equipment to
maintain. This would clearly be Seepex split rotor/stator PCP – for a positive impact on reducing
maintenance repair times.

18
6. CONCLUSION
In reflection, my knowledge surrounding abrasive sludge pumping was minimal. Initially I considered
myself to have extensive knowledge on PCP’s, it became clearly evident I knew very little throughout
this investigation. This study has allowed me to technically enhance knowledge in areas I considered
strong, also broadening in areas that required it.
Conducting the investigation has technically enhanced my knowledge of various abrasive pumping
methods, and their application. It has highlighted key improvements available, through practical and
professional methods. Applying the relevant practical equipment, lean maintenance activities and
field team training – could potentially make the business more efficient in terms of cost and time.
Completing this module has aided my professional development as an engineer in three key ways:
• Reflection and analysis of positive/negative aspects during an investigation.
• Improved Investigation Skills – research and analysis, gathering qualitative and quantitative data.
• Management of time – had small personal commitments that slowed the investigation, against my
wishes. This provided key motivation to stick to my planning schedules rigidly.
I would have preferred to conduct an experiment, consisting of different percentages of abrasive
material – with various pumping methods. In attempt analyse performance in those conditions, and
provide my own compiled results. Unfortunately time and cost constraints concluded this process,
channeling me towards looking at best practice between literature and other businesses.
When gathering data for the investigation, I learned to be very cautious when obtaining it from
manufacturers. They have a tendency to verbally enhance their equipment’s capabilities; this is
human nature from a sales perspective. Therefore I decided to focus on data coming from personal
experience, incorporating their process and maintenance issues provides clearer understanding of
potential performance.
I regret not widening the scope of my ‘questionnaire data’, particularly into separate industries. In
hindsight I should have collected data from other countries, those claiming to be ‘world leaders’ and
different industries e.g. oil and gas. I could also have made the questions slightly more specific,
allowing for a more concise collection of data. Another improvement I would include if investigating
again, would be to allocate time to research into grit/silt management techniques for best practice.
I learned considerable amounts about my learning style. Instead of gathering the majority of the data
initially, I tend to be unorthodox and enhance areas I wish to develop throughout the investigation.
Sometimes I would write the report, and improve areas I feel lack engrossing or required technical
content. It would be interesting to attempt another approach in future modules, although I feel my
current method allows me to question the investigation information at every opportunity. As an
engineer, questioning ‘why’ is an underpinning principle in my thought process.
This investigation highlights the importance of having senior Mechanical Engineers within NWG,
knowledge is key when designing an important process – the pumps in question are possibly a result
of inadequate design/knowledge. The investigation has given me a positive outlook; I feel I can
make a difference to the business when studying modules. I now face the challenge of having the
recommendations delivered, and contributing the knowledge to further PCP projects.

