Effect of Stratification on the Profile of an Anaerobic Swine Waste Treatment Lagoon in Kentucky

An understanding of the nature of wastes in an anaerobic swine lagoon is essential in the design and operation of alternative collection, treatment, and disposal facilities for environmental quality management such as odor control, nutrient and pathogen reduction. In this study, the characterization of an anaerobic swine waste treatment lagoon (0.40 ha) from a farrowing operation (~2000 sows) was carried out to examine the dynamics of the system due to stratification and seasonal variability. Swine waste samples were taken from an anaerobic swine lagoon at different depths (0, 50, and 250 cm) with a pulley system equipped with a special sampler that allows for sampling exclusively at certain depth. The sampling process was carried out from spring to fall season. The pH and temperature were monitored and recorded continuously from the epilimnion (top) and hypolimnion (bottom) layers of the lagoon. The samples were then analyzed for their mineral contents by using Inductively Coupled Plasma (ICP), Total Nitrogen, and Total Organic Carbon analyzers. Microbial dynamics were monitored by DNA extraction and Denaturing Gradient Gel Electrophoresis (DGGE). Results showed that nutrient (C, N, P, S) concentrations varied according to stratified lagoon layers and season. For example, total organic carbon concentrations range from 1800 mg/L (top) to 5400 mg/L (bottom) for late spring, and from 1100 mg/L (top) to 3600 mg/L (bottom) for the middle of summer. Trace minerals such as Al, Ca, Fe, K, Na, and Mg, on the other hand, appeared to be affected more by stratification than seasonal variability. The reason for the decrease in nutrient concentrations in summer time may be due to increase microbial activities which required more essential nutrients (i.e., C, N, P, S) rather than trace minerals for growth during active season. DGGE analysis also showed that microbial community structure appeared to be affected by the stratification and seasonal variability. There were distinct banding patterns for samples obtained from the epilimnion and hypolimnion. Based on these data, it is important to consider the effect of stratification and seasonal variability of waste loading from traditional anaerobic swine lagoon when designing and operating an alternative anaerobic digester.