Drinking water filtration with membranes widely adopted

With membrane filtration processes becoming more popular across a range of industries, pre-treating raw water has become increasingly important to extend the life of downstream filters, reduce maintenance costs and energy consumption and ensure reliability.

All wastewater and water treatment processes where membranes are used are fundamentally multi-stage processes.

Microfiltration and ultra-filtration require only pre-filtration of coarse contaminants (>50 μm), whereas with nano-filtration and reverse osmosis there is a further requirement that the raw solution should be free of particle and colloidal contamination. This explains why good pre-treatment of the raw water is so important, to be able to ensure reliable and above all economical membrane filtration.

In addition to mechanical pre-cleaning using conventional filters, chemical and physicochemical processes are also often used in the pre-treatment for membrane processes.

The first step in pretreatment generally consists of coarse filtration. This removes the coarse-grained solid material that can penetrate the system from the raw water. Screens or coarse filters in sizes 1 to 5 mm are used.

In the next stage, the raw water is further treated to obtain the required raw water quality for the membrane filtration that follows. This can be done both by using mechanical fine filtration and also in combination using physicochemical processes such as coagulation, flocculation and precipitation.

Membrane filtration is usually followed by an aftertreatment, e.g. disinfection.

Depending on the quality of the raw water and the water quality required after treatment, the engineering processes are adapted to the special requirements.

For HYDAC Process Technology division, pre-filtration upstream of membranes is an important market sector. HYDAC products such as the automatic back-f lush filters AutoFilt RF3 / RF4 / RF5 / RF7, the AutoFilt TwistFlow Strainer ATF and an array of strainer filters and inline filters are available for these applications.

With its new depth filter PLF1, HYDAC has the perfect high-f low fine filter which will protect the membranes effectively.

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