|GARCIA-GONZALES, M - Instituto Tecnológico Agrario De Castilla Y León (ITACYL)
Submitted to: Scientia Agricola
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2015
Publication Date: 9/1/2016
Citation: Garcia-Gonzales, M.C., Vanotti, M.B., Szogi, A.A. 2016. Recovery of ammonia from anaerobically digested manure using gas-permeable membranes. Scientia Agricola. 73(5):434-438.
Interpretive Summary: Anaerobic digestion is considered an efficient and cost-effective treatment capable of transforming organic content of manure effluents into biogas and energy. However, most of the nitrogen (N) in the digestate effluent remains as ammonia. In this study, ammonia was successfully recovered from swine manure digestate using a new gas-permeable membrane process. Although the results showed a total N recovery efficiency of 71 percent, it is possible to increase this recovery efficiency to more than 90 percent and to minimize N recovery time by adjusting the area of the membrane system to match the high free-ammonia concentration (FA) in swine manure digestate.
Technical Abstract: Nitrogen (N) can be recovered from different types of wastewaters. Among these wastewaters, anaerobically digested swine manure (digestate) is one with the highest N content in ammonia form. It is desirable to reduce the high ammonia content in swine manure because it reduces biogas production by inhibiting anaerobic digestion. However, if a large quantity of ammonia is removed during the anaerobic digestion process, inhibition caused by this compound will be minimized while improving anaerobic digestion and methane production. Therefore, the use of gas-permeable membranes to capture ammonia from digestate could be used to improve anaerobic digestion process and methane production. The research goal of this work was to apply the gas-permeable membrane technology to evaluate ammonia recovery from high-ammonia digested swine manure. The anaerobically digested swine manure with total ammonium content of 4,293 milligrams N per liter was reduced 91 percent (to 381 milligrams N per liter) during the 32-day experimentation. In contrast, volatile solids concentration was reduced only 12 percent and remained mostly available for methane production. Although the results showed a total N recovery efficiency of 71 percent, it is possible to increase this recovery efficiency to more than 90 percent and to minimize N recovery time by adjusting the area of the membrane system to match the high free-ammonia concentration (FA) in digested swine manure. Moreover, final digestate pH is maintained around 8.1, which is convenient for the anaerobic process or to incorporate in arable soil when the process is finished.