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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #156870


item Hubbard, Robert
item NEWTON, G. - U. OF GA

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2004
Publication Date: 12/1/2004
Citation: Hubbard, R.K., Gascho, G.J., Newton, G.L. 2004. Use of floating vegetation to remove nutrients from swine lagoon wastewater. Transactions of the ASAE. 47(6):1963-1972.

Interpretive Summary: Animal wastes pose a major threat to soil and water quality. Excess N and P from animal wastes may result in eutrophication of water bodies or contamination of drinking water. Technologies are needed to utilize these nutrients. Wastewater lagoons are commonly used for confined animal feeding operations (CAFOs) for dairy and swine. The lagoon wastewater generally is land applied. Potential also exists for removing nutrients from the lagoons if vegetation can be grown on floating mats and periodically removed. This study was conducted to determine if floating mats of vegetation could be grown on swine lagoons wastewater, and to measure the amount of biomass and nutrients than could be removed over approximately a one year period. Floating mats constructed of PVC pipe and chicken wire were sprigged with cattail, rush, or maidencane in June 2001. Replicated treatments of full strength wastewater, ½ strength wastewater, or an inorganic solution were evaluated. Cuttings were made beginning in August 2001 after the plants were well established. It was determined that rush was an unsuitable species for growth on floating mats. The rush grown on both the ½ and full strength wastewater ultimately died. Cattail was found to grow best on full strength wastewater, produce the most biomass, and removed the most nutrients. The results from this study are important to animal producers and wastewater lagoon managers because they provide new information on a potential method for managing lagoon wastewater.

Technical Abstract: Methods are needed to remove nutrients from wastewater lagoons. Most removal methods involve land application of the lagoon wastewater with nutrient removal by crops or forest or losses through such processes as NH4 volatilization or denitrification. However, potential exists for nutrient removal directly from the lagoons if vegetation can be grown on floating mats and periodically harvested and removed. A study was conducted to determine the feasibility of using floating mats of vegetation on swine lagoon wastewater. Wastewater from the University of Georgia swine wastewater lagoons was pumped to replicated tanks (1285 L) in which floating mats of vegetation were grown. Three different wetland species were tested; maidencane (Panicum hematomon Schult 'Halifax', cattail (Typha angustifolia L.) and soft rush (Juncus effuses). Full strength wastewater, ½ strength wastewater, and an inorganic nutrient solution (1/4 strength Hoaglund solution) as a control were tested. Vegetation from the floating mats was harvested periodically by removing all vegetation above 5 cm of the base of the floating mat. Measurements were made at each cutting of the total biomass per tank, leaf area (using a Li-Cor leaf area meter) and nutrient content (N, P, K) of the vegetative tissue. Growth responses were quite different between the three species. The cattail had tremendous growth during the summer months but went dormant during the winter. The growth rate of the rush was slow, and it did not go dormant during the winter months of 2001-2002, but it died during summer of 2002 at both the ½ and full strength wastewater. This clearly showed that this species is not suitable for growth on floating mats in swine lagoon wastewater. Total nutrient removal by both the cattail and maidencane was primarily a function of total biomass produced. The cattail species worked best for biomass production and removal of nutrients. Results from the study indicated that potential exists for using floating platforms to grow cattail, maidencane, or possibly other yet to be identified plant species in wastewater lagoons for nutrient removal.