19
7. REFERENCES
Continental Ultra Pumps (2016) How Progressive Cavity Pumps Work. [Online] Available at:
http://www.continentalultrapumps.com/store/kcfinder/upload/files/Pump%20Guide(2).pdf
(Accessed: December 2015).
Goulds Pumps (2015) Goulds SRL – Designed for Abrasive and Corrosive Slurry Services. Internal
Brochure: Goulds Pumps. Unpublished.
Grzina, A., Roudnev, A., Burgess, K. E. (2002) Slurry Pumping Manual. Internal Manual: Weir Group
PLC. Unpublished.
Huskey, C. (N.D.) Maintenance and Trouble Shooting of Progressive Cavity Pumps. [Online] Available
at:
https://www.cwea.org/sarbs/pdfs/Huskey_Maintenance%20and%20Troubleshooting%20of%20Progr
essive%20Cavity%20Pumps.pdf (Accessed: January 2016).
Mono (2014) Compact Range – Installation, Operation and Maintenance Instructions. Internal
Manual: Mono Pumps. Unpublished.
PC Pumps (2015) PCP Systems. [Online] Available at: http://www.pc-pump.com/pcp-systems
(Accessed: January 2016).
Petersen, J. E. (N.D.) Best Practices in Selecting and Applying Positive Displacement Pumps. Internal
Report: Viking Pump Inc. Unpublished.
PetroWiki (2015) Relative Advantages and Disadvantages of Artificial Lift Systems. [Online] Available
at: http://petrowiki.org/Relative_advantages_and_disadvantages_of_artificial_lift_systems (Accessed
January 2016).
Pizzi, N. G. (2010) Water Treatment: Principles and Practices of Water Supply Operations, 4th
ed.
Denver, CO: American Water Works Association.
Price, J. K. (1998) Applied Math for Wastewater Plant Operators, 2nd
ed. Florida: Technomic
Publishing.
Pump School (2007) When to use a Positive Displacement Pump. [Online] Available at:
http://www.pumpschool.com/intro/pd%20vs%20centrif.pdf (Accessed December 2015).
Punmia, B. C., Jain, A. K. (1998) Waste Water Engineering. New Delhi: Laxmi Publications.
Seepex (2016) Smart Conveying Technology. [Online] Available at:
http://www.seepex.com/uploads/tx_templavoila/SCT-APP_e.pdf (Accessed January 2016).
Seepex (2016) Smart Conveying Technology. [Online] Available at:
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0ahUKEwiehdur1-
vLAhVJORQKHTh3AaMQFggvMAI&url=http%3A%2F%2Fwww.seepex.com%2Ffileadmin%2Fuserfun

20
ctions%2Fdownload.php%3Ffile%3DFSCT1e.pdf&usg=AFQjCNF4Mv-rpn8l0FwNq84GULjU1I0GyA
(Accessed: January 2016).
Vetter, G., Wirth, W. (1993) Understand Progressing Cavity Pumps Characteristics and Avoid
Abrasive Wear. Erlangen, Germany: University of Erlangen-Nuremberg. Available at:
http://turbolab.tamu.edu/proc/pumpproc/P12/P1247-59.pdf (Accessed: January 2016).
Water and Wastewater Treatment Magazine (2013) Grit and Sludge Pumps get the Measure of
Wastewater. [Online] Available at: http://wwtonline.co.uk/features/grit-and-sludge-pumps-get-the-
measure-of-wastewater#.VsCC_sflfzJ (Accessed January 2016).

21
8. BIBLIOGRAPHY
Emerson Process Management (N.D.) Front End Engineering Design Capabilities. [Online] Available
at:
http://www2.emersonprocess.com/siteadmincenter/PM%20PSS%20Services%20Documents/Moderni
zation/Planning%20and%20Justification/FEED_Brochure6-05.pdf (Accessed: February 2016)
Energy Pumps (2016) Ram and Diaphragm Pumps. [Online] Available at:
http://www.energypumps.co.uk/thepumps.php (Accessed: January 2016).
Gamboa, J., Olivet, A., Iglesias, J., Gonzalez, P. (2003) Understanding The Performance of a
Progressive Cavity Pump with a Metallic Stator. Internal Report: Research and Development Institute,
Venezuela. Unpublished.
Gilbert Gilkes (2016) Air Operated Double Diaphragm Pumps. Internal Manual: Gilkes Pumps.
Unpublished.
Goulds Pumps (2015) Pump Selection Guide. Internal Manual: Goulds Pumps. Unpublished.
Michael, R., Lindeburg, P. E. (2003) Environmental Engineering Reference Manual for the PE Exam,
2nd
ed. Belmont, CA: Professional Publications.
Wastecorp Pumps (2009) Mud-Sucker Diaphragm Pumps. Internal Manual: Wastecorp Pumps.
Unpublished.
Weir Pumps (2012) Wemco Model CF Chop-Flow Pump. Internal Manual: Weir Pumps. Unpublished.
Whittaker, L. V. (2003) Evaluation and Analysis of Wear in Progressive Cavity Pumps. Internal Report:
University of Hull. Unpublished.

