As one of the largest raisin producers in the industry, National Raisin uses a lot of water to clean and process its raisins. As sales and production increased, however, so did the company’s wastewater costs. Now thanks to a reverse osmosis system from Xylem, the company is able to reuse its wastewater and save $300,000 a year.
Brothers Ernest, Krikor, and Kenneth Bedrosian founded National Raisin in 1969, and it is now one of the largest independent raisin processors in the industry. Its 60-acre, state-of-the-art facility in the heart of the fertile San Joaquin Valley, in Fowler, California, processes over 100 million pounds of raisins annually.
Every raisin at the National Raisin plant undergoes a 35-cyle cleaning process and a thorough quality inspection before shipment. During this rigorous process, between 60,000 and 80,000 gallons of wastewater are generated each day, mostly from washing dust, sugar and other contaminants away from the raisins.
The family-owned company decided to investigate ways to reduce the plant’s operational costs and minimize the environmental impact of its processes on the close-knit community of 6,000.
Wastewater with high sugar content
The wastewater produced by the plant contains sugar and other byproducts from the raisins that create a high biological oxygen demand (BOD). Water with BOD used for land irrigation requires special permits and ongoing regulations to ensure that groundwater quality is not compromised. Water with BOD can also produce offensive odors when disposed of via land application.
This sugar-laden wash water must be treated to remove contaminants, but transporting it to a municipal treatment plant would be expensive – approximately $50,000 per month. To remove the sugar from the wash water, the company opted for a reverse osmosis process – the most economical and environmentally friendly solution.
Turning a lost into a profit with reverse osmosis
After initial trials were completed, it was decided to install 80 B1 PCI Membrane modules from Xylem, fitted with AFC99 Tubular Reverse Osmosis membranes in a continuous system produced by Xylem’s partner Membrane Specialists. The system could be expanded up to 120 modules in the future as National Raisin increases their capacity.
The reverse osmosis process produces wastewater with lower levels of dissolved solids than the well water that feeds the plant, so the facility can safely reuse the wash water in the raisin cleaning process or to irrigate nearby vineyards.
When National Raisin began reusing its water, the company’s sewer bills dropped by approximately $300,000 per year, earning a return on investment in about three years. During this time, the company also partnered with a local distillery that wanted to purchase the treated wash water to make grape alcohol.