Date of Award
Master of Science (MS)
The use of stabilization ponds to dispose of municipal wastes has become popular with many North Dakota cities. When managed properly they are an efficient and economical method of waste disposal and may not adversely affect groundwater quality. In order to achieve efficient treatment, the ponds must be built in sediment that has permeability low enough to inhibit excessive percolation of wastewater into the subsurface. Some North Dakota cities have not met this basic requirement in the construction of their ponds. As a result, insufficiently treated pond liquids are allowed to reach the water table, potentially contaminating groundwater supplies. Three such sites located over important aquifers near Grand Forks were chosen for this study: McVille, Larimore, and Fordville, North Dakota.
Monitoring wells were constructed peripheral to and downgradient from the sites beginning in May, 1980. The wells served two purposes: to determine the flow system by recording water levels periodically, and to obtain water samples for subsequent chemical and biological analyses by the Department of Health in Bismarck.
In general, concentrations of constituents such as calcium, magnesium, total dissolved solids, chloride, ammonium, and iron increase immediately downgradient from the ponds, indicating that groundwater is adversely affected by wastewater percolation. In some cases, the elevated values exceed maximum pollution standards set by the U.S. Environmental Protection Agency.
The behavior of the contaminant plumes are complex and dependent on redox conditions both in the pond bottom sediments and the groundwater. Contaminants originate from three sources at the McVille site: continuous percolation of anaerobic wastewater from cell I, aerobic cell II discharges, and aerobic leachate from a dump at the site. Groundwater quality is severely degraded at that site. Groundwater at the Larimore site is generally of better quality; however, several constituents are excessive. The transfer of pond liquids from one cell to another at Larimore has a significant effect on groundwater quality at that site. Groundwater quality at Fordville is least influenced by the pond, although a few constituents are present at high levels.
Seepage from the waste stabilization ponds studied does not presently affect municipal water supplies of the cities that use them. However, because of severe groundwater contamination immediately downgradient from the McVille site, it is recommended that an impermeable clay liner be installed in the McVille ponds. Evidence of groundwater degradation adjacent to the study sites indicates that construction of wells near the sites should be prohibited.
Brown, David J., "The effect of waste stabilization pond seepage on groundwater quality of shallow aquifers in eastern North Dakota" (1983). Theses and Dissertations. 39.