Driven by heightened regulation and sought after cost savings, these very food and drink companies are now integrating advanced water treatment technologies into their operations.
Earlier this year PepsiCo scooped the Stockholm Industry Water Award for conserving nearly 16 million cubic meters of water in 2011, from a 2006 baseline.
The company's Casa Grande, Arizona, Frito-Lay facility was cited for using a filtration and purification system that recycles and reuses approximately 80% of process water used in production.
CDM Smith completed the design and construction of the 2460 m3/day process water recovery treatment system, which recycles up to 75% of the facility's process water. As a result, Frito-Lay has been able to reduce its annual water use by 378,541 m3.
Several processes at the facility are large consumers of water. Potatoes are moved and washed in a flume as they are prepared for processing. During peeling and slicing, starch is flushed away. For corn, water is used in a caustic soak that loosens the hulls, also in a starch reduction step and in cooking.
Starch water is sent into a segregated water line so the starch can be removed and processed. The water and starch are separated in a vortex, high speed separation process. The concentrated starch is dewatered on a vacuum filter, and then it is dried with a hot air dryer, bagged and sold for use as commercial starch product.
At the PWRTP, a pump station lifts the process water up to internal fed rotary screens that capture corn kernels and pieces of potatoes and any large material. Water flows out of screens to an equalization tank, where staff adjust pH. From there it goes to primary clarifiers. Fine particles of corn and potatoes that settle in the primary clarifiers are removed by a bottom scraper. The settled material is blended with the larger screenings and then dewatered on a centrifuge. The dewater solids are used for animal feed.
After the primary clarifiers, water flows to into bioreactor tanks, where an activated sludge step provides biological nutrient (nitrogen) removal, followed by a membrane bioreactor featuring ultrafiltration with GE Zenon membranes. A pressurized granular activated carbon system helps remove color and reduces BOD and COD. Water is disinfected in a ENAQUA UV system prior to flowing into a Low Pressure Reverse Osmosis (LPRO) system. The LPRO features use of Dow membranes but was assembled by ENAQUA. There are three membrane arrays, with two being used for average flows seen at the plant.
Influent BOD is around 3500 mg/l and non detect on discharge. TSS is about 4,000 mg/l coming in and non-detect on the discharge. "We are putting out drinking water quality water," said Al Goodman, P.E., Principal CDM Smith. "In fact, it's better than drinking water."
The LPRO recovers 75% of the water, while the 25% reject water goes to the city sewer. City makeup water is piped into the reclaimed water tank and blended with the recycled water. Water from the reclaimed tank is eventually pumped back to the head of the plant to meet production requirements.
The Process Water Recovery Treatment Plant started up in May 2010 and has performed as expected, meeting all water quality testing requirements. The Casa Grande facility was the first snack food manufacturing facility in the United States to be awarded LEED Existing Building Gold Certification from the U.S. Green Building Council, thanks to educational elements, enhanced process layout and energy-efficient motors.
With 80% of construction debris recycled for beneficial reuse, dewatered potato peelings and corn kernels sent to local farms for feedstock, and recovered potato starch sold for other manufacturing uses, the facility now sends less than 1% of its overall waste to landfill.
The facility has a 5-megawatt photovoltaic solar system that produces almost all of the plant's daytime electricity needs. CDM Smith completed the entire photovoltaic solar installation, including 36 acres of photovoltaic panels on dual-axis ground-mount systems, single-axis concentrated photovoltaic collectors, and dish collectors with Stirling engine generators.
Goodman said the Casa Grande facility demonstrates that the technology exists to recycle water to the highest standards.
"We are quoting and proposing on other systems and other food and beverage companies that have seen this system," Goodman said. "We definitely see this as the path of the future."