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Background

The expense and inconvenience of pump failures is unfortunately a recurring theme at some of the UK’s sewage treatment works (STW) and often the cause of the problem is a lack of reliable mixing of unscreened sludge – before it enters pumping systems. This was the situation at Flag Fen STW one of Anglian Water’s main sites in Peterborough where problems were occurring with blocked lobe pumps on a strain press feed application.

The Challenge

Unscreened sludge was being imported into the Flag Fen works which contained large accumulations of rag and surface crust (See Pic 1) and the key to finding an effective solution was essentially reliable mixing. P&M PUMPS the UK distributor of VAUGHAN PUMPS were invited to provide a self-priming chopper pump on a sale or return basis for a 4 week trial. The Vaughan model SP4C pump would be working alongside a new Gorman Rupp T4 trash pump with belt drive and 11Kw motor on a head-to-head evaluation basis.

The Result

The Vaughan chopper pump exceeded the performance of the GR pump in effectively handling the unscreened, rag-laden sludge with far fewer blockages. However, it was still susceptible to the large masses of reweaved material entering the pump suction line and it was clear to Anglian Water that there was a need to condition the sludge on a permanent, ongoing basis.

As a result, and in addition to the strain press feed pump, P&M Pumps supplied and installed (on a free trial basis) a mixing and conditioning solution to Anglian Water. This consisted of a Vaughan model SE8N chopper pump (See Pic2) powered by an 18.5Kw motor which was free standing along with an attached nozzle manifold all of which was secured to an existing submersible mixer gantry after being positioned by crane, (See pic3).

Following a short period of operation and a recirculation flow of 360m³/hr the imported sludge in the tank was effectively mixed (See pic4) and the surface accumulation was removed (apart from a large floating mass that had been static in the centre of the tank). The immediate result following the installation of the mixing system was a period of 5 days without a single strain press feed pump blockage. In addition, the performance of the sludge centrifuge improved resulting in a uniform performance and increase in throughput due to higher feed solids being achieved.

In Conclusion

Through their experiences at Anglian Water and numerous other waste water treatment sites across the UK, P&M Pumps have demonstrated that Vaughan Chopper Pumps are an effective solution to the most challenging ‘solids pumping’ situations where other types of chopper, macerating or whole solids passing pumps have traditionally struggled.

In most cases, retrofitting a Vaughan Chopper Pump into a problematic area improves the whole process and will be self-financing, with unrivalled payback periods in some cases being a matter of months, thereafter minimising the effect to the budget holders.

For further information on how SYSTEM MIX can help to maximise the potential of your AD
plant operations contact: Andy Parr, System Mix Ltd, Sawtry, Huntingdon, UK.

Tel: +44 (0) 1487 830123
Email: andy@pumpmix.co.uk
Website: www.pumpmix.co.uk

During 25 years of providing solids pumping and mixing solutions to numerous sites in the UK and Ireland, P&M PUMPS has met the demands of some of the most varied, large scale and interesting applications. A good example of this is the recent supply of 2 self-priming Vaughan Chopper pumps to replace 2 dry-dock sump scavenge pumps in Aberdeen Harbour.

First established in 1136, Aberdeen Harbour is, according to the Guinness Book of Records, the oldest existing business in the UK with a history that has spanned almost 900 years. Today, the harbour is regarded as Europe’s premier marine support centre for the oil and gas industry and the main commercial port serving North East Scotland. The harbour has seen continued development including the construction of a new south harbour in 2017 a key part of a £350m project to accommodate the larger vessels more commonplace on sea routes around the world today.

P&M Pumps, in conjunction with Ritchie Mackenzie their Scottish distributor for over 20 years, who specialise in pumping and control engineering, provided their extensive experience in helping to solve the pumping problems occurring in the dry dock at Aberdeen harbour. The existing scavenge pumps, originally installed to provide a duty of 600gpm at 35ft head, including a 7” suction lift, were failing due to problems of blockages. This was due to the variety of debris entering the sump and even when running successfully, they were struggling to keep up with constant inflow of sea water flowing into the dry dock via the sea gates.

