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Achieving significant improvement in the throughput of sludge combined with minimising reactive maintenance and the frequent need to purchase spares, were the important benefits achieved at a key Southern Water site, thanks to the installation of Vaughan Chopper Pumps and mixing systems, supplied by P&M Pumps. The site, a key element in Southern Water’s sludge strategy, serves a sludge catchment of approx 600,000 people and uses Mesophilic digestion and a thermal drying plant which needs to operate on a 24/7 basis.

The key processes at the site are split into two main functions. For the waste water process the stages are primary settlement, biological treatment and final settlement, and for sludge recycling; digestion, gas recycling, drying, the drying granules are recycled to agriculture. Pumps play a key role in the smooth running of these processes and Southern Water were experiencing problems prior to the installation of the Vaughan ‘chopper’ pumps.

The site has three 2400m3 Mesophilic digesters which are fed 24 hours a day with raw sludge containing a dry solids content (D/S) of between 6 and 8%. The digesters are heated using spiral heat exchanges with a primary heat source of around 60°C. Pumps then re-circulate the sludge through the heat exchangers to maintain a constant heat within the digesters and this temperature must be maintained at 35°C ± 2°C to ensure HACCP compliance. The previously installed screw centrifugal pumps frequently failed due to their inability to handle the amount of rag and grit in the sludge.

In addition, seal failure was common with one pump needing to be replaced on average every 4 to 6 weeks. The rag also caused blockages within the heat exchangers which meant they needed to be cleaned weekly to remove trapped rag from within, leading to operational process issues eg; expensive maintenance required to maintain the required throughput of the site 24/7. For example, if the temperature on any digester dropped below the critical control point, this would inhibit digester feed, reducing the site throughput by as much as one third. The financial consequences were monthly costs on the pumps of around £2000 each, plus the labour costs for contractors and call out of Southern Water staff.

P&M Pumps were asked to look at a possible solution and the recommendation was to install a HF4P6 15 kW Vaughan Chopper Pump to ensure the required flow was maintained and which would be able to cope with the rag and grit within the system. The first pump was installed and the operators reported how quiet the Vaughan Chopper pump was in comparison to the other pumps. As part of the maintenance process, operators continued to open up the heat exchangers, although they found that the build-up of rag was almost zero. It was also found that the digester temperatures consistently stabilised and remained so thanks to the ability of the heat exchangers to transfer the heat more efficiently without blockages or pump failures. Consequently, heat exchanger operational maintenance now consists of an annual inspection and there are no issues with rag build-up within the units.

A further two pumps have subsequently been installed at the site and have been running for over 3 years with no reported blockages and minimal reactive maintenance. P&M Pumps, exclusive UK distributor for Vaughan Chopper Pumps, initially became involved with the Southern Water site in 2002 and to date have installed 8 pumps and 2 Rotamix systems.

Equipment includes 3 digester recirculation pumps, 2 post digestion storage tank Rotamix mixing systems, 2 belt thickener discharge pumps and 1 tanker discharge submersible pump.

Commenting on the performance of the Vaughan Chopper pumps, Mark Catlin, Southern Water Senior Process Engineer says, ‘Installing the Vaughan equipment has made a significant improvement to asset availability and a large reduction in this sites operational costs’. The conclusions underlined by the subsequent elimination of the downtime problems occurring at the Southern Water site are for operators to have a clear understanding of the potential operating costs when specifying equipment. Life costs are a significant factor in today’s increasingly regulated environment as are the incessant demands for improved efficiency. All these factors need to be factored into the initial specifying / buying process where comparisons of initial purchase price with probable on-going maintenance costs should be taken into account.

P&M Pumps, through their experiences at the Southern Water site and other installations, have been able to demonstrate that their products and expertise can bring significant cost-savings. In most cases, retrofitting Vaughan Chopper Pumps in the correct areas to deal effectively with the process, can be self-financing, with payback periods of less than one year, thereafter minimising the effect to the budget holders.

Further information on Vaughan Chopper Pumps and associated mixing systems is available from;

Matt Harvey, P&M Pumps Ltd, Sawtry, Huntingdon, UK.

Tel: +44 (0) 1487 830123
Fax: 01487 832888
Email: sales@thesolidsolution.co.uk
Website: www.pumpmix.co.uk

Another successful installation of Vaughan ‘Chopper’ pumps, supplied by P&M Pumps, has resulted in a significant reduction in the problems which were caused by pump blockages that were occurring at an Anglian Water Services Pumping Station, in Huntingdon, Cambridgeshire. The Hartford Road Pump Station in Huntingdon is one of a number of facilities within the Anglian Water Region where raw domestic and industrial effluent is collected and processed, with raw sewage being transferred within a dry-well pumping application.

