Water is essential for many applications in dairy processing, including equipment cleaning, and uses up to 60 litres of water per kilogram of processed milk, a recent report in the US Journal of Dairy Science says.
But water shortages and their effects on food supply and prices have raised growing concerns in the industry. In response, University of Nebraska-Lincoln researchers have come up with a way of safely reusing reconditioned water in food processing plants.
Under American regulations only potable water can be used to clean food contact surfaces and equipment surfaces.
Yulie Meneses and Rolando Flores subjected wastewater from cheddar cheese whey to reverse osmosis and ultrafiltration as well as an additional step of spray drying. The resulting reconditioned water was used to clean stainless steel surfaces that had a biofilm.
Test results from both bacterial counts and scanning electron microscopy analysis were described as promising.
“Using the combined ultrafiltration and reverse osmosis system, 47% of water can be recovered from whey,” Meneses said.
By incorporating spray-drying and condensation into the process, more water can be recovered. After suitable treatment, this water could also be used in cleaning applications or other activities making heavy use of water.
Matt Lucy, editor-in-chief of the Journal of Dairy Science which published the findings, said the research demonstrated an unwanted by-product of dairy manufacturing – whey – could be processed to generate clean water, saleable food, and additional revenue for dairy manufacturers.
Because of its potential in terms of revenue and conserving natural resources, these wastewater reclamation techniques were “highly interesting”. But more research was required to further evaluate the risks and broader environmental issues.
Commenting on the American research, a spokeswoman for the Ministry for Primary Industries said New Zealand dairy manufacturers were required to operate under the ministry’s risk management programmes to ensure the products they produced were safe and fit for purpose.
The ministry also specified technical requirements that supported the development of effective risk management programmes.
Specifications for water used within the manufacturing process, such as cleaning in place, focused on the quality of the water used rather than its origin. Advances in water treatment and purification mean that recovering water for re-use has become more common.
Regulatory requirements allow for the use of modern water recovery systems where they can be shown to produce water that is fit for its intended use.
It was common for water to be recovered during milk powder production and treated to make it suitable for cleaning in place or for use in heat exchange processes, the spokeswoman said.
Cost, efficient management of resources, environmental responsibility “and a global drive for manufacturers to reduce their water footprint” are among reasons for introducing the principle of efficient use of water through recovery during the manufacturing process.
Fonterra used 42 million cubic metres of fresh water in its operations during the 2014 financial year and recycled or reused 6% of total use. This was an increase of 1m cubic metres on the previous year, mainly as the result of more milk being processed and a new processing plant coming onstream. Water use per tonne decreased by more than 2%.
Theresa Wilson, sustainability team leader at Dairy NZ, said cost was an issue because ultrafiltration and reverse osmosis “is extremely expensive and not something most dairy farmers could run with the expertise required.”
DairyNZ guidelines for farmers who contact it about water conservation and effluent issues have also been used “to inform companies that are working in this space what hurdles they need to overcome”, Wilson said.
“It is quite technical but it needs to be, as it is quite a complex issue.”
DairyNZ’s main message is that farmers must be prudent about the water being used around the farm dairy and for yard washing to avoid compromising food safety.
Dirty water must be stored, then pumped around the farm and spread on to land through irrigation equipment. Water used in the farm dairy must meet standards for turbidity and clarity and be E coli-free.
The Ministry of Primary Industries has developed a code of practice for the design and operation of farm dairies.
The code specifies: ‘Effluent, wastewater and water recovered from the farm dairy effluent system must not be used for any purpose in or near any part of the farm dairy other than the yard unless it has been treated to meet potable water standards’.
DairyNZ nevertheless cautions that a treatment technology which can meet the parameters of the turbidity, clarity and E coli standards can’t necessarily be used in the farm dairy.
