We’ve seen quite a few news stories recently about dairies being cited and fined for wastewater lagoon violations, namely biological oxygen demand (BOD) exceeding permit levels and odor complaints. So what’s going on? Why is dairy processing wastewater such a challenge, and what’s behind the odor complaints this spring? We’ll answer these questions and look at ways to optimize treatment and prevent dairy wastewater odor and the complaints it can cause.
What is dairy processing wastewater?
Dairy processing is a water-intensive agricultural industry, requiring as much as six gallons of water for every gallon of processed product. Much of the wastewater it generates is from sanitation, such as the cleaning of equipment, pipes, and floors. Sanitation wastewater is often contaminated with cleaning chemicals and detergents, like sodium hydroxide and sodium hypochlorite, both of which are very alkaline.
The rest of the dairy wastewater is milk components like whey and casein proteins; lactose; salts; and fats, oils, and greases (FOG); each of which presents its own challenge. Milk products range to the acidic side as the milk sugars ferment to lactic acid. Clearly, the pH of dairy wastewater can vary tremendously based on the proportion of more acidic milk products to more alkaline cleaning chemicals. (For more about wastewater lagoon pH, check out our blog post: Using Wastewater Lagoon pH as a Diagnostic Tool.)
According to the Wisconsin Department of Natural Resources, the BOD5 of normal dairy production wastewater is in the range of 2,000–3,000 mg/L, or 10 times the strength of domestic wastewater. In the event of spillage, BOD can go even higher.
In addition, dairy wastewater is high in suspended solids (TSS), which must be digested or they will settle to the bottom of the lagoon as sludge.
Complicating matters is batch production in the dairy industry, which leads to inconsistent flow and shock loadings. That’s one of the reasons that lagoon wastewater treatment for dairies is so popular—the long retention times offer the capacity to accept varied levels of influent and shock loads without jeopardizing the quality of treatment.
Why is it worse this year?
It’s likely that the unusually harsh weather last winter destroyed some of the lagoon’s resident microbial population. BOD-consuming bacteria are temperature sensitive, with every 10 degree reduction in temperature reducing their activity by half. The increased sunlight and gradual warming of spring cause the lagoon to destratify as the overall temperature equalizes, lifting the settled solids from the bottom and releasing the accumulated odorous gases that had been trapped, a process called lagoon turnover. With its exceptionally high BOD and TSS levels, a dairy lagoon’s turnover can be extremely unpleasant. An optimized lagoon requires a healthy, well established bacterial colony supplied with sufficient dissolved oxygen (DO). Otherwise, BOD loads get out of control, resulting in permit violations and objectionable odors.
How can dairy wastewater odors be prevented?
In order to keep BOD levels and odors in check, a wastewater lagoon needs mixing and aeration. Robust mixing throughout the water column keeps solids in suspension, where they come in contact with BOD-consuming bacteria instead of settling as sludge.
High BOD levels require high DO levels. Without sufficient dissolved oxygen levels, bacteria resort to anaerobic digestion, which is inefficient and creates odors. Fine bubble aeration, with its high surface area bubbles, provides the most efficient oxygenation.
Triplepoint’s portable, modular MARS unit combines both fine bubble aeration for oxygen transfer with coarse bubble technology for turbulent mixing through the water column. Together, these components allow the MARS to oxygenate and treat water effectively while still using energy efficiently. Each MARS unit has its own weighted legs and is fed air via flexible weighted tubing. Because it’s portable, it can be used to manage practically any wastewater treatment cell by simply lowering it in from the surface—no need to dewater the lagoon. Retrofitting an existing lagoon with a Triplepoint MARS Lagoon Aeration System to add aeration and mixing will maximize the existing lagoon capacity, providing more treatment in the same space.
Wastewater Dairy Lagoon Aeration: A Case Study, tells how MARS Aeration allowed Coopersville, MI, to cost-effectively treat wastewater from a dairy facility.
If your facility is already noncompliant or receiving complaints, call us at 800-654-9307. We can have a plan in place within hours and MARS aeration units onsite within days, to get BOD and odors under control and avoid fines, production disruption, and bad press. Triplepoint’s emergency aeration is a quick, cost-effective solution.