Reciprocating Constructed Wetlands for Treating High Strength Anaerobic Lagoon Wastewater

Innovative wastewater treatment systems are needed for removing nutrients, noxious odors, dissolved organic matter, and pathogens from high strength agricultural and processing wastewater. A novel reciprocating subsurface-flow constructed wetland, consisting of four cells totaling 3570 m (1.5 m deep), has been treating anaerobic lagoon wastewater from a commercial-scale confined swine feeding operation since November, 2000. The system, located near Aliceville, Alabama, has been monitored for twenty-one months. Hydraulic loading rates (HLR), from the anaerobic lagoon to the wetlands treatment system averaged 107 and 208 m/day for years I and II respectively. Results to date indicate that the system’s treatment efficacy is sustainable, with the exception of phosphorus removal. Doubling the flow temporarily reduced treatment efficacy with respect to monitored parameters. Average influent and effluent concentrations (ppm), of monitored parameters and their respective percentage removal rates were: CBOD5 (521, 117, 78%); COD (1388, 393, 72%); NH4-N (371, 51, 86%); and PO4-P (52, 43, 17%). Electrical demand to operate reciprocating pumps, influent pumps and irrigation pumps averaged 203 kWh/day and 234.1 for the two wastewater loading rates respectively. Based on comments from farm workers and subjective laboratory testing, the system was effective in removing odors from lagoon effluent. Fecal coliform bacteria removal rates ranged from 2-3 Log reduction. In conclusion, the reciprocating wetland system was user friendly, relatively cost effective, and efficient with respect to removal of organic compounds, nitrogen, odor and fecal coliform bacteria. Further research will be required to enhance phosphorus removal.