How to drought-proof infant formula plants
Monday, 18 December, 2017
The infant formula industry offers Australian manufacturers significant opportunities for water re-use.
Raw milk contains roughly 85–87% water, most of which is removed in the production of whole milk powders and high-value infant formula blends. Water is removed either by drying the milk using milk evaporators or by using membrane processes such as nanofiltration (NF) and reverse osmosis (RO).
An infant formula processing facility which takes in 1 million litres of milk per day can be left with 850,000L of wastewater commonly known as ‘cow water’. The quality of this water is extremely good, as it contains very little dissolved salts and very low levels of organic matter due to the distillation/membrane filtration processes used in production of milk powders or infant formula. This much water represents a significant opportunity for Australian manufacturers to improve their sustainability and ‘droughtproof’ their operations.
There are other separate wastewater streams generated by cleaning and general processes within the factory which are a far higher strength, and would require robust treatment before re-use; however, the opportunity to recycle this cow water presents the possibility for dairy plants to be either net neutral water consumers or even water producers.
This offers considerable savings in the upfront investment and operation of wastewater treatment plants. Even if the wastewater is clean enough to discharge to sewer without treatment, the fee for the volume that is discharged can be avoided by recycling. This offers savings of typically $1–$3 per kL of water that is recovered, with an additional offset to the purchase price of water.
There is a misconception that since the treated water is still regarded as recycled that it must have limited re-use possibilities within the dairy — this could not be further from the truth! The water can be used in any part of the process apart from make-up water in the final product (such as liquid infant formula blends). The key is to ensure it is appropriately treated before use.
It is important to note that the cow water should not be sent directly to the infant formula wet mix processing plant. This is due to the protein (carbon) content being too high in the cow water and leading to the growth of microorganisms within the pipe network. Although high doses of chlorine can be used to counter this, this leads to the production of carcinogenic trihalomethanes as well as an impact on final product quality and taste. Hydroflux has previously written about the importance of treating this process water to ensure the quality of this ‘white gold’ that is infant formula here.
Easy re-use options for cow water that can use basic chlorination for treatment include using the chlorinated cow water for washdown and first flush CIP.
Better treatment of the cow water increases its potential uses, which typically involves polishing with NF or RO. A common misunderstanding regarding the design of the treatment system is that a typical ‘dairy milk RO’ plant is all that is required.
Dairy milk RO plants and water treatment RO plants are very different. Dairy RO plants are designed for treating liquid with very high solids content, and require a higher cleaning frequency as a result — usually once to twice per day. Dairy ROs also operate an overall lower design recovery rate. Due to the high value of the milk-based products that these systems produce, the internal rate of return on the investment in the equipment is less impacted by the costs and downtime associated with higher cleaning frequencies. It is also possible to install multiple ROs to ensure there is continuous production.
This approach doesn’t work when considering dairy ROs for cow water treatment, where the alternative cost to purchase town water, use and treat water on-site is only around $0.002 to $0.004 per L. This is significantly lower than the cost of milk, at around $0.38–$0.45 per L. The cow water treatment plant must treat as much water as possible in the most efficient manner, and the system must operate with very infrequent cleaning, low operator input, low chemical consumption, high energy efficiency and high overall water recovery.
Utilising ultrafiltration or microfiltration followed by a high-recovery RO system offers a method to ensure the overall efficiency of the cow water treatment system is high. Although requiring additional capital investment, the overall return on the investment is significantly better than simply treating the cow water with a dairy RO as there will be lower operating costs and longer run times between treatments.
Following treatment with ultrafiltration and RO combination, the cow water can be used virtually anywhere in the process. This includes supplementing or replacing the town water supply to the infant formula sanitary water treatment system. Other uses include cooling tower make-up, boiler water make-up, final CIP rinse for the general processing areas and the infant formula processing equipment as well as other non-food contact applications.
Note here that even after ultrafiltration and RO the treated cow water should not be sent directly to the production of infant formula in the wet-mix plant. The organic carbon levels, which have likely been reduced from 5 to 10 mg/L to 0.5 to 1 mg/L are still too high and result in microbiological growth within the pure water pipe network over time, which can lead to product contamination. Generally, well-designed sanitary pure water processes do not require residual chlorination in any form. Strong oxidising agents like hypochlorite can affect flavour, produce trihalomethanes and damage the nutritional components of the final product. Other residual disinfectants such as chlorine dioxide or ozone can be utilised, but their effectiveness is limited.
The dairy industry is a key cog in the Australian economy. The continued growth of Australia’s infant formula industry depends on Australia maintaining world-class positioning with quality products that are produced in highly sustainable and water-conscious businesses.
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