Eliminating Odors from Cheese Processing Wastewater

The Bel Group, French parent company of Bel Brands USA, Inc. (Bel Brands), has been making cheese for 150 years. Maintaining that longevity has required a commitment to social and envi­ron­men­tal respon­si­bil­ity that equals the company’s mission of innovation and superior cheese production. Bel Brands’ facility in Brookings, South Dakota, which exclusively creates Mini Babybel® wax-wrapped cheese wheels, embodies that pledge. When hydrogen sulfide levels in the plant’s cheese processing wastewater that is discharged to city sewers started to cause odors downstream, the company sought to proactively address the issue.

Bel Brands hired CDM Smith’s industrial design-build team to investigate, design and install a low-cost treatment solution that would meet its goal: achieving a daily average of less than 5 parts per million of atmospheric hydrogen sulfide in the sewer. CDM Smith’s proposed solution was building a conven­tional sulfide oxidation system to eliminate the objec­tion­able odors from the sulfides.

Design-build delivery was crucial to meeting the project’s schedule. To beat the approaching South Dakota winter, CDM Smith’s engineers and construc­tion crews had to work collab­o­ra­tively to design and build the new system in five months. CDM Smith’s team established strong rela­tion­ships and worked closely with Bel Brands, Bel Brands’ contracted wastewater plant operator, and the city of Brookings to keep the fast-tracked project on pace and prevent disruptions to Bel Brands’ manu­fac­tur­ing operations.

The team began by performing onsite wastewater treata­bil­ity tests to verify the oxidation concept and determine design parameters. They directed a controlled flow of the facility’s wastewater to a bench-scale testing area, where the effluent was fed into buckets and tubs of various sizes with air diffusers installed in them. They then tested different combi­na­tions of air flow, retention time and tank size to find the optimal config­u­ra­tion to completely aerate and oxidize the hydrogen sulfides. The results helped CDM Smith size the full-scale oxidation tank so that it was not too small (where sulfides would not oxidize suffi­ciently) or too big (which would add costs for Bel Brands).

The constructed stainless-steel, 81,250-gallon oxidation tank processes up to 374,000 gallons of cheese processing water per day. Requiring less than 5 hours of retention time to fully eliminate the odors before discharging the effluent, the system can handle influent hydrogen sulfide concen­tra­tions as high as 128 milligrams per liter (mg/L). The tank features a fine bubble diffuser system to provide complete mixing and a maximum dissolved oxygen concen­tra­tion of about 8 mg/L at 25 degrees Celsius. Three positive displace­ment blowers adjacent to the tank provide the air to the diffusers.

The new oxidation system’s smart design enabled Bel Brands to avoid new chemical storage and feeding, as well as offsite waste disposal, minimizing long-term operating costs. Under an aggressive deadline, CDM Smith’s design-build team not only met the schedule, but their solution helped Bel Brands meet its treatment objective. The hydrogen sulfide odors were fully eliminated from the plant’s discharged effluent, allowing Bel Brands to maintain its strong commitment to envi­ron­men­tal and community respon­si­bil­ity.