22
APPENDIX 1 – NWG SCADA REPRESENTATION – SLUDGE PROCESS

23
APPENDIX 2 – WARKWORTH SLUDGE THICKNESS SAMPLES
Warkworth Sludge Thickness/Flow Data (Source: Warkworth WTW Samples – Electronically Inputted by
Author)
NOTE: Blank sample dates represent operator unable to obtain sample for various
reasons, e.g. treatment issues or maintenance work.
Warkworth
Thickener
Feed Samples Jun-15
Jul-
15
Aug-
15
Date
Thickness
(%)
Flow
!!
/! Date
Thickness
(%)
Flow
!!
/! Date
Thickness
(%)
Flow
!!
/!
1 1 1
2 4.43 15.23 2 2
3 4.43 15.93 3 3
4 4 4 4.68 14.59
5 5 4 13.5 5 4.12 14.72
6 4.63 15.67 6 4.36 14.9 6 4.85 14.76
7 4.34 14.86 7 4.2 14.11 7 4.45 14.92
8 5.49 13.57 8 4.44 14.26 8 3.53 14.74
9 5.72 13.98 9 4.09 14.78 9 3.47 14.64
10 10 4.45 14.65 10
11 5.73 14.8 11 4.39 15.03 11 3.68 14.63
12 4.94 15.76 12 12 3.45 15.25
13 6.36 14.67 13 13 4.16 15.31
14 6.12 15.83 14 14 4.44 15.44
15 6.46 15.55 15 15 5.88 15.23
16 16 16 4.1 15.36
17 17 17 4.56 15.3
18 18 18 4.68 14.68
19 19 4.88 14.23 19
20 6.57 16.37 20 4.79 14.75 20
21 4.2 16.31 21 4.99 14.52 21 4.48 14.98
22 3.57 16.12 22 22 5.94 15.28
23 23 23 3.23 15.41
24 4.53 16.38 24 24
25 4.59 16.44 25 25
26 4.39 15.97 26 26 6.78 15.19
27 4.58 15.35 27 27 5.12 15.3
28 4.8 12.42 28 28 4.68 15.13
29 4.63 13.48 29 29 3.98 15.26
30 30 4.32 14.71 30 6.63 15.38
31 4.53 14.75 31
AVERAGES 5.03 15.23 4.45 14.52 4.59 15.07

24
APPENDIX 3 – SEEPEX SPLIT ROTOR/STATOR DESIGN
Seepex Split Rotor/Stator Diagram (Source: Seepex 2016, p. 2)
Example of Seepex Split Rotor/Stator in Abrasive WTW Sludge Application (Source: Author)

25
APPENDIX 4 – WARKWORTH PSP PERFORMANCE DATA
Warkworth PSP Performance Data (Source: NOV/Mono Pump Manufacturer, 2014) – NOTE: Red Lines are
inputted by Author to demonstrate Warkworth Process Conditions, Pumps also have ‘Mark 1 Rotors’
Fitted