Problems arose, when during high flow conditions, the original pumps became blocked with fibrous rag material and other flotsam contained in the sewage streams. These problems were particularly severe when storm conditions occurred which led to sewage streams backing-up, causing spillage and flooding. Blockages were an on-going problem, with around 2 to 4 pump failures a week during extreme conditions, resulting in high maintenance and labour costs.

Following consultations with solids pumping specialists P&M Pumps, the UK distributor for Vaughan Pumps, Anglian Water purchased three Vaughan PE8N10 Chopper Pumps. These were supplied with 45kw electric motors for transferring sewage from the Hartford Road pumping station to their Huntingdon Sewage Treatment Works at a rate of 155 lit/sec. Since installation the pumps have not failed, despite ragging and other flotsam material being present in sewage streams, also, no mechanical failures have been reported due to abrasive wear.

The Hartford Road pumping station has been operating for 2 years without the need for any unscheduled visits due to pump failures. In addition the hydraulic performance of the Vaughan pumps exactly meets the target flows set by Anglian Water, with no drop in performance. Commenting on the pump’s performance, Mick Tomblin, Site Engineer at Hartford Road said, “We have overcome all of the operational problems we were experiencing, pump failures due to ragging etc. have been eliminated and we appreciate the pump’s ability to handle rag matter easily and efficiently”. He added, “P&M Pumps offered a guarantee from the outset that these pumps would not block and they have proven reliable within a very difficult application”.

Through their experiences at the Anglian Water site and other installations, P&M Pumps have been able to demonstrate that their products and expertise can bring significant cost-savings. In most cases, retrofitting Vaughan Chopper Pumps in the correct areas to deal effectively with the process, can be self-financing, with payback periods of less than one year, thereafter minimising the effect to the budget holders.

Further information on Vaughan Chopper Pumps and associated mixing systems is available from;

Matt Harvey, P&M Pumps Ltd, Sawtry, Huntingdon, UK.

Tel: +44 (0) 1487 830123
Fax: 01487 832888
Email: sales@thesolidsolution.co.uk
Website: www.pumpmix.co.uk

The words ‘Life cycle cost’ have become familiar in the purchasing departments of the UK water industry, where the drive towards improved efficiency, as in many other industry sectors, is more important than ever.

The words ‘Life cycle cost’ have become familiar in the purchasing departments of the UK water industry, where the drive towards improved efficiency, as in many other industry sectors, is more important than ever. Viewing the trends of efficiency and cost are now more clearly documented in many engineering departments and this analysis is particularly relevant to the performance of pumps. There are examples of single pumps which ‘cost’ 1000% and more of their purchase price, to run in a single year – surprising but true. In many cases these operating costs are a direct result of the presence of ‘problem’ materials such as, rag, grit, fat and hair, which account for the majority of pump failures and downtime in water and waste applications.

Around seven years ago, Cambridgeshire based P&M Pumps, introduced the revolutionary ROTAMIX from VAUGHAN and STM tank mixing systems to the UK. These systems always use a VAUGHAN Chopper pump to simply draw and return from the tank, vessel, lagoon etc. with the return flow being distributed through strategically placed, high velocity nozzles, creating the all important ‘Dual Zone’ mixing pattern. The chopper pump reduces any solids to ensure free flow through nozzles and thus maximum homogenous mixing.

date, over 400 ROTAMIX and STM systems have been installed, with tank sizes ranging from 20 cubic metres up to 6000 cubic metres. The results in all cases was better quality sludge, for example smaller solids, more consistency, ensuring better movement.

This results in less pump failures in post mixing applications, less press or centrifuge maintenance, and in some cases, more than a 25% increase of sludge DS though the system. These improvements resulted in significant cost savings and as a consequence, persuaded the operators to investigate other problem areas which would benefit from potential savings.

One particular pump application which emerges time and again was digester heat exchange re-circulation, especially where spiral heat exchangers are installed, as traditionally there is a tendency for them to ‘clog-up’ with rag, fat and other rogue solids.

As a result of using Vaughan Chopper pumps on these applications, the need to clear either the pump, or the heat exchanger of regular blockages have not only been reduced, but completely eliminated. Within days of start-up, process engineers recorded a stable temperature within the digester in addition to other benefits throughout the process, following digestion.

P&M Pumps realise that the efficiency of a sludge digestion treatment plant hinges upon two factors, stable temperature and homogenous sludge. Furthermore, they are confident these two factors are achieved when a Vaughan chopper pump and / or dual zone mixing system has been installed in the digester, on the heat exchangers or within any other ‘upstream’ stage of the waste water and digestion process.

their experiences with numerous installations, P&M Pumps have been able to demonstrate that a unique and unmatched product with expertise can bring significant cost-savings. In most cases, retrofitting a VAUGHAN Chopper Pump into a problematic area improves the whole process and will be self-financing, with payback periods of less than one year, thereafter minimising the effect to the budget holders.