The solution was to replace the existing dual macerator and sump scavenge pumps with progressing cavity pumps, specifically Vaughan Chopper Pumps with motors rated at 18.5kW at 1470 rpm, 415V/3ph/50Hz. The new pumps would be self-priming and mounted complete with the motors, including variable speed drive and capable of exceeding the original duty conditions.

Ritchie Mackenzie was responsible for all the modifications required to fit the new pumps including a new control panel enabling control of the variable speed drive. This would include the ability to alter the frequency of the pump motor which would help to optimise efficiency in meeting the duty point and subsequently reduce running costs.

The control panel also includes an ultrasonic level controller which monitors the level of water in the dry dock sump. The controller indicates the liquid level on an LCD screen on the panel facia after receiving a level signal from the ultrasonic head positioned in the dry dock and which is set to cut the pump off at low level to prevent dry-running. In addition, the pump motors have heaters installed to protect the electrical windings against moisture ingress along with a temperature sensor / fault indicator, which will trigger a warning in the event of over-heating.

Through their experiences at Aberdeen Harbour and numerous other sites across the UK, P&M Pumps continue to demonstrate that Vaughan Chopper Pumps are an effective solution to the most challenging ‘solids pumping’ situations. In most cases, retrofitting a Vaughan Chopper Pump into a problematic area will be self-financing, with unrivalled payback periods in some cases being a matter of months, thereafter minimising the effect to the budget holders. ENDS.

Further information on Vaughan Chopper Pumps is available from; Matt Harvey, P&M Pumps, Sawtry, Huntingdon, UK.

Tel: +44 (0) 1487 830123
Email: andy@pumpmix.co.uk
Website: <ahref=”https://pumpmix.co.uk/” target=”_blank”>www.pumpmix.co.uk

Efficient mixing is one of the most important stages in maximising the anaerobic digestion (AD) process and the ROTAMIX system from solids pumping and mixing specialists P&M Pumps Ltd is playing a vital role at many of the UK’s AD installations. A good example of this is at Southern Water (SW) where Rotamix systems are currently mixing in excess of 95% (85,000m³) of the total volume of sludge generated at Southern Water sites.

mixing is a pre-requisite when it comes to retaining digester volume, maximising solids reduction and ultimately increasing gas production with Southern Water in particular showing the foresight over a decade ago with their investment in the ROTAMIX concept. These systems are operating successfully on 14 of Southerns STC’s (Sludge Treatment Centres) which are more specific and focused on the sludge process than traditional wastewater treatment works digester volumes ranging from less than 1000m³ and up to 4500m³.

The first Rotamix systems were installed into Southern Water’s digesters back in 2004 and have been operating successfully for well over 10 years. Jason Curtis, P&M’s Southern and Thames Water Area Manager commented, “Southern Water have taken a very proactive approach to dealing with the issues around sludge treatment to ensure the assets they select are fit for purpose and offer efficient operation with minimal downtime. We welcome this opportunity to continue our relationship with Southern Water and its contracting partners”.

Commenting on the performance of the Rotamix Systems a Senior Sludge Operations Manager at Southern Water said, “It is the responsibility of maintenance management to continually seek ways to increase production or reduce costs.

We are delighted with the performance of the Rotamix Systems which help us to deliver cost benefits which we can pass onto our customers.”

The 38 digesters situated at the STC sites across the south of the UK include some tanks being both above and below ground and thus each mixing system is a bespoke design and often accompanied with a CFD (Computational Fluid Dynamics) analysis ensuring optimum mixing patterns and efficiency prior to even the first bolt being tightened on the pipe work at installation. The unique Vaughan SP range of auto self-priming chopper pumps are utilised for an above ground mixing solution to a below ground or submerged tank, something System Mix believe cannot be offered with any other pumped tank mixing design.