26
APPENDIX 5 – NWG JOB HISTORY ON WARKWORTH PSP’S
!
PRIMARY'SLUDGE'PUMP'2'–'DATA'OBTAINED'09/10/15'
!Date'Rep' JOB'REPORTED' All'Hours'SUM'
28$Sep$05! THICKENED!FEED!PUMP!2!REPACK!GLAND.! 4!
04$Oct$05! RE$PPM!REPLACE!GLAND!PACKING!(KEN!DARLING)! 0.5!
25$Nov$05! PUMP!FAILED!(DONE)! 4!
14$May$07! REPAIR!FAULT!ON!THICKNER!FEED!PUMP!2/4! 0.5!
21$May$07! CHECK!AND!REPAIR!SLUDGE!THICKNER!FEED!PUMP!NO!2! 4!
21$May$07! CHECK!AND!REPAIR!SLUDGE!THICKNER!FEED!PUMP!NO!2! 0.5!
25$May$07! CHANGE!ROTOR/STATOR! 8!
30$May$07! CHECK!INVERTOR!ON!NO.2!THICKENER!FEED!PUMP! 0.5!
30$May$07! CHECK!INVERTOR!ON!NO.2!THICKENER!FEED!PUMP! 1!
26$Nov$07! CHECK!FEED!THICKNER!PUMP!NO!2/04!(BEING!DONE)! 5.5!
23$Jan$09! REPAIR!THICKENER!FEED!PUMP!NO.2! 1!
23$Jan$09! REPAIR!THICKENER!FEED!PUMP!NO.2! 5.5!
29$Jan$09! PUMP!REPAIRS! 5.5!
22$Oct$09! NOISY!GEARBOX! 6.5!
02$Mar$10! NOT!PUMPING!SUSPECT!GEAR!BOX!PROBLEM.! 4.7!
02$Mar$10! NOT!PUMPING!SUSPECT!GEAR!BOX!PROBLEM.! 0.62!
29$Mar$10! REPAIR!GEARBOX! 16!
28$May$10! SLUDGE!THICKNER!FEED!PUMP!204!$!PUMP!RUNNING!BUT!NOT!PUMPING! 12!
22$Jun$10! PUMP!NOT!PUMPING! 6!
04$Aug$10! SLUDGE!THICK!TRANS!PUMP!RUNNINGNUT!NOT!PUMPING.! 2.77!
04$Aug$10! SLUDGE!THICK!TRANS!PUMP!RUNNINGNUT!NOT!PUMPING.! 0.02!
14$Sep$11! G/BOX!OIL!NEEDS!CHANGED!OIL!TO!SOURCE.! 0.47!
10$May$12! SLUDGE!THICK!PUMP!2/04!ROTOR!&!STATOR!REQUIRED.! 2.72!
10$May$12! SLUDGE!THICK!PUMP!2/04!ROTOR!&!STATOR!REQUIRED.! 9.71!
04$Dec$12! INVERTER!FAULT!ON!THICK!FEED!PUMP!2/04! 0.67!
04$Dec$12! INVERTER!FAULT!ON!THICK!FEED!PUMP!2/04! 45.21!
24$Jul$13! THICKENER!FEED!PUMP!NO!2!P2/04!BLOCK!PLS!INVESTIGATE! 0.02!
26$Jul$13! SLUDGE!FEED!PUMP!RUNS!BUT!NOT!PRODUCING!ANY!FLOW.! 6.65!
26$Jul$13! SLUDGE!FEED!PUMP!RUNS!BUT!NOT!PRODUCING!ANY!FLOW.! 0.5!
21$Jul$14! THICKENER!FEED!PUMP!NO!2!P2/04!GIVING!OUT!INCORRECT!FLOW! 1.61!
21$Jul$14! THICKENER!FEED!PUMP!NO!2!P2/04!GIVING!OUT!INCORRECT!FLOW! 0.02!
23$Feb$15! PUMP!PERFORMANCE!IS!POOR!AND!IS!REALLY!NOISY.! 1.36!
23$Feb$15! PUMP!PERFORMANCE!IS!POOR!AND!IS!REALLY!NOISY.! 20.43!
19$Mar$15! PUMP!NOT!WORKING,!PLEASE!INVESTIGATE! 5.82!
29$Jun$15! THICKENER!FEED!PUMP!NO!2!P2/04!$!FLUCTUATING!FLOWS!PLEASE!INVESTIGATE! 0.68!
29$Jun$15! THICKENER!FEED!PUMP!NO!2!P2/04!$!FLUCTUATING!FLOWS!PLEASE!INVESTIGATE! 6.29!
07$Sep$15! REPLACE!ROTOR/STATOR! 0.5!
07$Sep$15! REPLACE!ROTOR!STATOR! 6!
!
HOURS'TOTAL' 201.77'
Primary Sludge Pumps – Job Information for previous 11 years (Source – NWG Internal Job Recording System)
!
PRIMARY'SLUDGE'PUMP'1'–'DATA'OBTAINED'09/10/15'
!Date'Rep' JOB'REPORTED' All'Hours'SUM'
23$Sep$04! SETTLED!WATER!PUMPS!$!CHECK!PUMPS.! 1.5!
23$Sep$04! SETTLED!WATER!PUMPS!$!CHECK!PUMPS.! 0.5!
