CHANGING TIMES

Bryan Fawcett 28/10/2008

167 4 minutes read

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The UK’s population is growing and, combined with the large amount of solids and floatables now finding their way into sewers, water and wastewater treatment plants have got more to cope with than ever before. Gerald Muldoon, senior sales engineer of Mono NOV, looks at how new pump and packaged solutions technology is evolving to meet the changing needs of the market.

As key elements of the treatment process, both pumps and packaged systems, consisting of screens and grinders, can help provide solutions to dealing with higher levels of wastewater and difficult to handle materials.

For example, progressing cavity pumps can be used throughout treatment plants to manage both wastewater and waste materials.

They are designed to handle media more viscous than water, as well as where there are solid inclusions. Typical media include primary, secondary and dewatered sludges, as well as supernatant liquids and even filter cake.

The discrete cavities within the pump and the interface between hardened steel rotor and resilient stator make progressing cavity pumps far more efficient at dealing with difficult to handle media than centrifugal pumps.

Progressing cavity pumps are also designed so that flow volume is effectively linear to running speed, which means they can easily respond to changes in flow demand (for example with a variable speed drive), ensuring more energy efficient pumping and processing versatility. They can also run at a range of rotational speeds, without wasting energy.

Progressing cavity pumps are extremely robust and leading pump manufacturers offer warranties up to 10 years on special drive shaft connections, emphasising their reliability and low running costs over a long working life.

Centralisation

In addition to modernising equipment, many treatment works are centralising certain duties to improve efficiency and help deliver cost savings. It is therefore essential that pumps can handle larger capacities processed at main sites.

Progressing cavity pumps can easily handle volumes in the region of 500m3/hr plus, even at elevated pressures. For example, two high performance progressing cavity pumps from the leading manufacturer were specified by a northern water company to help meet its heavy duty demands.

The pumps were used on a desludging duty, which involves taking sludge from the plants primary tanks and feeding it into a sludge storage tank. The progressing cavity pumps were installed because the plant’s previous pumps could not cope with the high viscosity and volume of the sludge, which can contain up to 12% dry solids, coupled with a required suction lift of four meters.

The progressing cavity pumps, which were designed and installed with heavy demand issues in mind, have been running perfectly since installation without any need for spares.

Down the Drain

In terms of handling solids and floatables, more and more non disposable waste is entering the drains that needs to be processed by wastewater facilities. Items such as facial wipes, cleaning cloths and ‘disposable’ toilet brushes are being flushed into the sewers instead of being thrown in the bin.

For water and wastewater treatment works this can cause serious ragging issues at pump station collection. These inclusions are particularly damaging to centrifugal pumps, as the propeller vanes and shaft can be totally entangled.

However, to combat this, packaged solutions which combine a screen and grinder, can be used to screen and macerate any unwanted solids. This will protect the pump and maximise its efficiency, enabling pumping to continue at high pressure without fear of blockage.

The latest generation of high performance, packaged systems, have a capacity of up to 16,000m3/hr and have the ability to capture solids at 5mm or 9mm aperture sizes. These systems incorporate cutting discs on contra-rotating shafts, while the remaining shafts are fitted with overlapping and intermeshing discs, a combination that delivers highly effective size reduction of solids. They need no manual attendance or cleaning and eliminate the disposal costs of handling debris exacted by traditional screening processes.

Specialist designers and manufacturers of packaged pumping systems can work with treatment plant design engineers and installation contractors to meet their specifications exactly, with equipment packages tailored to their specific site conditions and process requirements.

They have the detailed knowledge and practical experience to devise a solution that will provide optimum efficiency and low lifetime costs, a valuable service that cannot be offered by supply-only sources.

Additional Support

This level of support and service has become increasingly important as, due to the automation of many plant processes, there are now fewer on-site engineers in wastewater facilities. This has resulted in a need for extra support and advice from pump manufacturers.

Project management and installation is now an area in which leading pump manufacturers can offer additional support. Dedicated teams can provide 3D design of equipment and installation into new or existing plants and qualified engineers will work to health and safety regulations to install necessary equipment quickly in order to minimise downtime.

Some manufacturers also offer planned maintenance contracts to help make sure a plant’s equipment continues to work, therefore maximising performance.

Importantly, systems and solutions providers need to work closely with the industry to raise awareness of the potential and versatility of pump, screen and grinder technology to help ensure treatment works can continually improve processes and cope with the increasing demands of our growing population.

Mono Pumps

Audenshaw

Manchester

Can be contacted on

Tel: 0161 339 9000

Fax: 0161 343 7340

E-mail: info@mono-pumps.com

Web: www.mono-pumps.com