Membrane filtration for recovery in dairies

Karsten Lauritzen looks at four different recovery applications where membrane technology is used.

Protection of the environment and the reuse of resources are in great focus these days, and environmental awareness has become essential to the dairy industry, who is putting still more attention to green image and sustainability.

Focus can be on many different factors in the production, such as raw materials, water, chemicals, and waste. Membrane filtration has proven to be a powerful technology for solving many of the challenges facing the dairy industry.

Water recovery

Today, water is an important but not unlimited resource in the dairy industry. In consequence, reverse osmosis (RO) has become an important technology for recovery of water from products or streams. In addition, recovery of condensate from evaporators is a well documented application, which enables the dairy to reduce the intake of well water by running condensate through an RO system.

RO technology has also proven helpful for concentration of product prior to evaporation or transportation. In this case the product, which can be whey or milk, is concentrated by removing water, which can be used for cleaning or other process steps. Like condensate recovery, this process will reduce the intake of well water and will have a significant impact on reduction of transportation costs, if the product is to be transported to another production site.

Milk recovery

Milk Recovery is defined as concentration of the intermediate phase of a flush, where flush water and milk is mixed. The intermediate phase is therefore diluted milk that ends up in the waste water, wasting the value of the solids contained. DSS has developed a membrane based technology, where the intermediate phase is collected in a silo and the total solids content is concentrated to that of the original milk (approximately 9-13 per centDM) by removing water by means of RO. Consequently, the dairy optimises use of the raw material (milk), and reduces the environmental load by not wasting the dry matter and making it possible to reuse the recovered water. So milk recovery will save you money and protect the environment at the same time.

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Caustic recovery

The caustic recovery technology is the latest development in the category of membrane based recovery technologies from DSS. Focus is on dairy ingredient installations where large volumes of caustic are used every day for cleaning of evaporators and dryers.

The principle of the technology is to collect all the spent caustic in a silo and send it through a filtration unit, where suspended solids and some of the dissolved solids are removed. Clear caustic is recovered and fed back into the clean caustic. Recovery can be up to 95 per cent, depending on the volume of suspended solids.

Caustic Recovery will reduce the consumption of caustic and reduce the need for heating, as the filtration process can run at 70°C.

Brine recovery

A brine bath is continuously being polluted by the cheese. Proteins, fines and other nutrients accumulate in the brine when the cheese is leaving the process step. This makes it possible for micro organisms to grow and eventually spoil the brine. For this reason the brine has traditionally been pasteurised or discarded.Today, DSS has a membrane-based technology (Brine Clear), in which bacteria, fines and some of the nutrients are removed by microfiltration. The system operates like a 'kidney' and is very flexible. Some dairies operate Brine Clear on a continuous basis; some only run the system when needed.

By use of the Brine Clear system from DSS the brine can remain in production longer than before, saving time and money otherwise spent on renewing and pasteurizing the brine.

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Karsten Lauritzen is Manager R&D, DSS Silkeborg, AS, Silkeborg, Denmark.

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