30$Dec$04! REPAIR!THICKENER!FEED!PUMP!2$30!NO!AMPS.! 2!
05$Apr$05! REPAIR!THICKENER!FEED!PUMP! 2!
05$Apr$05! FITTER!REQUIRED!REPAIR!THICKENER!FEED!PUMP! 0.5!
14$Apr$05! REPAIR!FAULT!THICKNER!FEED!PUMP!WILL!NOT!RUN!IN!AUTO! 0.5!
19$Apr$05! REPAIR!THICKNER!FEED!PUMP!PUMPS!WILL!NOT!RUN!IN!AUTO!AGAIN! 0.5!
19$Apr$05! REPAIR!THICKNER!FEED!PUMP!PUMPS!WILL!NOT!RUN!IN!AUTO!AGAIN! 18.5!
11$Jul$05! REPAIR!THICKENER!FEED!PUMP! 4.5!
09$May$06! REPACK!PUMP!DONE! 6!
12$Aug$06! REPAIRS!TO!THICKENER!FEED!PUMP!INVERTER!DONE! 5!
14$Aug$06! ASSIST!WITH!PUMP!REPAIR!(DONE)! 7.5!
21$May$07! CHECK!AND!REPAIR!SLUDGE!THICKNER!FEED!PUMP!NO!1! 0.5!
27$Apr$08! OVERHAUL!MONO!PUMP! 0.5!
27$Apr$08! OVERHAUL!MONO!PUMP! 15.5!
02$Jun$08! OVERHAUL!PUMP!DONE! 4.5!
16$Jun$08! INSTALL!PUMP!DONE! 3!
16$Jun$08! INSTALL!PUMP!DONE! 8!
25$Nov$08! UNBLOCK!PUMP! 0.5!
25$Nov$08! UNBLOCK!PUMP! 4.5!
22$Jun$10! REPLACE!ROTOR/STATOR! 0.5!
22$Jun$10! REPLACE!ROTOR!STATOR! 8!
02$Aug$10! THICK!FEED!PUMPS!203!LEAKING!SLUDGE!FROM!GLAND.! 0.6!
02$Aug$10! THICK!FEED!PUMPS!203!LEAKING!SLUDGE!FROM!GLAND.! 1.58!
07$Jan$11! NO!1!THICKENER!FEED!PUMP!FAULT! 7.27!
07$Jan$11! NO!1!THICKENER!FEED!PUMP!FAULT! 0.2!
22$Feb$11! THICKENER!PUMP!$!LEAKING!FROM!GLAND.! 0.12!
22$Feb$11! THICKENER!PUMP!$!LEAKING!FROM!GLAND.! 0.55!
14$Jun$11! THICKENER!FEED!PUMPS!203!LEAKING!SLUDGE!FROM!GLAND.! 0.65!
17$Aug$11! LEAK!FROM!SLUDGE!THICKENER!FEED!PUMP!203! 4!
14$Sep$11! OIL!TOPPED!TO!LEVEL....!GLAND!REQ'RS!PACKING.! 0.72!
14$Sep$11! OIL!TOPPED!TO!LEVEL....!GLAND!REQ'RS!PACKING.! 0.49!
08$Feb$12! LIMITED!OUTPUT!FROM!THICKENER!PUMP!1! 4!
08$Feb$12! LIMITED!OUTPUT!FROM!THICKENER!PUMP!1! 14.98!
10$May$12! SLUDGE!THICKENER!PUMP!2/03!INVERTOR!FAULT.! 4.44!
10$May$12! SLUDGE!THICKENER!PUMP!2/03!INVERTOR!FAULT.! 0.71!
13$Aug$12! THICKENER!FEED!PUMP!NO!1!P2/03!$!LEAKING!GLAND!NEEDS!TIGHTENED!REF! 23.5!
13$Aug$12! THICKENER!FEED!PUMP!NO!1!P2/03!$!LEAKING!GLAND!NEEDS!TIGHTENED!REF! 2!
11$Sep$12! PUMP!LEAKIN!PAST!PACKING!$!REQ!BILL!HIND!77575! 6!
23$Jul$13! THICKENER!FEED!PUMP!203!RUNS!BUT!PRODUCES!NO!FLOW.! 1.64!
23$Jul$13! THICKENER!FEED!PUMP!203!RUNS!BUT!PRODUCES!NO!FLOW.! 21.48!
28$Aug$14! THICKENER!FEED!PUMP!NO!1!MOTOR!NOT!RUNNING!BUT!RUNNING! 3.63!
28$Aug$14! THICKENER!FEED!PUMP!NO!1!MOTOR!NOT!RUNNING!BUT!RUNNING! 61.35!
11$Feb$15! PUMP!SHOWING!RUNNING!ON!SCADA!BUT!NOT!PUMPING! 31.48!
11$Feb$15! PUMP!SHOWING!RUNNING!ON!SCADA!BUT!NOT!PUMPING! 0.28!
29$Jun$15! THICKENER!FEED!PUMP!NO!1!P2/03!$!LEAKING!SLURRY!REF!NICK!GRAHAM! 1.91!
29$Jun$15! THICKENER!FEED!PUMP!NO!1!P2/03!$!LEAKING!SLURRY!REF!NICK!GRAHAM! 15.06!
!
HOURS'TOTAL' 315.14'

