Huge water savings in dairy production
New water technology from the Danish company Silhorko-Eurowater A/S reduces water waste by more than 75% at a Danish dairy. The dairy is located in Brabrand west of Aarhus and is owned by the Danish dairy company Arla Foods. Arla is a responsible food provider focusing on sustainable dairy production. In this context, water consumption plays a major role and water saving was high on the agenda in connection with replacement and modernization of the dairy’s water treatment plants.
The nearby waterworks supply the dairy with clean drinking water. Dairy production requires clean water in various qualities; drinking water quality is insufficient. The largest volume of water – approximately 90,000 m³ per year – is used for a number of purposes: condenser, cooling water for homogenisator, and heat exchangers for pasteurisation equipment and centrifugal separators. Here, it is important that the water is soft in order to prevent calcium deposits. In other words, softening minimizes operational costs and prolongs the life of technical plants and installations.
The solution is a softening plant type STFA comprising two vessels with ion exchange resins. The softening plant has a total treatment capacity of 40 m³/h and is designed with a distributor section that ensures smooth and uniform flow distribution whereby the capacity (the total volume of filter media) is fully utilized. The produced water is collected in a reservoir of 15 m³ from where frequency-controlled pumps distribute the water to the production sites.
When the plant capacity is exhausted, the plant is regenerated with a saturated saline solution known as brine. Costs for water and salt for regeneration constitute a large part of total operating costs. To optimize this process, the plant is equipped with a number of special features that minimize the consumption of water and salt:
- Monitoring of regeneration water quality. When the ion exchangers are cleaned, regeneration stops.
- Reuse of regeneration water from the various regeneration phases to the extent possible.
- Exact plant design enabling the plant to use exactly and only the amount of salt that the plant shall use – regardless of ambient temperature.
Brine for regeneration is produced by a brine maker, i.e. an automatic system for preparation of large quantities of saline solution. The system can handle one ton of salt at a time. The dairy uses fine salt in big bags. Filling is carried out once a week using an overhead travelling crane in accordance with environmental security standards.
Demineralized water by water-saving RO unit
An annual water volume of approximately 5,000 m³ of the softened water is further treated and used as make-up water for steam boiler, laboratory use, and internal cooling on filling machine. Here, it is important that the water is demineralized, i.e. free of salts. This is accomplished in a reverse osmosis system using membrane technology to produce demineralized water without the use of chemicals. The reverse osmosis system is of the type RO-PLUS, characterized by a particularly high water recovery. In comparison to traditional reverse osmosis systems, the water waste is reduced by 60%. In this case, a large operational saving on water consumption was achieved.
Total water saving
Annually, the water saving totals approximately 5,500 cubic metres. The dairy pays a water price of EUR 4,16 per cubic metre for water and discharge tariff. Thus, the dairy saves approximately EUR 23,000 a year on its water bill. Add to this saving on consumption of salt and energy, which is affected positively by all the modernization measures.
Photo Credit: Silhorko-Eurowater A/S