Facts & Figures
|Client||Sachsenmilch Leppersdorf GMBH|
Sachsenmilch Leppersdorf GmbH, part of the Unternehmensgruppe Theo Müller, processes approx. 1.8 billion kg of milk (fresh products, sliced cheese, mozzarella cheese, UHT milk and butter) per year. The product range is very large and in this complexity unique in Europe. From the whey, resulting from cheese production, high quality lactose powder, whey protein powder and calcium phosphate powder is directly refined on site. From the residues of the lactose production ethanol is won and successfully marketed.
All plants must be cleaned at regular intervals, as is usual in all dairies. The cleaning consumes water and detergents. The resulting wastewater is generally pre-treated and subsequently treated in municipal wastewater treatment plants. The Leppersdorf dairy has (due to quantities of processed milk and whey) its own wastewater treatment plant. The limits for the direct discharge of the treated wastewater are far below the legally prescribed values.
Milk is known to contain calcium and so the effluent of a dairy contains a high value of calcium. This calcium has the unpleasant property that together with the appropriate water hardness soluble calcium will scale in pipelines and other components. This is the case when the pH is increased, for example by the stripping of carbon dioxide from water.
This operation is even stimulated, when the wastewater is actively evaporated in e.g. cooling towers, which are needed to lower the effluent temperature to enable discharge to a water body. Because of the large amount of wastewater from the dairy in Leppersdorf (10,000 m³ to 12,000 m³ per day), water reuse projects have been built in the past. In one of these projects, the treated wastewater is used as process water for refrigeration.
The treatment includes an Ultrafiltration and Reversed Osmosis (RO) system. Again, the calcium carbonate deposited on the membranes led to frequent cleaning and backwashing. The only proven remedy against the deposits so far was the costly dosage of carbon dioxide in the water, to preserve the lime-carbonic acid balance of the water and prevent calcium deposits. Despite the carbon dioxide interference in the wastewater, the time-consuming and regular elimination of calcium deposits was not completely prevented. Various tests and pilot trials of different technologies for better cleaning of the facilities or to avoid the calcium deposits brought no satisfactory result.
The Dutch engineering/technology company Royal HaskoningDHV provided a solution with their "Crystalactor®” process, a well proven technology used for more than 30 years across the world with a strong reference base in softening municipal and industrial applications.
The Crystalactor® is essentially a fluidized-bed type crystallizer for the selective removal and recovery of components from water and wastewater. The pellet reactor is filled with crystallization material. This may be sand or a different ground material of defined grain size. The wastewater is pumped up in the Crystalactor® and holds the crystallization material in a fluidized state. The water is pumped in an upward direction, maintaining the pellet bed in a fluidized state. To crystallize the target component on the pellet bed, a driving force is created by a reagent dosage and where necessary pH-adjustment. The pellets grow and are discharged from the reactor at regular intervals. There are no new additional waste streams in the process. An advantage of the process provides a relatively high dry weight of the pellets produced. After removal from the reactor and a dripping phase, the dry content is already 75 - 80%.
The pilot trials lead to construction
As a first step between Sachsenmilch and Royal HaskoningDHV a pilot trial on site Leppersdorf was done. From approximately 4.4 m³ of wastewater calcium compounds were removed per day. The original concentration of 60 mg / l could be reduced in the trial to about 10 to 20 mg / l.
The result convinced Sachsenmilch and Royal HaskoningDHV took over the planning of a total plant for 18.000 m³ / day. This was a huge scale-up, but the engineers of Royal HaskoningDHV were convinced based on their experience with drinking water systems of similar magnitude. Royal HaskoningDHV took over the design and engineering of the plant and after completion of the tender documents the order to build the plant could be awarded to the company Sülzle Kopf GmbH. At the end of 2017, the plant was put into operation with wastewater and since then has been stable except for a few necessary optimizations. The lime deposits in the wastewater cooling system are already significantly reduced after a short time of operation, thus ensuring the profitability of the project.
From waste to a valuable resource
The pellets of the recovered calcium carbonate leave the Crystalactor with a residual moisture content of about 20%. Within Sachsenmilch one has decided to dry the pellets to be able to dispose them as a lime fertilizer to the farmers of the region. It was expected that, due to the origin of the waste water, the limit values of all pollutants in the pellets are far below the fertilizer regulation limits. In the meantime, compliance with all limit values of the lime fertilizer is demonstrated by measurements. Other applications are currently also looked at.
With the realization of this project, the company in Leppersdorf succeeded to generate a product from a supposedly waste material and thus the full use of all components present in milk is getting closer.