27
APPENDIX 6 – QUESTIONNAIRE FOR DIFFERENT UTILITY COMPANIES
QUESTION
COMPANY
OR SITE
1. What type of pumps do you
use for Primary Sludge Pumping
on your Water Treatment
Works?
2. Do you suffer with abrasive wear
on your equipment?
3. Can you provide me with details of your
primary sludge system and pump
specification?
4. Does your sludge system
incorporate wash water from
sediment filters?
5. Do you have any special measures to
counteract abrasion within your Primary
Sludge Pumps?
Anglian
Water
No Reply. No Reply. No Reply. No Reply. No Reply.
Severn
Trent 1
"Ram and Progressive Cavity
Pumps. We assess for rags,
abrasives etc. and combine with
the duty requirements to select
the pump with lowest WLC."
"On some sites but we identify
these and where we can, improve
the grit removal, we also work with
pump suppliers to ascertain the best
materials for wearing parts within
the pump."
"We use WIMES specifications for
progressive cavity and ram pumps."
"Some of the wash water will go
back to the head of the works
which will exacerbate the
abrasive issue."
"No special measures apart from careful
selection of materials and identification of
assets with high OPEX costs so we can
collaborate with pump suppliers to find
solutions."
Severn
Trent 2
"Usually Positive Displacement,
Ram or Mono type - sized and
selected depending on process
design parameters for sludge
thickness and head to lift.
Sometimes centrifugal are fine
for the duty, depending on
pumping distance/height."
"No - just standard. Nothing like we
experience on waste, where we
specify RAM pumps for primary
sludge and a special hard ceramic
coating for the worst sites."
"As all our water treatment works are
different having being built at different
times, the systems are site specific and
hence so are the specs. Pumps are selected
to deal with design flows and thickness (if
pumping sludge), and for the last 10 years
we have not had a framework supply for
sludge pumps - we have preferred suppliers
but our Design & Build contractors have
been free to choose - we mainly have Mono
pumps or Hydrostal. Our M&E specs align
with WIMES."
"Some treatment works return
backwash water to the
sedimentation clarifiers.
“Not really, it is very hard to be specific
for all our sites."
Southern
Water
South West
Water
Thames
Water
"Mono - progressive cavity
pumps."
"Yes, particularly stator wear and is
felt most when there are asset
availability issues around the grit
removal system."
"This is very hard to do as the system is
quite large."
"We do use sediment filters." "Yes we have grit removal in the
beginning of the sludge treatment
phase."
United
Utilities
No reply. No reply. No reply. No Reply. No reply.
Welsh
Water
"We use a wide range for our
sites due to the varying design.
Examples of what we use;
Progressive cavity pumps,
centrifugal, double diaphragm
and rotary lobe."
"In some areas yes, however we do
our best to tackle abrasive wear as
best we can."
"Our typical different pump suppliers are;
PCP pumps - Mono or Seepex, Centrifugal -
Flygt or Hydrostal, Double Diaphragm -
Farm Gas and Rotary Lobe - Borger.
Installations can vary from dry to wet well
systems. Typically pumping 4-6% density
"We do have some element of
filter backwash, but nothing
particularly testing for the
equipment."
"The carryover grit is typically picked up
by planned maintenance activities,
operations check for poor performance
(drop off). LEAN methodology being
implemented to carry out such checks and
also RCM (Reliability Centred