Further information on Vaughan Chopper Pumps and associated mixing systems is available from;

Matt Harvey,  Director P&M Pumps Ltd

Tel: +44 (0) 1487 830123
Fax: 01487 832888
Email: sales@thesolidsolution.co.uk
Website: www.pumpmix.co.uk

Heavily laden unscreened sewage containing rag and other debris occurring at pumping stations, is acknowledged as being one of the toughest challenges for pumps, particularly when the site is subject to low flows and slack gradients. This situation was occurring at a submersible foul pumping station near the Sinfin Golf Course in Derby, a Severn Trent Water facility. The pumping station was constructed as part of a major project to alleviate flooding in a residential area in Sinfin. The incoming sewer used to be a 1250mm trunk sewer and as part of the project the main flow was diverted away and into a new trunk sewer. However, the existing trunk sewer had to be retained to serve a smaller number of residential properties as it was not practical to relay this sewer due to access difficulties.

Severn Trent Water was using pumps with different types of impellers and these were unable to cope when large amounts of rags were washed into the pump well after storm conditions. Following each storm the volume of rags arriving at the pumping station was such that the existing solids handling pumps could not cope. Over pumping had to be arranged to protect against the potential flooding of local properties, whilst the failed pumps were lifted and unblocked.

Based on his previous experience, David Stone, the Derbyshire Pumping Station Manager, suggested a trial using Vaughan Chopper Pumps, supplied by solids handling pumping specialists P&M PUMPS.

4 months later and following 700 hours of operation the Vaughan Chopper Pump has not blocked, even after storm flows and high volumes of ragging occurred. As a result, call out charges and the associated maintenance costs have been eliminated.

When the Chopper pumps were inspected as part of routine maintenance no wear has been found since installation, even though normal amounts of grit were present. Severn Trent Water acknowledge the performance of the Chopper pump and it’s ability to meet the challenges arising from storm flows and large amounts of rag, when all other options had failed to cope with the conditions. STW have also installed Chopper pumps on 2 other similar sites following the inability of other types of solids handling pumps in dealing with high volumes of rag and debris.

Through their experiences at numerous installations, P&M Pumps have been able to demonstrate that Vaughan Chopper Pumps can bring significant cost-savings. In most cases, retrofitting a Vaughan Chopper Pump into a problematic area improves the whole process and will be self-financing, with payback periods of less than one year, thereafter minimising the effect to the budget holders.

Further information on Vaughan Chopper Pumps and associated mixing systems is available from;

Matt Harvey, P&M Pumps, Sawtry, Huntingdon, UK.

Tel: +44 (0) 1487 830123
Fax: 01487 832888
Email: sales@thesolidsolution.co.uk
Website: www.pumpmix.co.uk

The UK aim of achieving targets for zero food and packaging into landfill have clearly focused attention on ways of developing technology that can contribute to a significantly reduced reliance on carbon based fuels and reducing emissions. Of particular interest is the potential for converting problems associated with the disposal of organic waste materials into energy generation through the process of anaerobic digestion.

P&M Pumps Ltd have worked with the UK’s water utility companies for over 20 years in various anaerobic digestion applications and during the last 10 years have witnessed a very positive change in the way that waste has been considered as a source of alternative energy. During this time P&M have provided specialist knowledge and expertise along with their Vaughan ROTAMIX mixing systems which has resulted in a 100% performance over the life of the plant.

ROTAMIX is a large scale pumped mixing system that guarantees a complete mix inside the anaerobic digester by suspending all organics, fats, oils and grease (FOG), grit and non-organic solids into a homogenous mix. The system uses strategically positioned large orifice jet nozzles which create a mixing action compatible with mixing waste materials. At the ‘heart’ of the system is the Vaughan Chopper pump which allows optimum liquid velocity and pressure to be introduced at pre-determined positions inside the tank, without fear of clogging the pump or nozzles. This enables any solids that are fibrous and prone to re-weave, to be constantly reconditioned.

It also maximises the effective volume of the tank by eliminating settlement of solids on the tank floor – a process best described as ‘dual zone mixing’. Overall energy costs are comparable with existing mixing technologies due to the ability of the system to be operated on an intermittent basis, in addition to it being able to quickly move the entire contents of the tank from standstill. This also allows important maintenance to be carried out on the chopper pump that supplies the recirculation and mixing action inside the digester, without reducing the effectiveness of the digestion process.

Here are the many features and benefits of ROTAMIX.

