Wastewater treatment challenge to manufacturing

Ashley Shepherd, UK sales manager at the pumping specialist Watson-Marlow Pumps Group, considers the importance of accurate effluent treatment for UK business in the context of the Water Framework Directive

The process of wastewater treatment will change forever with the introduction of the Water Framework Directive (WFD), which aims to rationalise and update existing water legislation, as well as improve standards of protection for the water environment.

This coupled with other legislative pressures – such as REACH and the IPPC regulations – led companies to the conclusion that the management of wastewater is a complex and expensive process. Companies have the choice of treating their own effluent, or paying trade effluent prices. The latter option has become so costly that companies are increasingly building their own in-situ wastewater treatment plants.

Of course, this move towards insitu effluent treatment might be seen as challenging. However, it has the added benefit of allowing appropriately treated water to be recycled back into the manufacturing process. Such resource efficiency initiatives are heavily encouraged by all of the government environmental support programme schemes, such as Envirowise, as a means of saving money and resources.

Accurate dosing

With stricter control over effluent becoming more important, accuracy of chemical dosing is vital. Many existing pumping systems may not be able to perform to the levels that will be required by the Water Framework Directive, particularly for those wishing to recycle their own water.

Water industry representative, Water UK, revised the guidelines on treating effluent at the beginning of 2008, making them tougher, and reinforcing the importance of ensuring that polluted water doesn’t get out into the public sewerage system.

In the words of Steve Ntifo, science and environment adviser at Water UK: “Trade effluent consents are among the UK’s most important environment protection measures.

The revised guidelines provide a clearer process and will make it easier for businesses and sewerage companies to ensure compliance with legislation.

“The guidelines also carry a strong environmental message about the composition of products and overall impact on the environment. They should give businesses an extra incentive to improve their operations and bottom line by cutting out substances that need additional treatment and so attract higher discharge consent charges.”

Polluter-pays principle

Water companies are being encouraged to become more

proactive in terms of prosecuting, in line with the whole polluter-pays principle, which will be affirmed by the Water Framework Directive. The message is quite clear: effectively treat your effluent or face the financial consequences. This is the

last thing any business needs in such a challenging economic climate. Being held up for pollution charges is likely to have a detrimental effect for a company in

terms of reputation among customers and stakeholders, particularly in consideration of the UK’s current heightened environmental awareness.

So, how can plant managers meet the challenge of treating industrial effluent while incurring little in the way of system upheaval?

One route is to take a closer look at the technology being used to handle the chemical dosing needed for the water treatment. The majority of chemical dosing and metering applications require pumps capable of handling 4-6bar back pressure and traditionally this application has been fulfilled by diaphragm pumps.

However, while the pumps perform relatively well when there is no back pressure, flow rates can vary widely when line pressure increases. This variation in flow translates into under/over dosing into the main process flow line with

the potential to incorrectly treat effluent, or, add too much chemical.

Peristaltic pumps

Avoiding these issues and reducing costs can be achieved by specifying peristaltic pumps that can be controlled by process signal or run as part of a Profibus network and provide dosing accuracy of ±0.5%, irrespective of fluctuations

in line pressure or fluid viscosity.

Furthermore, peristaltic pumps do not require valves, strainers or pipework and do not suffer gaslocking problems, so maintenance of the chemical dosing system is greatly reduced.

Improving the performance of a wastewater treatment plant makes economical sense in terms of reducing operating costs as well as more effective regulatory compliance. Accurate dosing negates the need for corrective measures and ensures no excess energy is consumed.

If the Water Framework Directive is to meet its ultimate goal – that all inland and coastal waters reach “good” status by 2015 – there will have to be a huge revision of current wastewater regulations.

The sooner manufacturing companies accept full responsibility for the treatment of their effluent, the sooner pollution problems will improve and the need for water companies and regulators to enforce fines will be reduced.

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