Zetasizer Nano Delivers Easy, Operator-Independent Measurement for Optimising Water Treatment


Malvern, UK: The Zetasizer Nano particle characterization system from Malvern Instruments has become an essential tool at a water treatment production facility in the US. Here it is being used to monitor the zeta potential of raw water in order to optimise the concentration of alum added as a flocculating agent. Zeta potential values are key to monitoring and maintaining optimum conditions in the plant, and measurements using the Zetasizer Nano have proved to be both easy to make and operator independent.

Impurities in waste water are primarily anionic, and cationic additives have been developed for their neutralisation. By optimising the addition of additive, the amount of additive used and hence the cost of treatment, can be reduced.

The appearance of turbid water is due to the presence of suspended particles. By controlling the effective charge of these contaminating particles the efficiency of removal can be improved. The effective charge can be quantified through the measurement of zeta potential. At close-to-neutral charge, particles flocculate and sediment leaving the water clear. Zeta potential measurements provide a tool for quantifying the optimum concentration of additive required.

Studies of additive concentration versus zeta potential and turbidity have shown that flocculant addition beyond a certain point is counter productive. For example in one system, when the zeta potential of the water mixture is close to zero, so too is turbidity. At low doses of flocculating agent the zeta potential is approximately -16mV and turbidity is high. At +2mV turbidity it is at its minimum and beyond this point the further addition of flocculating agent reverses and increases the charge of the contaminating material, restabilising it in the water, increasing the turbidity.

The goal of the US facility is to maintain a zeta potential of around zero. Only by measuring and monitoring the zeta potential on a control chart can operators make rational and optimal adjustments in the amount of alum added.

The Zetasizer Nano series combines dynamic, static and electrophoretic light scattering, enabling the measurement of particle size and zeta potential in a single easy to use system. A unique cell for zeta potential measurement consists of an electrode and folded capillary moulded into a single chamber, that can be disposed of after a number of measurements instead of cleaning. Importantly for many water treatment applications, the addition of the MPT-2 Autotitrator allows zeta potential to be studied as a function of additive. www.malvern.com

About Malvern Instruments
Malvern Instruments provides a range of complementary materials characterization tools that deliver inter-related measurements reflecting the complexities of particulates and disperse systems, nanomaterials and macromolecules. Analytical instruments from Malvern are used in the characterization of a wide variety of materials, from industrial bulk powders to the latest nanomaterials and delicate macromolecules. A broad portfolio of innovative technologies is combined with intelligent, user-friendly software. These systems deliver industrially relevant data enabling our customers to make the connection between micro (such as particle size) and macro (bulk) material properties (rheology) and chemical composition (chemical imaging).

Particle size distribution, particle shape information, zeta potential, molecular weight, chemical composition, and bulk materials properties can all be determined with instruments from the Malvern range. The company's laboratory, at-line, on-line and in-line solutions are proven in sectors as diverse as cement production and pharmaceutical drug discovery.

Headquartered in Malvern, UK, Malvern Instruments has subsidiary organizations in all major European markets, North America, China, Korea and Japan, a joint venture in India, a global distributor network and applications laboratories around the world. www.malvern.com

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Trish Appleton, Kapler Communications
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Wyboston, Bedfordshire, MK44 3BY, UK
Tel: +44 (0)1480 479280; Fax: +44 (0)1480 470343 trish@kapleronline.com

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Marisa Fraser, Malvern Instruments Inc.
117 Flanders Road, Westborough, MA 01581-1042 USA
Tel: +1 508 768 6400 Fax: +1 508 768 6403 marisa.fraser@malvern.com

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