The amount of aeration needed to substantially reduce odor from a manure storage pond or from a lagoon depends on where the aeration is located (depth and distribution). An aeration distribution system may be located throughout the pond or lagoon, on the bottom or suspended at some depth, or located on the surface and depend more on mixing for distribution of added oxygen. For wastewater stabilization with aeration in treatment ponds, the dissolved oxygen should be maintained at 1 to 2 mg/L. A rule of thumb is to supply oxygen to satisfy twice the biochemical oxygen demand (BOD). A 150-lb pig produces about 0.5 lb BOD per day, but less than this may reach the storage pond because of some changes that may occur in the manure while it is stored in the barn. Aeration for wastewater stabilization can be rather costly for high-strength waste. Lower levels of aeration can be used for partial odor control, such as to supply one-third to one-half the BOD load.
If the objective is limited to partial odor control with minimum costs, then aeration can be confined to the upper layer of the lagoon, and the bottom layer may remain anaerobic. One laboratory study showed that continuous surface aeration at a depth of 0.5 to 1 ft with approximately 0.5 mg DO/L effectively controlled odors but may result in high ammonia emissions.
Intermittent surface aeration proved to be a feasible strategy for minimizing the energy requirements for aeration while controlling odors, but the depth for intermittent aeration may need to be deeper to achieve the same odor control effectiveness.
Although there have been several types of aeration systems proposed for reducing odor, relatively little actual aeration of storage ponds or treatment lagoons has been done because of the high energy cost of aeration. There is also concern that low-level aeration alone might increase emissions of ammonia to the atmosphere.
For more information on aeration for odor control, see:
LPES Lesson on Biological Treatments to Reduce Emissions
Author: Phil Westerman, North Carolina State University