All Rotamix systems feature a pre-determined internal jet nozzle layout, the number, size and orientation of which depend on the tank size, geometry and contents being mixed. This is always the case for the Vaughan Chopper Pump which is always at the ‘heart’ of each design ensuring suitable liquid velocity and pressure within the closed loop system is always maintained without the risk of cogging the pump or nozzle barrels.

This means fibrous solids (and other similar challenging materials) that are prone to re-weaving and growing in size are constantly reconditioned within the tank, while remaining in suspension and eliminating settlement of solids on the tank floor. The two-tier rotation of the sludge or DUAL ZONE mixing as it’s more commonly known, is what maintains maximum tank volume for the anaerobic process to achieve optimum gas production.

However, this mixing concept is not exclusive to AD digesters. Southern Water alone have over 80 other tank systems mixing imported sludge, RAS (Return Activated Sludge), SAS (Surplus Activated Sludge), blended, thickened and stored sludges, to name but a few.

The UK government has set ambitious targets for zero food and packaging to landfill in the future and this will in part be significantly affected by access to technology that contributes to reducing a reliance on carbon based fuels and reducing emissions. System Mix are therefore excited about the potential for solving problems associated with disposing of organic waste materials for energy generation by the process of anaerobic digestion.

Furthermore, having worked closely with most of the UK’s other water companies on numerous AD mixing projects to the extent that several major works have become energy self-sufficient by the use of their own excess gas production with the help of reliable and efficient mixing.

System Mix is confident that their knowledge and experience will continue to deliver systems that ensure optimum performance over the life of the plant. ENDS.

For further information on ROTAMIX and the potential of your AD
plant operations contact: Andy Parr Director P&M Pumps Ltd Huntingdon, UK.

Tel: +44 (0) 1487 830123
Email: andy@pumpmix.co.uk
Website: www.pumpmix.co.uk

Mixing is one of the most critical stages in maximising the efficiency of today’s Anaerobic Digestion (AD) processes and the ROTAMIX system has become established as the preferred choice of AD mixing systems at numerous waste water sites across the UK. Developed by Vaughan Co and supplied in the UK by solids pumping and mixing specialists SYSTEM MIX (a subsidiary of P&M PUMPS Ltd the UK’s distributor for Vaughan Chopper Pumps), the Rotamix system is now also being successfully utilised by an increasing number of the UK’s Energy Recovery Facilities (ERF’s).

Where Rotamix has yet to be adopted as the primary means of mixing digesters existing (or new), less effective mixing technology is being enhanced by the use of Vaughan Chopper pumps for heat exchanger re-circulation applications. Reliable performance and optimum temperature distribution is paramount to the success of the digestion process. Heat exchangers remain clean and free from blockages due to conditioned (chopped) sludge being re-circulated at steady pressure and flow conditions.

Efficient operation of heat exchangers within the process is vital to ensuring gas production and solids reduction is maintained. The key reasons for this success is that by using the Vaughan Chopper pump, blockage-free performance of heat exchangers is ensured where fibrous materials would normally foul them reducing their efficiency.

A recent example of this is the receipt of an order from Murphy Process Engineering to supply 4 x Vaughan model HE8K-305 55Kw horizontal end-suction chopper pumps for the expansion project at Yorkshire Waters’ Huddersfield ERF plant for digester heat exchanger re-circulation. This follows successful ERF projects at Blackburn Meadows, Sheffield in 2012 and Knostrop, Leeds in 2017, where Vaughan Chopper pumps were selected for similar duties.

Initially, utilising Vaughan Chopper pumps for heat exchanger re-circulation applications was one of the forerunners of the highly successful and universally accepted Vaughan Rotamix jet-mixing systems. There are numerous examples of this in the UK including Anglian, Thames and Southern Water, primarily for digester and sludge tank mixing.

