RENE WABL E S
ECONOMICAL WATER TREATMENT THROUGH BLENDING
Water conducts and controls industrial processes in industries such as manufacturing and energy generation as well as in heating, ventilation and air-conditioning applications. Before it can be used, it has to be processed appropriately. One technique that is often used consists of blending raw water with processed water until the required quality is achieved, directly in the end user’s plant.
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wo basic techniques are used for blending: proportional regulation and qualitative regulation. The type of treatment required determines which technique is best suited in any given case. This depends on the industry and the application concerned. Cooling towers and plant for ventilation technology (AC re-cooling) often require that the degree of hardness, the electrical conductivity, or the sulphate and chloride content be reduced. For irrigation systems in plant cultivation, the salt content is an important factor that needs to be measured to prevent substrate salinisation.
THE WATER TREATMENT TECHNIQUE DETERMINES THE BLENDING PRINCIPLE Where reverse osmosis is used to extract salts from water, what results is pure water known as the permeate, and because relatively few ions remain, it conducts practically no electricity. The salt content of blended water can then be determined very accurately by means of a conductivity measurement. On the other hand, if an ion exchanger is used, knowing the conductivity is of no help because ions are simply ‘exchanged’, the conductivity remains almost the same. In such cases an alternative is needed – if possible, this may be simple proportional blending. To produce blended water with a particular degree of hardness, both techniques require the raw water quality to remain essentially constant. However, if the raw water
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hardness varies, then a combination of proportional regulation and qualitative regulation is needed. In all cases, the regulation must be carried out exactly and rapidly, and even where boundary conditions change (e.g. variable flow rates), the quality of the blended water must meet the requirements as closely as possible to ensure constant production conditions.
A PRACTICAL BLENDING SOLUTION Whether the raw water quality is constant or varies – modified blending principles are used. Therefore, the most practical solution consists of stand-alone operation that saves the plant operator from having to intervene in existing plant processes. Bürkert Fluid Control Systems supply modular blending units that can deal with practically all usage scenarios that may arise. This is where the user profits from a broad product portfolio of components that are designed to work perfectly with each other. Analogue and digital interfaces are available if communication with the process is required. FAST, ON-SITE INSTALLATION The pre-assembled module with two infeed connectors and a blended water connector only has to be integrated into the existing water supply, or integrated into the water treatment plant as a pre-wired component solution. The values for the required quality or the blending proportions are pre-set, so the blending unit can be put into operation immediately. WWW.UTILITYMAGAZINE.COM.AU