28
sludge ranging 5-10m head lift.” Maintenance) when wear occurs it would
drive the change of an impeller/wear-ring
or rotor/stator depending on the pump
type."
Wessex
Water
"We use a various range of
pump systems for sludge, some
sites well have gravity feed and
others have progressive cavity of
centrifugal arrangements
depending on head/distance of
pumping."
"Nothing really out of the ordinary,
however we do have grit measures
in place on our larger sites."
"Unfortunately, giving specific details of our
sludge system and pump specifications is
difficult as there are many pumps and
systems. Some of the pump suppliers we
use are; Mono, Flygt and Hydrostal."
"Some do have wash-water
from sediment filters, but grit
control reduces the amount
actually pumped through the
sludge process."
"On larger sites we have, grit removal
reduces the wear on plant further down
the process. Any grit that does get
through the process will have an effect on
the life of the plant."
Yorkshire
Water
"All of our sites are set up
slightly different so we have a
range, typically using RAM and
progressive cavity pumps."
"This also depends on our different
sites, some have grit measures in
place and others don’t."
"Not particularly, because all of the sites we
use are set up different. The specs. are too -
the detailed information I received from
Sandall say they use EMS RAM pumps."
"Our sites do include washwater
from sediment filters, however
we don’t have information on
particular mixtures of the
sludge/wash water."
"Sandall have a good grit system in place
which makes a huge difference in regards
to abrasion on the pumps, meaning we
don’t have abrasion issues here."
NWG -
Broken Scar
"At Broken Scar we have five
Mono C1BK pumps that are fed
from sludge holding tanks,
which hold all the sludge
generated from the clarification
and RGF washes. These pumps
then feed the sludge onto two
sludge thickeners."
"Yes, this is made worse when we
dose PAC at the head of the works,
and in flood conditions with lots of
silt coming out of the river Tees into
the WTW."
"Sludge holding tanks, primary sludge
pumps, thickeners, holding tanks, centrifuge
- disposal of sludge product. The pumps are
Mono C1BK's."
"Yes." "As the pumps fail the Rotors are being
upgraded to a more robust stainless
steel."
NWG -
Lartington
"Pumps for primary sludge;
Recovery Tanks - x2 Gorman
Rupp, Flotation Sludge - x2
Mono."
"Medium abrasive wear." "Sludge system detail: Thickener feed
pumps - x3 Mono, Thickener de-sludge
pumps - x2 Mono and Centrifuge feed
pumps - x3 Mono."
"Sludge system incorporates
wash water from sediment
filters."
"Measures to counter abrasion: filter
backwash checks to review washout,
standard rotors/stators fitted."

SE4011 (D Herron)

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