A reverse osmosis system is helping Unilever reduce water and natural gas consumption as well as chemical usage. It's yielding both financial and environmental benefits
Just the Facts About Reverse Osmosis Reverse osmosis (RO) replaces water softeners and chloride anion de-alkalizers. RO is a mechanical process involving the reversal of flow through a semi-permeable membrane from a high salinity solution to the high purity stream on the opposite side of the membrane. RO softens and purifies municipal water. It also recycles process water captured throughout the plant for use as boiler make-up.
In the face of rising and unpredictable energy prices, Unilever's plant in Rexdale, Ontario, has embarked on a campaign to improve energy efficiency in order to remain competitive. The plant consumes huge quantities of energy for the annual production of 185 million pounds of margarine and other vegetable oil products. In fact, energy expenditures represent 15 percent of all production costs. To meet an aggressive goal of reducing energy consumption by at least 6 percent per year, the plant's energy team has implemented, and carefully documented, 120 projects since 1999, saving more than $4.2 million in energy costs and eliminating about 23,000 tons of greenhouse gases. The initiatives of the team are part of Unilever's corporate commitment to environmentally responsible practices at its 365 manufacturing sites across six continents. In 2005, for the seventh year running, Unilever led the food industry category of the Dow Jones Sustainability World Indexes, based on assessment of corporate economic, environmental, and social performance.
| The reverse osmosis system qualified Unilever for a $50,000 incentive grant from the city of Toronto for decreased water consumption. |
"By 2003, our energy team at the Rexdale plant had already attacked many of the more obvious ways of reducing energy consumption, but we needed to take additional initiatives to keep pace with our company goal of achieving further reductions of 6 percent per year," explains Doug Dittburner, chief engineer and head of the energy team. "We turned to GE Water & Process Technologies to investigate whether we could achieve significant, measurable improvements in the efficiency of our steam plant operations." The energy team worked with GE to analyze the total cost of purchasing and treating water used to produce the 218 million pounds of steam that the plant uses each year. Municipal water, chemically softened and de-alkalized, was the source of 100 percent of the boiler make-up water. GE recommended a reverse osmosis (RO) system to replace the water softeners and chloride anion de-alkalizers. RO is a mechanical process involving the reversal of flow through a semi-permeable membrane from a high salinity, or concentrated, solution to the high purity, or permeate, stream on the opposite side of the membrane. Pressure is used as the driving force for the separation. A turnkey system was commissioned in the Rexdale plant in January 2005. The RO system not only softens and purifies municipal water, but it also recycles process water captured throughout the plant for use as boiler make-up, significantly reducing the consumption of municipal water. The "concentrate" waste from the RO process is used in the plant's cooling tower and evaporative condenser for ammonia. The higher quality RO feedwater allows the boilers to operate at 100 feedwater cycles instead of 10, dramatically increasing energy efficiency. Blowdown has been reduced by more than 80 percent with a bleed-off of only 1 percent.
"The results of the RO project have greatly exceeded our expectations, and they are easily measured," says Dittburner. "In the first year of operation, we calculated that the project produced a net savings of $378,166, even after accounting for the full cost of operating and maintaining the RO system. We calculate that the RO system will pay for itself in less than 16 months." By converting to the RO system, the plant is consuming 13 million gallons less of municipal water ($68,000) and 8 percent less natural gas ($299,000). The plant is also saving $11,700 in boiler chemicals and $22,000 in commodity softening chemicals, allowing 240,000 less pounds of chemicals into the sanitary sewer. These costs savings do not include the safety and ergonomic benefits of eliminating the backbreaking work of handling 3,976 bags of salt, each weighing 44 lbs, and the related labor and storage costs. The RO system also qualified the Rexdale plant for a $50,000 incentive grant from the city of Toronto for decreased water consumption and a $14,000 incentive grant from local gas utility Enbridge Consumers Gas. According to Dittburner, "The RO project is easily justified by the direct financial benefit to Unilever, but we are also proud of the environmental benefits. The project has led to our producing 1.6 million fewer kilograms of carbon dioxide as well as reductions in methane and nitrous oxides. We are also consuming far less chemicals and reducing the environmental impact of producing and transporting those chemicals." GE Water & Process Technologies, a unit of General Electric, solves water challenges by providing industrial, agricultural, and potable water while lessening dependence on fresh water sources. Technologies to accomplish this include desalination, advanced membrane, separation solutions, water reuse, and wastewater management and process technologies. More information is available by visiting www.gewater.com.