Extracting Nutrients, Saving Resources through Livestock Water Recycling

However, Livestock Water Recycling (LWR), a company in Calgary, Alberta, Canada, has developed a technology with the potential to change how manure is treated around the world.

The concept behind the technology is simple but revolutionary and important enough that LWR squeaked past entries from more than 1,000 Canadian businesses to win a major grant. The funds will allow the company to spread its technology into the U.S. and international markets.

THE TECHNOLOGY

To illustrate the extent of the possibilities, Shiloh Dairy alone generates 30 million gallons of livestock manure each year. A dairy spokesperson said LWR’s technology is expected to recycle 18 million gallons of clean water, 6 million gallons of liquid nutrient concentrate (ammonium sulfate and potassium), and 6,000–12,000 tons of solid fertilizer (organic nitrogen and phosphorus) from that manure every year.

The recycled water can be used for cleaning or watering the cattle and it can be stored for crop irrigation or released. The fertilizer nutrients can be strategically applied to land in a way that can maximize fertilizer value, or it can be sold to generate new revenue.

Because of the huge environmental impact potential of this technology, VALVE Magazine spoke to LWR President Ross Thurston to find out why livestock recycling is important and how it’s done.

TOO MUCH OF A GOOD THING

For centuries, farmers have used the manure produced from their operations as fertilizer. Such manure is rich in nutrients and water, and it was simply spread on the fields to help crops grow. However, the huge livestock operations that dominate modern farming today produce much more manure than would have been produced on the same amount of land in the past.

“Although manure is a great fertilizer, spreading it can result in run-off, which contaminates valuable water sources,” says Thurston. “LWR’s technology can recycle and clean water, and concentrate nutrients from the effluent.”

Such processing also reduces the overall volume to be handled “providing a cost-effective and environmentally friendly alternative for livestock operators,” he says.

The process involves mechanical and chemical water treatment that segregates nutrients and pathogens from the manure, Thurston explains.

“It focuses on the isolation and concentration of solids and valuable nutrients such as phosphorus, potassium, ammonia and nitrogen,” he says.

Each step of the process captures a different nutrient, then, “The last phase of the process uses a membrane filtration system to recycle the clean water.”

Meanwhile, “there is zero discharge so all parts of the initial influent are reused and recycled as valuable outputs to be reused at the livestock operation,” Thurston says.

The intake material, which is a mixture of livestock manure and water, is fed to the LWR system by a progressive cavity slurry pump. Separators and screens remove the solids from the liquid. After the solids are separated, the liquid is collected in a transfer tank. A pump used to move the liquid to thefine solids removal stage is the same as the inlet pump. The liquid is then pumped into the feed tank of the membrane filtration system.

Centrifugal pumps drive the liquid through the membrane and separate the process stream into concentrated nutrient and clean water. A throttling globe valve at the nutrient discharge end of the membrane filtration system controls the performance of the membranes.

VALVES IN THE SYSTEM

LWR uses two types of valves in its systems—globe valves for throttling on the membrane filtration system and ball valves for isolation.

Thurston explains that most of the ball valves are PVC valves, which isolate system components for purposes of maintenance and service. Some smaller valves also are used to take analytical samples from the process stream. Globe valves regulate the discharge flow from membrane filtration so that the nutrients and clean water can be separated at a pre-determined percentage.

“The valves in these systems need to be able to stand up to the components in the manure,” says Thurston. “That can change according to the area and the livestock, but all our valves are constructed of either PVC or stainless steel. Valve seats are all EPDM or Buna,” he adds.

Most valves throughout the system are manually actuated, although a few valves that automatically switch the membrane filtration system from normal operation to an in-place cleaning process are electrically operated. When the cleaning process is finished, these valves are de-energized to switch the membrane filtration system back to normal operation.

The entire process is controlled with a programmable logic controller (PLC) and an operator interface. The system is accessible remotely for viewing system parameters, making operational changes and conducting troubleshooting.

“The biggest challenges for valves and actuators in this process is the corrosiver atmosphere,” Thurston says. “There is ammonium in the process fluid, and the building atmosphere also has low levels of ammonia and H₂S.”

While various geographical areas and kinds of livestock present different challenges, the overall base process is the same from site to site. Because there are small differences between systems to deal with different types of manures, “We test each clients’ manure in our lab prior to the construction of the equipment to determine the best treatment protocol. It is an individualized system,” Thurston says.

AN INCREASING NEED

According to the United Nations Water Development Report, agriculture currently accounts for 70% of withdrawals of freshwater in the world. Meanwhile, by 2050, world food production will need to rise by 70% to meet the needs of an anticipated 9 billion people. Without technological advances, it may not be possible to

meet that need. New materials and engineering breakthroughs such as livestock water recycling and the valve innovations developed to ensure the success of these efforts mean the planet is more likely to have the limited and precious resource of water that will help feed the world.

For more information on this process, visit www.LivestockWaterRecycling.com.

KATE KUNKEL is senior editor of VALVE Magazine. Reach her at kkunkel@vma.org