Andy Parr, Director of P&M Pumps says, “By being approved to supply our pumps to Yorkshire Waters’ Huddersfield site is testament to the performance of Vaughan pumps at Knostrop and Blackburn Meadows. Since the pumps were originally installed up to 7 years ago (at Blackburn Meadows) we have not needed to supply any wet-end spare parts to either the Blackburn Meadows or Knostrop sites. This illustrates that the simple, rugged design and hardened materials of construction of the Vaughan pump are the key factors in why the pump has secured and maintained its position as the market-leading pump in its field”.

The UK government has set ambitious targets for zero food and packaging to landfill in the future which will in part, be significantly affected by access to technology that contributes to reducing a reliance on carbon based fuels and reducing emissions. System Mix are therefore excited about the potential for solving problems associated with disposing of organic waste materials for energy generation by the process of anaerobic digestion. Having worked closely with most of the UK’s water companies on numerous AD mixing projects to the extent that several major works have become energy self-sufficient by the use of their own excess gas production with the help of reliable and efficient mixing.

System Mix is therefore confident that their knowledge and experience will continue to deliver systems that ensure optimum performance over the life of the plant.

Tel: +44 (0) 1487 830123
Email: andy@pumpmix.co.uk
Website: www.pumpmix.co.uk

Background

Pumps of all shapes and sizes can be looked upon as the beating hearts of the UK wastewater treatment process, especially when recurring storm events lead to increased volumes of rag and debris entering the system. This is when specific solids handling capabilities become ever more critical. So get the right pump in the right place at the right time and the expense and inconvenience of pump failures can be minimised. VAUGHAN CHOPPER PUMPS offer uninterrupted pumping even in the most challenging, arduous conditions and there is a growing list of success stories to prove this.

The Challenge

An ongoing example of reliable pumping performance with VAUGHAN is at a Thames Water Banbury. Although Vaughan was the immediate fix to the problem, as usual it was also the long run which was very important to Thames Water and the proverbial ‘marathon, not a sprint’ philosophy. As it was back in June 2006 a 10” Vaughan SP10R, the only auto self-priming chopper pump on the market, was installed in the RAS (Return Activated Sludge) line at Banbury. It was the first of its kind to be used in the UK and was replacing one of 4 existing old style, extended shaft axial flow pumps. In their heyday these pumps were giving over 720m3/hr in a lift and transfer situation. However, when rag and solids content became more and more evident failures were common due to continual blockages. The existing axial pumps were situated inside their own pipework with the flow passing through the centre of the pump then out through a reflux and onto the common line. As a consequence, removing them for maintenance was not an easy operation, especially when on some occasions they needed to be lifted twice a day.

The Solution

As floor space in the pump house was restricted a powerful, yet compact pump set was required and the SP10R with an over/under drive configuration and its suction line simply dropped approx. 3m down the existing axial flow discharge line, with no down well fittings, was installed in 2006.

It has been operating 24/7 for almost 13 years at the Banbury site with a reported flawless performance and no requirements to unblock or inspect the pump. With this success a second SP10R was soon installed.

Just recently both pumps underwent a well-deserved overhaul as a result of general wear and the engineering coordinator at Thames Water commented, “The Vaughan Pumps were removed one at a time by our sub-contractor and returned to P&M Pumps to have an overhaul carried out. The turnaround time for each pump from removal to re-install was approximately two weeks and this included the parts being sourced and shipped from Vaughan in the US. This was exceptional service and kept our temporary over pumping costs to a minimum. Heconfirmed, “Both overhauled pumps have been running for over a month now and are pumping as they were when first installed from new”.

Conclusion

Thames Water have benefitted not only at Banbury but numerous other of their waste water treatment sites across the UK with their foresight and planning for the future and not just the firefight of problem solving. P&M Pumps have demonstrated that Vaughan Chopper Pumps are an effective solution to the most challenging ‘solids pumping’ situations where other types of solids handling pumps have failed. All-in-all the original investment has returned yearly life-cycle costs for each pump of between £1400 and £1500 over the 13 year period.

In many cases, retrofitting a Vaughan Chopper Pump into a problematic area improves the whole process and will be self-financing, with unrivalled payback periods in some cases being a matter of months, thereafter minimising the effect to the budget holders.