Retained digester volume and minimal settlement with over 90% remaining  operational during its working life. Effective solids reduction and continuous recirculation during mixing ensures full distribution and breakdown of solids, both mechanically and biologically. Increased and retained gas production is maintained to levels seen at system start without drop-off. Minimal cleanout costs due to continuous solids suspension. And finally low installation costs as all rotating equipment is externally mounted and internal equipment is easily installed.

Further information on ROTAMIX is available from:

P&M Pumps Ltd, Sawtry, Huntingdon, UK.

Tel: +44 (0) 1487 830123
Email: sales@pumpmix.co.uk

Website: www.pumpmix.co.uk

Maximising the benefits of an anaerobic digestion system by achieving a higher gas yield, reducing foaming and eliminating maintenance problems were the important benefits achieved following the installation of a Vaughan Rotamix system at Basildon sewage treatment works.

Gas compressor mixing systems were originally installed on the two anaerobic digesters, receiving indigenous sludge from the site where it was digested by bacteria to reduce solids and provide a rudimentary cleansing of the sludge mass. The digesters harness the Mesophilic bacteria to volatise organic mass with the sludge, to produce methane. The methane is stored in gas bags and then used to heat the digester boilers, which in turn heat the pasteurisers and ultimately provide heating for their office buildings at the Basildon site.

Prior to P&M Pumps-System Mix Ltd installing the two Vaughan Rotamix Anaerobic Digester mixing systems, AWS were experiencing increasing process problems due to poor mixing in the digester including numerous operational and biological issues. These key issues were high grit deposition and thus reducing active volume of digesters threatening to significantly reduce output outside compliance requirements. Also, the compressors required high levels of maintenance and were proving costly to keep running, furthermore, as deposition increased, the maintenance issues escalated.

In addition, foaming issues were common and although the gas mixing process was not the primary cause it certainly exacerbated the problem. Not only did the rag mass reweaving within the digester impair their efficiency, it also caused blockage problems in the heat exchangers and further downstream pumps and systems.

Approximately 2 years ago AWS decided to replace the gas compressor type mixers with the ROTAMIX systems and to date they have been delighted with the results. A spokesman at Basildon STW site confirmed, “In the two years since installing the Vaughan Rotamix systems, we are confident that we have seen an increase (although this has not been quantified) in the gas yield from the digesters. He continued, “In addition, we think the system has contributed toward there being a reduction in foaming problems, although we are dosing anti-foam which we were not doing prior to the new mixer installation, so overall we have reduced operational costs.’’ Furthermore, AWS confirm that since installing the ROTAMIX system the digester temperature range from upper sludge level to tank floor has remained a constant ± 1°C, mixing has improved, volatisation of solids is better, gas production has increased and the constant rag issues have been significantly reduced, even eliminated.

When asked about the features they particularly appreciate AWS commented that the externally mounted pumpset and ‘in-situ’ adjustable design make accessibility simple. The overall performance of the VAUGHAN Chopper pump has significantly reduced maintenance expenditure. In fact, after carrying out the yearly inspection on digester pumps 1 and 2, which had been running for 12 months 24/7, all wet end chopping components were showing no wear. AWS feel that once the two systems are optimised and the operational philosophy is modified they will potentially realise at least 4 to 5 years normal operation before any replacement spares are required.

SYSTEM MIX and P&M PUMPS have worked with the UK’s major water utility companies for over 15 years in various anaerobic digestion applications and during the last 10 years have witnessed a very positive change in the way that sewage sludge has been considered as an alternative source of energy. During this time they have both provided specialist knowledge and expertise in selecting the ROTAMIX mixing systems and are confident that the majority of installations have resulted in up to 100% performance over the life of the plant.

Further information on SYSTEM MIX and their ROTAMIX and other tank mixing systems is available from:

Andy Parr, System Mix Ltd, Sawtry, Huntingdon, UK.

Tel: +44 (0) 1487 830123
Fax: 01487 832888
Email: sales@thesolidsolution.co.uk
Website: www.pumpmix.co.uk

Overcoming the unique challenges of Gibraltar’s waste water system which led to an effective solution to the pumping problems occurring is the latest example of success for Vaughan Chopper Pumps.

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As part of their increasing involvement in providing specialist knowledge and expertise on mixing technology for anaerobic digestion applications, SYSTEM MIX LTD has recently become a member of The Anaerobic Digestion and Biogas Association (ADBA).

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Reducing costs associated with unplanned maintenance and achieving significant savings on energy consumption were the important benefits achieved at a Severn Trent Water facility, following the installation of Vaughan Chopper Pumps, supplied by P&M Pumps.

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Solids pumping and mixing specialists P&M Pumps, UK distributors of Vaughan Chopper Pumps, are delighted to confirm that they have recently secured a Framework agreement with Southern Water to supply pumps and mixing systems.

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