Disposal of municipal wastewater on farmland : fate and environmental impact of applied heavy metals in the soil-water-plant ecosystem

Abstract

The city of San Angelo, Texas, has used agricultural land for disposal of municipal wastewater since 1958. The city's sewage treatment plant provides only primary treatment to the wastewater before it is applied to a 259 ha farm. The sewage flowrate to the treatment 3 plant ranged from 0.153 to 0.351 m??/sec in 1976. A border strip surface irrigation is used for wastewater management. This system allows a slow rate of wastewater infiltration into the soil. Much of the applied wastewater reaches the Concho River, which borders the sewage farm, by underground seepage. The impact of 18 years of wastewater irrigation on the heavy metal chemistry of the soil-water-plant ecosystem was studied from 1975 to 1977. Chemical analysis was conducted for selected heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in soil, water, and plant samples taken from the sewage farm and adjacent non-treated control areas. The interactions between applied heavy metals and sewage farm soils were also examined by adsorption and desorption techniques. ...