Effects on ground-water quality from irrigating pasture with sewage effluent near Lakeland, Florida

Since 1969 an average of 25,000 gpd of domestic secondary-treated effluent has been used to supplement irrigation of 30 acres of grazed pasture north of Lakeland, Florida. Monitor wells were contructed near the effluent-irrigated pasture. The water table in the surficial aquifer under the pasture varied from 1.0 to 3.3 feet below land surface. Total nitrogen was less than 20 percent of the effluent content after percolating 8 feet; no increase in nitrogen was detected 20 feet below the surface, or in down-gradient ground water. There was no evidence of phosphorus or carbon contamination of ground water. Low numbers of bacteria (generally coliform) were noted in some samples from nine wells. Four wells sampled contained bacteria of probable fecal origin. Low-rate application of the effluent to the pasture apparently has had little effect on the soil and ground water. (Woodard-USGS)