|Overview of the Barton plant and its wastewater treatment operation.
SCA (www.sca.com) is a global consumer goods and paper company that develops and produces personal care products, tissue, packaging solutions, publication papers and solid-wood products. It has sales in 90 countries and many well-known brands, including Tena and Tork. In 2008, SCA established a new carbon-dioxide target of a 20 percent reduction in emissions from fossil fuels from 2005 through 2020. It has also undertaken to reduce its water consumption by 15 percent from 2005 through 2010 and to reduce the organic content in its wastewater by 30 percent.
Here are some examples from one of the company’s American plants (which uses close to 100 percent recycled paper as raw material) of the creative ways in which SCA is achieving these ambitious green goals.
SCA’s Barton tissue plant, in Alabama, had an activated sludge wastewater treatment plant installed when it was built in 2003. The Barton plant, near the town of Cherokee on the Tennessee River, has an annual capacity of 180,000 tons of paper converted into napkins, towels and toilet tissue. The plant’s raw materials come from virtually 100 percent recycled paper consisting of sorted office waste, post-consumer waste and corrugated, sourced from the region.
All this recycled paper has to be washed and de-inked in order to be turned into new paper. This means the Barton plant, which gets its water from the Tennessee River, has to treat the water heavily before releasing it back into the river. According to Randy Paff, technical service manager at Barton, the activated sludge wastewater treatment plant treats 4 million gallons (15 million liters) of water per day. The system is designed for 5.5 million gallons (20 million liters) to accommodate a recent expansion. “We are currently discharging only about 10 percent of what the state allows us,” Paff says. “This translates into an average total suspended solids removal rate of between 99.6 and 99.7 percent, which is way above state and EPA requirements.”
In 2004, the Alabama Department of Environmental Management awarded the Barton plant a Pollution Prevention Achievement Award for the plant’s good environmental footprint and design. Wastewater treatment – from de-inking, papermaking, storm water, boilers and maintenance wastewater – at the Barton plant begins with mechanical screening, known as the headworks. This is followed by primary clarification, where solids settle to the bottom of the tank, are removed and are subsequently fed through a screw press for dewatering before being sent to a landfill. The cleaner water flows over weirs at the top of the clarifier to the cooling tower. Gravity then takes it to the aeration basin. The aeration basin and selectors (4 million gallons, or 15 million liters) inject air and nutrients into the water and use biological organisms, commonly called “bugs,” to clean the water by consuming the organic impurities.
The last stage is secondary clarification. Here, as in the primary stage, solids fall to the bottom of the tank. These solids are mostly biological so they are recycled back to the selectors and the aeration system. Some of the solids are purged and sent to the screw press. A lot of monitoring and sampling goes on throughout the process, including the final effluent, which goes through a trap to reduce foam before it is discharged via a diffuser along the bottom of the Tennessee River.
Paff says the mill is looking at alternatives to landfills for the sludge it generates. “Using the sludge in the roofing tile industry or as a fuel source for steam production are two options we are investigating,” he says. “Turning our waste into a beneficial use is our goal. We continuously look to optimize our processes even further.”