Dairy processing plants have a unique opportunity for water reuse: Condensate of Whey or “COW” water, is the water generated when milk products are evaporated or concentrated. Because milk is almost 90% water, a lot of cow water may be available for reuse. For example, a dairy plant producing 50,000 pounds of cheese a day requires about 500,000 pounds of raw milk and generates over 50,000 gallons of COW water for each day of production. That’s almost 20 million gallons of COW water annually. The economic and environmental benefits of reusing this water is significant both in terms of reducing fresh water requirements as well as the load on the wastewater treatment plant.
Cow Water Reuse
With proper treatment, COW water can be reused for many applications including cleaning and sanitization, boiler feedwater, or cooling water makeup. In the United States, the Federal Grade-A Pasteurized Milk Ordinance (PMO) provides strict standards that dictate the water quality, treatment, and monitoring requirements for different uses. The least stringent standard (category 3) allows COW water to be used as boiler feedwater where the steam does not have direct food contact or as cooling water makeup where there is no direct contact or the potential for incidental contact with milk or milk products. A higher standard (category 2) must be followed if the COW water is reused as boiler feedwater for the production of food contact steam or for clean in place (CIP) pre-rinsing, and cleaning solution makeup water.
It is important to understand that the quantity and quality of COW water varies based on what the plant is producing at a particular time. A storage tank with provisions to divert contaminated COW water and control microbiological growth is typically used to collect the water as it is produced. Depending on the end use, it may be necessary to blend the COW water with fresh water to obtain a consistent supply that meets water quality targets.
Using COW Water as Boiler Feedwater
Multiple-effect evaporators or process reverse osmosis units are used to separate the cow water from the dairy solids. If the processing plant uses a multiple-effect evaporator, the hot condensate from the first effect can often be returned directly as boiler feedwater without any pretreatment. Adding COW water to the feedwater will significantly reduce the makeup, chemical, and energy requirements associated with operating the boiler system. In fact, for every 2 gallons of COW water returned to the boiler system, 1 cubic foot of gas is saved. Process reverse osmosis permeate can also be used as boiler feedwater, but may require softening to remove any hardness. In all cases, it is important to understand whether the steam will have direct food contact to determine whether PMO category 2 or 3 applies. As a reminder, category 3 COW water cannot be used in boilers where the steam directly contacts food products.
Using COW Water as Cooling Tower Makeup
Using COW water as makeup in a cooling tower system is more complex than a boiler system. The main challenges are contamination with milk organics and microbiological control. Without effective control measures, severe microbiological fouling and slime deposits can develop. Fluctuations in COW water quality will need to be addressed as well. A system to divert COW water containing high levels of impurities before it is added to a storage tank is necessary. COW water being used in cooling applications is typically stored at ambient temperature and must be treated with chlorine or chlorine dioxide to oxidize the organics and manage bacterial growth. Recycled COW water should be blended with another water source to ensure a consistent makeup source with at least 50 ppm of calcium hardness. Providing a consistent makeup water chemistry is key for a successful water treatment program.
As environmental concerns and overhead costs continue to rise, companies will continue to look for innovative ways to save money. In this pursuit, the dairy industry has a unique option available to it; COW water. Chem-Aqua has a unique combination of knowledge and products to help in this process. We have the ability to provide chemistry and equipment solutions for any application. Our representatives work hand-in-hand with dairy industry partners on a daily basis and are ready to assist. Contact Chem-Aqua today to have an experienced representative survey your facility and lend their expertise.
Written by: Tim Daniels